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MikeOxon

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  1. MikeOxon
    Almost 10 years ago, I wrote a post about Dean’s experimental 4-2-4 tank engine , which made a brief appearance in 1882 before being hurriedly rebuilt as a more conventional 2-2-2 tender engine. Very little information has survived about the original engine, except that it had a chronic inability to stay on the track.
     
    With so little prototype information available – and even less that could be considered reliable – I felt justified in taking considerable liberties in the design of my model. The most glaring divergence from received opinion is my arrangement of the bogies, with the longer one at the back. I arrived at this decision after considering the layout of the rebuilt 2-2-2 version, which indicated that the outside Stephenson valve gear could not fit, if the longer bogie were at the front. I illustrate this point in the following diagram:
     

    Bogie arrangements compared to photo of Rebuilt No.9
     
    Other aspects of my model that are entirely fanciful are the extended cab roof and the decorative ‘fake’ wheel arch. So the following photo is my own interpretation, which may or may not have some similarity to Dean’s prototype.
     

    My representation of Dean’s 4-2-4T at North Leigh Station
     
    More information about the construction of my model, which was built by traditional methods, using brass sheet, and was powered by a Tenshodo SPUD motor in the rear bogie, was given in my original post .
     
    Coming to more recent times, the extraordinary 4-2-4 tanks that were designed by Pearson for the Bristol and Exeter Railway have entered my sphere of interest. I have modelled these recently, as described in my Broad Gauge blog . One fact that has emerged is that two examples of a version of the Pearson engines, with smaller 7’ 6” diameter driving wheels, survived into GWR ownership, when they were numbered 2005 and 2006.
     
    GWR No. 2005, which was built at Bristol in 1862, remained in its original condition until broken up in about 1887. The point here is that this date is after Dean designed his standard gauge version! Furthermore, Ahrons, in “Locomotive and Train Working in the Latter Part of the Nineteenth Century”, vol.4, reports seeing number 2005 frequently at Swindon and Bristol shed. Taken together, these facts suggest that there may have been a closer relationship between Dean’s 4-2-4T and the Pearson 7’ 6” GWR No.2005 than has been recognised previously.
     
    In order to examine this relationship further, I decided to create 3D models of both No,2005 (broad gauge) and No.9 (standard gauge), so that I could place them side-by-side and consider the similarities and differences.
     
    In this blog, I shall describe my creation of a 3D model of No.9, while I shall tackle the other engine in my Broad Gauge blog.
     
    Creating a 3D Model of No.9
     
    As I mentioned above, my existing model of No.9 was built by traditional methods, using brass sheet that I cut out by hand over paper templates. I still have the drawings, made using ‘Autosketch’ software, so I started by importing these drawings, as a ‘canvas’, into ‘Fusion 360’.
     
    I then followed my usual process of extruding the various components – boiler, firebox, frames, etc - from the drawings, to create 3D structures. I have previously described my methods in a blog post about creating a 3D model of a GWR ‘Sir Daniel’ class engine. For my current model, the initial layout of the components looked as shown below:
     

    Outlines of my Model Components over ‘Canvas’ in Fusion 360’
     
    I added various details such as the outside Stephenson valve gear and the bogie side frames, to bring the 3D model up to a similar stage of detail as my brass model and then rendered the computer model in appropriate colours. After taking a screen shot of the 3D model, I added some more livery details in 'Photoshop' to give ‘character’ to the result. Remember that most of this comes from my own imagination, as we know very little about how the prototype was finished. I have tried to make it look like a ‘prestige’ express engine, which was apparently the original intention.
     

    My 3D model of No.9, rendered in ‘Fusion 360’
     
    If the prototype really looked anything like this, I can understand why David Joy recorded in his diary, following a visit to Swindon in 1882 “I saw all about a mighty 'single' tank engine Dean and Charlton were building—8 ft-single and double 4 ft. - wheel bogies at each end. I saw drawings and all, and she looked a beauty. She was intended to do Paddington to Swindon in 2 min. under time,"
     
    Comparison with Pearson Broad Gauge 4-2-4T
     
    I have described my 3D modelling of Pearson's engine in my Broad Gauge blog.
     

    Pearson (broad gauge) and Dean (standard gauge) 4-2-4T Engines compared
     
    Looking at these two together, I think it is fairly obvious why the Dean engine had difficulty in staying on the track! With Dean’s inflexible bogie design and the excessive overall length, the lateral forces on any slight curvature must have been considerable, not helped by the large masses of water sloshing about in the long side tanks.
     
    Dean was faced with several problems. He wanted to emulate the boiler capacity of Gooch’s 8 ft. ‘singles’, which would soon have to be replaced, so he had to increase the length to compensate for loss of width possible on a broad gauge engine.
     
    According to the RCTS booklet Part Two, “The domeless boiler was itself a. phenomenon, for it was one of the first in this country to be made in two rings and withal had a barrel length of 11ft. 6in.. not destined to be repeated for another ten years.”. The firebox also had to be lengthened, to maintain a grate area comparable with the wide firebox that was possible on the broad gauge. Another problem was how to accommodate large diameter cylinders, like those used on the broad gauge, together with their associated valves and steam chests within the narrower space between the frames. He tried placing the valves above the cylinder, operating them through rocking shafts from outside Stephenson valve gear.
     
    Most authorities agree that this engine was a complete disaster and must have been a considerable embarrassment to Dean - it’s not surprising that he didn’t want it talked about too much!. But he got over it and eventually came up with his own ‘singles’, which moved the valves below the cylinders in the ‘Stroudley’ arrangement and provided a much improved design of front bogie (after a pair of leading wheels proved insufficient) to keep the machine on the track. The long side tanks had to go and greater water capacity was obtained from a lengthened 6-wheel tender
     
    It is possible that the two engines did actually come together at Swindon, since No.2005 was still around and, according to Ahrons, a frequent visitor to Swindon.
     

    Dean 4-2-4T meets Pearson 4-2-4T
     
    Mike
  2. MikeOxon
    After dissecting the workings of the extraordinary 9ft. Pearson 4-2-4T engines in my previous four posts , I was interested to examine how these engines compared with William Dean’s later attempt to create something similar for the standard gauge.
     
    To make the comparison on as level a playing field as possible, I looked up information on the slightly later Pearson engines fitted with smaller 7’ 6” driving wheels – similar to those on Dean’s standard gauge engine. I have previously modelled the Dean engine, as described in my Pre-Grouping blog .
     
    Thee were eight of the original Pearson 4-2-4T design, with 9 ft. driving wheels, all built by Rothwell & Co. and delivered in 1853-4. There must have been difficulties arising from their novel features, as they were all rebuilt, with the usual form of inside frames and conventional springs, in 1868-70.
     
    In between these batches, two more 4-2-4T engines were built for the Bristol & Exeter Railway (B&ER) in Bristol. These were similar to the 9 ft. engines but with smaller driving wheels of 7’ 6” diameter. No. 29 was delivered in September, 1859 and No. 12 in April, 1862.
     
    These engines survived into GWR ownership and, as GWR No. 2005, the former No.12 remained in its original condition until broken up in about 1887. Ahrons, in “Locomotive and Train Working in the Latter Part of the Nineteenth Century”,Vol. Four, 1953, reports seeing No. 2005 frequently at Swindon and Bristol sheds.
     

    GWR No.2005 formerly B&ER No.12, built 1862 and broken up 1887
     
    Taken together, these facts suggest that there may have been a closer relationship than has been recognised previously between Dean’s standard gauge 4-2-4T and the Pearson broad gauge 7’ 6”, GWR No.2005. Since I have already created a model of the Dean engine , I wanted to see how it compared with No.2005, by placing two models ‘side by side’.
     
    Creating a Model of B&ER No.12 (GWR No.2005)
     
    No.12 has been described as being similar to the earlier 9 ft. singles, although many of the ‘exotic’ features of the earlier engines had already been abandoned by then, even before the original engines were re-built. I found a fairly detailed description of the smaller engines, including an outline drawing, in ‘The Locomotive Magazine’, Vol . III. No. 36. Dec.1898
     

     
    According to ‘The Locomotive Magazine’: “Their driving wheels were only 7ft. 6in. Diameter…. The diameter of the bogie wheels was 4ft, and the total wheel base was 25ft. 2in, the leading bogie having a base of 5ft. 6in., whilst that of the trailing bogie was 5ft. 9in., the driving wheels were 9ft. 4in. behind the leading bogie centre, and 10ft. 3in. in advance of the trailing. The boiler was 9ft. 9in. long, its maximum external diameter being 4ft. 2in., and the height of its centre line above the rail level 6ft. 11in.”
     
    This information was adequate for me to create a 3D model, which I based on my existing model of one of the 9 ft. engines. It was actually an easier modelling task, since these engines had conventional inside frames. Some peculiar featured remained, however, such as the water tank underneath the ashpan!
     
    Following my usual method, I created the boiler-smokebox-firebox assembly by reference to the above drawing, imported into ‘Fusion 360’ as a ‘canvas’. In addition to the driving wheels being smaller, the boiler was 1 ft. shorter than on the earlier engines. I used the ‘Move’ tool in ‘Fusion 360’ to modify faces of the original models of the 9 ft. engines, so as to match the profiles taken from the drawing.
     

    Creating 3D Boiler Assy with reference to Drawing
     
    I had to make new driving wheels, by my usual method, but re-used the bogie wheels and then assembled all the wheels around a new pair of full-length inside frames
     

    Creating 3D Chassis with reference to Drawing
     
    I took advantage of the way in which objects can pass through one another in the virtual world, by creating the two cylinders as complete ‘bodies’ that were then largely enclosed within the smokebox with parts of the sides protruding. The coke bunker only needed slight modification and the chimney and safety valve cover had to be re-profiled.
     
    One item which I have not modelled before was the curved handrail, which is such a prominent feature as it loops above the driving wheel splasher. This feature is easy to create in ‘Fusion 360’ by using the ‘Sweep’ tool. The path to be taken by the handrail is first created as a sketch, using the ‘arc’ and ‘line’ tools. Next the circular profile of the rail has to be created in a perpendicular plane. The ‘Sweep’ tool then causes the ‘profile’ to be extruded along the ‘path’, as illustrated below.
     

    Using the ‘Sweep’ tool to create a curved handrail in ‘Fusion 360’
     
    So, it needed surprisingly little re-work before I had another model, representing the smaller-wheeled version of Pearson’s 4-2-4 tanks.
     
     

    My 3D model of Pearson’s 7’ 6” version of his 4-2-4T in GWR livery
     
    There’s a lot more detailing that could be added but I think this gives a good impression of the overall appearance of the real locomotive.
     
    Comparison with Dean’s standard-gauge version
     
    In parallel with developing this 3D model, I have also re-modelled the Dean standard gauge 4-2-4T in ‘Fusion 360’, so that I could place both versions together, to make some direct visual comparisons:
     
    I describe creating my 3D standard gauge model in in my Pre-Grouping blog.
     

    Pearson (broad gauge) and Dean (standard gauge) 4-2-4T Engines compared
     
    Looking at these two together, I think it is fairly obvious why the Dean engine had difficulty in staying on the track!  With Dean’s inflexible bogie design and the excessive overall length, the lateral forces on any slight curvature must have been considerable, not helped by the large masses of water sloshing about in the long side tanks.
     
    It is possible that the two engines did actually come together at Swindon, since No.2005 was still around when No.9 was built and, according to Ahrons, a frequent visitor to Swindon.
     

    Dean 4-2-4T meets Pearson 4-2-4T
     
     
    Mike
  3. MikeOxon
    I ended Part Three with the prospect of modelling the many rods and brackets on the underside looming over me. I had intended to write more at that time but found myself struggling to understand how various parts of the engine fitted together. I think all the ‘easy’ bits have now been done, so I could no longer avoid the complex underpinnings.
     
    To gain an overview, I ‘mirrored’ one half of the split plan-view from ‘The Engineer’ and then colour-coded various elements – blue for frames, orange for crankshafts, green for valve gear, and red for wheel bearings. I made a couple of ‘corrections’ to the ‘mirror’ process by moving the cranks on one side to represent ‘quartering’. I have repeated this plan as a ‘header’ to this entry. following its use in Part Three .
     

    My 3D model overlaid on ‘The Engineer’ plan view
     
    I was pleased to find more information, which helped me interpret the various drawings, in an article from ‘Engineering’, 11th Feb.1870 (reproduced in the Broad Gauge Society (BGS) journal ‘Broadsheet’ No.27, Spring 1992). Although the article refers to the ‘rebuilds’, some of the information appears to apply to the original engines as well. I quote:
     
    “…. There is also a centre stay for the crank axle fitted with adjustable wedges; this stay is bolted to transverse plate in front of the firebox which ties the frames and assists in supporting the stay;
     
    The eccentric sheaves are of cast iron, as are also their respective straps, these latter having cast on the half that receives the rod two ears which with a pin inserted vertically and eye in the eccentric rod make a lateral joint. The valve gear is of that class known as Gooch‘s stationary link. ... The valve spindles are. guided by a cast-iron bracket bolted to the plates which carry the bogie pin and unite the boiler barrel with the smoke-box tube plate; these brackets have each a flat bar of iron or steel fitted for the spindle crossheads to slide on; these crossheads being similar to the piston crossheads. The reversing shaft is carried by two brackets bolted to the bottom slide bars.”
     

    Gooch ‘Stationary Link’ Valve gear
     
    I then found a lot more useful information in articles by Douglas S Johnson, published in two issues of ‘Broadsheet’, Nos. 83 and 84 (2020), in which he described constructing a model the ‘hard way’, using nickel silver and brass. While very helpful, these articles also provoked great sighs of relief that I was using 3D computer modelling, rather than facing the problems raised by real model engineering.
     
    Modelling the ‘Motion’
     
    As before, I have tried to follow a ‘line of least resistance’, so decided that the moving parts of the motion were the easiest components to understand and place in their appropriate locations. My hope was that the locations of the various supporting brackets would become more obvious once I had the moving parts in place. One of the great things about 3D modelling in a computer is that individual parts will stay where they are placed, as though on ‘sky hooks’!
     

    Sketch of Motion over ‘The Engineer’ Drawing
     
    I started with the main drive-shafts between the cylinders and the driving wheel cranks. The rods are simply cylinders, produced by extruding their cross-section drawings. I have simplified the cross head by extruding from a plan view and then set in place two slide bars, above and below the cross head. I show these parts above the ‘canvas’ which provided me with the overall dimensions.
     

    My representation of the main drive components
     
    These parts will form a static representation of the motion – fully working motion would need metal bars and bearings, which are not on my agenda at present. Because of their prominent locations, they are needed for completing the external appearance of my model.
     

    Side view of the Motion in place on my model
     
    I followed up by using similar methods to create the various components of the valve gear. I made the profile of the Gooch stationary link by tracing over the above sketch of the valve gear and then created the various rods by simple extrusions from sketches. After creating the various components individually, I moved them into their appropriate locations on one side of the engine and then ‘mirrored’ the whole lot to the other side.
     

    My layout of Valve gear components
     
    Next, I put the components into the context of the rest of the model (minus boiler and smokebox), to help me to determine where the various supporting structures need to be placed.
     

    Setting the Motion in the context of my Model
     
    Before I could get much further, I needed to develop a better understanding of how this engine ‘worked’.
     
    Overall Engine Structure
     
    In most engines, the driving wheels transmit the force needed to pull the train, through a pair of strong plate frames running the full length on each side of the engine. These are linked at the back to a strong drag bar running across the width of the engine and carrying the couplings to following vehicles.
     
    In this Pearson engine, the strong plate frames are notably absent. The design has been likened to a road-going Traction Engine but, although there are similarities, they are not the same. In a Traction Engine, the driving wheels are near the back and transmit their forces through a strong frame at the rear end, which carries the necessary draw gear. The boiler in such an engine is a forward extension from the ‘pulling part’ of the engine, carried at its forward end by the steerable front wheels.
     
    A different analogy can be found in Brunel’s design for his Chepstow Bridge, in which he took advantage of the considerable strength of an iron tube to transmit both compression and tension forces. In Pearson’s engine, it is the boiler that provides this key structural component, being connected to the central driving axle through the yoke spanning the top of the boiler. As a tank engine, the design was intended to work in both directions. When running forwards the boiler transmitted the driving force in turn to the firebox, through a transverse frame member, and then to the rectangular tank underneath the coal bunker. The rear coupling hook was bolted directly to the back of this tank, which acted as a box girder. For running backwards the forces were carried by two plates riveted to the lower sides of the boiler, which transmitted the forces to the cylinder casting and then by a short shaft to the front coupling.
     
    I should point out that the above is my own interpretation after spending several days looking at drawings. If those with more engineering expertise see it differently then I shall be pleased to be corrected.
     
    This method of conveying the main driving forces through the boiler would not be permitted now. The fact that even substantial plate frames were subject to cracking under stress, suggests what could happen to a pressurised boiler in similar circumstances.
     
    Modelling the Structure
     
    It took a lot of head-scratching and poring over drawings before, largely by trial and error, I worked out how everything fitted together. The drawings show a plethora of riveted plates, which took me some time before I could understand their functions and how they fitted within the overall context of the engine as a working vehicle. I’m not sure that I can now recall all the steps that I made (and an account would be very tedious anyway) but the outcome of all my deliberations is shown below.
     
    I started with the basic rectangular frame, described Ahrons as “only 8in. deep for the greater part of its length except at the driving hornblocks. An arrangement of angle plates, 2ft. deep, was fastened to the side of the fire-box and to the front of the well tank. From this point to the back buffer beam there was no frame at all.”
     
    Next, I had to understand the curved plate that can be seen in ‘The Engineer’ side elevation, extending from the back of the smokebox and riveted along the lower sides of the boiler. I determined that there were actually two of these plates attached on either side of the casting that carries the front bogie mount. Their purpose was, apparently, to transfer tractive forces from the boiler to the front coupling on the engine. I placed them on my model as shown below:
     

    Modelling the Front-end Boiler Brackets
     
    I could now place the ‘motion’ I described earlier into the context of these brackets and the rectangular frame, as shown below:
     

    Setting the motion within the inside frame
     
    I could now work out the arrangements for the centre bearing of the crank axle and its fore and aft attachments to the firebox and front well tank.
     
     

    Centre-bearing for Crank Axle (outer bearings not shown)
     
    It all looks so simple now – it’s hard to take in how long it took me to figure all this out from the drawings I have 🙂
     
    Actually, when I put it all together, perhaps it doesn’t look quite so simple! Quite a step up from my previous modelling methods:
     

    My model of the ‘Works’
     
     
    It’s rather a pity that almost all of this becomes invisible once the boiler and outer frames are in place 😒
     
    I also find myself wondering how the real engine was erected, with so many ‘inter-dependent’ parts.
     

    My 3D model in ‘photographic grey’
     
    There’s not even much to see from underneath because it’s hidden by the well tank.
     

    My 3D model viewed from below
     
    After rendering in ‘Fusion 360’ my model looks like this:
     

    My 3D model rendered in ‘Fusion 360’
     
    You’d have to look at this rather carefully to spot any visible differences from my earlier renderings!
     
    Now that I’ve teased out most of the internal features, which has been an ‘interesting’ mental exercise, I shall have to return to considering the ‘cosmetic’ appearance. There’s still a lot to be done on the details, such as rivets, boiler bands, and so on … and on.
     
    Oh, and brake gear on the rear bogie.
     
    Enough for now
    Mike
     
  4. MikeOxon
    By the end of Part Two , I had modelled all the most visible parts of the engine and felt tempted to stop there but many of the peculiarities of these engines were below the platform, so I had to keep going ‘down there’.
     

    Photo by Snell of B&ER 4-2-4T No.42
     
    Although I have collected quite a number of drawings and photos, there are still some difficulties in determining the layout of all the parts, especially since some drawings omit features and others show some profiles, without indicating their locations in three dimensions.
     
    Well Tanks
     
    I decided to start with the two well tanks, once below the boiler and the other below the coke bunker, since these are well displayed in the three-view illustrations from ‘The Engineer’ supplement, 1910, which I showed in Part Two.
     
    I sketched the profiles by using the ‘Rectangle’ tool in ‘Fusion 360’ to trace over the end elevation illustrations. I then extruded the profiles to the lengths indicated on the side elevations. These steps are shown below:
     

    Locating model well tanks against ‘The Engineer’ illustrations
     
    The above drawings show the internal bracing struts inside the tank under the bunker, which served to reinforce the mounting for the ball on which the rear bogie was pivoted. While I have not modelled these completely concealed structures, they provided me with useful guidance on the placement of similar-looking braces at the font-end of the engine.
     
    The drawings show that there were two upward extensions from the tank under the bunker, leading up to the filler caps. These structures also served to separate the crew footplate from the coke bunker itself, behind them. A tool box and brake handle were also placed above the footplate. According to Ahrons: “An arrangement of angle plates, 2ft. deep, was fastened to the side of the fire-box and to the front of the well tank. From this point to the back buffer beam there was no frame at all.”
     
    I sketched the outlines of the tank extensions and the toolbox by tracing over the plan view from ‘The Engineer’ and extruded upwards from the sketches to match the illustration of the elevation. The results are shown below:
     

    Coke Bunker with Toolbox and Tank Fillers
     
     
    Front Bogie Mountings
     
    Having secured the rear bogie on its ball and socket joint, it was time to turn to the front end. According to Ahrons: “The ball of the leading bogie was secured to the underside of the cylinders by means of a casting with wings, to which two horizontal tie rods were fastened ; the other ends of the latter were secured to the bogie side frames, and prevented the bogies from slewing round across the track.”
     
    I attempted to identify these features from the front-end elevation shown in ‘The Engineer’ illustrations.
     

    Front Elevation from ‘The Engineer’
     
    I assume that the casting for the ball is the part I have coloured blue, while the ‘wings’ are the parts coloured orange. The tie-rods to the bogie frame can be seen extending outwards from pivots on these ‘wings’. Where, though, is the brace coloured red to be placed? It is shown crossing in front of the tie rods so, perhaps, as at the rear end, there were two braces – fore and aft of the tie rods.
     
