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MikeOxon

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  1. MikeOxon
    My progress, since the previous post in this series, has been slower than anticipated, mainly because of the need to build a chassis that deviated from that intended for the BGS kit. I also took a few false turns, which led to a significant amount of re-work.
     
    In the comments following my first post about this coach, I said that I prefer scratch building to kits. I suppose what I really meant is that I like to do things my own way. The down side of the scratch building approach is that it needs lots of research, if one wants to build an authentic replica.
     
    As it happens, the under-gear supplied with the BGS kit represents a later modification of the Mail Coach, with vacuum brakes that were not introduced until around 1878 – ten years later than the time in which my model is set. Hence, I have been forced into carrying out the research needed to design and then build an earlier form of chassis.
     
    Before starting, I made a deviation, to try and understand the operation of the brake system described in the kit instructions. This is the clasp brake with external rods connecting the brake shoes on opposite sides of each wheel. At first, I could not understand how this mechanism worked but, after receiving help from members of the GWR E-LIST, I realised that the reversing action is achieved by rocking levers working in a horizontal rather than a vertical plane, which is the usual method in most brake mechanisms. In the GWR system, which I believe was developed by Dean, a horizontal lever running across the back of each of the outer brake shoes both applies that brake to the wheel and pivots about the back of the shoe to pull the opposite brake shoe via a coupling rod that runs outside the wheel. I made myself a diagram to illustrate how this works:
     

     
    Diagram of Dean Outside Clasp Brake
     
    After this distraction, I could return to the design of the earlier type of break gear, in use during the 1860s.
     
    As I explained in my previous post, I found drawings that included early types of clasp brakes in Alan Prior’s book of 19th Century Railway Drawings. From these, I was able to produce a sketch of the gear, in general terms. In order to apply the gear to the Mail Coach, I needed to determine several key dimensions and also the locations of the various components, underneath the floor of the carriage.
     
    Fortunately, as a member of the Broad Gauge Society, I have access to their excellent series of data sheets, which provide many important facts about the design and construction of broad gauge vehicles. Although the Mail Coach is illustrated in a later form, the data sheets record that this vehicle was rebuilt from the Revised Standard 2nd class coaches, of which 40 were built in 1854. Carriages of this type appear in the photo that was used by Frith as a ‘model’ for his paintings of GWR trains. I have based my own coloured illustration, below, on this photograph:
     

    Note circular Normanville axle boxes
     
    According to the BGS data sheet, these coaches were fitted with clasp brakes, operating on all three wheels on one side only. The outside rods that operated these brakes are visible on the carriage in the centre of the photograph above.
     
    Six of these coaches were modified to meet Post Office requirements in 1858. The data sheet states that luggage rails were added to the roofs of the 2nd class carriages from 1859 onwards, with added tarpaulin sheets, but it is not clear whether this applied to the Post Office conversions. The photo evidence shown in my earlier post suggests that these rails and tarpaulins were fitted on the lower section of the roof.
     
    For further details and dimensions, I consulted the drawings of the original 2nd class carriages, as shown in the BGS data sheet, which formed the basis for my scale drawing of the chassis below:
     

     
    Comparing this scale drawing with the sketch I made for my previous post (repeated here, for convenience), I could now place the various components in their ‘correct’ positions under the floor of my Mail Coach.
     

     
    The components I needed to make comprised three pairs of brackets, to carry the cross shafts at the two ends of the carriage and at the location of the brake handle, the various levers mounted on these shafts, and the various lengths of rodding. In order to allow the wheels to be removed for maintenance I decided to omit the inner pair of brake pull rods, since these would not be visible in normal operation.
     
    It was now time to start actually assembling the chassis and I soon hit a problem with interpreting the instructions. The instructions started with a note that “these instructions were written after building a 7mm kit”. I started to realise that things were going to be different in 4mm, when I read that “the inside hornguides (xx) are fitted in the slots in the floor”. My floor had no slots but there seemed to be a secondary ‘sub-chassis’, labelled on the fret as Part [10], which is not mentioned in the instructions. I assumed (wrongly, as it turned out) that this was to be a complete separate chassis, to be fixed under the plain floor of the coach body.
     
    Hence, I started to look at how to fit the solebars to the sides of this sub-chassis but there seemed to be no provision for any proper support. Then, after reading a number of apparently irrelevant instructions about a sprung chassis (for which no parts were supplied), I found that the solebars were meant to be soldered into grooves in the coach floor. Perhaps this would work in 7mm but the solebars in 4mm scale are very thin, flat strips of brass, which I felt needed more lateral support than this very shallow groove. In addition, because I had assumed that the chassis would be a separate item, I had already spray-painted the body, so did not wish to start doing more soldering there!
     
    After a pause for thought, I decided to make two brackets, running across the under-side of the sub-chassis [10], to support the solebars along the outer edges of this component. The brackets for the brake cross-shafts, which I made in a similar manner, provided additional support near the ends of the coach. All the material for these brackets was cut from spare areas of the etches supplied for the kit, using my jewellers’ snips.
     
    With these modifications, the underside of the sub-chassis was as shown below:
     

     
    I soldered the axle-guards to the solebars before soldering the assemblies to the brackets on the chassis. I find that those small dressing stones, often included in accessory kits for mini-drills, are very handy for removing the small burrs from small parts, where they have been attached to the fret. I find that I can remove the burr without damaging the main profile of the part, as shown below:
     

     
    These stones are also good for rubbing down any excess solder or working on white metal, to avoid clogging up good-quality needle files.
     
    The springs supplied in the kit are brass castings but I decided to use super-glue (cyanoacrylate) rather than solder, to avoid the possibility of melting other joints around the axle guards. I find that, providing the surfaces are thoroughly cleaned, super-glue is very effective for attaching these small components. I have also discovered (initially by accident) that iso-propyl alcohol acts as an excellent accelerator when applied to super-glued components, making the glue polymerise almost instantly. Any surplus glue turns into a white residue that can be scraped off.
     
    So, after a few twists and turns, I now have a ‘rolling’ coach, which needs various bits of brake rodding to be added, to complete the appearance of the underframe. I shall look for some different axleboxes from those supplied with the kit, since the early photographs show the characteristic circular pattern of Normanville’s patent design.
     
    I have darkened the roofs and will probably paint the skylights white, before weathering them a little, for a more ‘realistic’ appearance. There are still several details to add but I am pleased to have solved the chassis problems.
     

     
     
    Mike
  2. MikeOxon

    GWR Posting Carriage - Part 2

    By MikeOxon,


    General
    I hadn’t expected to make quite such rapid progress with this model – I must be getting slightly more proficient at using the ‘Fusion 360’ CAD software!
     
    In part 1, I showed how I created the rather complex profile of the sides of the Posting Carriage by extruding a drawing of one end. I drew the end profile as a series of straight lines and arcs, traced over a drawing contained in one of the very useful Broad Gauge Society data sheets.
     

     
    While this process gave me the basic outline of my planned carriage, there are many aspects that needed further thought, especially since I have to create a model that can be printed with my Geeetech E180 FDM printer. In particular, this means avoiding overhangs wherever possible and adding support structures where there’s no alternative.
     
    With the above considerations in mind, my first step was to split the body horizontally into two. I created an offset plane parallel to the base of the carriage but raised to the top level of the window openings. I then split the body around this plane and worked on each of these two new ‘bodies’ separately, as described below:
     
    Lower Carriage Body
     
    The first step was to open out the interior of the carriage. To do this, I selected a drawing plane at the top of this body and used the ‘offset’ tool to draw a rectangle set back from the edges of the body by 1 mm all round. I then used the ‘push pull’ tool to push the rectangular opening down through the body to the lower level of the windows.
     
    Below this point, the carriage body becomes narrower, so I offset another smaller rectangle and pushed this downwards to ensure sufficient material was left around the edges to provide strong sides. I repeated the process again for the lowest and narrowest part of the carriage. This gave me an open body shell, which could be printed upwards from the floor, as shown below. There may be more elegant ways of doing this but this simple procedure gave me an adequate result.
     

     
    There are some small overhangs along the sides, where the upper part of the body is ‘jettied’ out from the lower part (rather like a mediaeval house!). I decided to do a trial print, to check whether my printer could cope with this amount of overhang, as support structures on the outside of the body are difficult to remove cleanly. I am pleased to report that my printer produced the curved overhangs with no apparent problems.
     
    To create the window openings, I drew a series of rectangles on one side of the carriage and used the ‘push-pull’ tool to extrude these through to the opposite side. By choosing the option to extend the depth of the extrusion to the opposite outer face of the carriage, the window opening will remain in their correct places if I make subsequent alterations to the width of the carriage. This ‘parametric’ approach simplifies editing of the model, if I decide to make changes later.
     

     
    The Whishaw drawing  shows that the ‘jettied’ appearance of the upper sides was continued around the ends of the carriage. To reproduce this feature, I used the ‘push-pull’ tool to inset the lower panels of the ends and then used the ‘chamfer’ tool to provide a rounded transition between the upper and lower parts of each end.
     
    Although it is not clear from the Wishaw drawing, I also used the ‘chamfer’ tool to round the corners between the upper body sides and the ends. This was a common feature in many early carriages, so I felt it was appropriate in this case.
     
    Adding the Doors
     
    The next unusual feature to tackle was the doors. These appear to be flat and flush with the upper side panels. Thus, the lower door-frames protrude outwards from the in-curving lower body.
     
    I tried a few experiments to work out how to add this feature. At first, when I tried using the ‘push-pull’ tool, I simply succeeded in making openings in the lower side panels! There may be settings to alter this behaviour but my own solution was to extrude the door and frame outwards from the carriage side, designating them as ‘new bodies’. I could then use the ‘move’ tool to slide these new bodies back into registration with the upper body.
     

     
    Finally, I used the ‘combine’ tool to ‘join’ these new bodies to the original body of the carriage, so that the whole structure became a single entity again.  By now, the body was beginning to look like a model railway carriage rather than a solid block!
     
    These steps have completed my basic design for the carriage body. I could, of course, add many additional features, including interior fittings, such as seats and table, but I’ve decide to pause here, to see whether the design works in practice.
     
    Clerestory Roof
     
    Returning to the second of the two ‘bodies’ that I created by splitting the original model, I used similar procedures to open out the interior of the clerestory and to create the rows of 6 windows on each side. I also had to add the upper part of the door frame, which protrudes from the lower sections of the roof and has its own ‘roof’ extending from the sides of the clerestory.
     
    There are significant differences between the Whishaw drawing and the Bourne lithograph (both shown in my previous post) regarding the shape of this part of the ‘porch’ but I feel that the curved top shown in the lithograph looks to be a credible representation of the prototype. In other matters, such as the number of windows in the clerestory, I have preferred to follow the Whishaw drawing and description, so I must point out that several parts of my model are conjectural.
     
    Just as I did for the lower parts of the door, I created the porch tops as separate ‘bodies’, which I then moved into their correct positions by means of the ‘move/copy’ tool. This part of the model is shown below:
     

     
    It now looks a bit like a cathedral roof with transepts!
     
    Preparation for Printing
     
    I exported the upper and lower bodies from ‘Fusion 360’ onto my computer as two separate STL files, which I could open with my ‘Cura’ slicing program.
     
    At this point, it is important to check the design carefully on the computer screen, to ensure that all the details will print as expected. Because the interior of the clerestory is hollow, it is necessary to include some supporting structures, to ensure that the uppermost roof will print correctly.
     
    This support is generated automatically by the ‘Cura’ software but there are several parameters that can be adjusted. Experience has shown me that this support structure needs to be as ‘skeletal’ as possible since, otherwise, it can prove surprisingly difficult to remove.
     
    Because I have created some poor prints recently, I gave careful attention to the setting-up of the printer. I replaced the blue masking tape on the bed and then carried out a careful levelling process.
     
    I was now ready to create some test prints. The clerestory roof took about 1 hour to print, while the lower body took almost 2 hours. On examining the test prints, I found that my printer had performed very well, with good surface finish and clean openings for all the windows. I believe that it showed the importance of checking all the printing parameters before starting.
     
    It was quite surprising to see how small this carriage appeared, when seen alongside some of my other Broad Gauge carriage designs from the 1850s. The lower part of the body of the prototype was only 6’ 6” wide, so there was no advantage in dimensions over contemporary standard gauge carriages.  It is clear that Brunel’s ideas for his Broad Gauge did not include any thoughts of more commodious carriages!
     
    In spite of my comments about keeping the support structures to a minimum, I still found it difficult to clean out the inside of the clerestory and, in doing so, I damaged one of the frames between the clerestory windows. I have described my removal method in an earlier post; my main tool for the job is a set of wax-carving chisels.  For the next print, I shall try reducing the amount of support even further.
     

     
    Now, I’ve started the process of checking the test prints and refining the model as necessary. This involves checking dimensions against the available data (not much of that!), and cleaning up lots of details, such as rounding the corners to all the windows and adding bolection mouldings.
     
    The great thing about computer modelling, as opposed to ‘real’ modelling, is that all this ‘fettling’ can be done from the comfort of my armchair, with a laptop on my knee! I find it quite a therapeutic activity, slowly nibbling away at small details, checking and re-checking, with a restorative glass close by my side   By the time I had finished, the model on the computer screen looked like this:
     

    Computer Model after ‘Fettling’ (rounded corners, etc.)
     
    Next stage will be to design a chassis, with it’s characteristic ‘outside’ wheels.
     
    Mike
     
  3. MikeOxon

    Wheels for my Wagons

    By MikeOxon,


    General
    I got something of a shock when I saw the current price of Broad Gauge wheel-sets so that started me thinking about 3D-printed wheels. I realised that I wouldn’t be able to make metal rims but it could be a way of making basic wagon wheels in bulk.
     
    Many early GWR wagons used the form of wheel ascribed to Losh and Bell, in which wrought iron spokes were cast into the hub and wrapped around the inside of the wheel rim, to give the characteristic appearance shown in the following illustration from D.K.Clark’s ‘Railway Machinery’(1855)
     

     
    Losh Wheel Drawing
     
    I scaled the drawing for a model of a 4’ diameter wheel and then traced the outlines, to create a DXF format drawing.  I extruded the spokes and rim to a depth of 2 mm and the flange to 0.5 mm, using ‘Fusion 360’, and printed the result with my E 180 printer.
     

     
    3D-Printed Wheel on Printer Bed
     
    As usual, there were lessons to be learned.
     
    My first printed wheel had a gap in the side of one of the spokes, which turned out to be due to slight misalignment of one of the oval cut-outs within the spokes, by around 0.1 mm. This was sufficient to make that part of the spoke too narrow to be rendered by the ‘Cura’ software.  Adjusting the positions of the relevant surfaces in ‘Fusion 360’ corrected this problem.
     
    Afterwards, I realised that this error could be observed on the ‘Layers preview’ screen within the ‘Cura’ software. A lesson to check the preview carefully before committing a model to print!
     

     
    Layer Preview showing Printing Error
     
    Once the spokes all appeared correct on the single print, I made an array from the drawing and printed a group all together. As each wheel took only about 4 minutes to print, I had a batch of nine in around half an hour, with no further input needed on my part.
     

