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MikeOxon

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  1. MikeOxon

    William Dean's Express Tank

    By MikeOxon,


    general
    Being somewhat of a back-water in railway history, the Witney branch via North Leigh became home to many unusual vehicles, rarely seen elsewhere. I have already shown the standard-gauge Tilt Wagon ('Hat Box') but a particular claim to fame for this line was that it became the 'stamping ground' for William Dean's experimental 4-2-4 express tank engine, shown below entering North Leigh station.
     
     
     
     
     
     
     
     
     
     
     

    William Dean's experimental 4-2-4T No.9 at North Leigh
     
    My first encounter with this locomotive was many years ago, through the pages of John Gibson's “GW Locomotive Design - A Critical Appreciation”, which portrayed it as such an embarrassing failure that all traces of it had to be expunged from the record, with an order going out that 'this thing never existed'.
     
    If that were true, Dean would hardly have provided an article for 'The Engineer, Sept.24th 1886', with a detailed drawing of the unusual outside Stephenson valve gear. Dean explained that this arrangement was intended to get rid of the excessive cramping up of the valve gear, necessary when large cylinders have the valve chests placed between them.
     

    Outside Valve Gear on Re-built GWR No.9 (from 'The Engineer')
     
    In fact, Dean had arrived in office knowing that the Broad Gauge was nearing its end and a new type of locomotive would soon be needed, to replace the Gooch singles. Amongst the ideas to be tested was the possibility of using express tank engines, as designed successfully by Pearson, for the Bristol & Exeter railway. E L Ahrons, who arrived at Swindon in 1885, described the original configuration of the engine as having a 30' overall wheelbase, including two carrying bogies of wheelbases 7' 3" and 5' 6" respectively. He also stated that the length of the platform was 36' 5-5/8".
     
    Very much later (around 1940), E W Twining produced an outline drawing, purporting to show the layout of the tank engine. A comparison of his sketch with the detailed drawing of the valve gear in 'The Engineer' reveals that it is simply not possible to fit this gear between the front bogie and the driving wheel, if the longer bogie is placed at the front! In my opinion, Twining's chassis seems to bear a very considerable resemblance to the Lehigh Valley inspection saloon, still in existence at that time, even down to the bicycle-style 'mudguards' over the front bogie wheels.
     
    My own solution places the shorter bogie at the front and, with this configuration, a well-balanced design results. The front bogie fits neatly under the smokebox, leaving room for the outside valve gear, while the rear 7' 3" bogie fits immediately behind the firebox, within the overall 30' wheelbase. Apart from the reversed bogies, the dimensions conform to Ahrons' description.
     
    The construction of my model followed similar lines to those I have described previously, when I built my 'Queen'-class engine.  I built the engine in two parts: a rectangular chassis, carrying the driving wheels plus two bogies, and a box structure for the upper body. The boiler is represented by a half round section soldered into position between the two side tanks.  The steps in my construction are shown below:
     

     
    I have fitted an extended cab roof, similar to those used on other GWR tank engines in the same period, and a rear spectacle plate, appropriate for high-speed reverse running. Other features include cutaways in the tanks, to allow access to the motion, and tanks that extend a short distance in front of the smokebox, both as mentioned by Ahrons. The long (11' 6") boiler, in two rings, was designed to provide similar steaming capacity to the large-diameter boilers of the Gooch singles.
     
    My model wears the new livery, introduced in 1881, with Indian red frames and vermilion lining (though at that time the wheels were still green). With this presentation, I believe that the engine is worthy of the description given by David Joy, when he visited Swindon around 1882 "I saw all about a mighty 'single' tank engine ... I saw drawings and all, and she looked a beauty".
     

    My Interpretation of GWR 4-2-4T No.9
     
    The real significance of this engine was that, while it showed that the 4-2-4 express tank engine concept was not appropriate for the standard gauge, it addressed an urgent need to re-visit valve-gear design for more powerful engines. The eventual outcome was, of course, the famous Dean Singles, with the same length of boiler and direct-driven valves, mounted below the cylinders. The family relationship can be seen in the following extremely rare photo of these two engines, side-by-side at North Leigh:
     

    Dean 'Single' alongside its 4-2-4T pre-decessor at North Leigh
     
    My model currently only has 'cosmetic' outside valve gear, cut from plasticard with my Silhouette cutter. It is powered by a Tenshodo WB28.7 SPUD, contained within the rear bogie, in the same way that my 4-2-2 uses a similar one in its front bogie. The model negotiates my small-radius curves with ease and does not share a tendency for de-railing, which apparently afflicted the prototype!
     
    Update:  I have created a 3D computer model of this engine - see https://www.rmweb.co.uk/blogs/entry/26347-william-dean’s-express-tank-revisited/
     
    Mike
     
     
    references:
    Great Western Locomotive Design, John C Gibson 1984
    The British Steam Railway Locomotive 1825 - 1925, E L Ahrons, 1927
    Swindon Steam, L A Summers, 2013
  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
    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
  4. 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
     
  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
    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
     
     
  7. MikeOxon

    Search and Rescue

    By MikeOxon,


    general
    It was only when I looked at the photograph of "City of Truro", which I took yesterday, that I noticed that the nameplate was missing! About half of my track is in tunnel, so there was an evens chance that it had dropped off in the tunnel. Fortunately, I have a 'search and rescue' procedure.
     
    Some time ago, I became interested in the idea of shooting video from the footplates of my model locomotive. I found that there was a miniature video camera, popular with aircraft RC enthusisats, which was both very small and gave good quality results, recording HD video onto a micro-SD card.. The camera I bought is known as an '808 #11' and it is packaged within a car key-fob, as a rather dodgy-looking spy-cam. There is now a slightly larger, but conventionally packaged version, called the 'Mobius Actioncam'. You can read loads of information about all these cameras at: http://www.chucklohr.com/808/index.shtml
     
    In addition to having fun running the camera around my layout, I also mounted it on a wagon, together with a small LED torch, so that I could view inside the tunnels on my railway. I was surprised to see several bit of debris, fallen off passing trains, and was able to recover these through the various hand-holes that I provided in the baseboard.
     