    I have enhanced the relevant area from the photo of No.42 above:
     

    Detail from Snell’s photo of No.42
     
    The photo clearly shows a reinforcing bracket on the bogie side fame and what looks like the end of a tie-rod just above the frame. It appears that there were bracing plates either side of the tie-rod, which may be what is represented on the front-elevation drawing. Unless anyone has any more information or I find another drawing, I have to go with this assumption.
     
    I created the following support structure by first tracing the profile of the ball and the casting immediately above it, followed by using the ‘Revolve’ tool to create a cylindrical ‘body’. Then I sketched ‘wings’ either side of the central body.
     
    For the bracket, I traced the front-elevation profile and extruded it, initially with a rectangular profile. I then used the ‘Cut’ tool across the extruded width to create the sloping sides seen in the photo above and the central slot through which the tie-bars pass. My result is shown below, with the component parts coloured as in the illustration above. I also show the completed model, assembled above the front bogie:
     

    My interpretation of the front bogie support frame
     
    With the well tanks and bogie attachments in place, the underside of my model now looks like this:
     

    My model underside with well tanks in place
     
    As an aside, I think this underside view demonstrates why Dean failed in his attempt to create a narrow (standard) gauge version of a 4-2-4 tank engine. There was no room for the large well tanks so he had to resort to large side tanks, which were a source of severe instability. I have previously modelled Dean’s experimental No.9, as described in my Pre-Grouping blog.
     
    There’s a lot more detail still to be added to the underside. To gain an overview, I ‘mirrored’ one half of the split plan-view from ‘The Engineer’ and then colour-coded various elements – blue for frames, orange for crankshafts, green for valve gear, and red for wheel bearings. I made a couple of ‘corrections’ to the ‘mirror’ process by moving the cranks on one side to represent ‘quartering’:
     

    My Colour-coded plan view, derived from ‘The Engineer’ illustration
     
    As I began to examine this underside view in conjunction with the various elevations, I realised that the complex array of brackets and plates was not going to be easy to unravel! On this engine, the motion is very visible in side views, so I cannot escape modelling its main features.
     
    It has become clear that it’s going to take me some time to work out how all these parts fitted together in three dimensions, so I’ve decided to take a break before starting on modelling the motion and various underpinnings. This will a new area for me, since I have neglected any detailed representation of the motion on the engines I have designed previously.
     
    Mike
     
     
  5. MikeOxon
    In Part One , I wrote that “this engine had several very unusual features” and, in regard to building a model, “I had to start somewhere and, with so many peculiarities, it was hard to choose. As a ‘gentle introduction’, I decided to start with the two bogies.”
     
    I intend to continue, as far as possible, to follow a line of ‘least resistance’ but before going any further, I collected as much potentially useful information , photos, and drawings as I could.

     
    In his book ‘The British Steam Locomotive 1825 – 1925’ p.106, Ahrons noted that “no description of them, beyond the meagre details in Colburn's " Locomotive Engineering," page 73, has ever been given, and the following account of their constructional details may therefore be of interest.”
     
     
    He continued with quite an extensive article, providing many key dimensions and descriptions of the rubber suspension system. This suspension anticipated Alex Moulton’s work for the Austin Mini by more than a century! Ahron’s also referenced an article in ‘The Engineer’ supplement, 16 Dec 1910 , which provided various sectional views of the engine from which I could make a start.
     
     
    Using these drawings, I started by creating some of those major components for which I had already gained experience in modelling other engines.
     
    Ahrons gave the boiler dimensions as 10ft. 9in. long by 4ft. 0½ in. inside diameter, so I created a tube of length 43 mm, inside dia. 16 mm, with 1 mm wall thickness, which provided a good match to an ‘The Engineer’ drawing. I then added firebox and smokebox by tracing over the drawing and extruding as required, to create solid ‘bodies’ in ‘Fusion 360’. The results were as shown below:
     

    3D model of Boiler Assy. Referenced from an illustration in ‘The Engineer’.
     
    The next ‘familiar’ item on the agenda was a pair of driving wheels. although these are a little larger than usual, at 36 mm diameter, and flangeless. The stages of my usual method are shown below:
     

    My steps in 3D modelling the Driving Wheels
     
    It always surprises me how rapidly something resembling an engine emerges, especially once the platform, chimney and safety valve housing have been added.  The chimney and safety valve cover were created by my usual method of tracing the profile and then using the ‘Revolve’ tool to create the cylindrical ‘bodies’.
     
    The platform was a simple rectangular extrusion from the plan drawing, with the exception that small ‘humps’ had to be raised over each of the bogie wheels. Those early designers did nothing to make life easier for the workmen having to fabricate these shapes by hand!
     

    First impression of my evolving model
     
    That has completed most of the straightforward parts of this engine and it is now time to start tackling its (many) peculiarities!
     
    Outside ‘Frame’
     
    According to Ahrons “The inside bearings were only 5in. long, and therefore additional outside bearings, 9in. long, were provided, the hornblocks of which were riveted to the triangular queen truss " frame," shown outside the driving wheel”.
     
    This ‘frame’ was my next subject for modelling. I created the truss and the outside rim of the splasher as a single ‘body’ in ‘Fusion 360’ by extruding from a drawing, as shown below:
     

    My sketch of the outside frame supporting the driving axle
     
    Most of the sketch was made by using the ‘three point arc’ tool in ‘Fusion 360’ and then I extruded the area coloured blue to form the frame. Next, I extruded the rectangle representing the axlebox, to house the outside bearing. I used another useful tool – the ‘offset’ tool – to create an outer rim around the frame and then ‘pushed’ the annulus (coloured yellow) backwards, to surround the driving wheel as the splasher.
     
    Yoke and Boiler Support Plates
     
    Now it was time to address two more peculiarities – the yoke across the top of the boiler and the curvaceous plates that supported the boiler from the platform. I created both these features by sketching over one of the front-elevation illustrations from ‘The Engineer’.   Again, the most useful sketching tool was the ‘three point arc’ and I then extruded the outlined area to form plates of 0.5 mm thickness, as shown below:
     
    There were two identical ‘yoke’ plates in tandem (blue in my sketch) straddling the top of the boiler, with pivoted brackets between them, to carry the vertical suspension rods above the riving wheels.  Two curved support plates (green) were placed, one on either side of the boiler, immediately ahead of the driving wheel splashers.
     

    Tracing the shapes of the Curved Plates around the Boiler
     
    I then move and rotate the parts I have made and align them against my reference 'canvas'.  I have hidden the rest of the model for clarity:
     

     
    After producing models of these plates, I moved on to the suspension units for the driving axle. These were illustrated and described by Ahrons.  I created my models of the suspension units by sketching the profile over the drawing from ‘The Engineer’ and then using the ‘Revolve’ tool in ‘Fusion 360’ to create the cylindrical rods and the brass pots that contain the india rubber ‘springs, as shown below:
     
     

    My extrusion of a suspension arm alongside ‘The Engineer’ Drawing
     
    Motion Plate
     
    The motion plate was, again, unusual in that its outer edges were shaped to follow similar curves to those of the boiler support plates. For details of their appearance, I had to turn to another drawing, shown in the Broad Gauge Society (BGS) journal ‘Broadsheet’ No.49 (Spring 2003).
     
    The original is one of those ‘split’ drawings, with halves of two different cross sections shown together. To help my visualisation of the engine, I 'mirrored' each half to provide two separate complete cross sections, although I cannot guarantee that all the details on the two sides were perfectly matched.
     

    Two cross-sections created from drawings in BGS ‘Broadsheet’ No.49
     
    In my drawing ‘B’, I have shaded the split motion plate, which has square apertures for the connecting rods to pass through. I copied the outlines of these motion plates, as for the other boiler support plates, and extruded them to 0.5 mm thickness.  The valves were placed between the cylinders and the valve rods are shown with supporting slide bars. There are many other unusual features in these drawings that I shall return to later, including the well tank suspended below the boiler on brackets from the motion plate.
     
    Cylinders
     
    The cylinders themselves were too long to fit within the very short smokebox, so they extended for about 1 foot forwards of the smokebox. They were connected across the width of the engine by a box, which enclosed most of the front end of the valve gear, although there were two tail rods protruding from the front face of this box. A photograph of the front end of No.42 also shows a small steam cock on the centre of his cover
     
    I constructed this box and the cylinder ends as a separate ‘body’, which I then fixed to the front of the smokebox.
     

    My model of the cylinder ‘front end’
     
    That has completed all the main components needed for a ‘top-side’ view of the engine. I have added buffer beams, copied from a different Broad Gauge engine, and extruded the outer sides of the coke bunker. Although simple in external appearance, this bunker has many unusual internal features but I shall come to these later.
     
    In the meantime, my 3D model in ‘Fusion 360’ now looks as shown below:
     

     
    I think this model is beginning to capture something of the ‘presence’ that the original engines must had. I still have a lot of work to do on the underpinnings – especially the attachment points for the bogies and the well tanks but right now I feel it’s time to pause for the Easter break!
     
    Mike
     
     
  6. MikeOxon
    In a comment on my previous post @Mikkel wrote “I never know what's next on your blog Mike”. Actually, I feel much the same – I never know where a whim will take me next!
     
    A week ago, the thought of a Bristol and Exeter Railway (B&ER) engine was nowhere in my mind and then @Annie posted some splendid photos of Pearson’s magnificent 4-2-4 Broad Gauge tank engines.
     

    B&ER No.42 4-2-4T designed by James Pearson
     
    It wouldn’t be true to say these engines have never crossed my mind but they were always rapidly consigned to the ‘too difficult’ box. Now, having built a few of Brunel’s so-called ‘freaks’, I have learned a lot more about 3D design and the capabilities of 3D printing. So – time to have a go ? …
     
    Back issues of the Broad Gauge Society (BGS) journal ‘Broadsheet’ provide a wealth of information, including both drawings and photographs of several versions of these engines. There is also a lengthy biography of James Pearson in ‘Broadsheet’ No.78 (Autumn 2017) which, in addition to providing useful career information, also busts a few myths.
     
    Before his appointment as Locomotive Superintendent, at age 34, on the B&ER, Pearson had a spell as the engineer responsible for operations of Brunel’s ill-fated atmospheric system on the South Devon Railway. That system has been the subject of another of the many deviations followed by my Blog.
     
    Almost all references to Pearson suggest that he was a Quaker which was supposedly the reason behind his adoption of black as the colour for his locomotives. The BGS biography found no evidence to support that assumption and reports that Pearson was Christened at his local Parish Church in Blackburn. It seems more like that the livery arose from the well-known concern for economy, which characterised much of the B&ER operations.
     
    There are also many stories of his 4-2-4 engines that do not stand up to close examination. According to an article in ‘Broadsheet’ No. 48 (Autumn 2002), they were originally ordered specifically for duty on the Yeovil branch and not, as often reported, for the Exeter expresses. Clement Stretton in his book ‘The Development of the Locomotive 1803 to 1896’ (published 1896) stated that he remembered a 9 foot single tank running smoothly at 60 mph and that “Mr Pearson many years ago informed the writer that his engines had been officially tested at 81 mph,” Sadly, many of Stretton’s claims have subsequently been shown to be inaccurate, so these statements should be treated with caution.
     
    Towards a Model
     
    I have commented before that making a model is a very good way of learning how the original engine was constructed. In this particular case, even a cursory examination shows that this engine had several very unusual features. For example the boiler carried a ‘yoke’ to which suspension rods from the driving wheels were attached. There were other brackets between the boiler and the very light frames, which only extended from the back of the smokebox to the front of the firebox. Thus, the boiler itself had to bear many of the forces associated with a locomotive engine – a practice that would not be approved now!
     
    I had to start somewhere and, with so many peculiarities, it was hard to choose. As a ‘gentle introduction’, I decided to start with the two bogies, which were attached to the rest of the engine by central ball and socket joints – no side-play allowed! I found some old frame drawings reproduced in ‘Broadsheet’ No.49 (Spring 2003) so, following my usual practice, I loaded these as a ‘canvas’ into ‘Fusion 360’.
     
    The collection of drawings included a plan view of the bogie and elevations of some of the main members. I started by tracing over one of the diagonal members and creating a solid ‘body’ in ‘Fusion 360’. I then made a sketch of the profile of the central pivot mounting and used the ‘Revolve’ tool to create a socket to receive the ball suspended below the engine itself. The next step was to align the diagonal members and the central bearing over the plan view, included in the drawings, as shown below:
     
     

    1. Tracing the Bogie components                                                          2 Arranged over Plan Drawing
     
    The rest of the frame comprised a very lightly built rectangular arrangement of plates, with the horn blocks attached at the four corners. I traced and extruded these components into the structure shown below:
     

    Bogie Assembly extruded over the ‘Canvas’ in Fusion 360
     
    I have made plenty of 4-foot diameter wheels before, so it was a straight-forward task to create these and fit them into the horn-blocks for a rendered portrait of the complete bogie in ‘Fusion 360’. According to Ahrons, in a lengthy description of these engines in his book ‘The British Steam Locomotive 1825-1925’, each bogie wheel had an independent india rubber spring.
     
     

    My 3D model of one of the two bogies
     
    That’s one small step* – or, perhaps, two, since there will be similar bogies at each end of the engine! It seems that I am now committed to working out how to fit together all those brackets and levers that hold together the complete engine.
     
    Mike
     
    * or one bite of the elephant as @Mikkel once described it
  7. MikeOxon
    Background
     
    Almost 10 years ago, I made a model of a lime kiln as a ‘scenic accessory’ on my North Leigh layout. For some reason, I never wrote a blog post about its construction but did write a short article for ‘Railway Modeller’, published in November 2015.
     
    I have, however, described how my model was based on the kiln at Fawler that originally had a siding from the Oxford Worcester & Wolverhampton Railway. Fawler is close to the real North Leigh, on which my pre-grouping layout is based
     
    My starting point for the kiln was the ‘Wills’ ref.8838 kit of a cattle creep, which provided suitable arches set into walls of stone blocks. To make my model, I placed the two arches from the kit side by side and set them into a hillside, behind my railway, as part of the back-scene.
     

    Model Lime Kiln on my North Leigh layout
     
    West Drayton Coke Ovens
     
    Now, I have realised that kilns (or ovens) for a different purpose but of a generally similar design played a significant role in the early development of railways. Because of Parliamentary Acts that required locomotive engines to ‘consume their own smoke’, the early engines burned coke as a ‘smokeless’ fuel. It wasn’t until the adoption of the brick-arch in the firebox, around 1860, that coal could be used as a fuel, without emitting large amounts of soot from the chimney.
     
    MacDermot, in his ‘History of the GWR’*, states that the principal railway companies made their own coke and, for this purpose, the Great Western established coke ovens at West Drayton.  Whishaw, writing in 1842, reported that “the coke-ovens are situate at West Drayton, about half a mile to the east of the station ; and are very similar to those of the north of England and Scotland, being without a lofty chimney, which adds so greatly to the cost. They are conveniently placed on the level of the railway, which saves much labour in filling the wagons.”
     
    *NB MacDermot Vol.1 is now available as a PDF Download from the ‘Internet Archive’ https://archive.org/details/historyofgreatwe0001etma
     
    I found a little more information in an article by the Greater London Industrial Archaeology Society , which states that there were fourteen coke ovens, built in 1839-40, which produced 440 cwt of coke per day, using coal brought along the Grand Junction Canal from Brentford. Initially, a daily coke train ran from West Drayton to Paddington. Once the GWR main line reached Bristol, however, forty coke ovens were built there, so that by 1850 the West Drayton coke ovens were discontinued. The site is clearly marked on the 25 inch OS map, which can be viewed on the National Library of Scotland website , although the ovens must have been out of use by the time the map was made. I show an extract below:
     

    West Drayton coke ovens – OS 25” second edition
     
    Operation of Coke Ovens
     
    I found it difficult to determine how the site actually appeared when operational but found illustrations of various sites in the North of England, which are said to have been similar. The coke was produced in a ‘coke battery’ comprising rows of ovens into which coal was loaded. The coking process involved heating coking coal to around 1000-1100ºC in the absence of oxygen, to drive off the volatile compounds. The process took from 12-36 hours in the coke ovens. The coal charge did not fill the oven. Space was left above the charge in which the gas liberated from the coal was burned. At first, no attempt was made to recover any of the gas, tar or other by-products, which were driven off from the coal when it was heated. In later designs, the gas was led through openings in the upper part of the walls into flues where it could be burned out of contact with coal and add its heat to the charge through the oven wall.
     
    There are two paintings by Wheldon, dated 1845, which show coke ovens associated with a colliery in North-East England. They include two views, apparently from opposite sides of a row of coke ovens in process of being fired. I have extracted the sections that show the coke ovens.
     
     


    Two Extracts from oil paintings by W.Wheldon of a NE Colliery and Coke Kilns
     
    In these paintings, there appear to be two rows of ‘beehive’-shaped ovens, with access doors arranged in a line alongside a railway track. There is a raised platform at the top for charging the ovens, or kilns, with coal. The second painting appears to show a person pushing a wagon along a track above the kilns, presumably carrying coal to be fed into the tops of the kilns.
     
    The first painting also depicts a ‘Hackworth’ type of locomotive in the foreground
     
    Taken together, I feel that these illustrations provide a fair idea of what once existed on the West Drayton site. The map suggests that there was probably a single row of 14 kilns, with the discharge doors adjacent to the railway, while coal was supplied to the kilns from a wharf on the Grand Union Canal.
     
    Designing a Model
     
    Although I couldn’t find much detailed information about coke ovens in Britain, I found plenty about similar beehive kilns that were used in the early 19th century around Birmingham, Alabama. There is a chapter in Peele’s ‘Mining Engineers Handbook’ Published 1918 that contains diagrams and detailed description of the operation of ‘beehive’ kilns
     

    Dimensioned Sketch from Peele’s ‘Mining Engineers Handbook’
     
    There have even been HO-scale railway models distributed by ‘Walthers’ (US) but I didn’t find anything that is currently available
     

    US models of Beehive Coke Ovens
     
    Nevertheless, these resources provided me with plenty of guidance on how to design a plausible model.
     
    From the map of West Drayton, the complete ‘battery’ of kilns extended for 675 feet – a little over 200 m – but the complete array seems to be divided into five individual groups, so I decided to start by modelling a single oven, which could be extended into ‘batteries’ depending on the space available.
     
    Brickwork
     
    Since the ovens were close to the clay pits and brick works that were scattered around the West Drayton area, it seems most likely that the ovens were constructed from bricks, rather than stone as in my previous model of the Fawler lime kiln.
     
    Of course, I could have used pre-printed sheets of brick-effect card but I decided to experiment with creating my own brickwork, by means of 3D printing. I soon found it was easy enough to produce a wall of ‘stretcher bond’ by drawing a single brick and then using the ‘rectangular pattern’ tool in ‘Fusion 360’ to produce a regular array of bricks.
     
    A photo of a surviving battery of ovens in the North East, said to be similar to those at West Drayton, showed that the facing was laid in ‘English Bond’ with alternating rows of ‘headers’ and ‘stretchers’.
     

    Remains of the last working beehive coke ovens in the country.
    Built in 1861 and worked until 1958
     
    So, as often happens in railway modelling, when additional skills are needed, I had to give myself a crash course in the art of brick-laying. I found a very helpful YouTube video that got me started – thank you Rodian.
     
    I started by creating a row of four ‘stretcher’ bricks, leaving suitable gaps for mortar. I then created a row of nine ‘header’ bricks, which needed to be carefully aligned so that the joints fell neatly between those in the row of ‘stretchers’. Once I had two rows, I could use the ‘rectangular pattern’ tool in ‘Fusion 360’ to repeat the initial pair of layers, to create a wall.
     
    There is one twist, which I learned from my course on brick-laying, and that is the use of ‘queen closers’ to produce a straight end to the wall. I decided to create three sections of wall, one cut square at both ends, so that several panels could be joined together to make a longer wall, and two others with left and right ‘queen closures’, as shown below:
     

    Steps in creating English Bond Brick Wall
     
    The symmetrical ‘centre’ section can be extended as necessary to create longer walls:
     

    Multiples of ‘centre’ wall section.
     
    I created the mortar (or ‘muck’ as the professionals call it) by extruding a rectangle from the back of the wall to a suitable depth below the front face. I then used the ‘Combine’ tool in ‘Fusion 360’ to make each section of wall into a single body.
     
    Creating the Doorway Arch
     
    I made the door and its arched frame as a separate body, creating the pattern of the arch from a single brick, followed by use of the ‘pattern on path’ tool in ‘Fusion 360’. The ‘lessons learned’ from creating the brick wall proved very useful and I found this to be an easier task than I had expected. I added a second inner ring of bricks as a door frame and then extruded a flat panel from the back to create the door. I used the 'Combine' tool in ‘Fusion 360’ to bind together all the bricks and the door into a single body. As before I show the series of steps in a group of screen-shots from ‘Fusion 360’:
     

    Steps in creating the arched door
     
    One useful aspect of working in the ‘virtual’ world is that solid bodies can slide through one another, so I could set the door into the brick wall without having to cut an aperture in the wall.
     
    Creating the Dome
     
    Having solved that first construction exercise, I turned my attention to the domed top of the oven, which was also made from brick-work, as shown in another photo of the Gateshead ovens.
     

    Top domes of the last working beehive coke ovens in the country.
    Built in 1861 and worked until 1958
     
    My approach to creating this structure in ‘Fusion 360’ was to start from a profile view of the dome. I then created notches in the slope of this profile to represent the gaps between the brick courses. I also create the aperture in the top, for products of combustion to escape and be burned off.
     