     
    Array of Wheels on Printer Bed
     
    I was surprised to find that there was still a stray chord of filament between one pairs of spokes in every wheel that was printed – all in the same place – even though I had checked the ‘print preview’ on the ‘Cura’ screen.
     
    The ‘penny dropped’ when I selected to show the paths traced by the printer, when moving from one part of the print to another. It was clear that there was a cluster of ‘paths’ causing stray filament deposition at the offending place. It was fairly easy to remove with a scalpel blade although the PLA thread is remarkable tough, even when in fine strands! Another lesson in checking before printing.
     

     
    Printer Travels in 'Cura' Layer View
     
    I found that this effect could be reduced or eliminated by moving individual items on the printer bed and checking the preview before printing.
     
    Now I have a handful of wheels that just need fitting onto axles. I am pleasantly surprised by the robustness of the finished wheels and by their smooth surface finish, especially considering that mine is a relatively low-cost machine.
     


    3D-printed Wheels
     
    EDIT:  As I mentioned in comments below "I could also try making a pair linked by a hollow shaft, which could rotate around a fixed axle.".  I have now tried this approach, with a clearance hole along the shaft, which I made half the back to back length.  I gently tapped the axle through the shaft to fix the first wheel and then tapped the remaining exposed axle into the second wheel until the halves met - instant alignment!
     

     
    Mike
     
     
  4. MikeOxon

    Wooden Goods Brake Van

    By MikeOxon,


    General
    In a previous post, I commented that I felt I was getting the hang of 3D-modelling. That didn’t mean that I can’t still get into a mess and sometimes things happen in ‘Fusion 360’ for which I have no explanation. For example, I was approaching the final stages of the chassis I shall describe below and found that one of the complete axle-box assemblies had moved about a centimetre from its proper place on the sole-bar. Back-tracking through the history made no difference, as the software seemed to think it had been like that from the outset!  I found that the simplest solution was to start from the beginning again, which went quite quickly as I remembered the steps I had taken before. This time, the parts remained in their proper places.
     
    After building a couple of cattle wagons and also having explored the possibility of printing my own wheels, I have turned my attention to the last vehicle in the ill-fated cattle train that was involved in the 1869 accident near Bullo Pill.
     
    To re-cap, the cattle train had left Carmarthen at 1.37 pm, with the “Tantalus ” engine and tender, 20 loaded cattle trucks, and a third-class break carriage. This carriage was placed at the tail of the train, and contained eight drovers in charge of the cattle, besides the guard. At Newport, six more trucks, loaded with general goods, were taken on, under the directions of the night foreman and the guard, but contrary, it appears, to the judgement of the engine-driver.  With that load, plus rails slippery from frost, the train made very slow progress, until a Mail Train caught up with it near Bullo Pill and its engine “Rob Roy”, a heavy engine, ran through the third-class carriage at the tail of the cattle train, mounted two of the cattle trucks in front of that carriage and rested part1y against the back of the third cattle truck.
     
    I am using the accident report as a ‘recipe’ for building authentic model trains of the period, since the report provides information about the vehicles involved. In this case, it is clear that a 3rd-class carriage was being used as a brake van on the goods train. For this role, it seems likely that an old carriage would have been used. The fact that it was completely ‘run through’ suggested to me that it was of light wooden construction.
     
    I have therefore chosen to model an early ‘Parliamentary’ carriage of 1844, which was converted from a previously-open 3rd-class truck by adding a roof structure to the basic wagon, in order to meet the Government requirement. I have based my model on a drawing in one of the Broad Gauge Society (BGS) data sheets, which also provides the following notes:  “The 1843 drawing is devoid of dimensions though includes a scale, while reference to the GWR 6/45 returns & Litho drawing prove helpful in establishing the [BGS] diagram. The 1842 drawing shows a superimposed outline of alteration, complying with impending Gladstone – Railway Regulations Act – Seating & Roof addition.”
     
    On the basis of the information from the BGS, I prepared my own drawings of the sides and ends of one of these wagons, which is shown as having outside wooden framing over sides which lean outwards towards the top, where extra panels of louvres and shutters have been added, up to the new roof level.
     
     

    My sketch of one side of 3rd class covered carriage, based on BGS information
     
    The construction of my model followed exactly the same steps as those previously described for my cattle wagon models.  I transferred my drawings, in DXF format, into ‘Fusion 360’, where I worked through the various panels, using the ‘push-pull’ tool to recess them behind the main frame components by suitable amounts.
     
    As before, I created the sloping louvres by using the ‘chamfer’ tool. To make this work, I had to recess one of the slats with the ‘push-pull’ tool, then select the edge of the adjacent slat and chamfer this edge to produce the desired slope. I then used the ‘push-pull’ tool again, to pull the original slat up to the original plane before repeating the procedure on another pair of slats. It was a tedious method but I couldn't think of another way of creating this effect.
     
    The next step was make the floor and ends as one ‘component’ and the roof as another, onto which I could fasten my already-printed sides. Once all the individual parts were completed, I transferred the 3D-drawings to the ‘Cura’ slicing software to provide files for my 3D-printer (all these steps have been described in my preceding posts)
     
    The end-point of these procedures was a small kit of parts, as shown below:
     
     

    Components of my Brake Van
     
    I bought some brown filament, because the blue looked so lurid, but the models will all be painted eventually. It is useful to show them in their raw form, to display the level of detail achieved by my printer. The flip-side of my change of colour is that the printed parts disappear more easily amongst the clutter on my work-desk!
     
    I assembled the parts using my previous method of welding the seams on the inside by means of a soldering iron tip set to 200°C. I noticed that the brown filament did not melt quite so readily as the blue, so there are differences between different brands that may need to be taken into account when setting up your printer. I had stayed with the same settings and they seem to have printed without a problem but it’s a point that needs to be watched.
     
    Making the model as an assembly of, mainly, flat components greatly speeds up the printing process. In the case of this carriage, with its outward-sloping sides, it also meant that I didn’t have to provide any support structures during printing.Once I had the body, it was time to move on to the chassis and, again, I used the same methods as previous described for my cattle wagon chassis.
     
    There is a trade-off to be made between being faithful to the prototype and providing a sufficiently robust structure from the plastic material. In this case, I made the springs a little too slender and two of them broke during printing but others held. This carriage has a six-wheel chassis with under-slung springs and, for future construction, I shall thicken up some of the components.
     
    Finally, there are the wheels, which were of 10-spoke Losh pattern. In a previous post, I described printing wheels of this type and I have now practised fitting these wheels to 2mm pin-point axles from the BGS. I had deliberately made the central holes in the wheels under-sized and I have used ‘Modelcraft’ broaches to open these out to fit the axles. I worked up to a 2mm broach in easy stages and it was then a matter of determining how much to open up the hole by trial and error. If the hole is slightly too small, the centre of the wheel distorts and the spokes can be damaged. It is tricky to get a firm fit without undue stress to the wheel and I shall probably need to make the centre of the wheels stronger in future designs. These wheels do work but I doubt they would stand up to regular use.
     
     

    Broaches used for fitting wheels to axles
     
    So, it was now time to put all the parts together and create the model shown below. This is unpainted and, apart from removing a few stray length of filament, is exactly as it came from the printer. The roof has a slight curvature towards the ends and is only resting loosely on the sides. As I mentioned above, the axle assemblies need to be strengthened for future models of this type.  I do rather like the ‘rustic’ appearance of this model, which seems to show something of its heritage in the wooden farm-cart. Many details, including brake gear, remain to be added
     
     

    My ‘rustic’ goods break van derived from a 3rd class carriage
     
    EDIT  I have now improved my wheels by adding an axle sleeve behind each printed wheel, to provide automatic alignment and back-to-back setting.
    see previous post for more information.
     
    Mike
  5. MikeOxon

    GWR Posting Carriage

    By MikeOxon,


    General
    After having constructed a range of models that were intended to replicate the two trains involved in the accident at Bullo Pill, in 1868, I have been casting around for ideas for new subjects.
     
    The trouble with a 3D printer is that it opens up so many possibilities that it is hard to decide what to tackle next. It would be easy for me to continue modelling various carriages, wagons, and locomotives but I have been looking for something that’s a bit ‘different’.
     
    One of the reasons that Brunel gave for advocating the adoption of the Broad Gauge, was that it would allow large wheels to be placed outside the bodies of the carriages. He considered that this would provide better running at the high speeds he envisaged for his new railway.  In fact, only one type of carriage was actually built on this principle, as it soon proved impracticable for carriages with several compartments, because the wheels would block access through the doors!
     
    The exception was the so-called ‘Posting Carriage’, which was intended as a luxury carriage for a small party of 1st-class travellers. The name was apparently derived from the French term: ‘post-chaise’.  Whishaw described this carriage in his book ‘The Railways of Great Britain and Ireland’, published in 1842, and he also provided a drawing:
     

    Wishaw wrote: “The posting-carriage, which is calculated to hold eighteen persons, is fitted up in a style of elegance not met with in any other railway-conveyance in the kingdom (save only the royal railway-carriage) : it is furnished with cushioned seats all round except at the doorways, and a table extending down the middle, so that for a family party or party of friends it is a most excellent contrivance. The whole length of the body is 18 feet 6 inches, and on a level with the seats 18 feet; the width of body is 7 feet 6 inches, and below the same level it is diminished in a recurving line to 6 feet at bottom, the height of body being 6 feet 8 inches. In the middle of each side there is a glass: door 2 feet 4 inches wide and 6 feet high, the glass-square being 19 inches high and 21 inches wide ; affixed to the sole of the carriage, and furnished with two steps, is an iron-tree, the bottom of which is 14 inches above the rails. On each side of the door there are two lights ranging in height with that of the door, and above these are three smaller lights, which fill up the whole of the top spaces between the door and the ends of the body.”
     
    There is another illustration of one of these carriages, included in a lithograph of Bath Station by J.C. Bourne, published in 1846.
     
     

    Extract from lithograph by J.C. Bourne
     
    Bourne’s illustration differs from the Wishaw drawing in several respects but it does serve to show the exaggerated curvature of the sides and the entrance door placed between the wheels.
     
    This vehicle piqued my interest and presented some interesting challenges in designing a 3D-printed model.
     
    First steps towards a model
     
    Because of the curved nature of the sides, I decided not to use my favoured method of printing the sides separately and then assembling the model from a ‘kit of parts’. Instead, I started by drawing the end profile and then extruding this, using ‘Fusion 360’, to produce a solid body, the length of the model carriage.
     
     

    Profiled Body of Posting Carriage
     
    That was an easy first step. Next, I shall hollow out the interior and add the detailing on the sides and ends. I expect this to involve many more procedures than a simple extrusion but it feels good to have a new project under way … more to follow.
     
    Mike
  6. MikeOxon

    GWR Posting Carriage – Part 3

    By MikeOxon,


    General
    In this post, I turn to the design of a chassis for my model Posting Coach. Fortunately, there is a detailed contemporary description and illustration, given in Whishaw’s book ‘The Railways of Great Britain and Ireland’, published in 1842.
     
    According to Whishaw: “The under carriage is formed of two soles, 7 feet 8 inches apart, 9 inches deep, and 4 inches thick, and projects 10 inches at each end beyond the body ; and six cross pieces, one at each end without the line of the body, which are 15 inches deep and 4 inches wide; and the others arranged one before and the other behind each pair of wheels, and equidistant from the centres of axles. The two ends of each of these cross pieces are finished with ornamented scrolls, and project six inches beyond the outer side of each sole. The diagonal braces, which are of 1½-inch iron, run from each angle of the carriage towards the centre of frame-; the carriage is furnished with complete buffing and traction-apparatus (see Plate XI.), and is mounted on four of Losh's wheels, 4 feet in diameter, and 10 feet from centre to centre of axles. The bow-springs are each 5 feet 4 inches in extreme length, the bed of each being 6 inches below the centre line of wheels.”

    Perhaps someone can enlighten me regarding the curious circular structures forming part of the draw gear?  I assume it is a shock-absorbing system.
     
    Rather than making my own drawing, I decided to import the Whishaw drawing into ‘Fusion 360’ as a ‘canvas’, on which I could build up the frames as shown below:
     

    Building the Frame over a ‘canvas’ in 'Fusion 360'
     
    I built the chassis ‘upside’ down and provided a thin floor, to ensure overall rigidity and to provided a firm mounting plate onto which the body can be fixed.  I created the undergear, axleguards, springs, etc. by using exactly the same methods that I described in a previous post about my early cattle wagons.  I did not print the headstocks at the same time, since these rise above the level of the floor and would not have allowed me to print from a level base. Instead, I drew these as separate ‘bodies’ in ‘Fusion 360’, aligned with the solebars.
     

    3D model of Chassis in ‘Fusion 360’
     
    I decided to take a risk by omitting any support structures in the openings above the springs, because I find it all too easy to damage fragile parts when trying to remove supports. In fact, the test print came out remarkably well and needed no significant cleaning-up before use. The following photo shows the model mounted on its wheels but, otherwise, exactly as it appeared immediately after removal from the printer bed, with no ‘cleaning-up’:
     

    Chassis with wheels fitted
     
    Once I had printed all the component parts, I could assemble them into my complete model of the Posting Carriage. I printed the headstocks separately and slid these into position over the ends of the protruding solebars, as shown below:
     

    Model carriage as printed
     
    This is my model exactly as it came off the printer. The remaining tasks are largely ‘painting and decorating’
     
    It is really surprising to see how small a ‘luxury carriage’ of 1838 actually was!  It is hardly surprising that Brunel’s idea of placing the wheels outside the body was swiftly abandoned. Unfortunately, this decision meant that very little space was left around the tracks, so Broad Gauge stock was never able to expand much beyond the confines of the British standard loading gauge.
     
    Within a few years, railway vehicles started to outgrow their ‘road coach’ forbears and even the primitive 3rd-class carriage of 1844 was considerable larger than this small vehicle! I have placed my two models together to illustrate the comparison.
     
     

    Posting Carriage model compared with closed 3rd-class Carriage of 1844
     
    Mike
  7. MikeOxon

    GWR Luggage Box

    By MikeOxon,


    General
    Following my recent series about modelling the GWR Posting Carriage,  @Mikkel asked “But where did the luggage go? Next project?”.
     
    In response, here is my next project!
     
    In the early years, the GWR addressed the need to transport passengers’ luggage by providing separate ‘luggage boxes’ – and it seems that Victorians always travelled with a very large amount of luggage! It should be remembered that, at that time, passengers’ ‘luggage’ might also include their personal carriage and horses so, to pre-empt the next question, I have added models of carriage trucks and horse boxes to my ‘to do’ list
     
    Two types of Luggage Boxes can be seen in a lithograph by J.C.Bourne of Bristol Temple Meads station, made in about 1840. This illustration has a great many features of interest but, in the present context, a smaller Box is shown immediately behind the tender of the ‘Fire-Fly’ class engine, on the right of the picture, while a larger one can be seen at the far end, in the centre of the picture.
     