     

     
    The small torch lights the track ahead and reveals any debris, as shown below:
     

     
     
    While on the subject of video, and since there are very few moving trains on these pages, here is a tiny movie that I call, with great originality, "Arrival of a Train". It shows my Stella-class 2-4-0, rebuilt from a Mainline Dean Goods, arriving at my station with a local train of four-wheelers. An original Mainline Dean Goods is waiting in the passing loop. (sorry it's so small - I was keeping within the 1MB limit)
     

     
    Mike
  8. MikeOxon

    Gilding Victoria

    By MikeOxon,


    general
    I've been starting to get my 'painting eye' in, by working on some of my 19th-century vehicles, before I attempt any people.
     
    For the Victoria carriage, described in previous posts, I first spayed the entire vehicle with red car primer. After that I painted the undergear, footboards, and folding hood with black acrylic. I chose Crimson Lake as the main body colour and painted all the relevant panels with Humbrol enamel (now RC403, though I used an ancient tinlet of HR116 - these paints seem to last for ever, providing the tin is well-sealed.) Once this was dry, I used Grass Green enamel (Humbrol 80) for the leather seats
     

     
    When I first put this model on the carriage-truck, I though it looked a little dull, so decided to brighten it up with some gold lining. It's easy to lose sight of how small this model is (at least in a 4mm modeller's eyes) but I found that 'extra fine point' pens, of the type intended for Birthday cards and the like, provided a fairly easy way to add the touch of brightness that was needed. I simply ran the tip of the pen, very lightly, along the edges of the mudguards and the hand-rails by the driving seats. I think it has given quite a 'lift' to the model and the photo below illustrates its small size alongside the pens that I used!
     

     
    It always surprises me how important a small bit of detailing can be in the appearance of a model. There's still some re-touching to do, and I must find some replacements for those rather very bent wheels
     

     
     
    Mike
  9. MikeOxon

    Slow Progress

    By MikeOxon,


    general
    Oil lamps are continuing to prove awkward!
     
    Following an appeal for help from the forums, I have established that the small circular fittings, adjacent to the lamp tops, are plugs to fill the apertures left when the lamps are removed for trimming and filling, rather than oil fillers, as I had originally thought.
     
    I've now drilled the roof of my U29 model, to take the lamp tops and have another small problem to solve! Since the roof slopes down from the sides of the clerestory, the lamps need small plinths to make them level. If anyone has a suggestion for a simple way to achieve this, I shall be pleased to hear from them!
     

     
    GWR dia.U29 with sloping lamps
     
    Following a suggestion from Mikkel, I have bought a set of Victorian figures by Andrew Stadden and think they are very nice castings indeed. I'm still waiting for some new paint brushes to arrive and then will attempt to provide some fine Victorian fashions for the girls!
     

     
    Victorian figures by Andrew Stadden
     
    i can see Sir John and Lady Wilcote on the right and young Blanche looks to be planning some sort of mischief, as usual, while elder sister Amy (with her parasol) looks on with disapproval. I'm not sure who all the other figures are yet, but we might have a glimpse of young Charles, as well as various retainers.
     
    Mike
  10. MikeOxon

    Bits and Pieces

    By MikeOxon,


    general
    The recent fine weather has kept me away from the modelling for a while, while I have been pursuing my outdoor photographic interests. I am also procrastinating a little, as my coaches are at the stage of needing a lot of fiddly detail work to be completed!
     
    Because of my small radius curves, 'fine' flanged wheels are a bit unreliable, so I prefer to use 'Hornby' or 'Bachmann' wheels, which hold on pretty well round the corners! For my 6-wheel coaches, I decided to try 'MJT' Mansell wheel inserts on standard 'Bachmann' coach wheels, and I think they look pretty good. I sprayed the white metal castings with red primer and then Ford Rio Brown car colour:
     

     
     
    I put these on a sheet of paper for spraying and then thought of how to use a similar method for other items. For the oil lamp tops, I placed the paper over a strip of Bluetac on top of a small piece of wood, and then pushed the mounting spigots through the paper, so that they were held firmly by the Bluetac. This made it easy to move them around as a group, for spraying, and meant that the Bluetac was not coated, so could be re-used.
     

     
     
    The same method can be used for figures:
     

     
    It looks rather as if the flighty young Blanche has just got the idea of making a snowball
    but Sir John has sternly admonished her to "desist now, young lady - most unseemly".
     
    In the photos, I show tissue paper but it's much better to use ordinary paper, as the tissue separates and sticks to the Bluetac.
     
    I've also found that Kirby grips are very good for holding the printed overlays in place on the sides of the Clerestory roofs, while the glue sets. These things are handy for all sorts of small holding jobs.
     

     
     
    Now that rain is forecast for the coming week, I may find time for all the chores to be completed on my coaches.
     

     
     
    The U29 needs lots of holes drilling in the roof for the lamp tops and their associated covers, then I have to remove the surplus brakes on the middle wheels and add loads of details, including springs, vacuum cylinder, buffers, couplings, etc., etc. It may have to rain for quite a long time 🙂
     
    Mike
  11. MikeOxon

    Match-built Carriage Truck - 2

    By MikeOxon,


    general
    My photo alongside might look similar to the final one in my previous post but is, in fact, the result of a complete re-build, in an attempt to correct at least some of the mistakes I'd made!
     
    I'd already found some of the problems in trying to adapt real drawings to an 00 gauge model, in that the wheels fouled the diagonal members of the chassis. Then, when my grease axle boxes arrived from 'MJT' (after 15 days and well within the 21 days maximum), I found that there was insufficient clearance underneath my solebars for the springs to fit. In this context, 0.25mm might as well be the proverbial yard, when something doesn't fit!
     
     
    So, a few lessons learned -
     
    1. don't try to build 00 models without thinking about the compromises needed to accommodate 'narrow gauge (4' 1½")' wheelsets
     
    2. test-fit bought-in parts before final assembly
     
    Fortunately, I had stuck the model together with 'UHU' glue, which softens in boiling water, so a short immersion was sufficient to break everything apart. Before I realised that, I noted that everything was, in fact, pretty well stuck together.
     
    I then fixed the axle boxes and springs to the W-irons before starting re-assembly of the chassis, without the diagonal support timbers. The stanchions and iron fittings on the solebars had remained in place, since I had used superglue for these, so the next step was to attach the sole bars to the W-irons, ensuring sufficient clearance for the springs. I soon found that my diagonal chassis members were not the only thing fouling the wheels - the 'Mainly Trains' W-irons were designed for scale wheelsets and the cutouts for the wheel flanges did not extend far enough inwards to accommodate 00 wheels! I used a diamond slitting disk on my mini-drill to open out a slot for my wheels. Now I could use 4' diameter Mansell carriage wheels (actually 'MJT' inserts in 'Bachmann' standard wheels).
     