    Once I had a domed top, with rings for brick courses, I sketched a narrow rectangle to extrude a gap between bricks in each course. I then used the ‘circular pattern’ tool in ‘Fusion 360’ to create a ring of bricks around the central axis of the dome. I repeated this process for each ring of bricks, varying the numbers in the patterns as appropriate for the longer courses, lower down on the dome. My procedure is illustrated below:
     
     

    Steps in creating brickwork dome
     
     
    Printing the Components
     
    The front face, with the arched doorway and the domed top of the oven are the only parts needing specialised design. I assembled these around a simple box structure, to show the overall layout of a single oven, rendered in ‘Fusion 360’
     

    My 3D-model of a ‘beehive’ coke oven
     
    All that remained was to transfer the design files to my ‘Cura’ slicer software and then to my 3D printer. I had been a little apprehensive as to whether the mortar courses would be discernible in the prints but need not have worried. Surface indentations usually print more reliably than small raised features, such as rivet heads, which easily disappear if the limits of the FDM printer are exceeded
     
    This is the dome, still on the printer bed, with no fettling having been applied. The time to print was 24 minutes.
     

    My 3D-printed oven dome, still on Printer bed
     
    The brick courses have also printed cleanly on the central panel of the front of the Coke Oven:
     

    My 3D-printed arched door, still on Printer bed
     
    Both these prints were made from Gcode files prepared by ‘Cura’ software when using its ‘Fine’ resolution setting. For detailed finishes, such as these bricks that are only a few millimetres long in 4mm scale, there is a significant advantage over the ‘Normal’ resolution, with a small penalty in terms of print time, using my Geeetech E180 printer.
     

    Detail Comparison between prints made at ‘normal’ and ‘fine’ resolution settings
     
    The following print times are those estimated by the ‘Cura’ software for :
     
    normal 1h 13m fine 1h 40m extra fine 3h 24m  
    I have not tested the ‘Extra Fine’ setting but, for this model, I felt the time penalty was excessive and that the ‘Fine’ resolution print is adequate.
     
    I’ve enjoyed making something ‘different’ with my 3D printer.
     
    Now I need to create an embankment, into which I can insert a row on ovens, once I have designed a layout 🙂
     
    Mike
  8. MikeOxon
    “Towards the end of July 1837 I heard that Mr. Brunel wanted some one to take the post of locomotive engineer on the Great Western Railway, and I at once went to him, on July 20th, preferring that department to railway making.”
     
    Thus wrote Daniel Gooch about the event that changed his life when he was just 21 years old. As a result, he left Manchester and went to London, beginning his duties with the Great Western Railway at West Drayton on the 18th August 1837. Because no engines had actually arrived at that time, he recalled that his first work was to prepare plans for the engine-houses at Paddington and Maidenhead,
     
    In such circumstances, one might have expected the engine-house designs to be rather perfunctory affairs, something to fill in the time until some ‘real work’ on engines became available, but my investigations into the design of the engine-house showed this to be far from the case.
     
    For Paddington, Gooch designed a ‘round house’ shed which, I suspect, was probably the first example of its kind. He was severely constrained in both timescale and costs. The accounts show an extraordinarily low figure of £1,402 for ‘general construction costs’, plus £216 for ‘other items’.
     
    An early site plan, probably dating from 1837, shows the engine shed as below:
     

    Paddington Site plan, 1837, showing the Engine Shed.
     
    At first glance, the octagonal form seemed to match the track plan but I was surprised to see that the locations of the tracks corresponded with the vertices of the octagon, rather than being placed centrally in the sides, as I would have expected. Indeed, an illustration of the interior in ‘Measom’s Guide to the GWR’, dated 1854, appears to show such a layout – a reminder not to trust all those early engravings!
     
    Looking more closely at the plans, however, I saw that the vertices were ‘squared off’, with entrance doors, where required, or short segments of wall. Thus, I started my modelling of the shed by copying the above drawing as a ‘canvas’ into ‘Fusion 360’ and tracing the foundations of the perimeter walls. That was the easy bit but where to go from there?
     
    I had a couple of sources to draw on for guidance:
     
    An early photograph of the demolition of the original station includes a glimpse of the engine shed roof in the background. This gave me a slope of 15 degrees for the main roof. Incidentally, several of the iron columns from the original station can be seen lying amongst the debris in the foreground, while a very tall disk & crossbar signal appears to the right. The sheer-legs appear on early plans of the original station layout.
     

    Paddington Demolition works, c 1854-5
     
    The other source was a much better engraving than the one in Measom’s guide. This one shows the clerestory roof over the centre of the shed and a rather bewildering forest of wooden supports for the roof. After studying this illustration for some time, I decided to take a ‘Stonehenge’ approach to the design of my model by concentrating on the locations of the upright pillars and hoping to fill in the rest of the details later!
     

    Engine Shed Interior c.1846 (Firefly-class ‘Ganymede’ was new in 1842)
     
    From this illustration, I deduced that there were two rows of pillars along the sides of each track between the entrance doors and the clerestory. Taken together, these formed an inner ‘ring’, supporting the edges of the clerestory, and an intermediate ‘ring’ between the perimeter. walls and the clerestory.
     
    Creating a 3D Model
     
    As I laid out the locations of all the pillars in ‘Fusion 360’, a very ingenious geometric pattern started to emerge, reminiscent of the vaults of a mediaeval cathedral. This seemed to me a far more sophisticated design than I had expected from a young man who had joined the GWR to do work on engines! It was a portent of the illustrious career that lay ahead for young Daniel Gooch.
     
    Once I had determined the locations of the bases of the various pillars, I had to adjust their lengths to correspond to a slope of 15 degrees in the roof that they were designed to support. Rather than attempting to describe the process in many words, I have made a series of ‘screen shots’ of each stage, as my construction progressed in ‘Fusion 360’
     

    Steps in my ‘Stonehenge’ approach to Modelling Paddington Engine Shed
     
    Now that I’d worked out the overall layout, I decided to go back to the beginning and start again!
     
    This time, having worked out the geometric pattern, I used the ‘Pattern on Path’ tool in ‘Fusion 360’ tu ensure that all the pillars and their linking ribs were aligned in a regular, symmetrical pattern around the central axis.
     

    Bird’s-eye View showing Symmetrical Design of Shed
     
    The various ribs connecting the tops of the pillars, in order to support the roof, were all copied from an initial 3D drawing of a square-section bar. After placing the first pair of ribs, I could use the ‘Pattern on Path’ tool to complete the rest of the pattern around the central axis.
     
    Adding details
     
    As an initial check on the general validity of my structure, I set up an internal view of my model in ‘Fusion 360’, to compare with the contemporary engraving shown above. I couldn’t match the perspective exactly but it gave me a good idea of what needed to be done to capture the ‘atmosphere’ of the original interior.
     
    I started by adding the diagonal ties at the tops of my pillars. This was a fairly easy ‘tweak’ that I could apply to one pillar and then copy around the complete array, again using ‘Pattern on Path’ to maintain the alignment around the central axis. The result at this stage is shown below. I have included my model of ‘Vulcan’ to indicate the overall scale:
     

    Interior view of my basic model of Paddington Engine Shed
     
    I could find no information about the entrance doors but then I remembered some drawings that Gooch created for Maidenhead depot. These included shed doors (NRCA161482) so I extruded my model from the Maidenhead design and found that these doors were a perfect fit into the doorways of the Paddington shed. An early example of standardisation!
     

    My enhanced version of NRCA161482 showing Doors for Maidenhead Depot
     
    I didn’t have much to go on for the design of the interior walls, except the engraving shown above, which indicates vertical planking and window openings with vertical bars. I took some further design cues from the Broad Gauge Transfer shed at Didcot Railway Centre, which suggested diagonal cross-bracing on the large panels.
     
    I started from a single rectangular panel on which I incised one ‘slot’ to represent a single vertical plank. I then used ‘Pattern on Path’ to complete the planking of the whole panel. Next, I created the various frame pieces and attached these to the inside face of the panel. Finally, I cut the rectangular openings for the windows and added an array of vertical bars within each opening.
     

    My model Wooden Planked Wall with Bracing
     
    The result looked pleasing and made me loath to add the roof, which would hide all this from view! Nevertheless, the roof was necessary to provide an overall impression of the interior scene.
     
    Adding a Roof
     
    For the roof, I could again take advantage of the circular symmetry of the structure, to reduce the amount of design work that was needed. I had only to design one triangular roof panel and one rectangular one, which then alternated around the ‘ring’. The clerestory roof is even simpler and only involves triangular panels.
     
    I started with what seem the easiest one to draw – the rectangular panel. I checked the lengths of the support ribs with the ‘measure tool’ in ‘Fusion 360’, to ensure that panel would be a correct fit. After that, the detailing followed similar methods to those I used for the sides, with a pattern of rafters as indicated on the contemporary engraving shown above.
     
    The triangular panels were rather more difficult. I established the lengths of the sides by again using the ‘measure tool’ and I also checked the angle at the top vertex, remembering that, because of the slope of the roof, this is not simply a fraction of the circle defined in the ground plan. I then added the intermediate supporting battens and finally the numerous cross-battens towards the apex. I wanted to use the ‘Pattern on Path’ tool again but realised that, if I started copying from the bottom edge, the battens would become too long as the roof segment tapered towards the apex.
     
    My solution was to create an array of same-length battens, which I then cut by applying the ‘Splitting’ tool to the plane defined by the edges of the panel, as shown below:
     

    Applying the 'Splitting' tool in 'Fusion 360'
     
    The triangular segments of the clerestory roof followed, by using the same methods, so I now had three different type of roofing panel, as shown below:
     

    Three Types of Roof Panel for my Engine Shed Model
     
    I should probably have done lots of trigonometry to work out exactly how to place these panels on the roof, sloped at 15°, but I opted for an empirical approach and used the ‘Move’ and ‘Twist’ tools, while checking from different directions until they were seated neatly over the relevant rafters.
     
    After that, it was back to the ‘Pattern on Path’ tool to complete the circular symmetrical pattern of the complete roof. The end result is shown below:
     

    External View of my model of Paddington Engine Shed 1840
     
    It all looks rather plain from the outside – a bit like a Victorian Gaol – but for a more interesting view, I could use the ‘Camera’ in the ‘Render’ section of ‘Fusion 360’ to look inside.  Here is an internal view with ‘Vulcan’ on one of the turntable roads:
     

    Internal View of my Model Engine Shed, showing panelled walls and roof
     
    I think the overall impression is in reasonable agreement with the contemporary engraving shown above and is probably as good as can be achieved on the surviving information. Another view, which includes the clerestory roof is shown below:
     

    View into my Model of Paddington Engine Shed, through open Doors
     
     
    Overview of Paddington Depot c.1840
     
    Finally, I have placed my model within the context of the overall site, as it was laid out in 1840. See my previous post for details of the other models shown.
     

    Overview of my Current Collection of Paddington Models
     
    There are still several more structures to consider, although with very little information to work from. One item, listed in the accounts, is ‘stables’ but these are not marked on any of the drawings that I have.
     
    I am currently thinking that they might be the extension on the side of the Engine Shed. I have not completed this part, except for the outer walls as marked on the overall plan. There would perhaps be a 19th-century logic in grouping together all the available sources of motive power within one overall building. Horses still played an important part in manoeuvring rolling stock between the various small turntables.
     
    If anyone has any other suggestions, I shall be interested to receive them.
     
    Mike
  9. MikeOxon

    Paddington Station 1840

    By MikeOxon,


    General
    Brunel’s great arched roof is to many people the epitome of Paddington Station but this was not built until 1854. The passengers who first travelled on the line from Paddington to Maidenhead, which opened on 4th June 1838, started their journey from a far less imposing structure – little more than a collection of wooden sheds.
     
    A London terminus for the GWR was needed in a hurry, after negotiations with the London & Birmingham Railway for a joint terminus at Euston broke down. With the line to Maidenhead almost ready, the GWR Directors desperately needed to start generating passenger revenue and, since authorisation for a route into Paddington was only agreed by Parliament on 3rd July 1837, there was no time for grand designs!
     
    A quick solution was to build the station offices into the arches of the new Bishop’s Road Bridge and provide simple wooden platforms to the West of this bridge. Goods facilities were established on the other side of the bridge, alongside the Forecourt from where passengers entered the booking office, under one of the arches. The great artist of early railways, J.C.Bourne, produced a lithograph of this façade of the station. I have annotated the locations of the passenger facilities on his illustration, as shown below:
     

    Paddington Station 1843 by J.C.Bourne (colourised Mike Flemming)
     
    I have not found any early illustrations of the layout of the platforms beyond the bridge but there are several early drawings, mostly in poor condition, that provide plans of the tracks and platforms, as well as details of the platform canopies. A selection of these drawings is available on-line, in the ‘Historical Engineering Collection’ of the Network Rail Corporate Archive (NRCA).
     
    3D Station Drawing
     
    I decided, as an experiment, to see whether I could use ‘Fusion 360’ to create an impression of the original station by using the techniques of extruding from drawings, just as I have done for my models of rolling stock.
     
    The NRCA drawings include sketches of various alternative proposals, from which I chose the plan view in NRCA161183 as a suitable base from which to create a 3D model. First of all, I had to digitally ‘clean’ the original drawing to create my working version, shown below.
     

    My annotated ‘working copy’ from NRCA161183
     
    There are many features of the track-work that seem strange to modern eyes. Note, in particular, the widespread use of wagon turntables and traversers for moving the small carriages and wagons of the time between tracks. Several tracks ended in carriage loading ‘shoots’ at the end of the central carriage road, between the Arrival and Departure platforms. This arrangement is shown in a lithograph of, Slough Station by J.C Bourne, of which I show an extract below:
     

    Slough Station (detail) by J.C. Bourne
     
    I also found a less detailed re-drawn plan of Paddington Station, which provided the all-important scale, in the book ‘Paddington Station - Its history and architecture’ by Steven Brindle, published by English Heritage 2013.
     
    With this additional information, I could import the NRCA plan into ‘Fusion 360’ as a canvas and use the ‘calibrate’ command to adjust it to the correct scale. I decided to work directly in ‘feet’, since these units are used throughout the NRCA elevation drawings.
     
    Bishop’s Road Bridge
     
    My first 3D extrusion in ‘Fusion 360’was from the plan view of Bishop’s Road Bridge (shaded pink in my annotated version, above). Initially, I extruded the rectangular ‘body’ to a height of 30 feet. I then compared my structure, marked with the locations of the various arches, as indicated on the plan, to check the proportions against the Bourne lithograph. (It is known that Bourne used a ‘camera obscura’ as a drawing-aid, so I was confident that his illustration is accurately proportioned.)
     

    Steps in creating my model of Bishop’s Road Bridge
     
    Once I had made sketches by tracing over the Bourne canvas, imported into ‘Fusion 360’, I could overlay these sketches onto the face of my rectangular Bridge ‘body’ and extrude the various arches.
     
    Platforms
     
    Details of the platform canopies are shown in drawing NRCA161326, of which my ‘cleaned up’ version is shown below. This drawing shows the end elevations of the canopies over both the Departure and Arrival platforms, together with details of the cast-iron support pillars.
     

    My ‘Working copy’ from NRCA161326
     
    As before, I imported this drawing into ‘Fusion 360’ and sketched the outlines of the roof trusses. I also created a model of a single pillar by drawing over the profile and then using the ‘revolve’ tool to create a cylindrical ‘body’, as shown below:


    Using ‘Revolve’ in ‘Fusion 360’ to create 3D-model of Pillar
     
    Once I had a single model of a pillar, it was simply a matter of using the ‘Pattern on Path’ tool in ‘Fusion 360’ to create the array of pillars shown on the NRCA plan of the platforms. Note that I have raised the platform surfaces and carriage road by 3 feet, above the level of the track bed.
     

    My 3D-model of the Arrivals Platform with Pillars and a single roof truss
     
    I was very pleased to find that the dimensions derived from the elevation drawings corresponded very closely to those derived from the plan view, indicating that my ‘calibration’ in ‘Fusion 360’ had been successful. After duplicating the trusses as required, again by means of the ‘Pattern on Path’ tool, I added roofs by extruding from the profile set by the trusses at one end of the structure.
     
    The end result of this stage of my modelling is shown below:
     

    My 3D-model of Paddington platforms viewed from the West
     
    Of course, the advantage of having a 3D-model in the computer is that I can choose to view it from whichever direction and in whatever detail I choose, for example:
     

    View across my model of Paddington Station from above the Forecourt.
     
    The above view demonstrates the sharp angle between the platforms and the approach road, by which passengers arrived at the station. Carriages could proceed through the central arch to reach the carriage dock set between the Arrival and Departure platforms. At that period, wealthy patrons of the railway loaded their carriages and their horses onto trains and, in some cases, chose to travel inside their own carriages, rather that the coaches provided by the railway.
     
    Adding other models
     
    Once the basic 3-D model was in place, I realised that it was perfectly easy to add some of my existing models into the scene. The ‘Insert Derive’ tool in ‘Fusion 360’ allows model data to be imported into a design from other folders already held in the computer. To demonstrate this procedure, I imported my existing models of Brunel’s Britzka and of a Carriage truck.
     
    I realised that these models had been dimensioned in millimetres, as 4mm-scale models. When first imported, they appeared at their small ‘model scale’. I could, however, select these model bodies and use the ‘Scale’ command in ‘Fusion 360’ to increase their dimensions by a factor of 76, so that they conformed to the overall building model. After re-scaling, I could use the ‘Move’ tool to position them as I wished within the Station, as shown in the example below:
     
     

    Loading my model of Brunel’s Britzka onto a Carriage Truck at Paddington Station
     
     
    Taking this idea a little further, I imported some other models, including my Horse Box, a horse, and the locomotive ‘Vulcan’, to create the following scene:
     

    Brunel’s carriage and horses being loaded for travel from Paddington Station
     
    Conclusion
     
    As I wrote at the outset, this is all experimental and I have had a lot of fun exploring the possibilities of scene modelling in ‘Fusion 360’. I realise that I am venturing into the territory of digital ‘Train Simulators’, which @Annie demonstrates in her thread can be very impressive and allow you to drive the trains as well.
     
    My own modelling has allowed me to bring to life some long-forgotten scenes and I intend to continue by re-creating some of the other buildings around the old Paddington Station. Apart from the offices within the Bishop’s Road bridge, there was also a remarkable ‘round-house’ engine shed, designed by Daniel Gooch, a Carriage shed and, on the other side of the bridge, the entire Goods Station, with sheds and offices.
     
    I think all this can keep me occupied and entertained for some time to come 🙂
     
    Mike
  10. MikeOxon
    I shall round off my modelling of the early wagons, produced for the GWR during the formative years before 1840, by considering three types intended for specific duties, rather than the ‘general purpose’ wagons described in my previous two posts.
     
    Sheep Truck 1840
     
    A sheep truck is one of the types mentioned in Whishaw’s ‘The Railways of Great Britain and Ireland’, published 1842. He described these ‘trucks’ as having high sides, four wheels, and to weigh 8,237 lbs. Apart from that, there is very little documentary evidence to work from.
     
    There is a rather fanciful lithograph by L.Haghe, dated c.1840, which is supposed to show a GWR train at Kelmston near Bath. Some of the wagons are suspiciously similar to ones shown in an illustration of the Liverpool and Manchester Railway but they also show some ‘Broad Gauge’ features – notably the large wheels set outside the wagon bodies. The engine carries the name ‘Wharncliffe’ – not a known GWR engine name but that of the MP who steered the GWR Bill through Parliament.
     

     
     
    Eddy Brown deduced that the low weight rules out most of the known vehicle types of the time, except the Small Box Wagons. An additional factor supporting this idea is that these wagons, with their wheels outside the body, are the only ones with unobstructed floors, which would probably be essential for carrying small livestock, such as sheep. A stock list of 1842 includes a ‘wagon’ (no description) with a Tare Weight of 3T.-14cwt, which corresponds to 8,288 lb – close to Whishaw’s figure.
     
    Another drawing by Seymour Clark, dated Dec.1841, illustrates modifications that were carried out on three Luggage Wagons that were returned to Goods traffic after use on Passenger trains. These had underslung springs, which seem to have been applied to most wagons by this date.
     
    Based on these fragments of evidence, Broad Gauge Society (BGS) Data Sheet 413 shows the possible appearance of one of these ‘Sheep Trucks’, as mentioned by Whishaw. For my conjectural model, I have raised the sides of my model of a Small Box Wagon and exchanged the axleboxes and springs for the underslung type, which I had already created for other models. Raising the sides in ‘Fusion 360’ was simply a matter of selecting the top faces and using the ‘move’ tool. The software automatically extends the sides at the same angle as the existing sides.
     

    My 3D Model of an 1840 Broad Gauge Sheep Truck
     
    I felt very tempted to introduce slats in the sides but this would be pure conjecture on my part. I decided to complete my model as shown on BGS Data Sheet 113.
     
    Coke Wagon – 1840
     
    The Coke Wagon is the other variant mentioned in Whishaw, 1842. Following a detailed description of the 4- and 6-wheel wagons, described simply as ‘small’ and ‘large’, he mentions that there were also coke-wagons, mounted on six wheels, and each holding from 150 to 200 bags of coke.
     
    It is hardly surprising that these wagons were needed from the outset, as the steam locomotives of the time were fuelled by coke, to meet the Government requirement that ‘locomotives should consume their own smoke’. Whishaw reports that “The coke-ovens are situate at West Drayton, about half a mile to the east of the station ; and are very similar to those of the north of England and Scotland, being without a lofty chimney, which adds so greatly to the cost. They are conveniently placed on the level of the railway, which saves much labour in filling the wagons.”
     
    At the time, West Drayton was the central depot on the first stretch of line from Paddington to Maidenhead, opened to the public on 4th June, 1838. Wishaw notes that in thirteen weeks, including July, August, and September, 1839, the quantity of coke consumed amounted to 3,323,376 lbs (almost 1,500 tons) so, even at this very early stage, the coke traffic was considerable.
     
    BGS Data Sheet 406 states that 9 coke wagons were listed in a Stock Account dated 6th Oct.1840, and that these were based closely on the 6-wheel Utility Wagon, although with several minor modifications.
     