     

    from a lithograph by J.C.Bourne, published 1842
     
    The early luggage boxes were constructed on the bases of carriage trucks, which helps to explain their rather curious profile. The boxes sat within the side rails of a carriage truck and then had sloping sides with lift-up side flaps, rather like those on modern road coaches or on many aircraft!.
     
    For further information, I am indebted to the Broad Gauge Society (BGS) Data Sheets, which were tirelessly compiled by the late Eddy Brown from many sources. These Sheets refer to the Bourne illustrations and point out that there are no official diagrams or drawings. What other information is available comes from Traffic Committee reports and supports the theory that these Luggage Boxes were based on Carriage Trucks, with similar frames and with the wheels set outside the body. All the evidence suggests a wheelbase of 5’ 6” with an overall length of around 10’.
     
    A Stock Account of 1840 indicates that 10 Parcels and Baggage Trucks had been delivered. Of these, one was an altered Carriage Truck, built by Braby, and three were Luggage Wagons with tarpaulins, built by Carr. The remaining 6, which I aim to represent by my model, were described as ‘Large Closed Baggage trucks for London’, built by Shackleford.  These last vehicles are described in the BGS Data Sheets as “Body - emulat[ing] the Original Carriage Truck with similar low sides, suitably positioned within wheel-sets though supporting deep end panelled sections. These enclose body and secure the over-all roof, forming a framework for the wide side panelled openings. Floor suitably boarded over”. A closer view is provided by J.C. Bourne’s lithograph of Bath Station, from which I have extracted the following detail:
     
     

    from a lithograph by J.C.Bourne, published 1842
     
    I decided to start by building a model of a BG Carriage Truck, which is on my ‘to-do’ list anyway, and then adapt it, as seems to have been done with the prototype, to create the original Luggage Truck.
     
    For the Carriage Truck, I can call on a description and drawing in Whishaw’s “Railways of Great Britain and Ireland”, dated 1842, as follows:
    “The carriage-trucks used on this line are each mounted on four of Losh's wheels, of 4 feet diameter, and 8½ feet from centre to centre of axles ; but having the ordinary springs 3 feet 4 inches from point to point, the bed being 4 inches above the centre-line of axle : this carriage is furnished with a Stanhope lever-brake. The length of the body is 15 feet 4 inches, the width 6 feet 8 inches, and the height of each side 14 inches; the weight of a carriage- truck is 7442 lbs.”

     
     
    To ‘convert’ this to the Shackleford type of Luggage Box, I have to reduce the wheelbase to 5’ 6” and the overall length to 10’, while retaining the main design features, including all those scrolled ends to the woodwork! There is an additional complication in that the BGS Data Sheets indicate that there were at least two version of these Carriage Trucks. The Whishaw drawings appear to show the later version with ‘Improved traction gear’ (I think that this refers to the circular structures within the draw gear), whereas the Bourne illustrations show an earlier version, with straight ends to the body, underslung springs, and no lever brakes.
     
    It’s important to remember that all these early vehicles were ‘hand-built’ by carpenters, so it is very unlikely that any two were exactly alike. In addition there is no opportunity to follow the usual modellers dictum “find a photograph of the particular vehicle you intend to model” – there are no photographs at this period!. It is, therefore, inevitable that many details have to remain conjectural.
     
    Modelling a Carriage Truck
     
    The Carriage Truck is basically a chassis, with two side rails and a flat bed for the load.  I was able to create my model chassis by adapting the one I’d already designed for my 3rd-class carriage, since the springs and axle guards appear identical in the two designs.  I had simply to adjust the wheelbase and overall length to suit the new vehicle. These modifications were made to the 3D model in ‘Fusion 360’ and followed what I can best describe as a ‘cut and shut’ procedure, mainly using the 'Move/Copy' tool.
     
     

    Modified 3D-drawing of chassis
     
    This proved to be a very simple build, since it was largely based on drawings of vehicles that I had made earlier. The headstocks, as seen in Bourne’s view at Bath Station, have some reinforcement around the draw gear, so I drew these areas onto the surface of each headstock and then extruded them by means of the ‘Push-Pull’ tool in Fusion 360.
     
    The two side rails were carried on ‘artistically’ shaped supports. I created the curved profile by using the ‘Spline curve’ drawing-tool in ‘Fusion 360’ and then extruded this profile, to form a solid body. It was then another case of using the 'Move/Copy' tool, to create the 8 supports needed for both sides of the vehicle. I positioned these along each side of the chassis, as shown in the BGS Data Sheet, and added top planks along each side.
     
    To avoid the need to allow for overhangs, I printed the chassis ‘upside down’, ‘growing’ the side frames and springs from the flat floor. I printed each of the two side rails separately, again printing them ‘upside down’ from the flat surface of the top planks.
     
    My model of the Carriage Truck, made up of three separate components – chassis and two side rails, bonded together using Superglue, is shown below:
     
     

    Two views of my 3D-printed Carriage truck
     
    In my next post, I shall describe my construction of the Luggage Box itself, which sits on this framework. For the moment, en passant, I already have a Carriage Truck
     
    Mike
  8. MikeOxon

    Hinged Doors for a Luggage Box

    By MikeOxon,


    General
    By the end of the previous post, I had completed the chassis for my planned Luggage Box. I expected the Luggage Box itself to be a simple construction: two panelled ends, two sides, and a roof.
     
    Following my now usual practice, I created each of these parts as a separate ‘body’ in ‘Fusion 360’, so that each could be laid flat on the printer bed and could be printed in a few minutes, to the required panel thickness. A wave of a 200° soldering iron to seal the joints and that would be that – Bob’s your Uncle, etc.
     
    It didn’t turn out like that because one of those pesky Danes  @Mikkel  raised a challenge (I thought King Alfred had settled things with
    them a long time ago), so Wessex honour was at stake.
     
    The challenge was to provide hinged sides, so that it could carry the wedding trousseau of the future mother of Amy and Blanche from Gloucester to North Leigh, for her marriage to Lord Wilcote.
     
    I’ve never tried to build jointed parts with ‘Fusion 360’ and had little idea of how to begin but a cunning plan soon emerged. In fact, I started exactly as originally intended by drawing the ends, sides, and roof to the required dimensions. One thing I learned, when thinking about moving parts, was how different the necessary clearances look on a computer screen from when reduced down to a 4 mm scale model. What I thought were gaps large enough to drive the proverbial bus through, turned out to be impossibly tight in the actual model.
     
     
     
    Adding Hinges
     
    Once I had drawn the end profile of the roof and extruded the drawing to create a solid roof, I added more drawings, to form two cylinders running along each side of the roof, as shown below. I used exactly the same procedure to add tubes to the side doors:
     

     
     
    After creating the cylinders, I used the ‘Hole’ tool in ‘Fusion 360’ to open them out into tubes, to take standard 2 mm diameter axles. In the case of the tubes along the roof, I drew two rectangles on the top of the roof and used the ‘Push-pull’ tool in ‘cut’ mode, to open apertures that would accommodate the hinge parts on the two side doors. Similarly, I limited the length of the tubes on the side doors to fit into the gaps that I had cut out from the roof.
     
     

    My 3D-model showing hinged components.
     
    The first attempt was far too tight and although the sides fitted in the closed positions, the axle pins would not thread though the relevant tubes. Rather than trying to calculate the clearances required, I took an empirical approach. I examined the first set of test prints and estimated the amount of extra clearance that was needed. I then returned to the design on the computer and used the ‘Move/Copy’ tools to re-shape the hinge components on the side panels. Amazingly, the 2nd test print fitted together quite well. I’m sure a little more fettling and adjustment would improve things further but, for the moment, I’m satisfied that the method works
     
     

    Hinge mechanism as printed.
     
    I covered the roof with a film of black self-adhesive vinyl. The roof is slightly curved, with a one-inch rise to the centre (in the prototype). My FDM (layered) printer showed obvious lines between the deposited layers, where it had tried to follow the curve. The vinyl hides these ‘steps’ and also masks the (small) gaps around the hinges
     
     

    Components of Luggage Box
     
    On the subject of roofs, I read an interesting snippet in D.K.Clark’s ‘Railway Machinery’, dated 1855, page 274: “The roof is covered with ox-hides stretched tightly over it, or stout canvass, well saturated with white lead; ox-hide is superior to canvass, when luggage is to be carried on the roof. The covering is turned over at the edges of the roofing and fastened under the cornice mouldings.” I have not read before of hides being used in this way.
     
    I extended the side rails from those shown in my previous post, so that they could pass through slots in the end panels and stand slightly ‘proud’, as shown in the ‘Bourne’ lithographs. The whole model looks quite complex, when viewed on the computer screen but, by breaking it down into separate ‘bodies’, I created a collection of simple components that could be printed in just a few minutes each and modified independently, if adjustments were needed.
     
    Once I had welded together the various components, my model looked like this:
     


    Two views of my model, as printed and assembled
     
    There’s a lot of ‘finishing’ to be done but I’m pleased to have the basis of an interesting model. I now need to move on to thinking about a complete train, perhaps with a ‘Fire-Fly’ class locomotive in charge.
     
    Mike
     
    The heading image to this post shows my models headed by one of the Gooch singles
  9. MikeOxon

    Broad Gauge Horse Box

    By MikeOxon,


    General
    My ‘Geeetech E180’ printer seems to be performing exceptionally well at present, so I have been cracking on with some items from my ‘to do’ list.
     
    After the poor results I was getting last year, I made a point of going through the long list of adjustable parameters in the ‘Cura’ slicing software. I suspect that the most significant change I made was to the ‘line width’ setting. The default setting matched the print-head diameter of 0.4 mm but I reduced the setting to 0.3mm. Since the print-head has a circular aperture, only a small part of the filament cross-section is as wide as 0.4mm. The closer spacing of successive paths does appear to result in a much smoother surface. Most of the model photos I have shown recently have been ‘straight off the printer’ and very little ‘fettling’ has been needed.
     
    The original design of GWR Horse Box was another Broad Gauge oddity, in that the wheelbase of 6 feet was shorter than the track gauge! The length of the box was apparently determined by measuring the girth of a ‘typical’ horse and then allowing sufficient room for 4 horses to stand side-by-side, standing across the vehicle. A loading ramp and doors were provided on only one side of the vehicle. There are drawings in Whishaw’s book ‘The Railways of Great Britain and Ireland’ and examples can also be seen in some of J.C.Bourne’s lithographs. I have also made much use of the invaluable information provided in the Broad Gauge Society Data Sheets.

    Creating the Body
     
    My model was constructed by my now usual method. I created the two ends together with the floor. I used the ‘push/pull’ tool in ‘Fusion 360’ to emboss lines of planking into the end panels and then drew the outside frames and extruded them to stand proud of the planking.
     
    I created the two sides as separate ‘bodies', with the detailing of the drop-down loading ramp applied to only one side. This method allowed me to print the sides lying flat on the print bed, so each side only took a few minutes to print.
     
    I made each louvred panel in the upper doors by drawing a ‘toothed’ side profile and then extruding this drawing along the width of the door panel. Previously, I have used the ‘chamfer’ tools to create the sloping slats but my more recent method is much quicker and easier to implement. I often look back at some of my earlier designs and realise that some of my methods were unnecessarily ‘long winded’ but that’s all part of the learning curve. I have always described my models as ‘experimental’.


    Creating a Louvred Opening
     
    I now had a set of components from which to construct the body of my Horse Box, as shown below, exactly as they emerged from the printer.


    3D-printed Components of Horse Box
     
     
    Creating the Chassis
     
    I was able to create the chassis fairly quickly, by adapting chassis components from earlier models. Thus, I did not have to spend time creating springs and axle-box details. I simply adjusted the wheelbase and overall length of the solebars to suit the current model.
     
    Unusually, however, for the early period on the Broad Gauge, this Horse Box ran on wheels of 3’ diameter, rather than the 4’ wheels preferred by Brunel. I used my existing models of 4’ diameter Losh-type wheels and reduced the diameter to 75% while keeping the same tread-width and separation.
     
    This size reduction led to some problems with printing the spokes since, when I checked the ‘printability’ of the new version on the ‘Cura’ print preview screen, the spokes turned out to be too narrow to print correctly. Once again, I used the ‘push-pull’ tool in ‘Fusion 360’ to move the side faces of the spokes, to ensure that there was sufficient width for my printer to resolve the outlines correctly.
     
    3D-printed wheels on printer bed
     
    Note the use of a ‘brim’, which can be applied automatically by the ‘Cura’ slicing software, that helps to ensure adhesion of small components to the printer bed. The half-axle sleeves are designed to fit around a standard 2 mm diameter steel pin-point axle, to provide automatic alignment of a pair of wheels.
     
    Assembling the Components
     
    I fitted the two panelled sides between the fixed end panels and added the roof. All the components had printed cleanly and fitted together easily, with no ‘fettling’ being necessary. The body is currently just resting on the chassis for the following photographs.


    my assembled Horse Box
     
    The small diameter of the wheels is very noticeable and, when combined with the extremely short wheelbase must have contributed to a rough ride for the unfortunate inhabitants of these vehicles. The comment by @Michael Hodgson on my previous post that they’d be OK for rocking horses seems very apt
     
    The three vehicles that I have produced over the last few weeks vividly illustrate the ‘primitive’ nature of railway design at this early period, around 1840. With the benefit of hindsight, it is hard to understand how anyone could have thought these designs were appropriate for vehicles intended to operate at the high speeds that Brunel expected to achieve with his railway. To set these thoughts in context, however, it was only a few years earlier that many people thought that a locomotive could not operate at all, by rotating metal wheels over a metal rail!


    my three recent GWR Broad Gauge models
     
    Following my recent rush of activity, I expect there will now be a pause while I contemplate the rather larger task of building a model of one of the early Broad gauge locomotives.
     
    My best wishes to those looking forward to the Easter holiday.
     
    Mike
     
    The header picture is of sketches from J.C.Bourne’s notebook
     
  10. MikeOxon

    ‘Fire Fly’ class - Research

    By MikeOxon,


    General
    Introduction
     
    One thing leads to another and what, for me, started as a small project to build the interesting-looking ‘Posting Carriage’ from the early years of Brunel’s Broad Gauge railway, for the GWR, rapidly extended to include a Luggage Truck and Horse Box.
     
    All these vehicles appeared in some of the beautiful lithographs by J.C Bourne, published in 1846. In particular, his illustration of Bristol Temple Meads Station, shows an engine of Gooch’s ‘Fire-Fly’ class heading a train including vehicles that I have now modelled.
     
     

    extract from a Lithograph by J.C.Bourne, 1846
     
    Thus, the next step for me was clearly to add a model of this type of engine, in order to create a complete train from the 1840’s period, when railways were on the threshold of transforming the mobility of goods and people throughout Britain.
     
    Background Research
     
    Before starting to create a model, I needed to learn a lot more about the ‘Fire-Fly’ class of engines.  These became famous as the designs by the young Daniel Gooch that transformed the fortunes of the GWR.  The first engines that had been delivered in accordance with Brunel’s specifications had mostly been complete failures, although some became useful after extensive re-building.
     