    After re-building the chassis, I refitted the deck between the vertical stanchions and got back to where I was at the end of the previous post 🙂  I added some additional details below the solebars, using shaped strips of plastic card, then I painted the solebars in GWR carriage brown and picked out all the ironwork in black. A useful tip, if you use paint in glass jars, such as 'Railmatch' paints, is to wrap some plumbers' PTFE tape around the threads for the cap. This makes it easy to remove the caps again later and solves the problem of broken plastic caps!
     

     
     
    I sprayed my 'Victoria' carriage, described in an earlier post, in red primer and placed it on the deck for a photo, to show the look of the assembly.
     

     
     
    The prototype vehicle has two cross-bars, mounted on a pin rail below the main hand-rails, to secure the carriage in position. I decided to fashion two tapered bars, to represent the prototype bars, out of the ends of some cocktail sticks. I expect I shall 'pass' on the iron bindings, though I may try a line of black paint, when I have the bars in position. This will have to wait until I paint the top-coat on the carriage and place it into the correct position.
     

     
     
    I followed up @buffalo's suggestions for the brake gear and then noticed that a photo of an early horse box (Fig.19 in Russell's GW Coaches, Part 1) showed no brakes but a vacuum through pipe. So, for the time being, I have decided to adopt this style. One of the nice things about scratch building is that you can add as much or as little detail as you like at the outset and then, providing the basic dimensions are correct, can add more details later.
     
    In the end, it seems surprising to me that such a 'simple' little vehicle could have caused so much trouble. I suppose that is partly down to my eccentric method of construction but it's all part of the learning curve and I'm getting ever closer to completing my 'Special' train 🙂
     
    Mike
  12. MikeOxon

    Match-built Carriage Truck - 1

    By MikeOxon,


    general
    I had intended to wait until my carriage truck was complete, before writing another post, but various events have introduced delays, so here is a 'work in progress' report. . Some of my readers seem to like my 'off-beat' approach to modelling and this one also has some unusual features!
     
    It all began when I saw a box of 'extra long' safety matches on the supermarket shelves. I had been looking at a drawing of an early wooden-framed carriage truck (1866) in Janet Russell's book on 'Great Western Horse Power' and suddenly got the idea of making the frame from these matches! The drawing shows several intriguing features, such as the diagonal-planked floor, with iron strips under the carriage wheels, and supports for moveable cross-bars that are below the side hand-rails.
     
    I constructed a simple under-frame from a selection of both 'extra long' and ordinary matches. I also had some small pieces of veneer from an old marquetry set, which provided a suitable deck. I glued the veneer to a rectangle of 10 thou brass sheet, to provide mountings for the under-gear.
     

     
     
    The first source of delay was that the 'MJT' compensating W-irons, which I intended to use, have been 'temporarily out of stock' all year, so far. When I had no reply to an e-mail querying potential availability, I looked for alternatives and found both the 'Mainly Trains' GWR running gear etch and their wagon detailing set. I fitted the running gear under the brass floor and found that I needed to cut recesses in the backs of the side frame members to accommodate the W-irons. Fortunately, the match wood was easy to cut with a scalpel blade.
     

     
     
    The 'Mainly Trains' detailing set contains lengths of rivet strip, intended for wagon bracing, which I used for the strakes along the deck of the carriage truck, together with some square riveted plates to complete the ends of the loading ramps.
     

     
     
    The next step was to mount the two side hand-rails. The prototype used angle irons as vertical supports at the wagon ends and T-section bars for the intermediate supports. I had some 1mm x 1mm brass angle rod, so cut this into short lengths and then fixed lengths back-to-back for the T-sections. This was very fiddly and I should have made up the T-sections before cutting into individual lengths. These intermediate supports also ended up too wide, though this is not really noticeable in practice. Perhaps I should have used styrene sections but I wanted to represent the metal of the prototype with metal parts. The top rails were too small in section for matches, so I used 1mm square styrene rod for these. Once these parts were all in place, I added additional iron-work details to the solebars, using parts from the 'Mainly Trains' fret. I think it took me as long to add these details as some people take to build a whole layout 🙂
     

     
     
    I'm now stuck again, waiting for grease axleboxes and other parts to arrive from 'Dart Castings' - those guys really mean it when they say 'allow 21 days for delivery'
     
    The 1866 drawing does not show any brake gear. I assume that, after 1880, the vehicle would have been fitted with the moving-cylinder vacuum brake with a single side lever. If anyone has any more information, perhaps they could let me know.
     
    Link to Part 2
     
    Mike
  13. 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
  14. MikeOxon
    Much of what we now accept as standard railway practice was actually developed towards the end of the 19th century, so that it is easy to forget that there was a long period of evolution, before the 'norms' with which we are so familiar became established. Whereas we have plenty of photographs to guide our perceptions of the later years of the century, our 'picture' of the earlier years remains much hazier, so it is easy to lose sight of the many major changes that occurred.
     
    For example, my modelling of some early coaches demonstrated to me how it was not until the 1870s that the design of railway coaches began to shake free of their stage coach roots. There was a dramatic change in both the scale and the construction methods of railway vehicles in the latter half of the century. Two of my (unfinished) standard-gauge models illustrate the point. On the left is an early 2nd-class coach, probably built during the 1850s, while on the right is the type of coach that was built in the new carriage shop at Swindon, to diagram S5 in 1875
     
    .
     
    Now that I have started looking at the Broad Gauge era of the GWR, linked to a specific event in November 1868 - the accident near Bullo Pill - I have started to look more closely at developments around that period. Research is an endless task and it is easy to become overwhelmed by all the facts that start to emerge, as one digs more deeply, but one has to start somewhere so, here is a look at the state of GWR rolling stock in 1868.
     
    The photographs of the accident at Bullo Pill clearly show the telegraph wires running alongside the railway. It seems almost inconceivable from our standpoint that these wires were not used to control the movements of trains. Responsibility for the running of the trains rested almost entirely on the driver, just as it had rested with coachmen in earlier times. In 1868, an express train could be running at 50 mph or more, with virtually no knowledge as to whether the line ahead was clear. According to the accident report: "The rules of the company require the signalmen to warn the driver of a passenger train when there is, after dark, a goods, cattle, or mineral train, less than 20 minutes in front of such passenger train." Since the interval at Lydney was 22 minutes, no warning had been given.
     