    The modifications included new wheel sets, with 11 split spokes, splayed outwards towards the hub. These represented my first new modelling task for this wagon. I created the flanged outer rim, and a hub to fit around a 2mm steel axle. I then drew a single spoke to the new design and completed the wheel by using the ‘pattern on path’ tool in ‘Fusion 360’. This automatically created a circular pattern of spokes around the central axis of the wheel. My models of both the original Losh wheel and the splayed-spoke wheels are shown below:
     

    My 4’ Dia Wheels modelled in ‘Fusion 360’
     
    In addition to the drawing included in BGS Data Sheet 406, the Coke Wagon is also shown in a more detailed drawing in Alan Prior’s book: ‘19th Century Railway Drawings’. I imported this drawing as a ‘canvas’ in ‘Fusion 360’ and compared it with my existing 6-wheel Wagons to determine the additional modifications required.
     
    The required changes included new 2-plank sides, without drop flaps. Because of the simplicity of the new sides, I decided that it was easier to create new sides than to remove the details of the doors from the existing model. In fact, when I created my previous variants, I sometimes felt it might have been easier to re-start some parts from scratch, rather modifying the old parts, which was often a very fiddly task.
     
    Other parts, including the end flaps and strouters could be re-used without modifications but the top rails along the side were now metal bars, for adding strength to the sides.
     

    Modified features in Coke Wagon
     
    There were some subtle changes to the chassis. The springs were now longer, still underslung, but mounted on bearings placed 3’ 6” apart under the frames (rather than 3’ 0” as previously).
     
    I created one new axle box and spring assembly and then copied this for all 6 wheels.
     
    The floor planking continued to run lengthwise and was laid over the headstocks and intermediate transverse bearers, which were higher than the tops of the Solebars, leaving a visible 3” gap underneath the floor, when viewed from the sides. This feature is shown clearly in Alan Prior’s book.. In addition, the Solebars were extended at both ends, so these could ultimately act as dumb buffers on tight curves.
     
    With these modifications applied, my 3D model, rendered in ‘Fusion 360’ is shown below:
     

    My 3D Model of 1840 Broad Gauge Coke Wagon
     
    Coal Wagon 1842
     
    These wagons are not mentioned in Whishaw’s account dated 1842 and probably came too late for inclusion there. The possibility of taking coal traffic in competition with the Kennet & Avon Canal presumably occurred to the Directors after the main line was completed between London and Bristol, with its proximity to the Somerset coalfield.
     
    According to Eddy Brown’s BGS Data Sheet 412, the evidence for existence of these wagons, specifically intended for carriage of domestic coal, comes from the 1842 Truck list, where one such vehicle has the description ‘Coal‘ and 9 others share similar Tare weights. There is also an 1840s drawing with the hand-written annotation ‘Coal Wg’
     
    The annotated drawing indicates a three-plank structure with sides supported by strouters and drop flaps at both sides and ends. Additional strengthening plates were shown over the axleguards, outwardly offset to disperse the greatest stress. As in the case of the coke wagons, described above, there was a clear space between the underside of the floor and the tops of the solebars.
     
    These coal wagons display most of the features included in the other ‘revised’ wagons, which were produced to meet the overall requirement for 250 wagons in time for the opening of the complete line between London and Bristol.
     
    My model is closely based on my Standard Box wagon. Because I had kept the various components as separate bodies within ‘Fusion 360’, it was easy to delete the original wheels and axle guards and replace them with the newer type, which I had already designed for the Coke Wagon, described above. I made a new top rail to encircle the whole body, above the sides and ends. In the prototype this rail was split into removable sections to facilitate loading and unloading.
     
    Following all these minor adjustments, my model of an 1842 coal wagon appeared as shown below:
     

    My 3D Model of 1842 Broad Gauge Coal Wagon
     
    For anyone interested in the onward development of Broad Gauge wagons, I have previously modelled another Coal Wagon, dating from the 1850s, described in an earlier post
     

    My 3D Model of 1853 Broad Gauge 12T Coal Wagon
    (iron frame, springs behind W-irons, brakes, & sprung buffers)
     
    Summary
     
    Over the course of three posts, I have described the creation of nine 3D models of Broad Gauge goods wagons dating from the earliest days of the GWR. Strictly, the Horse Box belongs to Passenger traffic since, at that time, horses were often transported along with the carriages owned by passengers. It seems, however, that some of these horse boxes were converted to Fish Trucks and appear as such in the July 1842 Goods Truck List. Conversely, some of the early goods wagons were used for the carriage of passengers, until the Government intervened and insisted on minimum standards for 3rd class passengers.
     
    The various wagon designs can be traced to three basic types – small box, large box, and 6-wheel box. My modelling has been an exercise in adapting models for different applications, which mirrors the procedures actually used for their prototypes. There are several cases where the amendments required for a new version were simply added to existing drawings.
     
    The complete ‘family’ of my 3D models, produced in this series, is shown below. Continuing my musical analogy with Trio Movements, I could describe these as ‘Variations on a Theme’:
     

     
     
    Mike
  11. MikeOxon
    In my previous post, I described modelling of some of the earliest wagons ordered for the GWR in the late 1830s. At that time, much of the railway was still under construction – the complete route from London to Bristol was not opened until 30th June 1841. Information on these early wagons is sparse, although we are fortunate to have several illustrations by J.C.Bourne, which are sufficiently accurate to indicate the main features.
     

    Bristol Goods Shed – J.C.Bourne 1842
     
    The late Eddy Brown went through a GWR Stock Account dated 27th.Sept.1840 with the proverbial fine tooth comb, to separate the goods vehicles into various types, depending on their descriptions and features such as Tare Weight. There were 61 vehicles, broadly described as ‘Luggage Wagons’, which he broke down into 5 categories, as follows:
     
    2 x Small Box + 3 transferred to passenger stock 24 x Standard Box 20 x Standard Tilt 10 x Standard Utility 5 x 6-wheel Box  
    The first two categories were covered in my previous post, including the addition of canvas covers to some of the Small Box wagons to adapt them for use as Passengers’ Luggage wagons. Now it’s time to consider the other three.
     
    The first 20 Standard Tilt wagons were a type that was to become characteristic of the Broad Gauge and continued to be used until many ended their lives on the Swindon Dump in 1892. Over the years, there were many variations in the style of the raised ends, between which canvas covers carried on hoops could provide a totally enclosed space. These wagons had many uses – for example, according to MacDermot’s ‘History of the GWR’, there were no dedicated cattle wagons until after 1853, the Tilt Wagons being used for this purpose.
     
    [N.B. – I have previously modelled a later iron-bodied Tilt Wagon in an earlier post in this blog ]
     
    Standard Tilt Wagons - 1840
     
    Although no proof can be found for the 'standard' format having being adopted in these wagons, Eddy Brown considered that the later GWR method of over‑drawing amendments, such as the bonnet-like structures was probably used for this design.
     
    I adopted this process of ‘amendment’ for my own models – re-using many of the components from my ‘standard’ Box wagon and adding new ‘bonnets’ and hoops.
     
    My first step was to make a digital copy of my entire 3D model of a standard Box wagon. I then placed the model, in ‘Fusion 360’, over a ‘canvas’ image of the Tilt Wagon drawing from Broad Gauge Society (BGS) Data Sheet 403. This confirmed that all the major dimensions were virtually identical.
     
    The most obvious differences were the ‘bonnets’ at each end, so I created these as new ‘bodies’ and deleted the previous drop flaps at the ends of my model. This is another advantage of creating my models as collections of individual parts – I do this mainly to make printing easier but it also facilitates changing individual parts for different versions. After drawing one bonnet as shown below, I used the ‘mirror’ command in ‘Fusion 360’ to create its counterpart at the opposite end.
     

    My conversion of Box Wagon to Tilt Wagon
     
    I used the ‘Pattern on Path’ command in ‘Fusion 360’ to create the planking running around the curved hood of the bonnet – I only needed to draw one plank and the software did the rest.
     
    The chassis and wheels continued unchanged but longer springs were fitted to the Tilt Wagons, bowed to run beneath the axles. I created new axle-box assemblies by extruding from the ‘canvas’ in ‘Fusion 360’, then copied the design to replace the four boxes on my previous model.
     

    Revised Axlebox with Underslung Springs
     
    With these alterations, plus the addition of hoops to support the canvas tilt, I now had a new model as shown below (rendered in ‘Fusion 360’):
     

    My 3D model of an 1840 Tilt Wagon.
     
    Standard Utility Wagons - 1840
     
    10 of these were built as another variant on the original ‘standard’ Box wagon, designed to be adaptable to a variety of applications. The body sides were reduced to 2’ 6” in height and the strouters were extended upwards to form an Enclosure rail, over sides & ends. The existence of these Utility Wagons is confirmed by J.C. Bourne's Litho, of Bristol Goods shed (shown above), which includes both covered and uncovered versions.
     
    These wagons, less covers, were notable for being given over to ‘Goods Train Passengers’, later referred to as 3rd.Class Passengers. Seating was probably arranged with 9 cross Benches 24" apart, seating 6 persons on each, resulting in a loading of 54 persons per wagon.
     
    Little modification to the ‘standard’ Box wagon was needed to create my model – narrower top planks and an additional rail. The axle boxes were fitted with underslung springs, as on the Tilt Wagons, described above.
     

    My 3D Model of 1840 Utility Wagon (uncovered)
     
    I also created 3D views of my models, with the hoops and a canvas tilt cover in place:
     

    Two of my 3D models with Hoops and a Canvas Tilt cover
     
     
    6-Wheel Goods Wagons – 1840
     
    These 5 wagons were substantially larger than the 4-wheel designs and set a pattern that persisted throughout the Broad Gauge period of the GWR.
     
    Initially, their field of application was rather limited, because they were too long to be turned on the small wagon turntables that were commonly used, in the early period, at stations and depots for moving stock between tracks – using a mixture of horse- and man-power.. Several of these wagons were adapted for the use of Goods Passengers, for whom seating was provided by 11 cross benches, set 24" apart, each seating about. 6 persons, giving 66 passengers per wagon.
     
    Following an accident at Sonning, in December 1841, the Board of Trade report expressed concern that passengers were thrown out on impact. The recommendation was that the sides should be raised to at least 4’‑6" height and this modification was soon applied. It was also recognised that the boxes over the central wheels created a problem with centrally placed drop-flaps. Replacement of these flaps with doors, between the wheels, was another of the modifications in adapting these wagons for passenger use.
     
    Further modifications were required later, as a result of the 'Railway Regulations Act 1844', which required “carriages protected from the weather and provided with seats”. The GWR anticipated this change in 1842, by amending the original drawings of these 6-wheel wagons with superimposed outlines of ‘seating and roof’ additions
     
    BGS Data Sheet 120 contains an account of the timeline leading up to the building of these ‘Parliamentary’ carriages. This account indicates that the GWR started operating ‘Goods Train Passenger’ services, once the line had reached Reading in 1840. Before that, contractors had offered places to ‘passengers’ in regular goods wagons!  The term ‘3rd class passenger’ only appeared later, after the line was completed through to Bristol in May 1841. After this date, new 6-Wheel Trucks were ordered specifically as 3rd class Passenger vehicles, with sprung buffers and sides raised to 4’-6” height.
     
    I have previously created a 3D-printed model of one of these 3rd class ‘Parliamentary’ carriages, described in an earlier blog post, and shown below:
     

    My 3D-printed model of a 3rd-class ‘Parliamentary’ carriage
     
    For my model of a 6-wheel goods wagon, I decided to re-use the chassis design from my earler model, then add a body based on the original low-sided design of 1840.
     

    My 6-wheel BG chassis from a 3rd-class Carriage
     
    I re-used the ends designed for my Utility Wagon, described above, and lengthened the sides to fit the 6-wheel version. I also re-used the strouters and buffer beams from the shorter version. By drawing on these earlier designs, I did not need to make any completely new parts for the following model:
     

    My 3D Model of 1840 6-wheel Wagon (uncovered)
     
    That completes my set of models of the wagons originally ordered for the GWR. It took a while for the Board to realise the potential revenue to be obtained from good services, on what they had originally conceived as a passenger railway. As a result, a crash programme of orders were raised, intended to increase the wagon stock to 250 vehicles by the time the line opened through to Bristol.
     
    This rapid expansion led to ‘revised’ versions of all the types of wagons described above. According to the BGS Data Sheets, new wheels were fitted with refined open spokes and the suspension springs were deeper in form, but, overall, the bodies and frames remained the same.
     
    In addition, some new types of wagon were ordered for specific types of traffic. These included Sheep Trucks, and wagons for coke and coal. These will be the subjects of my next post.
     
    Mike
  12. MikeOxon
    Following my stock review , I realised that, although I have quite a good selection of early broad-gauge carriages, there are relatively few examples of early goods wagons.
     
    While thinking about the possibilities, I looked at the contemporary pen and wash sketch by J.C.Bourne, which shows three types of early broad-gauge wagons, including one with wheels outside the body sides and a tilt cover.
     

     
    For more information and drawings, I turned to the invaluable set of Data Sheets that were produced by the late Eddie Brown for the Broad Gauge Society (BGS).  Although these are extremely informative, they are written largely in note-form using typescript, which can be a little difficult to follow at times. With the help of these Data Sheets, however, I could identify those in the above sketch as two types of early ‘Box Wagon’ and an early ‘Horse Box’.
     
    Horse Box
     
    The Horse Box is one of the few early wagons that I have already modelled.  The original design of Horse Box was one of those Broad-Gauge oddities, in which the wheelbase of 6 feet was shorter than the track gauge!  It is one of the early vehicles illustrated in Whishaw’s ‘Railways of Great Britain and Ireland’, 1842.
     

    My 3D-model of an early GWR Horse Box, 1838
    (see my blog post for construction details)
     
    Box Wagons
     
    The history of the early GWR goods wagons is somewhat confusing, since thy are variously labelled as ‘Box Wagons’, ‘Luggage Wagons’, or ‘Utility Wagons’ depending on their mode of use at the times they were recorded. Eddy Brown teased out some their ‘life histories’ by comparing details such as Tare Weights from the various stock lists. It was a period when railway wagon design was developing rapidly from their farm-cart origins
     
    The first wagons ordered for the GWR were a batch of 29 ‘box wagons’ built in 1838/9. According to the BGS Data Sheet 401, five of these were described as ‘small box wagons’  There are no known drawings but one of these appears in J.C Bourne’s engraving of Pangbourne station.
     

    Extract from an engraving by J.C.Bourne
     
    This illustration is of particular interest because it shows that these were some of the very few vehicles that conformed to Brunel’s idea of placing narrow vehicle-bodies between the wheel-sets. These wagons show their farm-cart origins in the sloping sides, supported by struts known as ‘strouters’. The floor planks ran lengthwise, like a farm-cart, and there were drop-doors at both ends as well as in the sides.
     
    To create a 3D-model, I followed my usual method if tracing over the drawings in the BGS Data Sheet, which I imported as a ‘canvas’ into ‘Fusion 360’. I then extruded the panels and their details to form ‘solid bodies’. I used the ‘mirror’ option in ‘Fusion 360’ to create the opposite sides and ends, which avoided having to produce the planking details twice!
     
    After extruding the various parts from the side and end elevation drawings, as appropriate, I brought them together within the software, as shown below:
     

    Extruding a 3D-model from a ‘Canvas’ in ‘Fusion 360’
     
    Once the modelling is complete, ‘Fusion 360’ offer the capability to ‘render’ the 3D-model in appropriate colours and under controlled lighting conditions, to give an impression of how the eventual printed design will appear.
     
    The rendering option in 'Fusion 360' can be very effective and I have seen some superb examples, where other people have created complete scenes within 'Fusion 360'. So far, I have only touched the hem of the possibilities that have opened up, but it’s something I intend to pursue further.
     

    My 3D model of GWR Small Box Wagon, 1838
     
     
    ‘Standard’ Wagons
     
    The other 24 wagons in the initial order became known as ‘standard’ box wagons. BGS Data Sheet 402 states that the Traffic Committee's Stock Account for 6th.October, 1840, listed 22 wagons being allocated to London and 4 to Bristol as’ Box Wagons’, plus 3 known as ‘Luggage Wagons’, for use in Passenger trains.
     
    The ‘standard’ wagons were longer and also abandoned the Brunel concept of placing the body between the wheels, which resulted in greatly increased carrying capacity.  In fact, the internal volume was doubled in these wagons, from 6.31 Cu.yards (4.82 m3) in the small wagon, to 13.55 Cu.Yd (10.36 m3).
     
    In those early days, when ‘lower-class’ passengers were not encouraged, it is evident that, by September 1839, several of these wagons had been fitted with bench seating to carry ‘Goods train passengers’. After a serious accident at Sonning on 24th December 1841, it was recommended that the sides of the wagons should be raised, to reduce the likelihood of passengers being thrown out in the event of a collision!
     
    I created my model by using exactly the same procedure as for the small wagon; in this case extruding from Data Sheet 402. In fact, I was able to re-use some parts, such as buffer beams and cross members, for this larger wagon. Although the body sides were placed outside the wheels, they still sloped outwards towards the top and were supported by strouters.
     

    My models of the ‘small’ and ‘standard’ GWR Box Wagons
     
    Placing my models together shows vividly the increased volume in the larger design. Notice that the wheels protruded into the load space and were boxed-in in the prototypes.. In fact, this was a feature of GWR wagons that persisted for several years, until the Brunel dictum of ‘large wheels’ was finally abandoned. I suspect that those wheel-boxes were frequently cursed by the people loading the wagons.
     
    No doubt @Mikkel could create an amusing story about a package that got lost in the corner behind a wheel box 🙂
     
     
    A Model Trio
     
    As a final flourish, I decided to use my models to re-create the scene sketched by J.C. Bourne in the early 1840s. Note that there are some additions on the wagons he sketched. The small wagon has an over-all tarpaulin, supported by hoops, while the standard wagon has raised side-rails, which may have been for the carriage of animals.
     

    My three models arranged as in the J.C. Bourne illustration
     
    Mike
  13. MikeOxon

    GWR N6 Horse Box - 2

    By MikeOxon,


    general
    In my very first post in this Blog , I referred to the need for plenty of horses and the facilities to support them. As part of "Turning Back the Clock", I decided that an essential railway vehicle would be a Horse Box, so I chose to build the Wizard Models/51L etched brass kit of the GWR diagram N6 box.
     
    Inspired by @magmouse description of his 7mm scale model, I decided to restore my own early post about my 4mm scale model.
     
    Although at that time (2013), I had not started writing detailed descriptions of my ‘builds’, I found that I had made a collection of photos, stage by stage throughout the build. So I am now able to add extra illustrations, which date back to 2012. I hope that my 10-year old ‘build’ may continue to be of interest to current modellers.
     
    I felt that construction of the ‘Wizard models’ N6 kit was achievable for a beginner in etched-brass construction, since the prototypes, dating from 1890, were of a particularly simple, straight-sided construction, albeit with quite a lot of panelling on the sides and ends. The panelling is, of course, taken care of by the etching process but I liked the fact that this model did not need any 'tumble home' to be formed, so everything looked pretty straightforward.
     
    Chassis Construction 
    I decided to start with the chassis , carefully following the instructions to bend the buffer beams, vee-hangers and axleguard-brackets down. This was followed by adding the solebars, which fit through slots in the floor and were soldered in place.
     

    Initial chassis construction
     
    I then moved on to adding the brake blocks to the axleguard etches – the instructions advise to do this before bending the W-irons. The axle guard is then fitted at ‘the grooms end’ with the linkage hanger pointing to the end of the vehicle. I puzzled for some time over which was the ‘groom’s end’. I eventually realised that the fold-out steps on the solebars are the key to this, though not mentioned in the instructions. The ‘linkage hanger’ is the fold-up part that looks rather like a sub machine-gun on the etch!
     

    Adding brake blocks to chassis etch
     
    After folding up the W-irons and adding bearings to the etch, I carried out a test fit of the Mansell wheels, to check for free running
     

    Complete axleguard assembly
     
    The second axleguard is assembled in the same way but is designed to pivot on a shaft between raised tabs on the chassis etch.
     
    I struggled for some time to understand how to bend the handbrake lever stirrup and then realised (too late) that it is necessary to fit this before fitting the pivoted axleguard assembly. Otherwise, it is impossible to solder the tab on the inside of the chassis, without removing the axleguard assembly again!

     

    Folded handbrake ratchet etch
     
    Next, I realised how little I knew about brake gear, so had to give myself a crash course on 'safety loops' and the like. The N6 underframe superseded the earlier outside rigged brake gear, by using the later standard pattern, with triangular tie-bars between the brake blocks on opposite sides of the vehicle. The basic method of operation of the clasp-type brake is shown below
     

    Clasp brake operation
     
    The triangular links between the brake blocks on each side were fitted next. There are several diagrams in the instructions to show how the various parts should be fitted together. Then the various ‘safety loops’ were bent and added to the axleguards as described in the instructions. These parts were fitted on the prototypes to catch any loose parts of the brake linkage that might otherwise drop and cause an accident. 
     
    Next, I added the vacuum brake operating cylinder (white metal casting), followed by the linkage to the clasp brake assemblies, as shown below. To describe this as a fiddly process would be an understatement and I found it easier to attach several small parts by using drops of superglue rather than soldering, which tends to loosen adjacent parts.
     

    Brake linkage and safety loops added to chassis

    I summarised the steps in the construction of the chassis in the illustration below:
     

    Stages in construction of the N6 chassis

     
    Body Construction
     
    Once the chassis was complete, I built the body as a separate item. This proved relatively straightforward, with just two etches that are each folded to form one side and end, then soldered together.
     

    Inner body shell folded and soldered
     
    The detailed overlays carrying all the planking details and framing then fitted easily over the tabs raised from the inner body shell (one tab ringed in above image). These tabs also serve to represent the hinges on the doors.
     

    Etched overlay added to inner body
     
    I had some difficulty in persuading the roof to sit flush to the ends, near the centreline of the body, so I soldered a pair of small right-angle brackets inside the body, to hold the centre of the roof in place – easy to do, if you assemble the body and chassis separately.
     
    Finally, I added the various white metal fittings and found that the spring and axle box assemblies tended to foul the rocking compensation of one axle. A fair bit of filing down was needed to keep everything working! Eventually, however, I had an attractive model, to play its part in generating the 'feel' of the of the earlier period that I am trying to represent.