    Gooch saved the day when he managed to procure the engine ‘North Star’,  which Stephenson’s had to hand from a failed overseas contract.  This engine and its subsequent companions inspired Gooch to create his own design, incorporating new principles that paved the way for ‘mass production’.  He supplied drawings and templates to several different manufacturers, insisting that they conformed to his detailed specifications, so that replacement parts would be common to the whole class.
     
    It was a period of massive development in workshop practice, with engineers like Maudslay and Whitworth introducing methods that allowed accurate machining of components, including such key items as screw threads, to standardised dimensions. A the same time, new metallurgical processes were producing hardened surfaces that resisted wear and tear, so allowing reliable operation of machinery over long periods.
     
    It was these overall design features, rather than individual mechanical innovations that were to make the ‘Fire Fly’ class such successful engines. Brunel’s adoption of the Broad Gauge helped, in that it enabled all the working parts to be laid out in a spacious and easily-accessible manner.
     
    Two reference books in particular proved very useful to me, in finding more details about the ‘Fire Fly’ class: (i) Part Two of the RCTS series about ‘The Locomotives of the Great Western Railway’ provides dates and dimensions of all the engines, with information about their service lives, (ii) a more recent publication by Rev. Canon Brian Arman in Part Two of his survey of ‘The Broad Gauge Engines of the GWR’ contains a wealth of drawings and photographs of the class, throughout its period of use until 1878.
     
    For a contemporary source, Wishaw’s ‘Railways of Great Britain and Ireland’, 2nd ed. published in 1842 contains the following drawing:

     
     
    There is another contemporary description in David Joy’s diary (he later designed the ‘Jenny Lind’ engine) from his early working days in 1842, with Fenton, Murray and Jackson: “… and then got at the interest in the engines. These were Great Western Railway passenger— engines, 16 in. by 20 in. cylinder; 7 ft. wheel. They were a very handsome looking engine, with bright brass dome, and wheel splashers—old fork and gab motion—and I fitted one of these forks, having learnt to file and chip and [he adds] to mash my knuckles with the hammer.”
     
     
    Similarities and Differences
     
    In spite of Gooch’s tightly controlled specifications, there were many differences in detail between the products from the different manufacturers, which affected the overall appearance of their engines. Thus, as so often happens in railway modelling, it is necessary to look at individual engines in order to create an accurate model.
     
    One very obvious difference lay in the shape of the outer firebox cladding (although the internal dimensions were standardised) Some manufactures used a ‘Gothic’ shape with prominent ‘arches’ on each side of the firebox, while others adopted the ‘Haycock’ shape, with a domed steam space above a rectangular lower cladding.
     
    Another obvious difference lay in the position of the manhole cover, provided to allow cleaning of the interior of the boiler.  In most cases, these covers were on top of the cylindrical boiler but, in those engines built by Fenton, Murray, and Jackson, the cover was on the front face of the outer firebox. This distinguishing feature is clearly visible in the engine shown in the Bourne lithograph, above.
     
    Rather surprisingly, these Fenton Murray and Jackson engines also had an overall wheelbase that was 2” (50 mm) longer than other engines. This alteration must surely have been approved by Gooch but the reason is unclear.  Gooch is, however, reported to have said that these engines were the best of the class.
     
    As with most engines, variations soon began to creep in, with various re-builds. Some changes were major, such as conversion to tank engines, while others related mainly to boiler fittings, such as removal of the separate safety valves, originally mounted towards the front of the boilers in tall cylindrical brass casings.
     
    When first built, all the engines used the ‘gab gear’ to operate the valves, which was based on that used by Stephenson in ‘North Star’.


    ‘Gab’ valve gear
     
    By the mid 1840’s the advantages of variable valve gear were being recognised, to allow ‘expansive’ working of the steam, which reduced coke consumption. The Gooch brothers devised their own version of expansion gear and this was applied retrospectively to existing engines, over a period of several years, with 26 engines having been converted by 1849.  Another improvement to the ‘Fire Fly’s was lengthening the piston stroke from 18” to 20”, which seems to have started in around 1844, some of the later engines being delivered new with the longer cylinders. It seems possible that this modification was applied to existing engines at the same time as the replacement of the valve gear.


    Gooch Expansion Gear
     
    In later years, round-top fireboxes were substituted for the ‘haycock’ design and the boilers were extended by about two feet, so that these engines came to resemble the proportions of much later locomotive designs, with cabs and other ‘modern’ features making their appearance!
     
    So, what to choose? I decided to be guided by the Bourne engravings and also by a very clear early photograph of ‘Argus’, which was a Fenton Murray and Jackson engine, as shown below:
     
     

    Fire-Fly class engine ‘Argus’
     
     
    My 3-D Model of the Firebox
     
    My main challenge in designing a model of this engine lay in the shape of the ‘Haycock’ firebox. I puzzled over this for some time, drawing arches in ‘Fusion 360’ and attempting to fill in the panels between them. It possibly can be done in this way but I didn’t find out how, so I eventually settled on a different method, as follows:
     
    I first drew the outline of the base and added an arc quadrant in the vertical plane as shown in ‘Step 1’ below. I then extruded the arc to form a half-arch, as shown in ‘Step 2’ below. Next, I drew a triangle in the horizontal plane below the arch and used the ‘extrude tool’ in ‘cut’ mode, to produce one segment of the ‘Haycock’ top of the firebox:


    Steps in Creating 3D ‘Haycock’ Firebox
     
    After that, it was simply a case of copying the first segment and moving and rotating it, to form the remaining three segments. Once all the parts were in position, I used the ‘Combine’ tool to join the segments of the firebox into a single body. As a finishing touch, I used the ‘Fillet’ tool, to round off the corners.
     
     

    3-D design for ‘Haycock’ Firebox
     
    Measurements of various drawings showed that the ‘Haycock’ tops on the prototypes were a little higher than indicated by my result, based on circular arcs, but this can easily be adjusted in the ‘Cura’ software, immediately before printing, by a change to the vertical scale.
     
    Next Steps
     
    Constructing the firebox top was the main difficulty I had expected to encounter, when designing my 3D-model of a ‘Fire Fly’ class engine.  I am now reasonably confident that I can continue with the design of the remaining parts of the engine, by using the same ‘hybrid’ techniques that I have used previously for my various existing designs, for both the Broad and Standard gauges.
     
    Brass tube for the boiler is now on order from Cornwall Model Boats.
     
    Mike
  11. MikeOxon

    Armstrong Goods - Adding a Tender

    By MikeOxon,


    general
    At the end of my last post, I felt that I had solved all the main problems associated with building my Armstrong Goods engine, although a lot of detailing remains to be done.
     
    To complete the model, I needed to add a tender, which I intended to contain the drive unit. I have made several powered tenders based on 'Hornby' ring-field mechanisms, around which I used components from either plastic or white metal kits. I have used two different 'Hornby' mechanisms: type X9105 with 7' 6" + 7' 6" scale wheelbase and type X2024 with 6' 6" + 6' 6" scale wheelbase. In both cases, only the outer axles are driven, while the centre axle is free running.
     
    There is a very useful overview of GWR Tenders by Jim Champ on the GWR.org website. In this, I read that “The earliest standard-gauge tenders, like the locomotives they were attached to, were a rather motley collection from a variety of manufacturers.” From 1866, however, Swindon-built tenders had iron-plate frames and most had the now standard 6' 2" + 6' 10" wheelbase. 306 were built, typically 1800 gallon capacity.
     

    Typical Armstrong Tender
     
    Note that the overall wheelbase of these tenders was 13 ft, which matches the 'Hornby' X2024 drive unit, in which the centre axle can easily be moved to represent the unequal spacing of the prototype axles. There are many photographs of Standard Goods engines with these tenders, some with or without coal rails but often with remarkably high loads of coal which, in model form, can be used to cover the drive motor! A particularly spectacular example is shown at Widney Manor Station on the Warwickshire Railways website.
     
    I found a drawing of an Armstrong tender at Fig.62 in Russell’s ‘Pictorial Record of GW Engines’, which I used as the basis for my model. There are many differences in detail between different photos but I decided that this drawing was a fair representation of the type.
     
    Whereas my practice in the past has been to prepare my drawings in a 2D program, such as ‘Autosketch’, I decided to try a new approach by using the drawing tools within ‘Fusion 360’, which meant that all my design work was done within the same software package. This proved very successful, as these drawing tools have many features that made it easy to align and replicate the various elements of the drawing. To guide my drawing, I used the ‘Insert canvas’ feature on ‘Fusion 360’ to display a copy of the drawing in Russell, as a background over which I could lay out my own drawing.
     
    By following this procedure, I drew one side of the tender as shown below:
     

    My Drawing of Tender Side in 'Fusion 360'
     
    Drawing all those rivet and bolt heads could have been extremely tedious but the ‘move and copy’ commands in ‘Fusion 360’ made it a lot easier! I drew one short line of rivets and then duplicated these, as necessary, to form long rows or regular arrangements, such as those around the hornguides. A line of five quickly duplicates to 10, then 20, and so on.
     
    Once I had completed the drawing, I could use the ‘push-pull’ tools to raise all the necessary features by appropriate amounts, to create a 3D drawing of the complete tender side. The selection tools make it easy to select many similar feature at the same time, so that these can be raised all together. The resulting 3D model is shown below:
     

    Tender Side extruded from 2D Drawing in 'Fusion 360'
     
    I also continued my method, as used in other models, of designing the complete tender as a ‘kit’ of separate parts that could be printed and tested individually, without involving long print times. Having drawn one side, it only required a single click on the ‘Mirror’ command to create the opposite side
     
    The front and back of the tender were created by using exactly the same methods and all the parts were transferred separately to my ‘Cura’ slicing software to prepare them for 3D printing. Even the long sides only took around 20 minutes to print, so I could make minor adjustments to the drawings without any very long delays.
     
    Once I had printed the individual parts, I could join them together by welding inside the corners with a soldering iron bit set to 210°C. Then I lowered the open box structure over my X2024 drive unit. It proved to be a very close fit and I shall have to re-arrange some of the wiring to pack everything in, within the narrow constraints of the overlays.
     

    Tender Sides fitted around Motor Drive Unit
     
    It is clear that the coal load has a lot of work to do!
     
    A highly visible feature of early tenders was the profusion of tool boxes that they usually carried, either all on the top plate or, in some cases, on a broad shelf immediately above the back buffer beam. In a study of GWR tenders published in the Broad Gauge Society magazine ‘Broadsheet’ vol.18.14, the authors speculated that these extra boxes held locomotive screw jacks.
     
    I 3D-printed a suitable collection of these boxes on a top-plate for the tender, which will also form a base for the considerable ‘coal load’. The two slots, adjacent to the central cut-out for the motor, are to fit over raised strips on top of the motor block. The following photo shows the tender top loosely positioned on top of the tender body, to check the fit of these components:
     

    Tender Shell with Four Tool Boxes & Filler Cap (in primer)
     
    In order both to conceal the motor and provide a base for a coal load, I first wrapped the drive unit in 'cling film'. This was to protect it from water and dust during the following process. I then cut a small rectangle of plaster bandage (‘Mod-Roc’), soaked it in distilled water, and wrapped it closely around the upper part of the motor unit. I laid my printed top plate over the bandage and weighted it down to hold everything in place while the bandage hardened overnight. I only used one layer of bandage since I did not want too rigid a structure but simply a conformal cover that would prove a suitable surface for adding ‘coal’ chips.
     
    Once the bandage had set, I trimmed away all the excess material but left a layer of cling film inside the bandage across the top of the motor. I then painted the exposed surface with dull black acrylic.
     
    The final task was to paint the tender sides and top with two coats of 'Precision Paints' 1881-1906 GWR Green for the sides, Indian Red for the outside frames, and Black for springs and other parts. The final result is shown below:,
     

    My ‘Armstrong’ Tender with base for adding ‘coal’ load
     
    I realise that many people do not like tender drives but there is no reason why my modelling methods could not be applied to any other type of chassis, if I decide to make changes in the future. The more recent 5-pole 'Hornby' motors run a lot more smoothly than earlier designs and I note that ‘Strathpeffer Junction' models list various ‘upgrade’ kits based on the use of CD/DVD motors, although these are currently not in stock. I may try one of these at some stage, to see if they make a significant improvement.
     
    I need to consider the addition of lining and will do this when I complete the detailing of + locomotive. In photographs of the prototypes, the lining always seems quite subdued and I feel that many models suffer from over-prominent lining. I shall probably make my own, using my Silhouette cutter, as described in earlier posts.
     
    Mike
  12. MikeOxon
    There is one problem that has been lurking in the background throughout my design of this outside-framed locomotive – how to fit the wheels? The wheels need to be pressed onto their axles and set to gauge, before fitting them to the locomotive.
     
    I had already decided that this engine will be tender driven, so I do not have to make provision for a gear train. After considering various options, I decided to adopt the method used in the tender-drive ‘Mainline’ Dean Goods model. Since I have previously converted one of these models into an outside-framed ‘Stella’ 2-4-0, I already knew that this was a feasible approach. [see : GWR 'Stella' 2-4-0', Railway Modeller, April 2013]
     
    I decided to reproduce the ‘Mainline’ method, by creating a ‘sub-chassis’ to hold the driving wheels in their correct alignment while also allowing them to be removed from the rest of the model for any servicing that might be required.
     
    To do this, I designed a hollow box girder to run the length of the locomotive with transverse holes to retain the axles in their correct locations. After creating this simple 3D object in ‘Fusion 360’, I split the ‘body’ in two, along the centre line through all the axles, as shown below:
     

    Sub-chassis to carry axles in correct alignment
     
    The two split ‘bodies’ could then be transferred separately to my ‘Cura’ slicing software and printed as upper and lower halves of the complete sub-chassis. Nuts and bolts can be used to hold the halves together around the axles, with the wheels already attached, although for my initial tests I have simply wrapped adhesive tape around the two halves, between the axles.
     
    I needed to open out the axle holes into slots on my 3D-printed outside frames, so that these could be lowered over the extended axles. The rest of the superstructure, starting from the footplate, could then be added in layers above the brass frame structure. The process of assembly is shown below:
     

    Assembly of Major Components of my Armstrong Goods
     
    By making the body as an assembly of separate components, wrapped around a brass cylinder to represent the boiler, it was easy to paint the parts in their appropriate colours, without any need for masking between differently coloured areas. Although I hadn’t realised at the outset, this ‘layered’ method of construction also facilitated alignment and rapid assembly into a complete locomotive.
     
    I now feel that my model is a viable ‘rolling’ engine. Of course, there is plenty more to be done, including assembling the final form of the running gear and then adding a lot of detailing, including lining and lettering, for which I will use the techniques I have previously described in this blog.
     
    There is also the matter of the powered tender. I have a variety of different designs all of which were designed to be transferable between different engines. All the ones I have built so far have been based on Dean designs, so I shall create a new body in the Armstrong style to fit around one of my existing power plants. My adoption of 3D-printing has greatly increased the scope for making different tender types.
     
    Mike
     
     
     
     
     
  13. MikeOxon
    At the end of the previous part, I had printed the main body components but was experiencing difficulty in printing small boiler fittings. The difficulty was that, on their own, these had no flat surface to lay on the printer bed. My next idea was to ‘slice’ these components just above the curved flanges that fit around the boiler and print the upper and lower parts separately, so that they could subsequently be glued together across their flat faces.
     