     
    In addition, the express train had no means of stopping quickly, if something untoward occurred, because there were no continuous brakes in 1868 and only a few carriages (including the Mail Coach) had hand-wheel brakes, operated by a Guard, who could respond to a whistle signal from the engine. Sanders' Automatic Vacuum Brake was trialled on a standard gauge GWR train in 1876 and only adopted more generally in 1878, long after my chosen period
     
    Early carriage brakes were often of the 'clasp' type, with large wooden shoes acting on the rims of the wheels. A typical arrangement, taken from a drawing of an early brake van, is shown below. The layout of the various levers varied but the principle remained the same.
     

    What does all this mean for the design of my model of a Broad Gauge Mail Coach, which was one of the three coaches on that ill-fated mail train? It turns out that my model will be rather different from my initial pre-conceived ideas, which were formed largely on impressions given by later re-builds of such vehicles. Much of the information in the following paragraphs is taken from MacDermot's 'History of the GWR', Vol.2.
     
    We all 'know', of course, that GWR coaches were painted 'chocolate and cream'. Except that they weren't!  GWR coaches were painted brown all over until some time after October 1864, when the Directors decreed that the tops of the carriages should be painted white. The cream appearance only developed as several coats of varnish were applied. Furthermore, the Broad Gauge had already been in decline for many years by then, with no new carriage stock having appeared since 1863, and the existing stock steadily became increasingly shabby and dilapidated.
     
    Although the Broad Gauge 'hung on' in the West Country until 1892, a major conversion had already occurred, much earlier. In May 1872 all the South Wales lines (plus other lines West of Gloucester) were converted to standard gauge. With this major upheaval already pending in November 1868, it seems very unlikely that much attention would have been given to updating any of the Broad Gauge stock running in that area, at that time.
     
    So, the colour and the brakes of my model should be more appropriate to a date in the 1850s, when these coaches were built, than to 1868. What other details might differ from my expectations?
     
    Early coaches were built with iron spoked wheels. These wheels were still fitted to almost all Broad Gauge coaches and vans as late as 1874, although Mansell wooden-centred wheels had been tried as early as 1866 and adopted for all new stock in 1868. My coach, therefore, requires spoked wheels.
     
    The long wooden foot-boards, widely associated with GWR coaches, were only introduced in 1876, so my coach should have a small iron step at each doorway, just like those fitted on stage coaches in earlier times.
     
    Less surprisingly, the axle boxes should be of the grease pattern, as oil boxes were a much later innovation, dating from 1886. Gas lighting had arrived a little earlier, in 1882, but, as with most such changes, it was many years before they were fitted in all stock. (I believe some oil lamps were still around in the 1930s)
     
    Even the 'communication cord', initially slung along the eaves of the coaches, was only introduced on the Broad Gauge in 1869, after initially running only from the leading Guard's van to the tender. Throughout the 1860s, luggage rails were fitted to the roofs of many Broad Gauge coaches but it is not clear whether this applied to the Mail Coaches. One photograph (P.W.Pilcher, 1885) suggests that luggage may have been carried on the lower section of the roof.
     

     
     
    With all this additional information, I am relieved that I have not yet started building the under-frame of my Mail Coach. I could easily have added many later details, without realising, and bought completely the wrong type of wheels. Some aspects will now be simpler, since I have already encountered the difficulties of modelling later brake gear, with all its rods and safety straps to prevent bits falling onto the track!
     

    sketch of planned model
     
    Mike
     
    Link to Part 4
     
    As an annexe to this post, I have placed the various dates mentioned above on a 'timeline', to help visualise when the various innovations were made.
     

     
  15. MikeOxon

    Broad Gauge Mail Coach - part 2

    By MikeOxon,


    General
    My previous post in this series ended on a 'cliff-hanger' – how was I to escape from the 'hinge' problem?
     
    After a little thought, the solution proved very simple. I used my jewellers' snips to cut a 1mm strip from the edge of some brass sheet and then folded the strip to make three staples, which pressed into the slots on the adjacent compartment doors. It was fortunate that the doors were hung 'back to back' so that the staples could be kept quite short.
     
    I did discover a small problem later, when fitting the partition between the compartments, since I had to file slots in the partition to clear these 'staples'. I could, of course, have used individual L-shaped strips but they would have been more fiddly to fix in place. I did, however, have to use this method for the single door at the other end of one side.
     

     
     
    It sometimes puzzles me how kit designers decide which details to include in their models. Why do these etches have slots for these almost invisible hinges but no provision for door handles or grab rails?
     
    Anyway – on with the build:
     
    The next step was to fit the two partitions. These have vestigial tabs, to register with slots in the floor. I 'tacked' both these partitions in position, with small blobs of solder, while I checked that the coach sides fitted snugly against the partitions and the floor. It is important to fit the taller partition the correct way round, so that the etched detail shows above the low section of the roof (I almost missed this!). As I mentioned above, I had to file slots in one of the partitions and also needed to trim the other a little, to ensure the sides would fit flush against the floor. Once I was satisfied with the 'fit', I ran solder along the partition seams and, similarly, soldered the sides to the edges of the floor.
     
    I always apply a fairly generous dose of phosphoric acid flux along the seams and then run 60/40 solder along the joint with a sweep of the iron. It is important to remember that the only role of the iron is to apply heat. It should never be pressed hard against the work and certainly not used to press joints together. If pressure is needed, use something non-conducting, such as wood, to avoid taking heat away. I often use fingers, at what I hope is a safe distance, but brass is a good conductor and the temperature rises very rapidly, even several centimetres away! It is important to wash the completed assembly thoroughly with water, to remove any residual acid which will otherwise continue to attack the metal. It's a good idea to dip any burnt fingers in cold water, too
     

     
     
    That's almost it, for the main body, but the the sting in the tail arrives with the ends! The sides have a 'tumble-home' but the supplied ends are straight. The instructions state “The top of the sides now need to be bent inwards so that the ends are vertical. The ends fit between the sides ….. The lower half of the sides now need to be curved in to meet the ends” The point seems to be that the front corners of the prototype are curved, as in many early GWR coaches.
     
    Making a rounded end may be possible in 7mm scale but I could not see how to achieve it at the smaller scale, without courting disaster. I decided to fit the upper part of the sides flat against the edges of the ends and then curve the 'tumble-home' to meet the end. Trying to get a smooth double curvature was not at all easy. I intend to try rounding the corners by using a file, later, possibly with a wire fillet along the inside of the vertical joint.
     