    As in the case of the chassis, above, I made a collection of images to show the stages in the construction of the body and the final assembly of my complete model:

     

    Stages in construction of N6 Body
     
    At the time of writing (2023), I must confess that this model is still missing lettering and various handrails.
     

    My model of N6 horse box after painting
     
    Later on, I built several other vehicles, such as a carriage truck, so that this model could be included in a complete train , to carry the Wilcote family together with their carriage and its horse to London for ‘the season’
     
    Mike
  14. MikeOxon

    Early GWR 'Absorbed' Engines

    By MikeOxon,


    general
    I wrote a Forum post about some of these ‘absorbed’ engines back in 2014 but it has now been archived and has lost its illustrations, so I thought it was worth restoring these in this blog post, which is partly based on my original text.
     
    Some time ago, I acquired a bound set of the RCTS "Locomotives of the Great Western Railway", mainly to learn more about the various pre-grouping designs by William Dean.  I had tended to skip over the volumes on 'Absorbed Engines' but later found myself browsing Volume 3 and realising what a strange and wonderful collection of engines made up the first standard-gauge locomotives to run on the GWR. These booklets are now available again on a print-to-order basis or in digital form.
     
    Of course, the early GWR was a Broad Gauge railway and it was only in 1854, during the drive Northwards, that it came to own any standard-gauge locomotives at all.  The first batches of these were acquired from the Shrewsbury & Chester and Shrewsbury & Birmingham Railways.  What an extraordinary mix of types these were, quite unlike anything we usually associate with the later GWR.  
     

    Shrewsbury & Chester Rly. as GWR No.14

    Some were Bury-type locomotives, with bar frames, others were 'long-boiler' types, with a gothic firebox hung behind all the wheels, and there was even an 0-4-0 with an intermediate drive shaft (built by the Vulcan Foundry).  At that time, there was a brief vogue for intermediate drive shafts, since these decoupled the valve gear from both vertical movements of the springs and lateral thrusts from the flanges on the driving wheels.
     

    Shrewsbury & Chester Rly. - GWR No.34
     
    This 0-4-0 was one of two that became GWR Nos. 34 and 35.  They were delivered in 1853 and both were withdrawn in December 1865. 
     
    Another former Shrewsbury & Chester engine that later gained notoriety was the long-boiler 2-4-0 GWR no.5, built by Longridge & Co., which was involved in a fatal accident at Rednal on 7th June 1865.
     

    Shrewsbury & Chester Rly. - GWR No.5
     
    A little later than this first group were the former West Midland Railway engines, which were added to the GWR fleet in 1863. This amalgamation brought in some of the old stock from the Oxford, Worcester & Wolverhampton Railway (frequently referred to as the 'Old Worse & Worse').  The only known illustrations of most of these early locomotives are drawings by E.L.Ahrons, a great chronicler of early locomotive history.  One of his drawings shows an ex-OW&W engine that would, perhaps, have seemed more at home in the Wild West than the West Midlands:
     

    OW&W Rly – as GWR 223
     
    There were two of these engines, one carrying the name 'Ben Jonson', and they worked branches in the Chipping Norton area until 1877, the other becoming known colloquially as "Mrs Jonson".  Note the outside steam pipes to the cylinders and the (somewhat squashed) safety valve cover.

    Another West Midland engine, which is better known because its photo appears in 'Great Western Way', had the unusual feature of outside Stephenson valve gear.  It became GWR No.219, from a class of six, originally built by the Vulcan Foundry for the Shrewsbury & Hereford Railway in 1853/54. 
     

    Shrewsbury & Hereford Rly. - as GWR 219
     
    I found that there are extensive records of all the locomotives built by the Vulcan foundry on the web. These records includes lists of locomotives deliveries by years, in which the S&H engines appear as below:



    There is also a drawing of one of these engines in ‘The Engineer’, showing both the locomotive and its tender, which gives a better sense of its proportions than the oblique photograph.
     

    Shrewsbury & Hereford Railway – as GWR No.215

    According to Ahrons, one of these engines could still be seen "lying in a heap of scrap behind Swindon Works in 1886".  

    Some of these early engines survived well into the 20th century, usually after having been re-built several times.  The last engine from the OW&W. 0-6-0 No.58, seems to have been around until 1921, by which time, after several re-buildings, it had acquired a conventional GWR appearance as GWR No.47.
     

    OW&W Rly. Re-built as GWR No.47
     
    After my initial look at thee ‘absorbed’ engines, I came across an article entitled "Some Early Great Western Recollections" by C.M.Doncaster in the April 1942 "Railways" magazine.

    The author photographed engines in the late 19th century at Reading Station, as a member of his school's photographic society, and recalls that he casually snapped No.184, never dreaming that this engine dated back to 1853, when it was supplied to the OW&W by E.B.Wilson and Co.  He wrote that, in 1895, it was not unusual to see these engines drawing trains of ten 6-wheel coaches   He even made a simple water colour of such a train, since, most unfortunately, he wrote that his photograph was not fit to reproduce.

    This article led me to explore these engines in more detail.  Six were supplied to the OW&W in 1853; they were 2-4-0 engines, somewhat similar to the 'Jenny Lind' 2-2-2 design produced by the same company.  As it happens, No.184 was not camera-shy and appears in two photographs in the RCTS survey of GWR Locomotives (Part Three): one as re-built at Wolverhampton Works in 1877 and another, after a further re-build in 1893. This particular engine was finally withdrawn in late 1899 and the whole class had gone by 1904.
     

    OW&W Rly. - rebuilt as GWR No.184

    I have looked into some of the background to both this locomotive and the Oxford, Worcester & Wolverhampton Railway, in general. so share this information, in case it is of interest to other modellers.

    The OW&W was initially planned as a mixed-gauge line, with Brunel as chief engineer.  Apparently, Brunel grossly under-estimated the costs and the money ran out in June 1849.  After a lot of wrangling, the line was eventually completed as standard-gauge only.

    David Joy (best known as the designer of the 'Jenny Lind' and of his radial valve gear) was appointed locomotive superintendent in 1852 and his diary (see https://steamindex.com/library/joydiary.htm ) gives some idea of the precarious state of the railway at that time.  He writes that when he arrived, the line was due to open in a fortnight's time, on May 1st, and he had to scour the country to get some locomotives for working the railway.   He scraped together a miscellaneous collection for the opening day, including a four-coupled " Jenny" (known as engine 'A') from the Railway Foundry in Leeds, with the cheque (£1,250) in his pocket to pay for it!  Remarkably, this ‘second hand’ engine survived into GWR ownership as No.206 and was finally withdrawn in 1876.
     

    David Joy’s engine ‘A’ – later GWR No.206
     
    Fortunately, after a few months working with these second-hand machines, relief came with the arrival of the first new locomotives, built by Hawthorns in 1852, and six more by the Railway Foundry (then recently re-named E.B.Wilson & Co.) arrived in 1853, starting with No.21.  It was these latter engines that later became the GWR '182-class' and they were clearly David Joy's favourites.  He wrote "This 21 class would always answer to any little nursing, and would go"  For example he: "received an order for an engine, two first-class carriages, and a van, and a driver who dare run........ We were at Yarnton or Wolvercot Junction on the morning, and all ready to take our passengers from the Great Western Railway special. I was, of course, on the engine — No. 21."  A report was sent from one of the stations that the "special train had passed at 60 miles an hour." , This report, in due course, came before Joy, who remarks " I countersigned it, ' Yes, all right.' ".  There are plenty of other fascinating insights into the running of these early engines in the diaries, including several accidents, which Joy described as 'spills'.


    OW&W Rly. No.21 (From David Joy’s diary)

    In 1860, the OW&W amalgamated with the Newport, Abergavenny and Hereford Railway and the Worcester and Hereford Railway, to become the West Midland Railway, which, in turn, was amalgamated into the GWR in 1863
     

    OW&W No.21 (later GWR 182)

    All this colourful history convinced me that one of these engines would be an excellent subject for a model.  I found that No.23, re-built as GWR No. 184,  survived until October 1899, still working trains in the Oxford area.
    The construction of my model is described in a series of posts, starting with   https://www.rmweb.co.uk/blogs/entry/14895-another-new-old-engine-1/


    My model of GWR No.184 with motorised tender (in Wolverhampton livery)

    List of OW&W Locomotives

    nos. 1 - 20     12 Passenger 2-4-0 and 8 Goods 0-6-0,  built by Hawthorn in 1852/3
            became GWR 171 – 181 (Pass - with some exceptions) and 239, 241 – 243/5/7 (Goods)

    nos. 21 - 26    6 Passenger 2-4-0 built by E B Wilson in 1853
            became GWR 182 – 187

    nos.  27 - 30/ 34    5 Goods 0-6-0 built by E B Wilson 1854/5
            became GWR 248 – 252

    no. 31        Engine 'A'  2-4-0, built by E B Wilson in 1849, bought second-hand 1852
            converted to 2-2-2 in 1855,
            became GWR 206

    nos. 32, 33    'Ballast' engines 0-6-0, built by E B Wilson 1854/5
            became GWR 278 & 279

    nos  35, 36    small 0-4-2ST, built E B Wilson 1853
            became GWR 221 & 222

    nos  37 - 39    3 Goods 0-6-0, designed Peacock,  bought from MS&LR 1854
            one (38) sold, others became GWR 237 & 238

    nos. 40, 41    2 Passenger 2-4-0,built by E B Wilson 1855
            became GWR 188 & 189

    nos. 42, 51    2 Passenger 2-2-2, built by E B Wilson 1856 (large 'Jenny Lind' type)
            became GWR 207 & 208 (51 named 'Will Shakspere' sic)

    nos. 43 - 46    4 Goods 0-6-0,built by E B Wilson 1856
            became GWR 264 – 267 (264 rebuilt as no.49)

    nos. 47 - 50    4 Goods 0-6-0T, built by E B Wilson 1856
            became GWR 231 – 234

    nos. 52, 53    2 Passenger 2-2-2T, built by R Stephenson 1859
            became GWR 223 & 224 (52 named 'Ben Jonson')

    nos. 54, 55    2 Goods 0-6-0,built by Kirtley, bought from MR 1860
            became GWR 280 & 281

    nos. 56 - 59    4 Goods 0-6-0, two built by Kitson and two by R Stephenson 1860
    became GWR 294 – 297 (294 rebuilt as no.47)

    Examples of each of these types are illustrated in RCTS 'The Locomotives of the GWR - Part Three'

     
  15. MikeOxon

    GWR ‘Sir Daniel’

    By MikeOxon,


    general
    A comment on my recent post about modelling Rocket reminded me that my first scratch-built locomotive was an Armstrong 2-2-2 that I constructed 10 years ago and described in ‘Railway Modeller’, July 2014 , as ‘Simply Victorian’. I explained in that article that I was encouraged by a drawing of one of these engines in Russell’s ‘A Pictorial Record of Great Western Engines’ with the caption comment that: "The utter simplicity of these early engines can be seen." The idea of ‘simplicity’ appealed to me!
     
    Later, when contemplating additional engines for my ‘North Leigh’ layout, I considered other Armstrong types, including the earlier ‘Sir Daniel’ class. At that time, I wrote of my first model that “It really was simple to build - basically a brass tube over a brass plate, with a very simple 'chassis' to hold a set of wheels at the right distance apart! It was really just a wagon that can be pushed along by a motorised tender. I would recommend an early 2-2-2 as a good subject for a first attempt at locomotive scratch-building.”
     

    Principal Components of my 1st model
     
    Whereas the 'Queen / Sir Alexander' class that I chose to model were the last engines designed by Joseph Armstrong before his untimely death in 1877, the 'Sir Daniels' were his first standard-gauge engines built at Swindon, starting in 1866,
     
    Writing in 2015, I decided that “In summary, I can see that I could make a model of a 'Sir Daniel' by using exactly the same methods that I used for 'Queen'. At the moment, I feel tempted but concerned that the two would end up looking too similar! If I do tackle a 'Sir Dan', I shall have to choose a prototype with significant differences from my existing model”
     
    I felt at that time that my options were limited by what I could make using the traditional methods of brass-sheet construction. Since then however, my horizons have widened considerably following my adoption of 3D printing which greatly eases the problems associated with matters such as open splashers and other awkward features.
     

    Sir Daniel No.378 in ‘as-built’ condition
     
    One elephant remains in the room, however, and that is the fact that a ‘00’ gauge model really is a ‘narrow gauge’ model, within which true-to-scale boilers may not fit! In the case of my ‘Queen’ model that meant taking jewellers’ snips to the brass sheet I intended to roll into a boiler – fortunately, it still rolled successfully! It also meant that I had to adopt covered-in splashers to hide the gaping hole that I had created, so my model had to be of the later Dean rebuild of the type.
     
    Now, with 3D printing, I felt able to look back to the original design of 1866 for an engine that would be significantly ‘different’ from a rebuilt ‘Queen’ prototype of 30 years later. I still had to take into account the constraints of ‘00’ gauge, with a back-to-back dimension between the driving wheels of only 14.4 mm (3’ 7” at prototype size) against a boiler diameter of 4’ 2” (plus cladding).
     
    According to RCTS ‘Locomotives of the GWR’,Part 4, the main dimension of interest to a modeller were:
     
    ‘Sir Daniel’
    Cylinders. Diam. 17" Stroke 24" Boiler. Barrel 11’ 0" Diam. outs 4' 2" Pitch 6' 11". Firebox. Length outs 5' 4" Wheels. Carrying 4' 0". Driving 7' 0" Wheelbase 7' 8" + 8' 4", total 16' 0".  
    For comparison, the later ‘Queen’ class had shorter boilers but larger fireboxes and a longer wheelbase of 17’ 6”.
     
    Creating a Model.
     
    I started by considering the design of the boiler and the need to accommodate ‘narrow gauge’ driving wheels. My references were the photograph of ‘Sir Daniel’ as originally built, shown above, and a drawing by Jim Champ, which I imported as a canvas into ‘Fusion 360’
     
    Usually, I like to make the boiler from a brass tube and add a 3D printed cladding, as on the prototype. In this case, however, I had to accommodate the driving wheels, so I decided to 3D print the boiler itself and add weight by lead strips afterwards.
     
    After some thought, I decided on the following procedure:
     
    1. create a cylinder of length 44mm and diameter 18mm, to represent the external dimensions of the boiler plus its cladding
     
    2. create a pair of 28mm diameter driving wheels, with additional 0,5 mm flanges, and mount these either side of the boiler at the ‘00’ back-to-back separation of 14.4 mm
     
    3. Assemble these parts into their correct locations within Fusion 360 to create a visual impression of what modifications would be required to the boiler model, as shown below..
     

    Tackling the 00 gauge Boiler Problem
     
    I realised that the diameter of the cut-outs in the sides of the boiler would have to be wider than this, because it would simplify the design of the splashers, if I could also recess these into the sides of the boiler. I drew a circle of the required diameter in Fusion 360 and then used the ‘extrude’ tool in ‘cut’ mode to create recesses of the depth required to accommodate the driving wheels.
     

    Cutting recesses for driving wheels and splashers
     
    After dealing with that problem, the rest of the construction followed a familiar course. I extruded a pair of outside frames from the drawing canvas and set these at a ‘true scale’ distance apart. This means, of course, that the driving wheels are inset, relative to the prototype, but the overall arrangement of the locomotive is correct. If I wanted to run the engine on scale track, this would be possible, simply by extending the driving axles. At this stage, the frames are purely ‘cosmetic’ and I shall consider the design of the real chassis later.
     
    All the other parts were similarly extruded from the drawing or, for the dome and safety valve covers, I used the ‘revolve’ tool on a profile sketch.
     
    One thing I always have to bear in mind is the ‘printability’ of a 3D model created in Fusion 360. I aim to divide up the component parts, so that each one has a flat surface to lie on the printer bed, from which the rest of the structure can be ‘grown’, For example, I provide flat plinths on the boiler, so that the various boiler fittings can be printed from flat bases. The ‘exploded’ view below shows the collection of parts that can be printed individually.
     

    Components shown separately in Fusion 360
     
    As usual, I also like to do a ‘test fit’ of all the components by assembling them within Fusion 360 as a final check before printing – they can be seen against the ‘canvases’ from which the parts were extruded below:
     

    My model of ‘Sir Daniel’ assembled within Fusion 360
     
    The next stage will be to design a chassis, which will be based on an inside-frame for the wheels. As in the case of my existing ‘Queen’ model, I intend this one to be driven from a powered tender.
     
    Mike
  16. MikeOxon

    25 years later - ‘Rocket’

    By MikeOxon,


    general
    Having gone right back to 1804 with Trevithick’s locomotives, I decided to start moving forward again - to Stephenson’s famous ‘Rocket’, which was to put passenger-carrying railways firmly on the map.
     
    When I built my Trevithick model, I wanted to put it alongside a model of ‘Rocket’ to illustrate the progress made over 25 years but, although I know I have a 4 mm scale model built from an Airfix kit, ‘somewhere’, I couldn’t find it!
     
    I did find however that there is a 3D printable model of ‘Rocket’ on the same Printables website, where I had found the Trevithick 3D model files. Again, the ‘Rocket’ model was designed for a larger scale than my usual 4 mm/foot but, in this case, the scaling factor needed was not so great.
     
    The model I downloaded was by Václav Krmela, who has made his .stl files available under the Creative Commons (4.0 International License) Attribution-NonCommercial   His model was designed for 1:32 scale, so needed reduction by 42% to print at 4 mm/foot.
     
    Most of the parts printed satisfactorily at the smaller scale but, as with the Trevithick model, I had to thicken the walls of the boiler and chimney to make them sufficient robust. I particularly liked the way in which the design incorporated location tabs, which made it very easy to assemble the printed parts in their correct orientations. For example. I show the basic chassis which has tabs to locate with both the firebox and boiler:
     

    Components of Václav Krmela’s model, showing helpful tabs
     
    These tabs worked perfectly well on my reduced-size prints and are a feature I must aim to include in my own future models.
     
    A feature I didn’t like was that the cross-heads on both sides of the engine were fixed in the same position, so didn’t allow for ‘quartering’ of the driving wheels. When I imported the relevant .stl files into ‘Fusion 360’, however, and converted the mesh bodies into ‘base features’, I found that they split into two parts – the piston body and the piston rod and slide bar – so I was able to re-position the cross heads to appropriate positions along the slide bars. This was unexpected and a feature that must have been ‘lost’ when the .stl files were created!  I have found that the ability to import .stl meshes and convert them to ‘base features’ in ‘Fusion 360’ is very useful, as it allows modifications to be made to downloaded model files.
     
     

    Bodies created in Fusion 360 from original .stl file
     
    To check the overall assembly, I brought all the parts together within ‘Fusion 360’, as shown below.
     
     

    Vaclav Krmela’s mesh model, assembled in ‘Fusion 360’
     
    So now, all I had to do was print the parts. I printed some of the smaller parts in groups, including a set of wheels and a set of various small pipes, rods, and stays. The latter group was on the borderline of what is possible at my chosen scale and I made several attempts before I managed to print a reasonably ‘clean’ set. These tiny parts only took 1 minute to print but adhesion to the print bed was rather ‘hit and miss’ until I tried applying some ‘Pritt Stick’, which increased the success rate considerably – here’s a set, as printed, warts and all:
     

    3D printed pipes, rods, and stays, before fettling
     
    I attached these fragile parts by applying a touch of a 200° soldering iron tip  while holding the ends in place with fine tweezers.
     
    It has been an interesting print job although, looking at the assembled model, the pipework in particular is rudimentary, when compared with the full-size replica. A very significant omission is the pair of pipes carrying exhaust steam from the cylinders to the base of the chimney – this use of the exhaust blast to ‘draw’ the fire was an important factor in the success of Rocket at the Rainhill trials.
     

    Full-size Rocket replica at Tyseley, 25 June 2011
     
    I felt I had to rectify this omission, so I made 3D prints of the two upper pipes and the pipe at the bottom of the firebox. Again I used ‘Pritt Stick’ to ensure that these tiny parts didn’t wander on the printer bed.
     

    My additional 3D-printed pipework
     
    Printing this model has served my purpose in providing a comparison to the Trevithick model, so demonstrating the progress made over the intervening years. The appearance of the ‘Rocket’ model does suffer, though, from the ‘Tri-ang’-like profile to the wheels!
     
     

    3D prints of the downloaded Trevithick and Rocket models
     
    Whereas Trevithick conceived his engine as a ‘general purpose’ machine, ‘Rocket’ was built to meet the very specific requirements laid down for the Rainhill Trials. In particular, ‘Rocket’ was designed to haul light loads at high speed and Stephenson realised that, for this task, adhesion weight would not be a critical factor.
     
    Nevertheless ‘Rocket’ needed improvement for general service use, so there were further rapid developments by the Stephenson company. The next step was the ‘Planet’ class 2-2-0, which introduced the use of a pair of inside cylinders under the smokebox, an enduring feature of British locomotives. ‘Planet’ was followed by the ‘Patentee’ in 1833, which established the 2-2-2 as the archetypal British express engine and could be described as the first ‘modern’ locomotive.
     
    A detailed description of Stephenson’s ‘Patentee’ Locomotive Engine was published by John Weale in 1838 “by the liberality of Robert Stephenson, Esq., having been written under his direction and revision by Mr W.P. Marshall”
     

    Stephenson’s ‘Patentee’
     
    My model of the broad gauge ‘missing link’ is an example of this type of engine, which set the pattern for express engines until increasing size and weight dictated the use of more carrying wheels.
     
    Mike
     
  17. MikeOxon
    I’ve now managed to produce a set of ‘printable’ parts from the original download from the ‘Printables’ website described in my previous post.
     
    I’m still puzzled by the theories on exactly which of Trevithick’s locomotive engines was actually used for the Penydarren trial, which was the moment in history that put the steam locomotive on the map.
     
    There is a print in the Science Museum collection, said to be the Penydarren engine but it has been discredited because, according to the attached scale, it shown an engine on a 3-foot gauge track.
     