    To my surprise, the tiny components printed remarkably well and could be glued together as I had anticipated. Considering that my E180 printer had only cost me £185 (it was on offer at the time), I considered this a remarkable achievement. Below, I show a couple of these tiny parts in the palm of my hand.


    3D-printed Dome & Safety Valve Cover
     
    I have always tried to arrange items for printing so that there are no overhangs, which are a major problem for fused-deposition printers like mine. This is because they cannot lay down plastic filament over empty space. I’ve found, however, that my printer appears to be fairly tolerant of small overhangs, where the new layers can adhere to adjacent layers in the same plane. I found that this was the case when printing flanged wheels, when the flanges were reproduced without any support below them.
     
    As another step along these lines, I decided to try printing the flange below the chimney of my current model as an integral part of the smokebox and found that it worked very well. I followed this by re-printing the boiler with protruding flanged bases on which to mount my flat-bottomed dome and safety-valve components. The revised boiler and fittings printed successfully, as shown below:
     

    Boiler & Smokebox with flanged mounting points
     
    Printing the chimney raised some interesting new challenges. Since the mounting flange was already printed on the smokebox, the main task was to produce the flared cap. I started by extruding a cylinder and then, as shown below, used the ‘fillet’ and ‘chamfer’ tools in ‘Fusion 360’ to create a suitable cap.
     
    Stages in 3D-printing a flared chimney
     
    Some of the finer points are beyond the resolution of my printer but it’s good to know how to do them. Once I had worked out the methods, the actual design went very smoothly and the chimney printed successfully in less than 10 minutes. When printing, I included a wide brim as a support structure at the base, in case the chimney toppled during printing. I suffered this experience with one of my boiler test prints, when I forgot to provide a brim and ended up with a messy blob of plastic on the printer bed!
     

    Chimney with support brim on printer bed
     
    It was by way of light relief from the design effort I had expended on the chimney that I also printed the smokebox front, with a sloping cover for the fronts of the cylinders. The smokebox door has a very shallow curve, which is obviously layered in the 3D print but I’m hoping that priming and painting will minimise the visibility of the steps.
     
    The next, more complex task, was to print the cab. I had decided to provide the later style of cab with a roof, rather than the vestigial version originally fitted by Armstrong. It is said that Armstrong believed that enclosed cabs were unhealthy, which was probably true when coke was the fuel and considerable amounts of carbon monoxide were produced.
     
    I designed the cab so that it would lie on the printer bed with the flat front downwards. The first stage was to extrude the cab front and rectangular sides. I then copied a drawing of the side of the cab, including the shape of the side openings and the wheel arch. I overlaid this drawing as a DXF import over the cab side and used the ‘push-pull’ tool in ‘Fusion 360’ to open out these shapes. I also added an arc to the top of the cab front and extruded this to form the roof.
     
    Having extruded a drawing of the outline of the back-head and used the ‘fillet’ tool to create the rounded edges, I started adding representations of various controls and pipes, with reference to photographs. In 4 mm scale, I feel it is sufficient to trace the general outlines, rather than attempting to add too many details. I illustrate the steps below:


    Stages in printing the Cab
     
    After printing all these items, none of which took very long to print, although the design time was much longer, it was time to see if they would all fit together and clear the 00-gauge wheels. There are rather large gaps around the wheels, which will be filled when I add the tops to the wheel arches, either from brass strips or plasticard.
     

    current stage of my Armstrong Standard Goods
     
    I think the result has captured the ‘look and feel’ of Armstrong’s prototype rather well. There are of course, many fittings still to be added but I think my work so far has demonstrated the feasibility of making attractive and robust models by means of a combination of brass sub-structure and 3D-printed overlays. This is not an example of skilled model-engineering but it demonstrates that pleasing results can be obtained from low-cost equipment operating in a domestic environment.
     
    The difference in ‘character’ between the Armstrong Standard Goods and its successor, the Dean Goods, came across very clearly when I placed my model head-to-head with my ‘Mainline’ Dean Goods, as shown below:
     

    my models of Armstrong and Dean Goods engines head-to-head
     
    The boiler of the ‘Dean’ is both shorter and higher in pitch than the earlier design, which give it the ‘pugnacious’ look that I once commented upon in an earlier post, The ‘Armstrong’ has the less robust look of an engine from the mid-nineteenth century. One of the pleasing aspects of ‘rolling your own’ is that you do not have to accept the compromises that are inevitable when relying on ‘bought in’ components, which are rarely designed to meet the needs of the modeller of 19th century prototypes.
     
    Mike
  14. MikeOxon
    Never become complacent! After a long spell of trouble-free printing, I started to encounter problems a couple of weeks ago. First off, the old problem of lack of adhesion to the printer bed returned. I had become lazy about replacing the blue masking tape and the surface had become worn. After replacement and re-levelling, all seemed well again ... until the heat wave struck. The next problem was uneven printing.  It was too hot for me in my work room, so I left it alone while I got on with designing components for the Armstrong Goods on my laptop.
     
    When I ventured back to the ‘hot room’, I noticed that the printing filament seemed to have become hard and brittle. Some reading on the web confirmed that this is a symptom of water absorption in high humidity. I unwound the outer layer and it seemed better underneath. I must take care to keep my filament reels in desiccated containers, as recommended. Next, I tried a test print of one of my outside frame overlays and found that filament was ‘stringing’ between the rivet heads, so that they merged into raised lines. Earlier prints of frames for my Gooch tender had been very good, so I had yet another problem to investigate.
     
     

    Poor-quality 3D Print
     
    From more reading on the web, the principal suspect was filament temperature. I realised that, with my work room almost 10°C warmer than usual, the filament exuding from the print head was cooling less rapidly, so I lowered the print-head temperature by 10°C to try and compensate. Results improved considerably, although still not as crisp as I had on my earlier tender. I shall have to wait until the room temperature drops, to see if the previous performance is restored.
     
    While trying to solve the problems, I made several test-prints of the side frames, which profligacy was fortunately not too serious, since the cost, calculated by the ‘Cura’ software, was only £0.02 per frame In addition, each print only took 10 minutes to complete, so I was able to assess the effects of changing parameters quite rapidly.  This is an important advantage, gained by assembling a model from small individual components. 
     
    I needed to print four main components to add flesh to the brass skeleton, plus a set of wheels from ‘Alan Gibson’. The quickest to print were the outside frames at 10 minutes per print, followed by the smokebox at 19 mins., then the footplate and splasher fronts at 40 mins., with the boiler and firebox taking the longest, at 57 mins. None of these times was sufficient to present a deterrent to making trial prints for testing clearances and fit during assembly.
     
    I printed the boiler vertically from the firebox end. Unfortunately, this precluded adding boiler fittings, such as the dome, as they would require additional support which might be difficult to remove without damaging the surface finish. I decided to print these fittings separately.
     


    3D printed cladding on brass boiler tube
     
    After the other printed components were complete, I glued the outside frame overlays onto the sides of the brass chassis assembly. To check the clearances around the wheels, my method is to thread the wheels onto long M3 machine screws and then add nuts to hold the wheels at an appropriate back-to-back spacing between the frames. I have used this method for my broad gauge models as well and find it a convenient way of checking the overall alignment before committing to fixing the wheels onto their axles. The component parts are shown below:
     

    3D-printed parts added to the brass components, with temporary wheel fittings
     
    My checks showed that the clearances for the footplate and splashers were appropriate, so I could now assemble the parts to make the main body of my Armstrong Goods engine.  With its strong brass skeleton, my model has a good ‘solid’ feel.


    Components loosely assembled on chassis
     
    I tried 3D printing a dome and, while the main shape printed well, the flange to the boiler did not. I shall need to give more thought as to how to support this part of the structure during printing.
     
    I did include the dome when I pasted a photograph of my model over the illustration of prototype No. 661. I am very pleased with the results so far, although there is still quite a lot to do in order to complete this model. My next steps will be to print the smokebox front and the backplate.


    My Model (brown) superimposed over Engine No.661
     
    EDIT - On looking at the photos, it was clear that the hind splashers were incorrectly positioned.  Re-measurement of the computer drawing showed I had placed them 1 mm forward from their correct position.  I have no idea what happened except that "to err is human".  I have re-positioned them and will re-print. this component
     
    Mike
     
  15. MikeOxon
    In my previous post, I showed the brass components that will form the ‘hard’ skeleton of my planned model of an Armstrong Standard Goods engine. The fireman’s side of No.661 is shown below to complement my previous illustrations of the driver’s side of No.31:


    Armstrong Standard Goods No.661
     
    Now, I shall describe my procedures for producing 3D-printed parts to form the ‘flesh’ of the model, which will carry the details of the outside frames, footplate, boiler cladding, smoke-box, and firebox. The methods I used are similar to those that I have previously described for my model of a Gooch Standard Goods.
     
    The frames should have been easy but I hit a glitch for which I have a work-around. Since I had a drawing of a frame, including all the rivet details (shown in my previous post), I used ‘Silhouette Studio’ software to trace this drawing. I used this software because I am familiar with it but I also know it has limitations when saving files.
     
    Fortunately, there is a website that can convert ‘studio3’ files into SVG format on-line.  Unfortunately, however, for reasons that I haven’t yet investigated, the resulting SVG files do not import correctly into my ‘Fusion 360’ 3D-modelling software. My ‘work-around’ was to open my SVG file in ‘Inkscape’ and re-save it as a DXF file. The resulting DXF file opened correctly in ‘Fusion 360’ and allowed me to continue with creating the 3D model.
     
    My first step was to select all the raised rivet heads and raise them by 1.33 mm above the drawing surface. I then selected the rest of the frame outline and raised this by 1 mm. This leaves a solid frame with the rivet-heads protruding from the surface. My reasons for doing things in this order is that the original drawing remains visible whereas, if I raised the whole frame first, I would not be able to access the rivet details. Once drawn, I exported the file into my ‘Cura’ slicing software, where I could preview the appearance of the frame before printing:


    Preview of 3D-model of an Outside Frame
     
    For the other components, I used ‘Autosketch’ as an intermediate step towards creating my own 3D drawings. In principle, the footplate was the simplest of these parts but needed care in ensuring clearance was provided for the 00-gauge wheels that intend to use. It is basically a rectangular plate with cut-outs for the wheel apertures. I decided to add the outer faces of the wheel arches and the sand boxes to the plate since it was convenient to add these at this stage.
     
    Autosketch Drawing of Footplate
     
    My 2D drawing is shown above and, after saving it as a DXF file, I opened it in ‘Fusion 360’ to raise the 3D elements above the footplate. This is the first time that I’ve added details from a drawing in a different plane from the original, then using the Push/pull tool from the new plane. So, another step along my personal learning curve.
     
    Adding wheel arches from a drawing in the vertical plane
     
    A big attraction for me, as an impatient modeller, is that the print times for these individual components are quite short. This makes it easy to review my designs and to make corrections and re-print as necessary. I found the printing process was extremely tedious when I was printing entire vehicles at one go, which usually took several hours to complete. The print time for one of my outside frames is only about 9 minutes, while the footplate, complete with sand boxes and wheel arches, takes less than 45 minutes.
     
    My design for the smokebox followed the same process that I have used previously for the Gooch Goods, in that I simply extruded the length of the smokebox from a 2D drawing of the front face. The shell includes openings for the boiler barrel and the chimney.
     
    Similarly, the boiler cladding was designed as for the Gooch Goods, with the addition of the sides of the firebox in the relevant area. Both these component proved straight-forward to print.
     
    Before actually physically printing anything, I realised that it was possible to open several components at once in the ‘Cura’ software and arrange them on the build plate, in their correct relative positions, in order to check that they all fitted together neatly. I made a couple of screen-shots of these ‘virtual test builds’:
     
    Print previews of 3D Component Assemblies
     
    Because it’s rather too warm in my work-room at present, I’m going to leave things on a ‘cliff hanger’ for the moment but I feel reasonably confident that I have a good way ahead, towards a physical model. I also need to wait for my wheel-sets to arrive from ‘Alan Gibson’, so that I can check that all the clearances I have allowed will be sufficient but not excessive.
     
    Boiler Mountings
     
    Whilst in the 3D-modelling mood, I decided to investigate the possibility of adding boiler fitments such as domes and safety-valve covers to my boiler designs. I recall some correspondence, several years ago, when several fellow modellers were experimenting with ‘Blender’ for 3D modelling. I must admit that my impression that it was all rather difficult has remained with me ever since.
     
    Fortunately, times have moved on. I see that, back in 2014, I wrote a comment “It will be nice when there's a 3D equivalent to the Silhouette cutter!” to which @JCL replied “Yep, there's no way I'll be able to afford a printer“. How much the world has changed in six years!!! Fortunately, 3D software has also advanced so that, when I set out to try creating a dome, it turned out to be much easier than I expected.
     
    In ‘Fusion 360’, it is possible to make a 2D cross-section drawing and use the ‘Revolve’ tool to rotate it around a selected axis, to produce a solid component. This works in a similar way to the ‘Push/pull’ tool that I now use routinely for linear extrusions. There are one or two caveats, in that the axis has to be outside the area enclosed by the drawing but that is easily overcome by splitting the profile down the centre-line. I created a ‘profile’ by combining drawings of a rectangle and a circle and then ‘revolved’ the profile through 360° to create a dome-shaped object.


    Extruding a Dome in ‘Fusion 360’
     
    The next move along my ‘learning curve’ was to add this newly created object to my existing boiler model. This was not an intuitive process but, fortunately, the solution was to be found on the web.
     
    The first requirement was to select and copy the dome ‘body’ and then to open the existing model of my boiler. The tricky step is to select ‘Create Base Feature’ from the ‘Create’ menu. After that key step, you can ‘Paste’ the body of the dome into a ‘base feature’. Finally, click on ‘Finish Base Feature’ and the dome becomes a new ‘body’ alongside the ‘body’ of the boiler. I have no idea what all that means but it works.
     
    Once the two ‘bodies’ are in the same drawing window, it is only necessary to use the ‘Move’ tool to slide the dome into its desired location on the boiler. The lower part of the dome can be slid ‘through’ the shell of the boiler until the height above the boiler matches the required specification. Any excess length inside the boiler can easily be removed by selected the circular end face of the boiler then extruding this face through the length of the boiler, where it acts as a ‘reamer’, to remove any intrusions!
     
    The next step is to use the ‘Combine’ tool, to join together the dome and the boiler as a single ‘body’. As the finishing touch, the ring where the dome meets the curved surface of the boiler can be selected and then the ‘Fillet’ tool applied, to achieve the desired radius around the join.  Once you know how, it is all very straight-forward and, flushed with success with the dome, I quickly added a safety valve cover as well:


    Adding Boiler Fittings in ‘Fusion 360’
     
    Well, I may not not have produced any new hardware yet but I have learned quite a lot about 3D modelling, which will hopefully be useful in all sorts of future projects.
     