    The two roofs have a very slight curvature. I used a steel tube as a rolling pin, to make the curve, with the roof laid on a mouse mat, to provide a soft surface. In fact, the curvature is so slight that I over-did it the first time.
     
    Particularly interesting features of the prototypes were the skylights on the roof, which were presumably a Post Office requirement. When I looked at these items on the fret, I was a little apprehensive but they actually work very well.
     
    The important thing to note is that the fold for the triangular sections is part way down the main sides. It is very easy to inadvertently bend the fragile glazing bars, if these are not clamped firmly in a vice, while making this initial fold to an angle of around 60°. I have taken a photo through my illuminated magnifier to show how I did this, by using some aluminium-angle, clamped in the vice together with the fret, to define the fold line. In 4mm scale, these parts are quite small.
     

     
     
    After making this first fold, the brass strip then has to be folded to make a box shape, with two tabs at the sides, which secure the completed assemblies to the roof, from below. I found that the completed skylights were a good close fit in the cut-outs that are provided within the upper roof. I got better at making these skylights, as I worked through the set, but photographs are always cruel and I can see that some straightening of the glazing bars is still needed.
     

     
     
    That essentially completes the body of the coach apart from some cast fittings, including oil lamps and ventilators. I may try the technique described by Dave John , to hold down the roofs with magnets.
     
    The next task will be to build the chassis, which looks reasonably straight-forward, although I need to think about the type of break gear that would have been in use in 1868. I think the overall effect, so far, is quite pleasing:
     

     
     
    Mike
     
    Link to Part 3
  16. MikeOxon

    Broad Gauge Mail Coach - part 1

    By MikeOxon,


    General
    In my first post in this blog, I explained that the inspiration behind my exploration of the Broad Gauge was the discovery, when researching family history, that during the 1860s, my wife's great-grandfather worked for the GWR on the South Wales line at Bullo Pill.
     
    During his time there, there was a serious accident in 1868, south of the station, when the 5 pm fast Mail train from New Milford ran into the back of a special cattle train, making its way laboriously from Carmarthen to Gloucester.
     

    Bullo Pill Accident – 5th November 1868
     
    The Accident Report provides details of the two trains involved and I decided to use this information as a basis for my start in Broad Gauge modelling. The Mail train was headed by the large 4-4-0 locomotive 'Rob Roy', of the 'Waverley' class, with three passenger carriages, and a luggage van. The leading carriage had a break (sic) compartment in it, in which rode a guard; and the third carriage, which was a mail carriage as well as a break carriage and passenger carriage, also carried a guard.
     
    I was quite surprised to learn from MacDermot's 'History of the Great Western Railway' that, in 1855, the GWR introduced the first Postal Train in the world and then, in 1866, apparatus to allow mails to be picked up and delivered without stopping was installed at Slough and Maidenhead. A number of carriages were altered to meet Post Office requirements; the modifications included an increased ceiling height, wide access doorway, PO designed delivery arms, and net apparatus. It is also recorded that three Second Class Mail Carriages with Net apparatus (Nos. 20 86 & 87), fitted with one delivery arm, were assigned to work the South Wales line.
     
    As I was considering these facts, the Broad Gauge Society (BGS) announced that they were introducing a model of a GWR Mail Coach, initially in 7mm scale and then in 4mm. I immediately placed an order for one of the first of the 4mm models and, while the brass etchings were soon available, the cast parts took longer to arrive.
     
    In the meantime, my wife and I had planned a long holiday in New Zealand, so my modelling activities have been 'on hold' for some time. At last, the time has come when I can once again set up my work table and start working on the Mail Coach kit.
     
    The major components of the coach are contained on two etched-brass frets. The instructions, which are based on the construction of a 7mm scale model, seem clear, although they assume reasonable knowledge of etched-brass kit construction. I was a little apprehensive that a 'scaled' kit might have some problems, such as in the fit of various tabs, but, initially, the sides have gone together very well.
     

     
     
    The first step, according to the instructions, is to build the two sides. There are tabs running along the tops of the sides and these need to be folded over, to provide additional strength. I find it best to place a steel rule along the back of the side, with its edge aligned with the fold line. I then press the tabs against a hard surface and rotate the sides upwards, holding the rule firmly against the fold line. This pressure causes the tabs to move quite easily into the right-angle position, from where they can then be pushed over, by hand, to lie flush against the inner sides. The next step is to form the 'tumble-home' on the lower sides.
     

     
     
    The 'tumble-home' needs to be a smooth curve so, to achieve this, I first marked a line along the back of each side, to indicate the top of the curved section. I then used my fingers to roll the lower sides gently around the cylindrical body of a ball-point pen. I found that by working along the length of a side with my thumbs, it was possible to achieve a smooth curve, since the grade of brass used for the frets seem quite 'soft' and pliable.
     
    Two more folds are required, to form the sides of the inset doorway, on one side of the coach. These folded sides carry tabs, which fitted readily into slots etched into the door itself. The lower edges of the folded sides are curved to match the 'tumble-home' of the coach body. Making these folds is more difficult than the tabs along the top since, after making the tumble-home, the sides are no longer flat. I used the end of my steel rule, laid along the length of the coach, as a jig to make these folds.
     

     
     
    The drop-lights have to be be fitted to the insides of the window openings. I found that this was a tricky procedure, since there are no alignment marks on the inside and it is hard to hold the drop-lights in the correct positions, which need to be viewed from the outside, while fixing them on the inside. In the end, I decided to tack them in place with a small dot of super-glue before turning the sides over for soldering. I used 60/40 solder with phosphoric acid flux.
     

     
     
    At this point, the instructions start to describe assembling the body. I always 'read ahead' a little, to help understand the processes and to foresee potential pitfalls. In this case, it proved valuable since, after assembling the body, the instructions move on to fit the hinges from the inside. This might be reasonable in 7mm scale but space is very limited for this sort of assembly, inside a 4mm scale body.
     
    There are several 'hinges' provided on the fret but, even with the sides laid flat and fully accessible, I soon realised that fitting these was going to be the proverbial PITA. They may have been a reasonable size in 7mm scale but, even using my finest tweezers and a good magnifier, they were, to put it mildly, 'difficult' in 4 mm. I tried soldering one but when I looked again the 'hinge' had disappeared. I next tried a dot of super-glue but alignment was still a great problem and I lost another one! (eventually, these all turned up – two stuck to the Q-tip I had used to apply flux and one to the nozzle of the super-glue bottle)
     

     
     
    The instructions suggest “you may prefer to replace the etched ones with 2mm wide pieces ...” - yes, indeed, although this translates to 1mm at my scale.
     