     
    When I compared this print with the illustration in Francis Trevithick’s book, however, it was obvious that they were extremely similar, although the book states that gauge was 4’ 4”. On further inspection, I realised that the Science Museum print became a very good match (not identical but very similar), if I increased the scale of the print to correspond with a 4’ 4” gauge. Can it really be the case that subsequent authors have been misled by the scale appended to the drawing? I’ve seen so many examples of a wrong scale on a drawing to feel that it is not that unlikely an occurrence!
     
    Incidentally Francis Trevithick, son of Richard, was himself a railway engineer, having been appointed Locomotive Superintendent to the Grand Junction Railway at Edge Hill, Liverpool, in 1841. I mention this to show that he was very knowledgeable about engines
     
    Printing my model parts
     
    Making the parts downloaded from the ‘Printables’ website printable at the smaller scale of 4mm/ft did not prove to be too arduous.
     
    I made all the gear wheels a little thicker by a simple scale change in the ‘Cura’ software. The boiler and chimney were both too thin-walled to print, so I created new versions as simple cylinders in ‘Fusion 360’. The triangular front support for the piston-rod was also too fragile, so I re-drew a stronger version. After assembling all the parts together, I made a ‘rendered’ view of the model within ‘Fusion 360’. The piston-rod and slide bars are indicated as brass rods, which is how I intended to create them for the physical model.
     

    Model of Trevithick’s engine rendered in Fusion 360
     
    Apart from these rods, I transferred all the revised files from ‘Fusion 360’ to the ‘Cura’ slicer program and thence to my printer. In the case of small parts, which take only a few minutes to print, I collected several items together as a single ‘print job’. For example, all the gear wheels were printed together in the printer build plate.
     

    Various wheels and gears printed together – on my printer bed
     
    A curious observation was that, in a couple of cases, small parts which did not print cleanly the first time, gave a far better result when I immediately repeated the print, over the same location on the printer bed (i.e. no change to any of the print parameters). Could the fact that the print head was still warm have resulted in a cleaner start to the re-print?
     
    Assembling my model
     
    When I first viewed the collection of tiny parts that I had printed, I quailed at the thought of ever being able to connect them all together! Fortunately, I have a good illuminated magnifier and, very importantly, have recently had cataract surgery that has restored my acuity of vision!  I’m also pleased to have found that my hands are still steady enough to thread small-diameter rods through barely visible holes in tiny parts!!!
     
    Of course all you 2mm FS modellers will wonder what I’m talking about but it was a delicate-seeming operation for me to attempt. I don’t know if Julia Adams still visits this site but it was seeing her demonstrations at various shows that assured me that such fine work is possible.
     
    So, where to begin?
     
    I decided to try threading the main drive-shaft through the lugs on the boiler end-plate, to connect to the flywheel on one side and the primary gear wheel on the other. It turned out that a 1 mm diameter brass rod slid through the lugs, after just a slight touch with a reamer, so I soon had these parts joined together:
     

    My Primary Driveshaft Assembly
     
    I realised that there is a boiler extension below the drive shaft, which may explain why the boiler length is described in the references as being 6 feet. This extension presumably accommodated the curved end of the return flue inside the boiler.
     
    This initial step demonstrated that there was a good chance that other shafts and gears would all fit together so, with a little more confidence, I assembled the main driving wheels onto their 2mm diameter steel axles. In the prototype, the axles were fitted to a very basic wooden ‘boiler truck’, to support the main components of the engine. This illustrates the concept that Trevithick had of designing his engines as ‘multi purpose’ machines. In a letter to Mr. Giddy dated February 22nd 1804, Trevithick wrote “An engine is ordered for the West India Docks, to travel itself from ship to ship, to unload and to take up the goods to the upper floors of the storehouses by the crane, and in case of fire to force water on the storehouses. The fire is to be kept constantly burning in the engine, so as to be ready at all times.”
     
    I fitted a second 1 mm diameter rod into the raised mounting on the side of the boiler, to carry the ‘intermediate gear’, which conveyed the drive from the primary gear to the gears on the faces of the driving wheels. After setting the model boiler onto its ‘boiler truck’, this part of the assembly appeared as shown below:
     

    My 3D-printed Boiler on its wheeled carriage
     
    I was pleased to find that the gears meshed together well, so the next step was to attach the boiler end plate, carrying the primary drive shaft: and its gear wheel.
     

    Assembly of the Main Gear-train
     
    These parts all fitted together well, so it was time to look at the thorny issue of the cross-head and its associated support structure.
     
    I decided to attach all the relevant parts to the end-plate of the boiler, before adding the completed assembly to the boiler itself and the main gear-train.
     
    I started by cleaning up the details on the end plate of the boiler since, in the small scale, some of the detailing had become a little obscured by stray filament, where the printer had attempted to negotiate some very convoluted paths.
     
    Once this was done, I used a reamer to open out the central hole in the end-plate to accept the 1 mm diameter brass piston-rod. I thought that the printed cross head might prove too frail but, in fact, the central hole opened out successfully, by careful use of a 1 mm drill in a pin-vice. I slid the end of the piston-rod into this hole, adding a drop of super glue to keep it firmly in place.
     
    For the two slide bars on either side of the piston-rod, I used 0.5 mm diameter brass rods. Again, I used a reamer to help insert the rods into the appropriate sockets on the boiler end-plate and in the cross head. I cut two slightly over-length rods and slid them into their places alongside the piston-rod.
     
    As the last part of this assembly, I added the rather fragile print of the triangular support structure. The two arms fitted into two notches on the sides of the end-plate. I put a small dot of gelled-superglue into each of these notches and then manoeuvred each of the arms into place, in turn, holding them until the glue ‘caught’. After re-checking the alignment of all these parts, I set the whole assembly on one side, to allow the glue to harden.
     

    My assembly of the Cross Head and its associated Rods.
     
    To call this a delicate operation would be something of an under-statement! The end bracket holding the outer ends of the slide bars is the smallest item I've ever printed and the main problem was keeping it from the clutches of the carpet monster😆 I show it being held on the shaft of a reamer, against my thumb for scale:
     

    End support held on a reamer
     
    Note the two small ‘ears’ above the bracket, which replicate those on the cross-head. These are supports for rods to operate the four-way cock by means of tappets, moved by the cross-head to change over the cock as the piston nears the ends of the cylinder. They were also used when starting, to ensure that this single-cylinder locomotive started to move in the desired direction. I’m afraid I shall omit these parts, as they are simply too fine (for me) to create at 4mm/ft scale.
     
    The next items to add to the end-plate were the chimney and its right-angle connecting pipe. A key part of the original design was that the exhaust steam from the four-way cock was directed up the chimney, so that the steam blast helped to ‘draw’ the fire and so improve the steaming of the engine. As I had anticipated, the tall slender chimney did not print very smoothly and, a length of metal tube would be a better solution. The printed one serves the purpose of showing the overall appearance of the engine.
     
    After gluing this assembly to the end of the boiler, the remaining task was to add the long connecting rods, between the cross-head and the drive-shaft at the opposite end of the boiler. I couldn’t manage to fix pins into the end of the cross head so the rods are glued together here. The other ends are pinned to the flywheel and primary gear crank. In practice, although the cross -head will slide, the movement is too tight for this to be considered as a working model … perhaps, next time, with a few improvements to those components that are really insufficiently robust at this scale 🙂.
     
    So, at last, the rather spidery contraption looks as shown below:
     

    My 4 mm/ft scale model of a Trevithick locomotive c.1803
     
    So, why did I do it? Partly of course because it was there but also, I wanted to place the earliest GWR engines within the context of what had gone before. Even the earliest GWR engines were rather late on the scene – 35 years later than this Trevithick engine, which is rather a long time in a period of rapid technological development.
     
    I can write about dimensions and show models against a ruler but a much more ‘real’ impression is formed when I place my models from different periods alongside one another.
     
    Below I show the Trevithick locomotive in context with some of my early GWR models placed on the same table. I believe this brings home much more vividly what progress was made during the first half of the 19th century!
     

     
    Mike
  18. MikeOxon
    I have not forgotten about my plans to create a diorama, as described in my Broad Gauge blog. 
     
    While I was researching the early days of the GWR, however, I found myself thinking about what had gone before – back to the ultimate pre-grouping period!  This led me to Trevithick’s engines, of which I photographed a replica at Blists Hill Museum near Telford:
     

    Trevithick replica at Blists Hill Museum
     
    Trevithick was a remarkable inventor but, sadly, not a good businessman. He not only demonstrated, by 1802, that a compact high-pressure steam engine could be adapted to both road and rail uses but also that such a vehicle could be propelled by adhesion alone. In his Penydarren locomotive of 1804, possibly his most famous design, he turned the exhaust steam up the chimney, so creating the ‘blast pipe’ which was to prove an essential component of later locomotives. He sold all the rights to his designs and emigrated to South America to seek his fortune. He eventually failed there and died in poverty, back in England.
     
    His son, Francis, wrote a two-volume biography ‘Life of Richard Trevithick’, published 1872, which describes his father’s life and inventions. In Vol.1, page 181, there is an illustration of the Tramway engine that was built for South Wales in 1803:
     

     
    Next, as so often seems to happen when I start a new research project, an entire ‘can of worms’ began to open up!
     
    The book also notes, however, that “particulars are taken from Trevithick's letters where other evidences are conflicting . It is probable that more than one tramroad - engine was constructed in Wales at that time.” The dimensions listed above do not correspond with the associated drawings! For example by scaling from the drawing, if the wheelbase is 4’ 1” then the boiler is only about 5 feet long, while the flywheel is about 8’ 9” diameter, so there is no way it could have fitted through the Plymouth-works tunnel on the Penydarren tramway!
     
    Later in the book, there are references to three different engines, including the one that I saw (in replica) at Blists Hill museum, Coalbrookdale.
     
    “We have no account of the railway work done by the Coalbrookdale travelling engine of 1802. The Welsh tramroad - engine of 1803 took a gross load of 25 tons, at the rate of four miles an hour, over a bad road, with sharp curves and stiff inclines, and without load ran at a speed of sixteen miles an hour. The Newcastle locomotive of 1804 was, in general outline, similar to the Welsh locomotive, but in detail superior. The wheels were to run on rails instead of trám-plates, and were 9 inches farther apart than the Welsh locomotive, giving increased steadiness. The boiler and return tube were wholly of wrought iron; the fire -door and chimney were at one end of the boiler, and the cylinder and guide-rods at the other end, giving more room to the engineman than on the Welsh locomotive, which had all those things at one end of the boiler. The cylinder of the Newcastle locomotive was of the same size as the Coalbrookdale engine of 1802 , being 7 inches in diameter, with a 3-feet stroke, and therefore was probably made at Coalbrookdale, from Trevithick's drawings and patterns of 1802, with its regulating blastpipe and steam of from 60 to 145 lbs . on the square inch .”
     
    At this point, there is even a Swindon connection, as shown by correspondence between Joseph Armstrong and Francis Trevithick:
     
    “F. TREVITHICK , Esq . May 10th, 1870
    DEAR SIR,
    By this post I have forwarded a tracing of the old locomotive for Mr. Trevithick, and likewise some copies of an extract from the Gateshead Observer.' They would have been sent ere now, but I have had some difficulty in procuring an original from which to get a tracing, and have also spent time in hunting up this extract, and having it reprinted .
    Yours truly,
    JOSEPH ARMSTRONG Esq, Swindon.”
     

    In Plate V. , a is a steam-cylinder 7 inches diameter, 3 -feet stroke , fixed in the boiler ; b , piston-rod ; c, crosshead ; d, guides ; e , stay ; f, connecting rod ; g, crank ; h, driving axle ; i, fly-wheel ; j, gear-wheels ; k , four driving wheels, 3 feet 1 inch diameter, 4 feet 8 inches from centre to centre ; 1, four-way cock ; m, lever for working cock ; n, plug-rod ; o , cylindrical wrought- iron boiler, 4 feet diameter , 6 feet 6 inches long ; p, firegrate ; q, return fire - tube of wrought iron , 2 feet 3 inches diameter at the fire -door end, 1 foot diameter at the chimney end ; r, chimney ; s , fire-door ; t , railway of longitudinal timbers, 3 inches wide, 4 inches deep ; u, cross-sleepers, 4 inches wide , 3 inches deep ; 1 foot 1 inch apart ; gauge between wood rails , 4 feet 10 inches ; weight of engine in working order, 4 tons.
     
     
     
     
    Trevithick's 'Newcastle' engine
     
    After searching for more information, I found Anthony Dawson’s much more recent book ‘Before Rocket: The Steam Locomotive up to 1829’, published 2020, in which Chapter 1 reviews Trevithick’s work between 1802 and 1814.
     
    This text agrees that there were at least three similar locomotives. Dawson points out, however, that the Penydarren locomotive “was built to be convenient for the driver to work the engine and for the witnesses to see what was going on” He suggests that “this would probably rule out the cylinder being at the same end as the chimney. Thus, it is more likely that the Penydarren locomotive had the cylinder at the opposite end to the chimney and firebox, somewhat analogous with the Gateshead [Newcastle] Engine.”
     
    I do not know why he discards Francis Trevithick’s description and statements in reaching this conclusion, since the earlier work appears to be clear about the differences between the two engines.
     
    There is also the matter of a ‘replica’ built by The Museum of Wales (Waterfront Museum, Swansea), completed in 1981.  Their guidebook states “that the replica was built working from Trevithick’s original documents and plans (now in the National Museum of Science and Industry).” This leaves the question “which plans?”. Their ‘replica’ places the chimney at the opposite end of the boiler from the cylinder, unlike the illustration in Francis Trevithick’s book but similar to the later Newcastle engine
     
    Perhaps I am missing some recent piece of scholarship but it is hard to see why the layout of the later Newcastle engine was preferred for the Welsh replica over Francis Trevithick’s 1872 description of the Welsh engine. Francis T. did, however, note that there was conflicting evidence and that “It is probable that more than one tramroad-engine was constructed in Wales at that time”. As I noted above, the engine, as drawn in his book, could not have run through the tunnel on the Penydarren tramway, although reducing the size of the flywheel would be a relatively simple modification.
     
    It seems that, after a lot of reading and thinking, the can of worms remains open!
     
    Creating a Model
     
    Naturally, I felt the need to create my own model but then I found a 3D printable design, created for the Prusa printer on the ‘Printables’ website  This work is licensed under a Creative Commons (4.0 International License) Attribution—Noncommercial—Share Alike @ThorinOakenshield.
     
    This model, however, is a much larger and more sophisticated model than my own usual designs but I thought I might re-scale and simplify the design. Then, there is the question of ‘which engine does it represent?’
     
    I tried my method of overlaying the drawing on p.181 of Trevithick’s book over a still from the video of the ‘Printables’ model and … in all the major respects they fit well together! (note that the video image is not quite ‘side-on’)
     

    Overlay of Trevithick drawing (red) on ‘Printables’ model
     
    So, whether or not this is actually the Penydarren engine or another Trevithick prototype, I feel that I am close to the appearance of one of the very first locomotive engines ever to run on rails!  I decided to reduce the dimensions of my version, to fit a 4’ 4” gauge trackbed in 4 mm/foot scale, as the track gauge seems to be the only firm figure we have!
     
    To do this, I imported the drawing on p.181 of Trevithick’s book into ‘Fusion 360’ as a ‘canvas’ and then scaled it to the correct gauge at 4mm/foot scale. This confirmed the wheel diameter as 15 mm (prototype 3’ 9”).
     

    Drawing from Trevithick's book scaled in Fusion 360
     
    Next, I loaded the .stl file for the wheels, downloaded from the web, into ‘Fusion 360’ as a ‘mesh body’. I laid this body over the above drawing and adjusted the size until the wheel diameter matched the drawing. This needed a scale factor of 21.34%.
     
    I imported all the .stl files for the web model into the ‘Cura’ software and re-sized them all by the same scale factor.  Then I loaded all the re-scaled files into ‘Fusion 360’ as mesh bodies.
     
    I could then move each of the parts within ‘Fusion 360’ into its appropriate location around the boiler, as shown below against the ‘canvas’ backdrop:
     

    ‘Printables’ files, re-scaled and loaded into Fusion 360
     
    This confirmed that the re-scaled parts should all fit together as required. It also indicated, however, that some parts would be too thin to print successfully at the reduced scale. In particular, the boiler casing would be far too thin, so I decided it would probably be easier to design a new part for this component and, maybe, for some other parts as well.
     
    The next step will be to review all the parts for their suitability for printing at 4 mm scale and make modifications where necessary.  In the meantime, I show a couple of 3D views of the model, rendered in ‘Fusion 360’:
     

    Two rendered views of 3D-model assembled in Fusion 360 from ‘Printables’ files
     
    Mike
     
  19. MikeOxon

    Taking Stock

    By MikeOxon,


    General
    On one or two occasions, I have received comments along the lines of “we want a layout”. From the beginning of my exploration of the broad gauge, it has been my intention to produce some sort of layout or diorama to display the various models of rolling stock that I’ve constructed.
     
    Of course I already have a small layout carrying both narrow and standard gauge routes, based in Oxfordshire, towards the end of the 19th century. This layout continues to provide entertainment to my grand-children and I do not intend to replace it with a broad gauge version. Unfortunately, broad gauge railways in 4mm scale require considerably more space than a traditional 00 gauge layout, so I shall be restricted to something rather simple .
     
    At the beginning of this blog, I described how my exploration of family history led to my exploring the area around Bullo Pill and the Forest of Dean. I also found a very thorough Accident Report on a collision in November 1868, which provided detailed descriptions of the make-up of both the mail train and the cattle train that were involved in the accident. While I did not intend to model the accident itself, I did use these descriptions to recreate two trains of the mid 19th century period. My first thought was to lay out a simple section of track representing the cutting close to Cockshoot Bridge, where the accident occurred but soon began to realise that this would not make a very interesting scene.

    Simple diorama plan
     
    During the period when I was building the models for these two trains, I discovered the possibilities opened up by 3D printing . The restrictions imposed by Covid gave me plenty of time to practice my 3D modelling skills, using 'Fusion 360' software, and I was soon enjoying the excitement of creating models of prototypes that I had previously placed firmly in the ‘too difficult’ box.

    Mail train

    Cattle train
     
    Gradually, I began to realise that virtually any type of early 19th-century rolling stock was within my grasp, given the limited dimensions of the actual vehicle at that period. I got somewhat carried away and started churning out models of all sorts of prototype – whatever caught my fancy at the time!
     
    An advantage of creating small models by 3D printing is that once designed, they take very little time to print, such that I soon found myself with quite an extensive collection of models covering prototytpes that operated from the earliest days of the GWR.
     
    Although more of these prototypes than I initially expected did appear in the Bullo Pill and Forest of Dean areas, it was clear that I was also creating stock more appropriate for other areas, such as the South Devon railway and the original stretch of the GWR between Paddington and Maidenhead. This left me with much food for thought, when I came to think of how to create a scene that could be representative of all these areas.
     
    As a first step I assembled a few representative trains from the various models that I have made so far.
     
    My first model train shown below is based on contemporary illustrations by J.C. Bourne of Bath and Bristol Temple Meads stations. The very short wheelbase carriages (6 feet on 7’ gauge) did not survive very long and were ‘ordered off the line’ following a Board Meeting on 12th July 1838!

    ‘Argus’ (Firefly-class) with 1840s passenger train, comprising:
    luggage truck, closed 2nd, open 2nd, posting carriage, horse box, carriage truck
     
    When I first made a model of ‘Aurora’, I thought of these 4-4-0ST engines as primarily South Devon engines. Later, I discovered that several engines of this class were employed on trains working into the Forest of Dean from Bullo Pill, so they tied in with my earlier plans! To my surprise, no fewer than 11 of the ‘Bogie-class’ engines were deployed there between 1854 and 1861.
     
    My ‘removals’ train, shown below, was inspired by an article in the Broad Gauge Society journal ‘Broadsheet’ No.26, p10 , which featured the Bristol firm of Knee Brothers and their first recorded use of a Pantechnicon being transported by rail in 1847.

    ‘Aurora’ 4-4-0ST with Furniture removal train, comprising
    Henson patent Van, pantechnicon,brake van, horse box, luggage van
     
    I was very surprised to discover that engines of the ‘Sir Watkin’ class, original built as condensing engines for the Metropolitan Railway, served for a short time at Bullo Pill. I only know this because my wife’s great-grandfather was fined £1 on 26th April 1870 for “passing the danger signal running ‘Sir Watkin’ into collision with ‘Bulkeley”.
     
    I found that there had been another accident on the Forest of Dean line in 1863, when a train of 70 wagons broke free and led to a ‘pile up’, said to be 15 wagons high, which took 5 days to clear! After that, trains were limited to 45 trucks, although these were reported to be ‘12 tonners’. My collection of 12 ton wagon models was built when I was struggling with a problem of ‘stringing’ with my Prusa 3D printer, so they form a motley collection, including some poorly-printed models.

    ‘Sir Watkin’ with Bullo Pill coal train with seven 12 ton wagons
     
    My last group of models comprises three of the engines ordered to Brunel’s impossible specifications. 'Vulcan' was the first engine to be steamed on the GWR, having been delivered by barge to West Drayton in 1837. I confess that these are my favourite models and are currently displayed on a case on a shelf in the living room, where their gleaming brass-work always attracts attention. As Brunel once wrote “we have a splendid engine of Stephenson's, it would be a beautiful ornament in the most elegant drawing room.”
     

    Brunel’s engines: ‘Aeolus’ (rebuilt), ‘Vulcan’, and ‘Eagle’
     
    In addition to all these, I also have made a model of a piston carriage as used on the South Devon Railway:
     

    South Devon Atmospheric Railway piston carriage and train
     
    So, what to do with all these models?
     
    One common factor in the early operations of the GWR is their close association with canals and docks.
     
    At the London end, materials for construction of the new railway were brought by the Grand Union Canal to depot set up at West Drayton, the place where Daniel Gooch first started his work for the GWR.  Notably, the first engine ‘Vulcan’ was unloaded from a barge there through the use of lifting tackle and a convenient Elm Tree!  Later, coal was delivered by sea and canal from Newcastle to coke ovens established between the canal and railway at West Drayton. Similarly, the small dock at Bullo Pill was used for the export of coal brought down by railway from the Forest of Dean.
     