    In the meantime, we must all wait to see how this will turn out in practice, once I start printing
     
    Mike
     
    P.S. Some time ago, I expressed concern about non-availability of spares for my Geeetech E180 printer. I am now pleased to report that I have received spare print heads directly from the manufacturer in China. It took a while but I’m now set up to continue for a reasonable time ahead.
     
     
  16. MikeOxon
    It’s some time since I’ve scratch-built a standard gauge locomotive, having been spending my time recently on Broad Gauge models.  I learned several lessons, however, during the construction of my previous 00-gauge models, the most important of which was to remember that 00-gauge is actually a narrow gauge – closer to 4’ than 4’ 8 ½”, when scaled.
     
    My first scratch-build, described in 'Railway Modeller', July 2014, was of a 2-2-2 ‘Queen’ class engine, which was a simple choice because single-drivers create no problems of coupling rods and their alignment. As I commented at the time, building a ‘single’ is little different from building a wagon, especially if tender-drive is used for the model.
     
     

    My ‘Queen’-class model
     
    The problem of ‘narrow gauge’ raised its ugly head when trying to fit the large driving wheels since, in 00 gauge, they intercepted space occupied by the boiler! The solution was to cut oval apertures in the sides of the boiler, where they are hidden behind the splashers.  It’s a good job I didn’t attempt an earlier version, with ‘open’ splashers. A rather wide gap between the wheels and the outside frames remains obvious at some angles.
     
    Later, I built a model of one of the former West Midland Rly. Engines, which was absorbed by the GWR as No. 184, where it retained the ‘Wolverhampton’ livery.


    My model of GWR No.184, with ‘517’ class
     
    In this second case, the ‘narrow gauge problem’ appeared when attempting to fit the outside coupling rods. I found that I had been over-generous in my frame spacing and couldn’t prevent the outside cranks from rubbing on the frames. Because of the way I had constructed this model, it was not simple to reduce the separation of the frames, I had formed the frames by folding down the edges of the rectangular plate that represented the footplate. Part of the problem was that I had forgotten to take account of the thickness of the folded edges, which made the outside dimensions wider than I had intended. Another ‘lesson learned’.
     
    With these ‘lessons’ firmly in mind, I began to prepare drawings of my new engine, taking account of 00-gauge constraints.
     
    As noted in my previous post, I have a side-on photo of No.31 and a drawing of Armstrong’s earlier No.361, which differed in the style of the frames. By merging information from these two sources, I prepared outline drawings to form a basis for my model, as shown below:
     
     

    My Interpretation of an Armstrong Standard Goods with Original Boiler - derived from various sources
     
    In the head-on view, I have marked in red the positions of 00-gauge wheels.  Although they will just be clear of the boiler (including an allowance for cladding), they will interfere with the smokebox cladding and the lower sides of the firebox, so I shall need to make allowance for these intrusions.  In both cases, the necessary openings will be concealed by the splashers, which I shall maintain close to their ‘true’ locations.
     
    I have examined several different early photos of the prototypes and it is clear that some fittings, such as the location of the injectors on the sides of the boiler barrel, varied quite widely. I decided to add a cab, since these were adopted quite soon after the introduction for these engines although initially in a more truncated form.
     
    My plan for the actual ‘build’ is to adapt techniques I developed when making broad-gauge engines, such as my Gooch Goods, in that I intend to use a combination of brass components and 3D-printed overlays. This is the first time I have adopted this approach for a standard gauge model engine.  It follows my tradition of trying out new techniques with every model I build
     
    My starting point, therefore, was to construct a set of outside frames, For strength, I decided to make these from lengths of 6 mm x 1 mm brass strip. In fact, I took a single length of strip, marked off the lengths of the sides at 95 mm and marked the width to give clearance to the ‘narrow gauge’ 00 wheels.
     
    I then used a square-section needle file to make vee-shaped grooves in the brass strips at the appropriate positions to fold the strip into a 95 mm x 21.5 mm (inside) rectangle.
     
     

    Cutting groove and folding into rectangle
     
    I ‘squared up’ the resulting box form over a sheet of graph paper. Once the assembly was ‘square’, I soldered the final joint and trimmed off the excess strip by using a diamond cutting wheel in my mini-drill. Careful trimming with needle files removed any remaining rough edges.
     
    The main boiler assembly was even simpler. I bought a length of 21/32” (16.7 mm) brass tube from ‘Cornwall Model Boats’, which provides an outside boiler diameter equivalent to the prototype’s 4’ 2”. I shall add cladding by means of a 3D-printed sleeve, as I have done previously for my model of a Gooch goods.
     


    Brass skeleton of my planned model
     
    These brass components will form the ‘hard’ skeleton of my planned model and, in the next stage, I shall add 3D-printed parts to carry the details of the outside frames and of the boiler cladding, smoke-box, and firebox.
     
    I intend to use ‘Alan Gibson’ wheels on extended (32 mm) axles, to carry the outside cranks and coupling rods.
     
    I hope that my next post will show something that looks more like a locomotive
     
    Mike
     
     
  17. MikeOxon
    On a number of occasions over the years, I have posted comments indicating my dis-satisfaction with the ‘Mainline’ Dean Goods that is currently serving on my North Leigh layout. It’s really too late for my period, with Belpaire firebox and other details that place it long after the turn of the century.
     

    My model Dean Goods at North Leigh
     
    I have recently been following Mikkel’s conversion of a ‘Belpaire’ Dean Goods into an earlier ‘round-top’ version and have thought of following suit but several events have sent me towards modelling an Armstrong Standard goods instead.
     
    As readers of my Broad Gauge (BG) blog will know, my BG models were inspired by the knowledge that one of my wife’s ancestors was based at Bullo Pill at the time of a major accident in 1868. The official accident report provided me with ‘recipes’ for building two ‘authentic’ GWR trains of the period: an express mail train and a goods cattle train. Since then, however, more research into the family history has revealed a number of other engines that were driven by members of the family and one of these was (standard gauge) Armstrong Goods No.684 (built 1872).
     
    As I thought about this, I realised that I had completely forgotten about having commented last year on ‘RosiesBoss’s conversion  of the ‘Mainline’ model. Looking again at his version, I thought it also looked too ‘late’ for my modelling period, so I decided it was time to go back to some basic research.
     
    Armstrong’s Standard Goods
     
    The Standard Goods started life as the ‘388 class’ in 1866 and set a pattern which was closely followed by Armstrong’s successor, William Dean, with his own well-known ‘Goods’ class. The Armstrong version had a slightly longer wheelbase (by 2 inches) and a boiler that was 9” longer (at 11 feet), although the engine was a little shorter overall, owing to a much smaller footplate for the enginemen. The earliest engines had no cabs but these were added from 1879 onwards. As was usual with long-lived GWR engines, a long list of modifications was made at both the Swindon and Wolverhampton works, resulting in a bewildering number of variants. If only GWR engines really did all look the same, as some commentators have suggested!
     
    To build a model, the first thing I needed was a reasonable drawing and I soon found that there are several pitfalls that I shall record briefly. I first turned to Russell’s ‘Pictorial Record of GW Engines’, which contains several photos and drawings of these engines but they all show examples after they had been re-built with many Dean-type features, including large domes and shorter chimneys.
     
    I tried tracing some drawings from this book to compare the dimension with the Dean Goods and realised that they are not always reproduced accurately. When looking at a drawing by Maskelyne, it became obvious that the vertical dimensions as printed did not match the horizontal scale. Because of this, the boiler pitch appears very similar to the Dean Goods, whereas at should be 3½” lower, which makes a noticeable difference to the appearance of the prototypes.
     
    Next, I turned to Holcroft’s ‘Ouline of GW Locomotive Practice’, where I found a good side-on illustration of engine No.31 (built in 1872) with a cab but still with the smaller type of dome as originally fitted. This book also contains a drawing of Armstrong’s earlier goods engine, No.361. By E.L.Ahrons. When I overlaid this drawing onto the photo of No. 31, it was clear that they were virtually identical above the footplate, so I decided to use this drawing as a basis for designing my model. The earlier design had a shorter wheelbase to the leading axle and a different design of safety valve cover
     

     
     
    My plan is to use the technique I used for my model of a Broad Gauge ‘Gooch Standard Goods’,  with a length of brass tube to provide a strong structural component around which I shall 3D-print the other features, such as smoke box front and backplate. I have not yet decided on the chassis. The wheelbase is so close to the ‘Dean Goods’ that I may look to use a commercial chassis.
     
    My intention is to present my model in the livery introduced in 1881. This was the first move away from the original Holly Green and also introduced Indian Red frames and orange chrome lining. At that stage, the wheels remained green, although this was changed to red a few years later. I have colourised an early photograph to show the effect I wish to achieve:


    My coloured impression of Armstrong Goods No.31, c.1881
     
    I have taken the plunge and made a plan. In succeeding posts, I hope to follow through to a complete model – it may take some time
     
    Mike
  18. MikeOxon

    A Different Type of Railway

    By MikeOxon,


    general
    In my previous entry, I mentioned some of the research that I have been doing into Brunel's 'Broad Gauge' railway. There are several old books that provide a detailed survey of the early days of the GWR. One that I found particularly useful is the 'History of the GWR' by G A Nokes (2nd edtion, 1895). The preface begins: "I would remind the reader that it is 'The Story of the Broad Gauge' that is here chronicled, so that while in the first thirty years or so of the Great Western Railway's existence the work is, de facto, a 'History of the Great Western Railway,' "
     
    [George Augustus Nokes (1867–1948), often known by his pen-name G.A. Sekon, was the founding editor of The Railway Magazine.]
     
    When Brunel decided to build on a grander scale than the early colliery lines built by Stephenson, he took the pragmatic engineer's view that, if you're going to change things, do it by at least 50%. People often ask why Brunel chose 7' 0-1/4" but they don't seem to ask why Stephenson chose 4' 8-1/2". In fact, Stephenson chose 4' 8" as the gauge but found he needed to leave 1/2" clearance to allow the wheel flanges to negotiate curves successfully. Brunel simply increased the Stephenson gauge by exactly 50% and then, because he intended his track to be as straight as possible, he only allowed 1/4" clearance for curves.


    Mixed Gauge Track at Didcot Railway Centre
     
    It wasn't just a change in the gauge of the rails that defined the 'Broad Gauge' but a completely new approach to railway design. Whereas earlier railways had developed out of 'waggonways, which had iron or wooden rails laid on stone blocks, Brunel's vision was of a system that could carry people smoothly at high speed. He thought the answer was to support his running rails on continuous wooden 'baulks' that could provide a rigid support. It turned out that he was wrong and that a good track needs some flexibility or 'spring' to provide a smooth ride but it did result in a railway which looked very different from any other, before or since.


    Broad Gauge Track (Didcot)
     
    I enjoy modelling as a way of visualising the differences between the railways of the 19th-century and those which are directly familiar. So, it is a natural progression from my pre-Grouping GWR models to try and re-create some features of Brunel's vision.
     
    For a modeller used to commercial 00-gauge track, modelling the broad gauge is an even larger leap than that faced by Brunel because '00' is actually a 'narrow gauge'! Putting a 4mm-scale broad gauge wheel-set alongside '00' wheels shows the huge difference between the two types of model.


    00 and Broad Gauge Model Wheelsets
     
    In addition, the bridge rail produced by the Broad Gauge Society is of true scale dimensions and thus very much 'finer' than commercial '00' track. The modelling standards that have to be adopted are equivalent to P4 and therefore demand much more 'precision' that I have been used to in my work so far. Notice, for example, the flanges on the broad gauge wheels when compared with commercial '00' wheels. I think it is going to be quite a challenge!
     
    Because this will be a completely new project, I intend to record my activities in a separate blog. It will probably take me some time to get going but I shall build on the techniques that I developed during the writing of this current blog.
     
    I have shown the following illustration before (from G A Nokes' book) but think it captures the essence of the Broad Gauge very well:
     

     
     
    Mike
     
    EDITED to add link to new Broad Gauge Blog
  19. MikeOxon
    As I carried out my research for this project in Part One (Research), I realised just how difficult it can be to decide what these old engines were actually like!
     
    One of the problems seems to be that, in those days, engines were hand-built by craftsmen who. perhaps, were not so keen on trying to follow a drawing but knew how things should be done!   I noticed, for example, that the shape of the firebox casing on the ‘Fire Fly’ replica is actually quite different from that seen in an early photograph of the original.  I suspect the Didcot team worked to drawings, whereas the original builders did not. The more I looked at old drawings and photographs, the more differences I discovered.
     
    I shall derive as many details as possible from the early photograph of ‘Argus’ that I first showed in my previous post.


    Fire-Fly class engine ‘Argus’
     
    The boilers of these early engines did not rest on their frames in the way more modern designs do but were supported on brackets from the outside frames.   In the case of the ‘Fire Fly’ class, there were also four inner ‘frames’, which were slender bars between the smokebox and the firebox that carried multiple bearings for the long Broad Gauge axles. The ‘machinery’ was laid out in the spaces between these inner frames, as indicated below.


    Fire Fly Frame Plan (from below)
     
    The smokebox, firebox, and boiler seem somewhat lost within the width of the Broad Gauge outside frames. Since my intention was to build these three body components around a length of brass tubing to represent the boiler, this was where I decided to commence building my model.
     
    My Construction Plan
     
    I decided to start from the idea that the smokebox and firebox would be attached to the ends of a brass tube representing the boiler. These two components will be 3D-printed and the boiler itself will be clad by a 3D-printed outer sleeve.
     
    At the outset, I thought that the greatest design problems would lie in the design of the ‘haycock’ cover over the outer firebox. I have already described how I created the shape of this component in my previous post.
     
    Haycock Top
     
    I have added the type of manhole cover that was characteristic of those engines built by Fenton, Murray, and Jackson, such as ‘Argus’, to my existing design of the ‘haycock’ top to the firebox.
     
    I thought it was going to be difficult. until I remembered that, in the 3D computer world, solid objects can happily slide through each other! All I needed to do was to create a small cylinder, tilt it to the appropriate angle and merge it into the haycock body, as shown below:


    My 3D Model with Manhole Cover
     
     
    Lower Firebox,
     
    The lower firebox is essentially a rectangular box, stretching upwards from the ash-pan to the base of the ‘haycock’ top. The sides of this box carry vertically-planked lagging, while the front has a circular opening at the junction to the boiler tube.
     
    I created the appearance of vertical planking by drawing a series of narrow rectangles, to represent gaps between the planks, on each side of the box and used the ‘push-pull’ tool in Fusion 360 to recess these by 0.25 mm.
     
    The circular hole for the boiler was a little more difficult, since the top of the boiler connects to the sloping front surface of the ‘haycock’. I joined together the 3D models of the upper and lower fireboxes in ‘Fusion 360’ and then set up a vertical construction plane, parallel to the front face of the lower section. By using this as the reference for the ‘hole’ tool, I could extend the hole through the sloping top of the ‘haycock’ as well as through the lower box. I then separated the two parts again for the actual printing.