    I've decided to take a break at this point to think about the best way forward
     
    Regarding the prototypes, they seem to have been rather shy of photographers, although one can just be seen (note the stepped roof), next to the engine, in the 1880s photo of a train at Ivybridge, which appears in 'Great Western Way' (1st edition, p.6) There is also an excellent article in the BGS Journal 'Broadsheet' No.75 (Spring 2016).
     
    Mike
     
    Link to Part 2
  17. 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
  18. 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
  19. 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
  20. MikeOxon

    Narrow-Gauge Maintenance

    By MikeOxon,


    general
    I have mentioned in some recent posts that I intended to work on the scenery of my layout and, in the course of doing that, I found some problems with the narrow-gauge track, where it climbs from the station area, up over the main line towards the quarries.
     
    What followed has been a frustrating few days, when my little railway has been showing its age! I suppose it is hardly surprising that some of the track is giving problems, as it was first laid in 1979.
     

     
    The above photo, dating from May 1979, shows my wife demonstrating her skills with laying plaster bandage over chicken wire alongside the brand new track, which is now the station area. It seems that the track was never properly supported, where it leads onto the bridge in the left-hand side of the photo and so, of course, the rails eventually parted company with their plastic base! I have now rebuilt the underpinnings with the help of some plaster filler and thought that everything was sorted 🙂
     
    Alas, when I ran the first train, it passed over the newly-repaired section with aplomb and promptly derailed on the next curve - a feat which it repeated with absolute consistency! More testing then revealed a similar problem on another curved stretch, which was working perfectly just a week or so ago.
     
    I was left with the feeling that repairing one problem seems to cause two more to spring out - in this case, quite literally, as some curved sections of rail had sprung out of their moulded plastic 'chairs' - presumably the plastic has de-plasticised over time.
     
    In the course of diagnosing the problem, I discovered a useful addition to my modelling toolbox. I have a pair of Pentax 'Papilio' binoculars, intended for butterfly watching, which have the ability to focus as closely as 18" (~50cm) from the objective lenses. This makes them rather like a long-working-distance binocular microscope that is great for looking for defects on model railway trackwork!  I made some track spacers, to set the gauge, and made a 'temporary' repair with superglue (the sort of repair that becomes 'permanent' until it fails again), so that my narrow-gauge engines are, once again, running smoothly.
     
    To celebrate this success, I have taken a few photos of narrow-gauge operations around the quarries. For these, I applied another new gadget, in the form of a 'Seagull' SYK-5 Remote Flash Trigger. This enables my small compact camera to trigger my high-power flashgun in sync with its internal flash. The Seagull trigger has an adjustable time-delay, which is needed to overcome the pre-flash that most compact cameras use when focusing. Now, I can get my small camera into otherwise inaccessible locations but still use a high-power bounced flash, as I described in an earlier post.
     
    My first view is from behind the narrow gauge engine shed, where a newly-laid incline leads down from some lime kilns. The timber yard is just ahead, while the loading dock and North Leigh station are to the left. I've 'extended' the backscene a little from what is actually there, to hide my off-layout work area.
     

     
    From here, the track continues over my newly repaired section, crossing over the main line and passing under a now disused quarry. A little further on, the line to the saw-mill diverges to the left, while the right-hand track leads past the workshop towards the working quarries.
     

     
    At the quarries, the men are ready to attach a couple of mine trucks for taking down to the loading dock at North Leigh station.
     

     
     

     
    Mike
  21. MikeOxon
    In my previous post, I described a little about the location of North Leigh station on the branch line to Witney, originally planned in 1849. For some reason, this line was omitted from Bartholomew's 1/2inch map of 1903 but I have restored it to its rightful position, in order to show the location of the station and its proximity to the tunnel through the ridge of high ground between North Leigh and New Yatt.
     
    The later, cut-off, which allowed trains to run directly from the Worcester line towards Witney is not shown on the map but it diverged close to North Leigh station, to join the OW&W main line near Wilcote. The map clearly shows Wilcote Manor, home of Sir John and Lady Wilcote, plus their lively daughters.
     
    This region of the Cotswolds was long famous for its many stone quarries, perpetuated in the name of the nearby village of Stonesfield. Some of these quarries were served by a narrow gauge (2' 6") railway, with an exchange dock at North Leigh station.
     
    Unfortunately, all these lines seem to have been omitted by the map-makers, and even diligent searching will fail to find any traces on the ground, today. My own model, therefore, seeks to re-create this lost world and provide a glimpse of what life might have been like in the area, towards the end of the 19th century.
     
    The following photograph shows the chute that was used to transfer stone from the NG railway to the main GWR system.  A Hudswell Clark 0-4-0ST has recently taken over from horse power, for shunting wagons under the chute. On the upper level, a stone train has just arrived from the quarries, ready for unloading.
     

     
     
    The quarries run along the edge of a steep scarp slope, above the town, and the following scene shows the small workshops nestling under the much-quarried slope. Small farms dot the countryside immediately below the quarries and the railway also serves to bring goods and to carry animals, and occasionally people, to and from these scattered communities. The sheep-nibbled turf is represented by dyed lint, whereas the longer rough grasses are made from pieces of a very old long-haired camel coat, suitably dyed and painted!
     

     
    In addition to the quarries, the NG line also serves a saw mill, since there are extensive woodlands in the area of Wychwood Forest. The saw-mill has a curiously 'Black Forest' look, probably a whim of Sir John's. The following scene shows a short train of bolster wagons, which has delivered several large logs to the mill for sawing. The water-wheel that powers the mill can be seen towards the right of the picture. Later, the sawn timbers will be taken to the yard, on the upper level at North Leigh.
     

     
    There is still a lot of work to be done in all these areas and a large part of my purpose, in taking these photos, is to help me visualise possible ways ahead. The back-scene behind the saw-mill does not yet exist - just a plain white frieze - but I intend to print something similar to the scenery that I have added to the photo. Another aspect, revealed by the photos, is a distinct lack of human activity! I have a substantial backlog of painting to do, both of several sets of figures and of various horse-drawn vehicles, which I hope will add more 'life' to these scenes. Plenty to keep me occupied
     
    Mike
     
    EDIT : I felt that I had cheated a bit with the last photo, so I printed the back-scene onto some sheets of A4 and stuck them onto the frieze. Here's a genuine photo - un-retouched!
     