    The first major civil engineering work on the GWR was the viaduct at Hanwell, named after Lord Wharncliffe, who had chaired the committee leading the GWR Bills on their passage through Parliament.
     

    Wharncliffe Viaduct - by P.G.Champion 8th July 2007- Own work, CC BY 2.0 uk,
     
    Other characteristic features of the early railway were the Brunel-designed stations, the round-house engine shed at Paddington, and the prolific use of wagon turntables for the movement of rolling stock at stations by manual labour and horses.
     
    I have an idea that it might be possible to illustrate these various features in a ‘generic’ diorama designed to capture the ‘character’ of the broad gauge... not forgetting, of course, that Elm Tree 🙂
     
    The 1879 OS map of the area around Bullo Pill dock contains many of the features that I would like to represent. I could modify the ‘dock’ into a generic canal basin and rotate the main line running North-South over a viaduct on the left hand side of the map to run across the top as a backdrop to the scene.
     

    Extract from OS 25” maps surveyed 1879 CC-BY license as shown
     
    I’d be interested in any suggestions my readers might want to make about how this could become an interesting scene covering a wide range of potential presentations.
     
    Mike
     
     
  20. MikeOxon

    A Missing Link?

    By MikeOxon,


    General
    In my last few posts, I’ve been delving into the almost lost world of the early days of the GWR broad gauge. I notice that my previous post aroused little comment so, perhaps, I have moved rather too far from what most people think of as ‘railway modelling’ - but I do like using models as a way of improving our understanding of these early engines.  I do appreciate the various 'likes' that many of you have given me.
     
    Before I move back into more familiar territory, there is one more piece of history to record, regarding an engine that may not have existed at all – at least not in the form in which it was described.
     
    Francis Whishaw on the GWR
     
    One of the earliest books to survey the British railway scene was Francis Whishaw’s “The Railways of Great Britain and Ireland” of which the 2nd edition, with additional plates, was published 1842.
     
    He wrote “THE Great Western Railway is by far the most gigantic work of the kind, not only in Great Britain, not only in Europe, but, we venture to say, in the whole world. Mr. Brunel, not satisfied with the beaten track pursued by those who had gone before him, determined on carrying out this important work on entirely new principles; and, notwithstanding the numerous adversaries he has had to contend with from every quarter, has thus far been eminently successful in his favourite project, and will, no doubt, ere another summer shall have passed away, pronounce this mighty work to be completed throughout.”
     
    I should add, though, that Whishaw did go on to criticise the great increase in the costs incurred, over the original Parliamentary estimate … something with which we are all too familiar!
     
    Concerning locomotives, Whishaw left us with a puzzle, when he wrote :“we have ... classified these machines according to their magnitude, and the gauge of way to which they severally belong. Thus the six-wheel engines for the seven-feet gauge, as those on the Great Western Railway, belong to class A ; ...An engine belonging to class A is shewn in elevation in Plate 1, the frontispiece. and sections and details of an engine belonging to this class are exhibited in Plates 7, 8, and 9.”
     
    Whereas Plate 1 shows a locomotive of the ‘Firefly’ class, the engine shown in Plates 7, 8, and 9 does not correspond to any engine known to have worked on the GWR!:
     

    Whishaw Plate 7
     

    Whishaw Plate 8
     
    Whishaw does not specifically state that this is a GWR engine, although that assumption has been made by many later writers and is reasonable, considering that no other British railway used a 7 foot gauge..  The image has also sometimes been referred to as being a member of the ‘Firefly’ class, which it superficially resembles, at first glance.
     
    I have also noticed that there are many similarities between these drawings and the example of Stephenson’s ‘Patentee’ engine, illustrated in Tredgold’s ‘The Steam Engine, Vol II’, Plate LXXXXIX (99), published 1838. To demonstrate this, I overlaid the two drawings to the same scale, as shown below:
     

    Comparison between Whishaw’s Plate 7 and Stephenson’s ‘Patentee’
     
    Creating a 3D Model
     
    I decided to create a 3D model based on Whishaw Plates 7 and 8, shown above. As usual, I imported the two images as ‘canvases’ into ‘Fusion 360’. I used the various sketching tools in this software to create drawings, which I could then extrude to create the main components of the engine. I also copied details of the frames and axle guides from the drawing of the ‘Patentee’ engine in Tredgold’s book..
     

    Examples of Components extruded from Whishaw plates
     
    Once I had extruded all the necessary components, including use of the ‘revolve tool’ for the chimney, safety valve, and manhole cover, I assembled them together, within the Fusion 360 software, and created a ‘rendered’ 3D image:
     

    My 3D model created from Plates in Whishaw.
     
    Comparing Models
     
    When viewing the images of the Whishaw engine in isolation, it is not difficult to conclude that this image has similarities with the GWR ‘Firefly’ class. That idea is quickly disposed of, however, when I bring together the above model with the model of ‘Argus’, a member of the Firefly-class that I created in 2021.. Note that both these models were created to the scales indicated on the original drawings.
     

    My 3D models of the Whishaw engine and Firefly-class ‘Argus’ brought together
     
    Once the two models are placed together, the profound differences between their overall dimensions is immediately apparent! Notice too, the much lighter frames and smaller driving wheels of Whishaw’s engine.
     
    Similar Engines
     
    There was a Stephenson 2-2-2 of the ‘Patentee’ type, named ‘Harvey Combe’, which was built n 1835 and was used by Messrs. Cubitt, the contractors, during construction of the London and Birmingham Railway near Berkhampstead. The scene was captured by the artist J.C.Bourne, as shown above in my header image:
     
    According to an article in ‘The Engineer’ by J.G.H. Warren, dated 24th Sep.,1926, Nicholas Wood, in a “Report to the Directors of the Great Western Railway,” December 10th, 1838, gave results of experiments on the ‘Harvey Combe’ of the London and Birmingham Railway, to compare with contemporary experiments with the North Star of the Great Western Railway.
     
    I have not read Wood’s report in full but it suggests the possibility, at least, that similar engines might have been used by contractors engaged in construction of the GWR. It does seem to me that an engine similar to that shown in Whishaw would have been far more suitable for that task than the large-wheeled engines specified by Brunel, as the initial engines for the GWR.
     
    Perhaps, then, the engine shown in Whishaw’s book represents a ‘missing link’ between the engines built by Stephenson for the London and Birmingham railway and an engine or engines used during the construction of the broad gauge GWR?
     
    Mike
  21. MikeOxon

    A Galaxy of Stars

    By MikeOxon,


    General
    In my previous post, I wrote that I needed to make a model of one of the longer-boilered ‘Stars’, to see if it made a better comparison with the photograph taken at Cheltenham shed around 1850.
     
    According to the RCTS booklet Part Two, two ‘Stars’ were built with boilers that were 2 feet longer than the others – these were ‘Rising Star’ and ‘Bright Star’. We are very fortunate that E.T. Lane not only made several sketches of ‘Rising Star’, including end-elevations, but also produced a finished and very detailed drawing of the same engine.
     
    E.T. Lane
    I have made considerable use of sketches by E.T. Lane in my blog posts, so I thought I should find out a little more about him. It proved to be a far from easy search but I eventually found information on the ‘Ancestry’ website.
     
    Edward Theophilus Lane, to give his full name, was one of two sons of the engraver and lithographer Richard James Lane. Both sons died young.
     

     
    Richard James Lane, was born at Berkeley Castle in 1800, He became a Royal Academician and, in 1829, he drew a well-known portrait of the young Princess Victoria, later to become Queen. In lithography, he is reputed to have attained a delicacy and refinement which have never been surpassed.
     
    In addition, Edward’s grandmother was a niece of the celebrated painter Gainsborough, so there was a history of artistic talent running in the family.
     
     
    With that background, it is hardly surprising that Edward should have developed his own artistic talent, with which he chose to provide us with a remarkable series of sketches and drawings of engines and other rolling stock at Swindon, up to his early death at the age of 20. In addition to sketch books, he left 41 sketches of locomotives, carriages, and wagons on separate sheets.
     
    It seems likely that he succumbed to one of the many epidemics that plagued ‘New Swindon’ in those years, including outbreaks of cholera and smallpox. He must have returned home to London, where he was buried at St. Pancras in 1850.
     
    His elegant drawing of ‘Rising Star’ stands as a fine example of his art:
     

    Finished drawing of ‘Rising Star’ by Edward Lane, dated April 25, 1849
     
     
    My 3D-model of Rising Star
    I created my model by modifying the drawings of ‘Evening Star’, described in my previous post. I lengthened the frames by inserting an additional 8 mm (scale 2 feet) between the leading and driving wheels and, similarly, I extended the boiler length by 2 feet. I created a new firebox. which had a reported case length of 5 feet, as opposed to 4’ 10” on ‘Evening Star’. I also created a new ‘haycock’ top, to the profile shown in the Lane drawing. On the sketches by Lane, the smokebox is shown as 1” longer than ‘Evening Star’, while the trailing wheels have only 14 spokes compared with 16 spokes on the leading wheels. (this last is a characteristic shared with his sketch of ‘Vulcan’ and applied to my model of that engine.
     

    My 3D-model created by reference to Lane’s drawing
     
    These various minor differences demonstrate the way in which each of these early engines was ‘hand made’, with various small discrepancies between one engine and the next, apart from any significant design changes. As I pointed out in my earlier post ‘From the Stars to Firefly’, the great innovation by Gooch was to ensure that all his Firefly-class engines were built to standard templates, so that components were interchangeable between different members of the class.
     

    My 3D-model of Rising Star
     
    My two models of ‘Evening Star’ and ‘Rising Star’, rendered in ‘Fusion 360’, appear together below. These are not ‘finished’ models but are intended simply to show the more obvious differences between members of the same class. Neither Lane’s drawing nor his sketches of ‘Rising Star’ show a manhole cover on the ‘haycock’, so I have not included one in my model, although I strongly suspect that one was, in fact, present on the prototype.
     

    My 3D-models of ‘Evening Star’ (left) and ‘Rising Star’
     
    My next ‘test’ is to see how my model of ‘Rising Star’ compares with the engine in the photograph taken at Cheltenham:
     

    My model of ‘Rising Star’ compared with Cheltenham photo
     
    Of course the match is not perfect. It is, in fact, rather difficult to adjust all the display parameters, so that the ‘Fusion 360’ model has the same perspective as the photograph. I do believe though that the longer boiler matches the photo rather well and that the firebox is more appropriate than the one on Lane’s sketch of ‘Evening Star’. Without more information about the photograph, which is probably lost in the mists of time, I can’t take matters any further.
     
    Expanding the Galaxy
    There is another finished drawing by Edward Lane of the last of the Stars, ‘Royal Star’, delivered in November 1841, four years after the first of the class – the famous ‘North Star’ – and some time after many of Gooch’s own Firefly-class had entered service.
     
    ‘Royal Star’ reverted to the shorter (8’) boiler used on ‘Evening Star’ and the most obvious difference from the earlier engine lay in the shape of the firebox casing. This was shorter (4’ 6” length) and taller, with wood-lagged sides in the shape of a ‘Gothic arch’ up to the high-mounted safety valve casing.
     
    I made a ‘haycock’ top some years ago by a rather convoluted method.  With more knowledge of the tools in ‘Fusion 360’, I tried a simpler method but it was soon obvious that adding the wooden lagging to the curved sides of the ‘Gothic’ box was going to be a new modelling challenge!
     
    To create the Gothic box, I first made a cuboid box and then drew the ‘Gothic’ profile on one side. I then used the ‘push-pull’ tool in Fusion 360 to produce the ‘Gothic’ arch in one direction. After that, I rotated the box though 90 degrees and repeated the ‘push pull’, to create the second, orthogonal arched profile. A diagram helps:
     

    Creating ‘Gothic’ Firebox in Fusion 360
     
    That proved to be a very straightforward method but adding the planked lagging needed more thought. I eventually found a solution from watching this video on YouTube..
     
    For this solution, I created a new body by extruding from the inner outline I had already sketched, as shown in the diagrams above. I then slid this body through the firebox body – fortunately, this is allowed in the virtual world, where bodies pass freely through one another! Next, I had to cut the arched faces of this new body to match the profile of the firebox itself. Again, a diagram helps:
     

    Creating the Lagging on Firebox Sides
     
    The finishing touch was to represent the planks of the wooden lagging To do this, I made a single horizontal slot near the bottom of a lagged side. I then used the ‘pattern on path’ command in ‘Fusion 360‘ to repeat this feature upwards, along a path following the profile of the side of the firebox. This procedure almost magically created the feature that I wanted.
     

    My 3D-model of a Gothic Firebox for Royal Star
     
    All that remained was for me to place this firebox into my model of ‘Royal Star’, which was mainly just a copy of ‘Evening Star’:
     

    My 3D-model of Royal Star
     
    Later Re-builds
    Most of the ‘Stars’ were converted into Tank engines during the 1850s. The conversion included replacement of the leading 4’ diameter wheels by pairs of 3’ 6” diameter wheels and lengthening of the boiler to 10 feet, where this had not already been done.
     
    Since I now had the ‘bit between the teeth’, I thought I would illustrate this later development by modifying my model of ‘Rising Star’, which already had a 10’ boiler. The re-design was generally straight-forward: just adding a saddle-tank and bunker. These parts were similar to those I have previously designed for my model of ‘Leo’.  The most difficult modification was to redesign the front end of the frames to accommodate the paired wheels. It didn’t take very long, however, before I had a 3D-model, which I have named ‘Red Star’
     

    My 3D-model of ‘Red Star’
     
    One again, I should point out that these are not ‘finished’ models but are only intended to indicate the different characteristics of the various members of the ‘Star-class’. I hope I have shown that not all GWR engines look the same!
     

    My Galaxy of Stars
     
    There’s a lot more work needed before any of these become printable models but that means I have plenty of material to keep me going through the coming winter months 🙂
     
    Mike
  22. MikeOxon

    A Tangled Web

    By MikeOxon,


    General
    I’ve referred before to the problems that arise from using published drawings as the basis for creating 3D models of early locomotives. The usual dictum of “find a photograph of your selected prototype” simply doesn’t apply to the years before photography became established.
     
    That leads to the next problem – so much of the information we read about early locomotives comes from books that were written decades after the time to which they refer. Even Gooch’s own ‘diary’ is considered suspect, since the pages about the early years were clearly written much later. It’s by no means a new problem either – Sekon, in his book ‘The Evolution of the Steam Locomotive’, published in 1898, made the following comment: “Readers may wonder why such obviously inaccurate statements should be published. One can only conjecture. Many lists of early locomotives have during the past few years been published. These should, however, be accepted with the very greatest caution.”. Matters have got considerably worse with the passage of much more time!
     
    We are very fortunate to have the sketch books and drawings made by the young apprentice at Swindon in the 1840s, Edward Lane, who sadly died at the age of 20. In his short life, he made an invaluable record for posterity of first-hand views of early Broad Gauge locomotives and other rolling stock. Even though many of his illustration are only rough sketches, they present a ‘from life’ impression and many of them are annotated with measurements and additional sketches of small details.
     
    Much later, early in the 20th century, another set of illustrations was produced by G.F. Bird and these appeared in a special supplement to ‘The Engineer’ magazine. Later still, after WW2, the RCTS produced a booklet covering the Broad Gauge Engines of the GWR as Part Two of a series on GWR Locomotives. On page B3, the booklet comments that “Bird's line drawings, the early ones mainly derived from the sketches and drawings made by E. T. Lane at Swindon in 1848/9, still remain a classic. They are the only known illustrations of many of the early engines and some are used yet again in this volume”. We must not, however, forget the caution sounded by Sekon back in 1892 and, from my own experience, Bird appears to have misinterpreted some of the information contained in Lane’s sketches.
     
    In replying to comment in my previous post about Leo-class engines, I wrote that “Another example I have found is the case of 'Evening Star', where Lane shows appropriate-looking safety valve covers but with figures above them that seem to indicate a much larger diameter. Bird has drawn extremely fat covers, presumably based on his reading but, to me, they do not look 'right'.”
     

    Comparison of sketch by Lane and later drawing by Bird
     
    I reported that “One day, I must study this engine in more detail”, so here goes!

    Modelling ‘Evening Star’
     
    In the case of the ‘Stars’, we are especially fortunate to have a couple of very early photographs of three Broad Gauge locomotives outside Cheltenham shed, possibly as early as 1848. One of the engines is alleged to be ‘Polar Star’, although I have not found a good reference to the source of that attribution.
     

    Early Photographs taken in Cheltenham c.1848

    According to the RCTS Part Two, ‘Evening Star’ was similar to ‘Polar Star’, so the photographs shown above are a useful point of reference.
     
    I also wanted a larger version of the Bird drawing than that shown in ‘The Engineer’ supplement published 16th December 1910, which included charts showing various Broad Gauge engines. This led me to another of the pitfalls that are frequently encountered with published drawings! I turned to Arman’s ‘Broad Gauge engines of the GWR, Part1’, published 2018, where on p.82, there is a reproduction of Bird’s drawing from the Locomotive Magazine 1901. It is immediately obvious (from the elliptical wheels) that this reproduction is compressed in the vertical direction. These distortions always have to be watched out for!
     
    Returning to the Lane sketch, I decided to create a sketch in Fusion 360, using Lane’s written dimensions. The result, shown below, looks to be proportioned similarly to the Bird drawing.
     

    My Sketch based on Lane’s Dimensions
     
    Although some Lane sketches appear to be accurately proportioned, this one clearly is not. Even some of his written dimensions appear to be incorrect. For example, the overall length of the boiler between smokebox and firebox is clearly marked as 7’ 9” (31mm in 4mm scale) but there are three figures written below, apparently referring to the boiler rings, that do not add up to this total – they are “2.3”, “4.3”, “3.2”. Perhaps the central figure refers to the boiler diameter over the cladding?
     
    At this point, I must state that I have not made any pilgrimages to Kew or York, to study original drawings. I note that there is a lot of detailed information about dimensions of the various ‘Stars’ in the RCTS booklet but I do not know the original sources. Therefore, please exercise the caution advised by Sekon, when reading the following paragraphs concerning my own speculation.
     
    Now I return to the matter of the safety valve casings. The ‘Polar Star’ photos do not show any fitted on the boiler of ‘Polar Star’, so these photos are of no help. The only guide I have is that Lane’s ‘from life’ sketch shows tall, narrow casings, similar to those on the ‘North Star’ replica in Swindon Museum, rather than the odd-looking fat tubes in Bird’s drawing.
     
    I have been looking at other Lane sketches for clues and found one of ‘Hesperus’, a ‘Sun-class’ engine, with a carefully drawn casing but, unfortunately, without any dimensions being shown. To my eyes, it looks like a better-drawn version of the casings shown on the rough sketch of ‘Evening Star’. The plinth is wider than the main column and I suggest could be the source of the “1” dimension, marked on the ‘Evening Star’ sketch. Perhaps, I am just adding more ‘errors’ by my speculations but I am influenced by the ‘jizz’ of Lane’s sketch.
     
    So I have continued to create a 3D-model in Fusion 360, drawing on the information contained in the photographs and the Bird drawing, as well as the Lane sketch, to re-create the frames and the haycock top of the firebox. The RCTS Part Two states that the firebox casing on ‘Evening Star’ was 4’ 10” long, which agrees exactly with Lane’s dimension, so I am content to use this figure.
     

     

    My 3D-model of ‘Evening Star’ created in Fusion 360
     
    Now, though, I come up against a major discrepancy between the Lane drawing of ‘Evening Star’ and the supposedly similar ‘Polar Star’, alleged to be the engine in the Cheltenham photograph.  In Lane’s sketch, the joint between the rectangular firebox and the ‘haycock’ top is well below the level of the boiler top, whereas the photograph shows a much taller rectangular box with a more ‘squashed’ haycock top.
     
    In the caption to the Cheltenham photographs on p.84 of Arman’s book ‘Broad Gauge Engines of the GWR, Part One’, he asserts that “Polar Star had its frames and boiler lengthened by 2’ 0” by 1849, so we can date the photograph as prior to that work being carried out”. I am not at all sure about that. I oriented my model in Fusion 360 as closely as I could to one of the Cheltenham photographs and the comparison shows that the boiler appears significantly longer in the photo, ahead of the driving wheels, than in my model:

     
    My 3D-model of ‘Evening Star with photograph of ‘Polar Star’
     
    As a further test, following a method I have used on other photographs, I used the ‘perspective’ control in 'Photoshop' to allow comparison between the diameter of the driving wheel (known to be 7’) and the length of the boiler in the photograph of ‘Polar Star’
     

    ‘Cheltenham Photo’ with Perspective Adjustment
     
    Knowing the diameter of the driving wheel was 7 feet, this comparison indicates the boiler length was (330/230) x 7 feet, i.e. 10 feet. This supports my suggestion that, at the time of the photograph, the frames and boiler of the ‘Star’ had been lengthened by 2 feet from the original 8 foot boiler length. The design of the firebox also matches Lane’s sketch of ‘Rising Star’ which was built with the longer boiler.
     
    It now looks as though I shall have to make a model of ‘Rising Star’ to take this investigation further!
     
    Mike
     
     
     
  23. MikeOxon

    Photographic Evidence

    By MikeOxon,


    General
    Having wandered into South Devon territory with my atmospheric caper, I started to look at some of the steam engines used on that line. I realised that, although I have modelled several early passenger engines, including the Firefly class, I have not tackled any of the early goods engines.
     
    The Leo class 2-4-0 were built as goods engines, starting in 1841. It was soon realised, however, that they had insufficient adhesion weight, so all the engines were converted to carry saddle tanks. We are very fortunate that the young draftsman, E.T.Lane made sketches of ‘Leo’ both before and after conversion at Swindon Works in 1849. In fact, his two sketches were dated 13th September 1849 and 21st September 1849, which indicates how rapidly the conversion was carried out! Although these are only notebook sketches, I found that overlaying the two versions showed how similar they are and indicates that the sketches are actually rather accurate. Many of the key dimensions are written on the sketches, although the later one only shows those which changed as a result of conversion. Unusually, he also sketched end elevations for the tank engine.
     