    My 3D- Model of Firebox
     
    Smoke Box
     
    I drew the front elevation of the smoke box with ‘Autosketch’ and imported the drawing into ‘Fusion 360’, where I extruded it to the appropriate length. I intend to create the details of the front, with its door and rivets, on a separate overlay. The three parts, as designed in ‘Fusion 360’, are shown below:
     
     

    My 3D-models for Boiler End Components
     
    Boiler Cladding
     
    At first, this proved easier than expected, since I had already designed the cladding for my Gooch Goods boiler. All that I needed to do was to re-scale the cladding, to suit the ‘Fire Fly’ dimensions, using the ‘scale’ tool in ‘Fusion 360’    BUT … what about that wooden cladding?
     
    Fortunately, I found the answer in another of the series of excellent videos by Lars Christensen from ‘Autodesk’.  This one is about How To Use The Pattern Function and the relevant bit for me starts about 20 minutes from the beginning.
     
    It turned out that all I needed to do was to draw one plank along the side of the boiler cladding and then select ‘Pattern’ from the ‘Create’ menu.  There are options for ‘rectangular’ or ‘circular’ patterns.  I chose ‘circular’ and, after selecting my single ‘plank’, I then selected the outer surface of my cylindrical boiler-cladding. and increased the ‘quantity’ until I had a whole array of appropriately spaced ‘planks’.
     
    This proved far easier than I had anticipated and is a very powerful feature of ‘Fusion 360’. I expect that this ‘pattern’ tool will also be very useful for adding arrays of rivets and the like.  I must acknowledge that it was @Timber who first drew my attention to the ‘pattern’ tool in ‘Fusion 360’, when he commented on one of my earlier posts.


    Creating the Wooden Cladding
     
     
    Assembly
     
    After printing the various components, assembly is simply a matter of sliding the printed smokebox and firebox onto the ends of the length of brass tube representing the boiler. I have shown the printed boiler-cladding separately, so that the brass tube, which gives rigidity and weight to the whole assembly is visible:
     
     

    Boiler Tube with Cladding
     
    Once I had fitted together the various parts , the complete boiler assembly appears as shown below:


    Main components of my Boiler, Assembled
     
     
    Next Steps
     
    These assemblies were all initial test-prints and I expect to add more details in due course, including an overlay for the front of the smokebox and lots of rivets
     
    It’s good to feel that this project is now well under way
     
    I now need to start thinking how to tackle the underframes and how to incorporate brass parts for additional strength. There is so much space between the outside frames of these Broad Gauge engines that I feel it necessary to include more details of the motion than I would do on a standard-gauge engine. I hope that 3D- printing will be a help in producing the necessary components,
     
    Mike
     
    I created the ‘header’ illustration from one of J C Bourne’s lithographs, using the Dynamic Auto Painter software.
     
    Edit: replaced last photo with improved 2nd. print.
  20. MikeOxon
    It has taken me a considerable amount of thought before deciding how to proceed with the next stage of building my my ‘Fire Fly’ class model. The obvious method would be to construct a strong frame around the outside, as I have done for previous models, but it doesn’t really work with this prototype.
     
     

    Fire-Fly replica at Didcot showing Boiler Support
     
    As I showed in the previous post, the prototype was built with four short frames linking the smokebox and firebox. Two of these frames can be seen in my photo of the Didcot replica, above. These frames carried bearings for the driving axle and all the ‘motion’. The drag bar at the back of the engine was attached to the rear end of the fire box, The only links between this ‘inner’ structure and the outside frames were six diagonal brackets between boiler, smokebox, and firebox. The role of the outside frame appears to have been limited to distributing the weight of the engine across the two pairs of carrying wheels.
     
    Brass Inner Frame
     
    I decided to adapt this approach to my model, by constructing a strong brass frame that follows the outermost pair of the four inner frames of the prototype, extended to the drag box at the rear of the engine and with a cross member behind the smokebox. This would give me a strong centre-section for the model, with the outside frames being largely ‘cosmetic’. This idea is illustrated below, overlaid on the frame plan of the prototype.
     
     

    My plan for an inner brass frame
     
    I constructed the inner frames from 6 mm x 1 mm brass strip, cut to length, with reference to the frame drawing and soldered into a rectangular ‘box’, as shown below:


    My soldered brass inner frame
     
     
    3D-printed components
     
    I realised as I started to build this model, how much my ideas have changed since I started using my 3D-printer, a couple of years ago. In those early days, it always seemed ‘touch and go’ whether a print would work or not – models detached themselves from the base-plate, filament failed to feed properly and so on, such that I always felt the need to ‘baby-sit’ the process during printing.
     
    Gradually, I learned to adjust the various parameters, to get more reliable printing and much smoother surfaces. A breakthrough occurred when I developed the concept of printing a model in sections, rather like a kit, that would be assembled after printing the various parts. In this way, individual print times reduced from several hours, for a complete model, to less than one hour and, often, around 20 minutes or less for individual parts. This changed my approach to modelling completely, since I could lay out each part on the printer bed, in a way that optimised the print quality. It also gave me confidence to leave the printer to itself, while I enjoyed a coffee break The printer became just another useful tool, rather than something requiring special attention.
     
    The shorter print times encouraged me to experiment with different techniques, before finalising a model. An example of this arose when I printed the footplate for my ‘Fire Fly’ model. The foot-plating follows a rising curve in the outside frames, over the axle boxes for the driving wheels, as shown below, where I have marked out the 3D model over an imported image of the frame plan, imported into ‘Fusion 360’.


    My 3D model footplate, built over an imported drawing in ‘Fusion 360’
     
    According to the ‘rules’, I should provide ‘support’ for this raised section when printing but, since the print time was very short, I decided to take the risk and see what would happen if I omitted these supports.   I don’t like supports, because they can be difficult to remove without damage or leaving traces on the surfaces where they were attached. My temerity was rewarded by cleanly-printed arches    It’s good to try these things, as it helps one to learn the true limits of the printer. 
     
    Splashers
     
    Another recurring problem with modelling early broad-gauge engines lies in producing those close-fitting bicycle-like splashers.  For ‘Rob-Roy’ I fabricated the splashers from brass strip, with Silhouette cut outside faces, finished with gold-coloured foil.  For ‘Tantalus’, I used 3D-printed wheel arches, finished with etched brass facings from the Broad Gauge Society (BGS) kit.
     
    This time, having learned that I could ‘get away with’ some overhangs, I tried 3D printing the entire splasher, laying the back of the splasher on the printer bed and crossing my fingers that the front faces would print, without filling the cavity behind with spurious filament.  Well, it worked very well - just a few individual threads of filament crossing the void, where the print head had traversed from one side to the other. These strands were easily removed to leave remarkably clean prints, as shown below (cruelly enlarged):


    my 3D-printed Driving Wheel Splasher
     
    Considering that each splasher took just 6 minutes to print, I feel that the result was well worth the time spent on this test.
     
    Footplate
     
    I have already described the footplate. It’s sufficient to say that it printed exactly as expected.
     
    Outside Frames
     
    I obtained dimensions for these frames from a sketch in Gooch’s notebook, reproduced in Brian Arman’s book ‘The Broad Gauge Engines of the GWR – Part Two’. I discovered that these sketches are by no means to scale but are a useful source of dimensional information. I chose a different scale drawing to use as a template for building my 3D model in ‘Fusion 360’. This software has a useful feature to ‘calibrate’ an imported ‘Canvas’ from a single known measurement.
     
    Then I followed my usual method of tracing the outlines over the imported drawing (canvas), using ‘line’ and ‘arc’ drawing tools. I then extruded the side frame using the ‘push-pull’ tool in ‘Fusion 360’ and continued to add details, such as rivets, spring and axle boxes, extruding these parts as appropriate. Drawing all those rivets was assisted by using the ‘pattern’ tool described in my previous post.


    My 3D model of Outside Frames
     
    It is worth pointing out that it is not necessary to design separate left and right frames, as the ‘mirror’ command can be used to create the opposite side.
     
    Assembly of 3D-printed parts
     
    I brought together all the separately designed parts on the screen of ‘Fusion 360’, with each ‘body’ labelled separately. Each of these parts could be transferred individually to my ‘Cura’ slicer software and laid out in the optimum orientation for 3D printing.


    Individual Components identified in ‘Fusion 360’
     
    For the record, the print times for each part were as follows:
     
    Firebox – 51 minutes
    Boiler cladding – 45 minutes (not shown above)
    Smokebox – 43 minutes
    Footplate – 23 minutes
    Haycock – 15 minutes
    Outside frame – 8 minutes (2 needed)
    Wheel splasher – 6 minutes (2 needed)
     
    After printing, I assembled the parts together, using a soldering iron set to 200°C to attach the outside frames and the splashers to the footplate. This is a very quick and easy method to fuse together separate 3D-printed components. The smokebox, firebox, and boiler cladding are currently just slipped loosely over the brass boiler tube.
     
    Once assembled around the brass boiler and inner frame, the model so far looks as shown below:
     

    My 1st assembly of 3D-printed components on brass frames
     
    I’m very pleased with the progress so far but there’s still a long way to go. The front of the smokebox awaits details and several lines of rivets need to be added.
     
    There is also the matter of wheels – the prototype wheels had a set of straight spokes alternating with spokes splayed toward the inside of the hub. At present I have no idea how I shall create such a wheel but ‘thinking is in progress’
     
    Then there are the more mundane tasks, such as support brackets, handrails, buffer beam, buffers …
     
    Mike
  21. MikeOxon

    More Waverley Thoughts

    By MikeOxon,


    General
    Over two months have passed since I last wrote about my attempts to build a model of a Waverley-class 4-4-0. To re-cap, I have built a boiler, by using the Broad Gauge Society (BGS) kit for a Gooch Standard Goods, and have cut out some inside frames from card, to carry 24-spoke driving wheels taken from a Tri-ang ‘Lord of the Isles’ model. After putting these parts together, rather roughly, I felt that I had achieved an approximation to the appearance of the prototype.
     
    As I continued to look at this basic outline, however, I began to feel less and less satisfied with the appearance, which made me reluctant to press on with the difficult job of cutting out real frames in brass sheet. As a distraction, while waiting for inspiration on how to move things on again, I built a couple of broad gauge carriages and a luggage van, to make up the rest of my planned mail train.
     

     
    During this fallow period, I was contacted by another BGS member, who has also been constructing a model of a Waverley-class locomotive, and he has provided me with several useful tips.
     
    This is a post about the difficulties and compromises that are involved in constructing a model that captures the appearance of the prototype, while using commercially available parts and minimal engineering skills.
     
    The first area to consider was the boiler, which came from the BGS Standard Goods kit.
     
    Although the boiler of the Waverley class was the same as that used for the first three lots of the Standard Goods, the information provided in the RCTS volume covering the Broad Gauge shows that it was pitched considerably higher. Whereas the Goods boiler was pitched at 6’ 4¾”, that of the Waverley was at 7’ 1½”. This difference in heights could be expected to alter the relationship between the boiler and the cylinders and, hence, raises questions about the suitability of the smokebox components provided in the BGS kit.
     
    Photographs of the front end of Waverley-class locomotives indicate that the cylinders were horizontal so, with 7’ diameter driving wheels, the centre-line of the cylinders is expected to be 3’ 6” above the rail tops. On the other hand, the cylinders of the Goods engines were angled, to enable the connecting rods to clear the leading axle. Because of this upward slope from the centre axle, the fronts of the cylinders are considerable higher than might be expected for driving wheels of only 5’ diameter.
     

     
     
    The actual distance between the centre line of the boiler and the centre lines of the cylinders on the prototype Waverley-class locomotives is expected to be 7’ 1½” minus 3’ 6”, which is 3’ 7½“, or 12.5 mm in 4mm/ft scale. Fortuitously, my measurement of this distance on the front plate of the smokebox in the BGS kit was also 12.5 mm !
     
    So, by sheer coincidence, it seems that the smokebox front of the BGS kit for the Standard Goods has the correct separation between boiler and cylinders for the Waverley class!
     
    The next areas to consider are the frames and wheels.
     
    I chose to use driving wheels from the Tri-ang ‘Lord of the Isles’ because these appear to be the only commercially available wheels with the required 24 spokes. I admit that I had hoped that, like most ‘toy’ models, the Tri-ang wheels would have been considerably under-size but, alas, thy are not. Even after turning down the tyres as much as possible, they were still about 1 mm over-size for my model.
     
    So, as so often happens in modelling, I was faced with a compromise! After careful measurements, I decided that the minimum wheelbase I could set between the pairs of driving wheels was 31 mm, compared with the prototype’s 7’ 5” (29.7 mm). Initially, I compromised by spreading out the wheels symmetrically, around the mid-point, but this had the knock-on effect that the rear pair of leading wheels had also to be moved forward slightly to maintain clearance.
     
    Whereas the change to the driving wheels was barely noticeable, the resulting ‘crowding’ of the leading wheels was all too obvious and changed the ‘character’ of the locomotive, giving a ‘front-end’ appearance more like the 4-2-2 ‘singles’. In fact, this is an example of where the ‘eye’ can be more important than the measurements, since the leading wheelbases for the two classes are actually the same but the leading wheels of the ‘singles’ are of larger diameter.
     
    I used the technique of laying my model on its side in my scanner, to get a direct visual impression of the relationships between the wheels. One advantage of making a scanned (scale) image was that I could make a direct comparison with published drawings of the prototype, by overlaying a drawing (blue) over my scan, by means of ‘Photoshop’, as shown below:
     


    Scanned image of my model, overlaid with a drawing from Mike Sharman’s ‘The Broad Gauge of the GWR’, originally from ‘The Locomotive Magazine’, 1902
     
    This comparison shows very clearly the ‘crowding’ of my front wheels. Incidentally, I had also glued the frame rather too high onto the side of the smokebox but I laid the front wheels on the scanner in their correct locations, relative to my frames. . Although I had only ‘tacked’ the frames in place, with dabs of ‘Uhu’ adhesive, I found them surprisingly difficult to remove, when I came to replace them with revised versions!
     
    I decided that the ‘visual impression’ would be improved, if I moved all the driving wheels, and the rear pair of the leading wheels back a little, to achieve the correct spacing between the leading wheels. This meant the the rear footplate would be a little longer than on the prototype (perhaps to the delight of the model drivers).
     
    This change was very simple to implement by lengthening the frames on my drawing, between the leading wheel pairs, and re-cutting on my Silhouette cutter.
     
    The revised model now looks like this and I feel that it is a fairer representation of the prototype:
     

     
     
    Although it is far from finished, I feel sufficiently confident to proceed to the difficult task of cutting out splashers and frames from brass sheet. My fellow BGS member has already warned me that “The splasher top / running boards are a real pig, there is no other way to describe the making of them.” Oh well, something to look forward to
     
    Mike
  22. MikeOxon

    Aeolus Valve Gear

    By MikeOxon,


    General
    Interpreting the Valve Motion
     
    At the end of my previous post, I commented on the surprising layout of the valve gear, as shown on the Lane sketches. The Works drawing of the engine, as originally designed, shows a more usual arrangement, with the weigh-bar placed under the boiler behind the smokebox.
     
    Following further research, however, I have re-interpreted the drawings of Aeolus by E.T. Lane and have, therefore, revised this post on 16th April.
     