     
     
    This is an example of using test photos to suggest the way ahead 🙂
  22. 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
  23. MikeOxon

    Printing ‘Eagle’

    By MikeOxon,


    General
    In my previous post, describing my design method, I wrote:  “This method also means that I do not need to make any of my own measurements but simply rely on the drawing being accurate and traceable”
     
    A lot of early railway drawings were far from accurate!  I found the following in a collection belonging to William Strickland, an American architect:
     

     
    According to Wikipedia, “William Strickland's Reports are the starting point of American railway engineering, and represent the state of knowledge as the first railways were planned in that country." - so that’s where they went wrong 🤠
     
    I should also add a caveat that the drawings I use need to be complete.  In the case of ‘Eagle’, there is only the side-elevation by E.T. Lane, so a lot of details that might be be revealed by plan and end-elevation views remain as guesswork. This guesswork can, however, be informed by other sources of information.
     
    There are fortunately more drawings of the contemporary engine ‘Aeolus’, albeit from a different manufacturer. The general layout of items such as smokebox doors and back-head controls can be assumed to have been reasonably standard at that time, so I drew on my earlier model of ‘Aeolus’ for these details. I also know that ‘Eagle’ was based on similar engines built by Sharp, Roberts & Co. for the standard gauge. This knowledge enabled me to make further deductions about the layout of the frames, which were inside the wheels for the broad-gauge.
     
    In addition, there is the curious omission of springs on the rear axle in the ‘Lane’ drawing, although springs are clearly shown on similar standard-gauge engines from the same builder. Even more curious is that the much later drawing by G.F. Bird (Locomotive Magazine 1901) of the sister engine ‘Lion’ also omits rear springs.! I strongly suspect that, although purporting to be ‘Lion’, this Bird drawing was actually based on Lane’s earlier drawing of ‘Eagle’, although the Sharp, Roberts valve gear, shown on the Lane drawing, is missing.
     
     

    ‘Lion’ – drawn by G.F. Bird – Locomotive Magazine 1901
     
    I made the decision to add rear springs to my 3D model.
     
    Splashers
     
    To return to the problem of modelling splashers … I have tackled similar splashers on other broad-gauge engines but those shown in the Lane drawing pose additional problems. There appear to be no backs to the splashers, which removes any potential means of support in a model. The drawing does not indicate how these splashers were attached to the frames of the engine, either.
     
    After some thought, I adopted the following method:
     
    I first traced the outline of the outside valance from the Lane drawing and used this to extrude into a solid component of 4 mm depth.
     

    Splasher Component based on Lane drawing
     
    This gave me a robust structure to place over the wheels but which needed thinning on the underside to clear the wheel flanges. I moved this component into position relative to the rest of the model and added extensions on the inside, to butt up against the main frames of the engine. I also reduced the thickness by using the ‘offset’ tool on the underside faces, so that the splashers would be clear of the wheel flanges. Finally I added some tabs to the extensions which I intended to fit into matching slots cut into the frames. I have often complained about the absence of alignment tabs on commercial kits, so I felt that I should not make the same omission on my own model!
     

    Underside of splasher after adding extensions
     
    Now, after adding various details, including springs, buffers, and lines of rivets, which are easily created with the aid of the ‘pattern on path’ tool, I had a set of components ready for printing.
     

    My 3D model of Eagle in Fusion 360
     
    One further detail that I have considered is the ‘box’ that appears behind the smokebox in the Lane drawing, where the front axle might normally have been expected to be placed. According to Ahrons (‘British Steam Locomotive’, p.39): “The exhaust passages of Sharp's engines of 1839-1842 were peculiar. Both exhausts were discharged from the cylinders into a cubical box placed midway between the inside cylinders, and the blast pipe was connected to the top of this box, which was intended to act as a form of " air vessel " to equalise the blast. It caused considerable back pressure in the cylinders.” I am guessing that this may be the box shown in the Lane drawing behind the forks of the valve gear.
     
    Printing
     
    That’s the hard part finished, so now it’s a matter of exporting the files for each of my components from ‘Fusion 360’ into the slicing program ‘Cura’  I use this program to align each component in an appropriate orientation on my printer bed and I also check the ‘preview’, after slicing, to ensure that all the parts should print correctly. At this stage, I found that the driving wheel spokes were a little too narrow, so went back to Fusion 360 and used the face offset tool to increase the spoke widths by 0.1 mm.
     
    After these minor adjustments, it was then simply a case of loading the GCODE files onto a memory card, inserting this into the printer, selecting a file on the touch screen, and pressing the ‘Print’ button.
     
    After several short printing sessions, my ‘kit of parts’ looked like this:
     

    3D-printed Collection of Parts
     
    I was especially interested to see whether my planned method of assembling the frames and splashers would work. The slots in the frames needed a little cleaning out with a scalpel but, after that, everything fitted together neatly. The splashers themselves are very fine and not too robust – this will not be a model for the grandchildren to play with!
     

    Frames and Splashers after assembly
     
    I used my now-standard method of applying a low-temperature soldering iron to ‘weld’ the splashers to their associated frames.
     

    Using a soldering iron to join the splashers to the frames
     
    I was pleasantly surprised by how well my printer managed the boiler fittings, including the safety valve housing, which is only 1.6 mm diameter.
     

    3D-printed Dome and Safety Valve Cover
     
    The boiler, smokebox, and firebox fit together over a 14 mm diameter brass tube, which provides weight to the model and aligns these parts on a common axis:
     

    3D-printed Boiler, Frame, and Wheels
     
    Chasssis
     
    Next, I need to think about assembling the chassis. Because I only have a side-elevation drawing, there will have to be some informed guesswork, especially as the drawing gives no information about boiler supports or other structures.
     
    I shall pause here and do some more research before continuing with painting and final assembly.
     
    Mike
     
  24. 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
  25. MikeOxon
    The ‘tilt wagon’ seems to have been a popular design in early broad gauge (BG) history but I hadn’t got round to building a model before now. A very few of these wagons were converted to standard gauge and I did model one of those back in 2014, regarding it as an interesting curiosity!
     