    Sketches by E.T.Lane of Leo at Swindon in 1849
     
    I decided that the saddle tank version was the one I would like to model and so I started to examine the available information in more detail. I should mention that there was a later ‘upgrade’ to many of these engines, when larger bunkers were fitted and that there are a few photos available of the larger-bunkered form. They must have been useful engines, because many of them survived until the great cull of Broad Gauge stock in the 1870s.
     
    I have mentioned before that caution is needed when taking dimension from drawings. In the present case, G.F. Bird made some more ‘finished-looking’ drawings, clearly based on Lane’s sketches, early in the 20th century. When I looked at one of these, reproduced in Mike Sharman’s book of Broad Gauge drawings, I thought that the tank tops looked very low, in comparison to the Lane sketches drawn from life. This could be seen clearly when I overlaid the Bird drawing over the Lane versions:
     

    Three drawings overlaid
     
    There are actually three drawings here – the first by Lane as a tender engine (Red), the second by Lane after conversion to a tank engine (Black), and the Bird drawing (Blue). Considering they are described as ‘sketches’, the Lane versions appear remarkably consistent in their scaling but the Bird drawing is very different in its portrayal of the tank.
     
    Fortunately, there is a good photo of ‘Aries’ (Leo-class) standing outside Faringdon shed, probably in the late 1860s by which time its bunker had been enlarged. Although it is not quite side-on, it is possible to compare the overall height of the tank with the diameter of the driving wheels (known to be 5 feet). The result looks to be much closer to the Lane sketches than to the much later Bird drawing (overlaid in red).
     

    Comparison of photo with Bird drawing
     
    To take the matter further, I decided to create a 3D model that I could then align with the photograph, to check how well the Lane dimensions agreed. I extruded the tank body, using ‘Fusion 360’, from one of the Lane end-elevation sketches and created the boiler as a cylinder, scaled from the prototype dimensions of 8’ 6” length by 3’ 6” diameter, as shown below:
     

    Extruding from drawings in Fusion 360
     
    I copied the frames and buffer beams, by extruding in my usual way, and ‘borrowed’ a Haycock-style firebox from my earlier ‘Firefly’ model.  Next, I assembled all these parts together, within ‘Fusion 360’, and then imported the photo of ‘Aries’ at Faringdon as a ‘canvas’. I could now rotate my basic 3D model until it appeared to be in a similar orientation to that shown in the photograph.
     

    Model and ‘Canvas’ in Fusion 360
     
    I then overlaid the model and photograph, in order to compare the major dimensions. The result, shown below, confirms that the Lane sketches are an accurate representation of the height of the saddle tank.
     

    Overlay of my 3D model and photo of ‘Aries’
     
    This is one of those rare occasions when one of the early engine designs survived long enough to appear in a good photograph. I have used 3D modelling as a research tool, to validate Lane’s sketch and to show that the much later Bird drawing is not accurate.
     
    Having got this far, I suppose can now proceed with a complete model of a Leo-class tank engine. According to Ian Pope & Paul Karau’s book “The Forest of Dean Branch, Vol.1”, the former station master at Cinderford recorded that the line was opened with a Leo-class engine ‘Virgo’, so I even have an excuse to include this engine in my ‘Bullo Pill’ collection .
     
    Mike
  24. MikeOxon
    Assembling the Parts
     
    In tackling the assembly of the components that I printed as described in Part 2 of this series, I was reminded of President Kennedy’s words “We choose to … do the other things, not because they are easy, but because they are hard“
     
    I had realised that the assembly of the parts was not going to be easy but it turned out even trickier than I had expected. To re-cap, the parts I printed were as shown below:
     

    3D printed Atmospheric Apparatus Components
     
    The tricky aspects arise from the need to align the four axle bearings with the appropriate axles. The locations of these axles are, in turn, determined by the placement of the axle boxes on the main carriage under-frame.
     
    My idea was to suspend the hangers, which carry the cylinder frame and the two cylinders, from a brass rod passing across the centre of the octagon. The inboard ends of the longitudinal frames have sockets to accept the ends of this brass road, thus holding together the entire upper part of the apparatus. I included holes in the octagon and hangers, plus sockets in the longitudinal frames, within the 3D models of these components and, rather to my surprise, they actually appeared as required from my basic 3D printer.
     
    A little opening out with a reamer was all that was required to enable a 1mm brass rod to pass through the octagon and the hangers, as I had intended. This stage of the assembly is shown below:
     

    Octagon, with Hangers suspended from Brass Rod
     
    In this photo above, the octagon is actually upside down, as I soon realised, but it does show the method of assembly quite clearly. I used superglue to attach the lower ends of the hangers to the piston frame, then clamped these parts together to allow the glue to harden.
     
    Next, it was time to press the longitudinal frames onto the ends of the brass rod and align the whole assembly with the axles of the carriage wheels. At this point, I realised that the octagon was upside down and also that the brass road had to be removed to allow the central axle to pass through the bearings on the octagon – now turned downwards.
     
    Getting everything to fit together proved to be something of a trial! [understatement] The parts are small and it was difficult to hold every thing still, in order to set up the correct alignments. Fortunately, the brass rod was quite a firm fit into the ends of the longitudinal frames, so this helped me to wiggle everything into place, without it all falling apart.
     
    I think some more thought about this part of the assembly might result in a better method but we are where we are! After a certain amount of cursing and swearing, the assembly looked like this:
     

    Atmospheric apparatus attached to Carriage Chassis
     
    It was a great relief when I found that the sloping longitudinal frames did not clash with the lateral parts of the carriage frame, although it was close! My 3D model proved itself to be accurate!
     
    When in the operating position, the piston carriage hangs below the level of the running rails but, in my model, it is hinged like the prototype, so it can be swung to one side to allow this vehicle to run on normal track.
     
    All that remained was to attach the two pistons, connected by a brass piston rod to the piston carriage and the model was complete – hurrah!
     

    My 4mm scale 3D-printed model Piston Carriage
     
    On the evidence of the contemporary paintings by William Dawson, it seems most probable that the carriages were painted brown overall, so I have adopted this colour for my model.
     
    After fettling, painting, and general ‘tidying up’ of the model, I posed it on my short length of broad gauge track. The roof is covered in self-adhesive vinyl. I used a leather punch to create holes in the vinyl for the oil lamp housings. The windows are glazed with overhead transparency sheet. The piston for the atmospheric apparatus can be seen below the front buffer beam of the carriage.
     

    My 4mm scale model of SDR Piston Carriage
     
     
    The Atmospheric Train in Operation
     
    To add a sense of realism to the scene, I placed a few of my models against a back-scene representing the red sandstone cliffs at Dawlish Warren:
     
     

    Diorama showing some of my Broad Gauge models

    I think it might be useful to add a few notes on how the trains were operated and how the pistons under the carriage were inserted into the propulsion pipe.
     
    The first point is that the system was designed for single-line working only. Because the flap valve was hinged to one side of the slot along the top of the pipe, it had to be raised by the apparatus below the carriage from the side opposite to the hinge. Research by the BGS strongly suggests that the hinge ran along the ‘seaward’ side of this coastal railway, from which it follows that the lifting apparatus must work from the landward side. Surprisingly, the protective metal covers, shown in Samuda’s Patent illustrations, were not fitted, despite the obvious detrimental effect on the leather arising from the seaside environment.
     

    Patent Illustration showing hinged leather seal
     
    Because of this ‘handed-ness’ the carriage always had to work in one orientation and could not be turned. That is why there had to be two pistons and driving compartments at both ends. Brakes were only fitted to the wheels on the landward side, so the drivers position was towards that side, where the brake operating levers were situated.
     
    The propulsion pipes were laid in 3 mile lengths, each length attached to a pumping station. Flap valves at the ends of the pipe were opened in response to a trigger device, operated as a train approached the end of one of the pipes. Once the pistons had entered the evacuated pipe, the driver had no means of regulating the speed of the train other than by applying the brake.
     
    The propulsion pipes stopped short of stations and the train ‘free-wheeled’, in the manner of a slip coach, after leaving the pipe until stopped, hopefully at the station platform, by the driver. Under- and over-runs were apparently not infrequent. At that time, manhandling or horse-shunting of railway vehicles were not unusual and these were, in general, the only methods available, if the train had to be moved when ‘off’ the pipe.
     
    The exception was for starting a train from a station. An auxiliary pipe was laid alongside the track ahead of each station. This pipe contained a piston attached to a length of rope that could be hooked to the front of the piston-carriage. The rope started the train into motion until the pistons entered the main propulsion pipe, when the driver released the staring rope. The flying end of the rope was a potential hazard to any gangers that might be near the line at the time!
     
    Before the train could start, the pumping engine for the appropriate section of pipe had to be operated. This was done according to the timetable so, if a train was late, the pumps had to be run for much longer than was strictly necessary, which increased the costs of running the system. Curiously, although the electric telegraph was installed along the line, it was never used to signal when the pumps were needed!
     
    Whenever the piston carriage had to be taken off the main line, its atmospheric apparatus had to be raised, in order to clear any pointwork and crossings. This was achieved by use of a winding handle fitted into a socket on the seaward side of the carriage.
     
    All these factors were clearly inconvenient, when compared with the flexibility of steam locomotive working.
     
    For any one who wishes to learn more about this railway, I can recommend the book ‘Brunel’s Atmospheric Railway’ which, apart from containing the set of 25 contemporary watercolour illustrations by William Dawson (1790-1877), provides extensive text and drawings, edited and produced by Paul Garnsworthy of the Broad Gauge Society (BGS). A new edition has recently been printed.
     
    Addendum
     
    Robert Stephenson carried out a technical review of the Kingstown & Dalkey atmospheric railway in Ireland in 1844.
     

    Kingstown & Dalkey atmospheric railway
     
    His conclusions were:
     
    1st That the atmospheric system is not an economical mode of transmitting
    power, and inferior in this respect both to locomotive engines and stationary
    engines with ropes.
     
    2nd That it is not calculated practically to acquire and maintain higher
    velocities than are comprised in the present working of locomotive engines.
     
    3rd That it would not in the majority of instances produce economy in the
    original construction of railways, and in many would most materially augment
    their cost.
     
    4th That on some short railways, where the traffic is large, admitting of trains
    of moderate weight, but requiring high velocities and frequent departures, and
    where the face of the country is such as to preclude the use of gradients suitable
    for locomotive engines, the atmospheric system would prove the most eligible.
     
    5th That on short lines of railway, say four or five miles in length, in the
    vicinity of large towns, where frequent and rapid communication is required
    between the termini alone, the atmospheric system might be advantageously
    applied.
     
    6th That on short lines, such as the Blackwall Railway, where the traffic is
    chiefly derived from intermediate points, requiring frequent stoppages between
    the termini, the atmospheric system is inapplicable ; being much inferior to the
    plan of disconnecting the carriages from a rope, for the accommodation of the
    intermediate traffic.
     
    7th. That on long lines of railway, the requisites of a large traffic cannot be
    attained by so inflexible a system as the atmospheric, in which the efficient
    operation of the whole depends so completely upon the perfect performance of
    each individual section of the machinery.
     
    I remain, Gentlemen,
    Your most obedient servant,
    ROBT. STEPHENSON.
     
    Stephenson’s assessment, especially his 5th point, is being re-applied with modern technology in both Indonesia and Brazil. See https://www.youtube.com/watch?v=GM2Zxn7ybNQ
     
     
    Mike
  25. MikeOxon

    My Atmospheric Caper - Part 2

    By MikeOxon,


    General
    Introduction
     
    In Part 1 of this series, I described my model of the piston-carriage for the South Devon (SDR) atmospheric railway, based on drawings by Paul Garnsworthy in the Broad Gauge Society (BGS) Journal ‘Broadsheet’Nos 44 and 46.
     
    It’s been great to receive so many positive comments – clearly some of my viewers like reading about ‘forgotten’ corners of railway history. They spurred me into getting on with the next phase. Thank you!
     
    The carriage body was relatively straightforward, being similar to other broad gauge carriages that I have already modelled. I felt, however, that I should attempt to understand the workings of the system and I find that the best way of doing this is to build a model.
     
    There are several drawings in the Patent Application by Clegg and Samuda but these were only intended to illustrate their ideas and contain features that were never used in practical applications of their idea. It was pointed out to me recently by a fellow member on this site @drduncan that the principle is the same as that used in the steam catapults on aircraft carriers in the Navy. It was in that context that I found some very clear drawings that illustrate the principle very well:
     

    Slotted Pipe for Steam Catapult
     
    In the SDR application, the sealing flap was made from leather strips that were hinged along one side of the slot. This meant that instead of being lifted bodily, as in the illustration above, it had to be raised at an angle, from the side opposite the hinges.
     
    As a result of research by members of the BGS, negatives of drawings of the original SDR piston carriage were found in Bristol Museum and re-drawn by Paul Garnsworthy for the BGS Journal ‘Broadsheet’. This was no mean task, as the originals were not only very faded but consisted of a series of partial or split views, typical of the period. There are various plan and elevation views of the mechanism, which I found needed careful study to determine how the various components were arranged (N.B. I’m no expert in reading engineering drawings!)
     
    The description in the two ‘Broadsheet’ articles helped to shed light on the various complexities. The following is based on those articles
     
    How it Worked
     
    The chassis framing beneath the carriage was quite conventional for the period, except for the central bay, where a wide space was left for the atmospheric apparatus. This apparatus was carried by bearings on the wheel axles, with two bearings on the central axle and one each on the outer axles,
     
    The atmospheric apparatus. had its own substantial frame composed of iron plates, In the centre these formed an octagon, carrying the two bearings on the middle axle. From this octagon, longitudinal plates extended to single bearings located centrally on the outer axles. Two hangers, pivoted from the octagon, suspended a longitudinal plate, which hung below the carriage and passed through the slot in the top of the main propulsion pipe, set between the running rails. These hangers were angled to raise the leather sealing flaps on the opposite side from their hinges, running along one side of the slot.
     
    Once the hangers were inside the propulsion pipe, they were attached to a pair of 11 foot long piston frames. Between these frames there were five rollers, which functioned to raise the hinged sealing flap, fitted along the upper slot of the propulsion pipe, and let it down again, once the plate connecting the pistons to the carriage had passed. There were two additional rollers mounted on the main assembly, above the pipe, to ensure that the flap valve was pressed down firmly after the carriage had passed.
     
    Piston rods extended from each end of the piston frames, inside the propulsion pipe, to the pistons themselves, which were located towards each end of the carriage. The two pistons allowed the carriage to be operated in either direction, so that it did not need to be turned at the end of a journey.
     
    In operation, the propulsion pipe, set between the running rails ahead of the carriage, was evacuated by stationary steam engines. Atmospheric pressure acting on the piston from the back of the carriage then pushed the carriage and its train forwards. Behind the leading piston, the rollers on the piston frame raised the sealing flap so that the blade connecting the carriage to the pistons could pass through and then, towards the back of the piston carriage, a top roller re-made the seal, so that the pipe could be evacuated again for the next train.
     
    Creating my Model
     
    Once I had worked out how all the gubbins were supposed to work, I could start to create a model. The drawings show lots of additional rods and levers, not all of which are understood, so I concentrated on the major elements of the system.
     
    As usual, I started by importing drawings as ‘canvases’ in ‘Fusion 360’ and extruded the various components by tracing over these. Although the following description may seem straightforward, the actual design and fitting together of the various components involved a great deal of trial and error!
     
    I started with the main carriage frame, which provides an overall orientation reference and defined the mounting points for the wheels and axles. I added the springs and axleboxes by the same methods as for my earlier designs.
     

    3D sketch of carriage underframe and wheels
     
    With these key reference points in place, I could then start to create the atmospheric equipment, described above, around them.  As usual, I extruded these parts from a drawing. I placed axle bearings on the central octagonal plates and on the longitudinal plates, in their proper locations over the three axles.
     

    The frame (red) carrying the atmospheric equipment underneath the carriage
     
    The next major component to create was the piston frame and pistons, which ran inside the propulsion pipe when the train was operating. This component is made up of several parts: two frames, the piston rods, the pistons themselves, rollers, and the hangers which couple this component to the octagon and thence to the train..
     
     

    The piston assembly that runs inside the propulsion pipe
     
    In the prototype, the hangers were connected to the octagon on pivots. These allowed the complete piston assembly to be raised clear of the track, in case the piston-carriage had to be attached to a normal train or simply to negotiate points and crossings (which were another problem for the atmospheric system)
     
    Having created the various parts separately by tracing over the drawings, I then used the ‘move’ tools in ‘Fusion 360’ to bring them together into the correct alignment. At this stage, it became apparent that several minor adjustments to dimensions were necessary, to ensure that all the parts fitted together neatly in the correct orientations. I made two screen shots of the assembly: first with the pistons in the operating position and then hinged to one side by 45°, in order to clear normal trackwork.
     
     

    The Atmospheric Equipment in raised and operating positions
     
    I should re-emphasise that these 3-D sketches are simplified, to illustrate the basic operating principles of the atmospheric equipment. The raising of the piston assembly was achieved by pinion gears and shafts, which could be operated by a removable handle, rather like the starting handle on an old-fashioned car. Other control rods could adjust the pressure applied by the flap-closing rollers, as appropriate for the direction of travel. There may also have been linkages to open relief valves in the pistons since, apart from applying the brake, there was no provision for regulating the speed of the train.
     
    This last factor once caused a major panic for the crew of a train on the Kingstown and Dalkey Railway, when they forgot to attach the piston-carriage to its train before starting. It is said that the carriage, operating as a ‘light engine’, reached a speed of 80 mph but, fortunately, was stopped before there was a disaster at the top of the incline!
     
    In addition to the atmospheric gear, a braking system, controlled by handles in both the driving positions at the ends of the carriage, was fitted to operate on one side only.
     
    Printing the Model
     
    It was immediately apparent, from the small sizes of some of the components, that a working model in 4mm scale could not be created solely by 3D printing. In particular the various rollers and the piston rods would need metal components.
     
    Unless, however, I was also prepared to build some miniature slotted pipe and flexible valve strips, the model would not be operational anyway so, simply as a demonstration model, I felt that a realistic ‘impression’ could be obtained by taking a few ‘short cuts’.
     
    These applied mainly to the piston assembly that runs inside the propulsion pipe. I decided to embed the rollers within a solid piston carriage and run a brass wire longitudinally to connect this part to the two pistons. This proved more awkward than it sounds, as I also wanted a flat face, to lay on the printer bed but, after much trial and error, I found a solution that involved splitting the piston carriage into three printable pieces.
     
    I similarly embedded the two flap-closing rollers into the upper frame and fitted another brass wire across the length of the octagon, to carry the pivoting hangers. Now, at last, it was time to think about making some trial prints.
     
    Once I had a collection of what I considered to be ‘printable’ parts, I passed the drawings to the ‘Cura’ slicing program. At this stage, a few more problems emerged. I still don’t know how it happened but some parts were inclined at very small angles, such as 0.3 degrees. I do know that I have never experienced this problem before so, perhaps, there has been some change to the ‘Fusion 360’ software that allowed this to happen. Fortunately, it could be corrected by simple rotations in ‘Cura’, until the components lay flat on the printer bed.
     
    Another problem emerged because I had failed to note that the body of the piston carriage was unusually narrow for a broad gauge vehicle, at only 8’ 4” wide. I should have been warned by the comment in the ‘Broadsheet’ article that “Nevertheless, [the frames] came perilously close to the wheels (7’ 7 ½ ” over wheels / 7’ 8½ ” between solebar flanges”. I had left insufficient clearance between the body sides in my original design to fit around BGS wheelsets, so I have had to widen and re-print the carriage body.
     
    I knew that I was taking risks with some of the ‘printable’ parts I created but, in fact, my old Geeetech printer coped admirably with some rather small dimensions and awkward shapes. The first step was to print the main chassis members and fit the wheelsets. This went well, as shown below:
     

    My 3D-printed underframe and BGS Wheelsets
     
    The next step was printing the octagon and longitudinal members that carry the atmospheric apparatus. I designed these to be linked together by a brass rod passing across the width of the octagon, which I intend to use for suspending the lower parts of the equipment.
     
    Since these are all small parts, I added the piston frames to make a ‘set’ of parts for printing together. The complete set printed in just 19 minutes. As mentioned above, I simplified the design of these parts so that they all had flat faces that could lie on the printer bed. The ‘rollers’ are not movable but printed as integral parts of the frames. After printing, the complete set appeared as below:
     

    My 3D-printed Atmospheric frame parts
     
    I printed the remaining small parts as a separate group, since they all involved more complex shapes, which I anticipated might prove difficult. To minimise the possibility of these parts toppling over while printing, I selected the option in ‘Cura’ to surround each part with a ‘brim’. I prefer to avoid support structures whenever possible, as they can be difficult to remove cleanly – even very thin layers of printed PLA can be remarkably tough!
     
    In fact, even the very small ‘hangers’ came out better than I had expected, though the brim was not easy to remove from these. I find the only successful tool for this job is a finger-nail. I show these parts still in place on the printer bed - note that the cylinders are only 11 mm long. Note also the holes in the hangers, to allow them to be suspended from the octagon. The thin strips attached to the hangers are to allow these very small parts to be glued to the piston frame (the one with 5 rollers) shown in the previous illustration.
     

    My 3D-printed cylinders and hangers on Printer Bed
     
    As I mentioned above, I had to re-print the carriage body a little wider, in order for it to fit over the wheels, after which the whole kit and caboodle looked as below:
     
     

    All parts for my model Atmospheric Piston Carriage
     
    As with many jobs, it all looks quite simple now it’s done. Perhaps it’s down to my increasing age but this one cost me more “tears and sweat” than anything else I’ve made since I started trying my hand at 3D printing.
     
    I shall pause here for a stiff drink and then tackle the job of assembling all those small pieces, which will disappear out of sight underneath the carriage!
     
    I’m still thinking about the colour of the carriage. I think it looks nice and rather ‘rustic’ in brown.
     
    Mike
     
    Feature Photo - William Dawson, "From the Station in St Thomas to the Alphington Meadows", detail
     
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