    In the early days, it seems that most goods (and 3rd class passengers) were carried in open wagons but a growing need for weather protection led to the addition of canvas covers, known as ‘tilts’ (from an Old English word ‘teld’ meaning tent). Hoops were fitted, to support the canvas, and some wagons had raised ends to provide a more enclosed structure. The late Eddy Brown collected information about these early wagons, which is contained in the Data Sheets available to Broad Gauge Society (BGS) members. A review of early BG wagons appeared in the BGS Journal ‘Broadsheet’ no 34 (Autumn 1995), including the following sketches by J.C.Bourne:
     

     
    Over the following years, many different variants of the same basic style appeared, produced by several makers, of wood or iron construction, most with 4 wheels, although larger ones with 6 wheels were also built.
     
    These wagons became very popular and were used for many different purposes, including carriage of livestock. Evidence of this usage is seen in the lime-washed wagons photographed in the Swindon ‘dump’ after the broad gauge ended in 1892. Overall, the following photograph shows that there was a great range from which to choose, for model-making!
     

    Broad Gauge Wagons at Swindon ‘Dump’ 1892
     
    Several ‘standardised’ wagons, of all-iron construction except for a wooden planked floor, were built in two batches between 1853 and 1854 by various builders. The wagons were generally l7ft. long with side-doors. The inside width was either 9’ 9” or two inches wider. The wheelbase was 9’ 9” in all cases. They had 3’ long springs, set behind the axleguards, with 3’ 6” wheels and Normanville high-filler patent axleboxes. Drawing NRM 4832, below, does not show brakes but they may have been fitted at some stage.
     

     
    This old drawing is rather distorted but there is a better version in Alan Prior’s book ‘19th Century Railway Drawings’. Thus, I had the basis for constructing a model by following my usual method of copying over a printed drawing using ‘Fusion 360’ software.
     

    My 3D-model of an 1850s Tilt Wagon
     
    The chassis was a direct copy of the one I designed previously for my 12-ton coal wagon, of which the prototype was built to the same specification as the tilt wagons of the period. I had to lengthen the ends a little, to match the body of the tilt wagon, but this was a simple adjustment in ‘Fusion 360’.
     

    My 3D-model of the Underframe
     
    Although these wagons used smaller (3’ 6”) diameter wheels than the 4’ wheels of earlier versions, it was still necessary to provide apertures in the floor, for the tops of the wheels to protrude into wheel boxes.
     
     
    Printing my Model
     
    As I reported in my previous post, I am now using a ‘Prusa Mini+’ printer to create my models. As well as learning about the printer itself, I have been learning how to use the associated ‘Prusa Slicer’ software, which has several differences from the ‘Cura’ software that I used previously.
     
    ‘Fine Tuning’ the printer
     
    Fortunately, the printer itself is so smooth and quiet in operation that it seems to encourage experimentation, so I have been trying out various software settings in order to improve the performance, particular in respect of ‘stringing’ and ‘oozing’ of filament, as the print head moves between different areas of the print.
     

    Filament stringing around printed edges
     
    Although, when using my E180 printer, I frequently saw straight lengths of filament along lines where the nozzle had transited between different parts of a model, I have not seen this gossamer-like ‘fluff’ before and shall be interested to receive any comments from others who may have experienced this problem.
     
    It’s fairly easy to remove, by rubbing with fingers and an old toothbrush but, although I have reduced it considerably by adjustments to temperature and retraction distance, I have not yet eliminated it entirely.
     

    Tilt Wagon on Printer Bed before Cleaning
     
    I found that a useful tool for removing the ‘gossamer’, without damaging rivet detail, is a silicone rubber shaper, intended for controlling painted edges.
     

    Artists Silicone Colour Shaper as a Cleaning Tool
     
    Incidentally, during the course of my experiments, I suffered a break in the filament, as it loaded from the spool. The sensor, which I had bought as an optional extra for the printer, immediately detected the break and paused the print. The LCD screen displayed instructions for re-loading the filament and the print then re-started from where it had paused, without a hitch.
     
    Print ‘Quality’ Settings
     
    The layers of print produced by the Mini+ were noticeably more even than those from the E180. This very even-ness, however, made them more noticeable under close examination. At the 0.15mm ‘QUALITY’ setting for layer height, the layers are clearly visible in the close up photos below. There is also noticeable ‘trailing’ of filament around raised details. By changing to the 0.1mm ‘DETAIL’ setting in the slicer software, the printed layers blended together and, perhaps more importantly, the rivet detail was more cleanly defined. There is still a little ‘trailing’ but this is not noticeable under normal viewing conditions. These are unpainted surfaces with no additional surface smoothing after printing, apart from removal of the ‘gossamer’ referred to above.
     

    Close-up Comparison of Two Quality Levels
     
     
    Preparing the Model for printing
     
    I often like to break a model down into separate components, both to reduce individual print durations and to allow optimum positioning of components on the printer bed, to reduce the need for additional support structures.
     
    This particular model presented difficulties in adopting this approach, because there are very few flat surfaces, apart from the floor, while the ‘bonnets’ at the ends have substantial overhangs under the curved canopies at the top. I did initially try printing the sides and ends separately but it proved awkward to assemble the resulting parts neatly, so I thought I would risk printing the body all in one piece and see how well my new printer coped with the overhangs.
     
    I should not have worried, since the body printed cleanly and accurately. This, in the end, was by far the simplest and most satisfactory solution! There was still some fine ‘stringing’ of filament, appearing rather like spider webs between isolated structures, such as the ‘strouters’ (posts) that support the iron sides of the prototype. These fine strands of filament were easy to remove but I am hoping that further adjustments to the printing parameters will eliminate this minor problem.
     
    When I placed two models together, one printed with 0.15mm layer height and one with 0.1mm height, the quality difference is barely visible and would probably disappear under a coat of primer and a final coat of paint. There are still some whiskers of filament that need to be cleaned off before painting.
     

    Two models printed to different ‘quality’ standards
     
    There is a significant difference in the times taken for these two models to print. The 0.15mm resolution print took 1h 30m whereas the 0.1mm resolution tool 2h 40m. Whether this difference is significant depends, perhaps, on the overall size of the model and for small items such as these, I did not feel it was any hardship to adopt the finer quality.
     
    The following picture shows the complete model, with both body and chassis printed at 0.1mm ‘Fine’ quality. I have added wire rails between the ‘strouters’ or posts.
     

    My 3D-Printed Tilt Wagon + Chassis before painting
     
    Mike
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