    According to the recently published book by Brian Arman: ‘BG Engines – Part 3’, several engines built during the 1840s were fitted with a regulator that was placed immediately above the cylinders. Drawings of, for example, the ‘Prince’ class show that the regulator was operated by levers from a shaft across the front of the smokebox, by means of a control on the right-hand side of the footplate.
     
    I had not been happy with my previous thought that these components might have represented a ‘throw back’ to much earlier type of valve gear as used on Stephenson’s ‘Planet’ series of engines. It appears that Gooch started fitting his fixed link expansion gear from 1843, so I now suggest that the rebuilt Aeolus may have been one of the first engines to have been fitted with this gear. Far from being a ‘throw back’, this engine may have a been a test-bed for the new arrangement, which was fitted to Great Western and other engines shortly afterwards.
     
    This change of interpretation does not actually affect the design of my model very much, it is simply that the parts that I have modelled serve a different purpose from what I initially had thought. The new interpretation is much more convincing than my earlier thoughts.
     
    Initially, I produced every piece of the regulator mechanism as a separate ‘body’, so that I could move them all around independently to what seemed to be the most appropriate positions. The plausible outcome looked as below:
     

    Potential Layout of regulator mechanism in ‘Fusion 360’
     
    The next requirement is to provide supports for all these gubbins and, on this matter, I find the available sketches and drawings very confusing.
     
    Lane’s sketches, which were clearly used as the basis of the much later G.F.Bird drawings, show what appears to be a rather massive support structure carrying a shaped boss to hold the transverse shaft, presumably in the centre-line of the locomotive. There is no clear indication of how the outer ends of the shaft were supported. As an interim measure, I decided to add support brackets extending forward from the smokebox, as shown in drawings of  ‘Prince’, but there is no indication of such supports in the Lane sketches. There also seems to be a pillar supporting horizontal bars but with no indication of where these were placed laterally. Was there perhaps a curved rail around the front of the engine?
     

    20th Century drawing by G.F. Bird, derived from Lane’s sketches
     
     
    Another puzzle is provided by those rather splendid curved side-brackets shown on the original Works drawing of ‘Aeolus’. It is not clear whether these were retained when the smaller wheels and consequently lower outside frames, were fitted during re-building. It is also not clear where they appeared along the length of the engine, although the photograph of ‘Vulcan’ suggests they were at the front of the smokebox and rear of the firebox, with intermediate straight supports to the sides of the boiler. Bird seems to have assumed this in his drawing but it not clear on Lane’s sketches.
     
    Adding Surface Details
     
    One of the pleasures of using 3D modelling tools is the ability to add rows of rivets, either in regular arrays or following a defined path, by using a few keystrokes and the ‘pattern’ commands.
     
    For the frames, I drew one rivet and then used the rectangular pattern tool to create a 2 x 36 array for all the rivets on one side and then the Copy command to replicate them on the other side. For the smokebox front, I drew one rivet and then told them to follow a path around the edge of the smokebox – job done! With these additions, my 3D model in ‘Fusion 360’ looks like this:
     

    Assembly of parts within ‘Fusion 360’
     
    Preparation for Printing
     
    As I have pointed out before, there is a difference between a 3D model and a printable 3D model.
     
    My approach is to break the complete model down into several parts that can be printed individually and then assembled as a ‘kit’. In deciding how to separate the parts, I try to ensure that each part has a flat surface which can be laid on my FDM printer bed. An advantage of this approach is that the print times for individual parts can be quite short so, if some re-design is necessary, it can be done without having to re-print the entire model.
     
    Smokebox Front
     
    I felt that the most demanding task for my printer would be to reproduce the details on the smokebox front, including the supports for the valve gear. For this reason, I did a test print of this part first, since the overall success of my model depends on how well this region can be represented. After printing, my first trial looked as below (Note that I shall print the weigh bars and levers separately.):
     

    My first test 3D print of the Smokebox Front
     
    There were a few stray strands of filament that had to be carefully removed with fine tweezers but overall, I was very pleasantly surprised to see how well the details had been rendered, including the supports for the valve gear and the protruding piston rods, etc.
     
    Further Components
     
    Encouraged by this first trial (which took only 10 mins to print), I continued to select and print the various other components.
     
    I have learned to keep the various parts in the form of individual ‘bodies’ within ‘Fusion 360’, so that I keep as many options as possible open for printing. In this case, the front of the smokebox, shown above, is a ‘body’ in its own right, separate from the rest of the smokebox. The back of this part is completely flat, to lie on the printer bed, while the front has some very fine details, including the piston rods and eccentric rods, protruding from the front surface.
     
    Most of the other parts are simpler and very similar to the equivalent parts on models that I have constructed before. For example, the boiler, smokebox body, and firebox appeared as below, immediately after printing:
     

    My 3D Printed Boiler Components on Printer Bed
     
    I am especially pleased with the way the combined dome/safety valve cover has turned out. I printed this in two parts: the fluted barrel and the curvaceous top cover. I provided each part with dowels and mating sockets, so that they plugged together on top of the firebox. After fitting together, the printed parts look like this:
     

    My 3D-printed Dome/Safety Valve Cover on Firebox
     
    I am reminded of Brunel’s statement in a letter to the engineer T. E. Harrison on 5th March 1838. Forgive the sexist remarks but I am quoting verbatim: “Lastly let me call your attention to the appearance - we have a splendid engine of Stephenson's, it would be a beautiful ornament in the most elegant drawing room and we have another of Quaker-like simplicity carried even to shabbyness but very possibly as good as engine, but the difference in the care bestowed by the engine man, the favour in which it is held by others and even oneself, not to mention the public, is striking. A plain young lady however amiable is apt to be neglected. Now your engine is capable of being made very handsome, and it ought to be so.” [MacDermot, History of the GWR]
     
    I do think this dome is very handsome and has printed very well!
     
    Now, I have all the parts needed to complete the boiler assembly. The major parts all plug together, while the smokebox front is glued to the flat front-face of the smokebox itself. I have not yet attached the weigh-bar and rocking levers, to actuate the valve rods, which can be seen protruding from the front face:
     

    My Model ‘Aeolus’ Boiler
     
    This is a good place to pause before embarking on the running gear, which will support these completed parts. That will be my next post.
     
    Mike
     
     
     
  23. MikeOxon

    One Step on a Broad Road

    By MikeOxon,


    General
    After spending a long time reading and thinking about Brunel's broad gauge railway, I knew I had to make a start somewhere. The thought of plunging straight into a layout was proving too daunting so, I decided to buy a display case of the type sold by Antics models This case has a plain wooden base, measuring about 330mm x 80mm, onto which I could build a short length of broad-gauge (BG) track.
     
    I wanted to build my track base using materials and techniques that mirror the original construction devised by Brunel. In searching for materials, I found that Cornwall Model Boats supply a wide range of materials and fittings, many of which are potentially useful to railway modellers. For the 'baulks' of my planned track, I bought lengths of 5mm x 2mm mahogany strip, while the transoms are made from 1.5mm x 2mm strips.
     
    One feature of the BG trackbed is the use of pinewood packing underneath the running rails themselves. After some thought, I decided to simulate the appearance of this packing, by sticking narrow strips of 2mm squared graph paper on the top faces of the baulks. The rails themselves would then be glued over these strips. The appearance of one of my baulks, built up in this way is shown below:
     

     
    I drew out a scale template, with the baulks in their correct relative positions and with the locations for the transoms marked at 8' (32mm in 4mm scale) intervals. Because the wooden strips were slightly warped, I used a straight-edge to hold them in position, exactly over the template lines, while I glued them down with PVA adhesive. At this stage, the actual running rails were not fitted. The 'bridge section' rails, to scale dimensions, were obtained from the Broad Gauge Society (BGS). I glued down one length of running rail, again using a straight-edge to ensure it ran down the centre-line of the baulk. I then used a roller gauge from the BGS to fit the other rail in position on the opposite baulk, at the correct gauge (28.08mm) for 4mm-scale track.
     

     
    To complete the 'wood-work', I finally added the transoms, gluing each into position over the reference lines marked on my template.
     
    The next task was to add ballast, which I first spread dry into the rectangular openings between the transoms, smoothing down the dry material by hand (finger tips). On the basis of photos from the Bullo Pill accident site (shown in a previous post), I chose a 'medium' ballast in dark brown, to match the ironstone colour typical of the Dean Forest area. After laying the dry ballast, I fixed it down by adding a dilute solution of PVA glue from a dropper. I use about 3-parts water to one of PVA and add one drop of washing-up liquid to the mixture, in order to make it flow freely. This last step is important as, without it, the solution tends to stand in beads on top of the ballast.
     

     
     
    Once the ballast is in place, one really gets a good impression of the 'different' appearance of broad-gauge trackwork,
     

     
     
    Finally, I printed a simple back-scene. I set my printer to 'draft' mode, which produces a low-saturation image that naturally recedes into the background, when photographed. I placed my old 'Gooch single', originally built from a 'K's Milestones' kit, many years ago, and, for the first time in her life, she stood on some track, in a pose reminiscent of 'official' Swindon photos of the period.
     

     
     
    My methods were fiddly to carry out and probably not suitable for a more extensive working layout - and then there is the issue of points! One thought I had, to simplify the process, is that a laser cutter could be used to make wooden frames in the equivalent of 30' sections, onto which the rails could be mounted. Frames for pointwork could be made in a similar manner. Perhaps an idea for someone to take up?
     

     
     
    Mike
  24. MikeOxon

    Printing 'Edith'

    By MikeOxon,


    general
    Despite what I wrote in my previous post , I decide to add a ‘rolling’ chassis to my model of ‘Edith’, to help me assess the overall appearance of this little engine. Printing and assembling some of the very small parts created some new challenges.
     
    Our heating system failed last week, just as the weather turned colder. I had not noticed before how sensitive my 3d printer is to the temperature in my work room. For the first time, I experienced a fractured filament as it wound off the reel. I then had continuing trouble with several prints, until I found that the bed levelling needed to be re-set. Something had upset it more than usual.
     
    On the plus side, I did get some of the cleanest rivets I have ever printed, with virtually no whiskers of filament between the individual items – possibly because the extruded filament was solidifying more rapidly than usual.
     
    As usual, I broke the overall design down into sections that were optimised for printing by having a flat surface to lie on the printer bed.  I made the exploded diagram below, to show all the individual parts that I printed. In some cases, I printed several small items together, such as the cylinders and wheels
     

    ‘Edith’ broken down into Printable Parts
     
    It really brought it home to me, just how small the engine ‘Edith’ was, when I started to print some of these parts:
     

    3D-printed Smokebox for Edith
     
    As I started to assemble these parts together, I realised once again the challenges that 2mm FS modellers have to meet and overcome – apart from good eyesight, they also need to pay far more attention to tolerances, which can seem very tight indeed.  For the first time, I became aware of the limitations imposed by the 0.4 mm extruder nozzle diameter, when I was creating the smallest parts, such as the inclined cylinder blocks.
     
    I also had difficulty when mounting the rather tiny chimney onto the smokebos.  Although I thought I had left sufficient tolerance for the spigot on the base of the chimney to fit into the socket on the top of the smokebox, the ‘quantisation’, imposed by the extruded filament got in the way!  In this case, it was easy enough to ream out the hole in the smokebox a little but it was a reminder that I was working close to the limits of my printer.
     
    Once again, I found the gel-type superglue to be very good for attaching tiny parts such as the cylinders. I used a cocktail stick to spread a thin film of glue on the mating surfaces and then held the parts together, using fine tweezers, for a few seconds until the joint hardened sufficiently to keep the parts in place.  I read somewhere that superglue doesn’t work with PLA but that’s not my experience.
     
    Eventually, everything came together and the newly assembled model looked as below:
     

    Two views of my 3D-printed ‘Edith’
     
    Over on my Broad Gauge blog, I have been writing about the early GWR broad-gauge engines that were often regarded as ‘freaks’ , although some of them were simply far too under-powered to handle the tasks expected of them. All things are relative and what might be regarded as too small in one context can seem very different, when compared with engines designed for a different purpose.
     
    Many narrow gauge engines, like ‘Edith’, were very small indeed, in comparison with main-line engines, but well suited to the task of moving agricultural produce around a large farming estate. The profound difference is apparent when I bring the models of ‘Edith’ and ‘Aeolus’ together for a joint portrait:
     

    My models of ‘Edith’ and ‘Aeolus’ together
     
    In term of boiler size, there is less difference between these engines than might appear to be the case at first glance. The boiler of ‘Edith’ is stated as having 2’ 8” inside diameter and length 7’ 6” (including internal firebox), whereas that of ‘Aeolus’ was 3’ 6” diameter and 8’ 2” length. The very considerable difference in appearance is largely down to the higher pitch of the ‘Aeolus’ boiler, needed to clear the driving axle of the large diameter wheels.
     
    One of my objectives in building ‘Edith’ was to provide alternative motive power on my my narrow-gauge system around North Leigh . Since Buscot was not many miles South from the area covered by my layout, it seems reasonable that similar engines could have been used on both systems!
     
    To turn my model ‘Edith’ into a working locomotive, I plan to adapt it to take a similar type of chassis to that currently under ‘Jeanette’.
     

    Peco ‘Jeanette’, with ‘Edith’
     
    The two engines have quite different appearances but the use of a common chassis seems feasible, with some modifications to the body of ‘Edith’. These modifications will be the subject of a future post.
     
  25. MikeOxon
    In my previous post in this blog, I described my chance discovery of the former narrow-gauge system that linked the farms on the Buscot Park estate to a distillery and other works, located at a wharf on the upper River Thames.
     
    This was especially interesting to me because I had introduced an imaginary narrow-gauge (NG) line on my ‘North Leigh’ layout, to serve the local quarries for Cotswold stone and the sawmills around Wychwood Forest, by connecting them to a railhead at North Leigh – itself never actually served by railway, although a branch to Witney had been proposed in 1849.
     
    My model NG railway is worked by two aged ‘Peco’ NG locomotive body kits, mounted on ‘Arnold’ 0-6-0 and 0-4-0 chassis.  Although I still like the saddle tank version (known as ‘James’ in the Peco catalogue), I’ve never liked his side-tank sibling, known as ‘Jeanette’, very much – something about the proportions never felt ‘right’ to me.
     

    NG engines at North Leigh NG engine shed
     
    So, having discovered ‘Edith’ on the Buscot railway, I thought I might design a body based on her, to fit onto my existing Arnold 0-4-0 chassis. There are going to have to be a few compromises, to make the ‘Edith’ body fit over this chassis, so it may not be an accurate model but it will provide a ‘memorial’ to a long-lost prototype, which did in fact operate for a short period in this area of the Country.
     
     
     
    In order to create my model, I needed more prototype information than the illustration that I found in Lowe’s book called: ‘‘British Steam Locomotive Builders’.  Fortunately, I found a reference to an article in ‘Engineering’, 20th January 1871. This can be downloaded from 'Grace’s Guide', now behind a paywall but still an excellent source of information about locomotives and engineering in general, during the 19th century.
     
    The ‘Engineering’ article includes drawings and several views of the engine ‘Edith’, together with a detailed description, providing all the main dimensions. There are some inconsistencies between the various illustrations but I now had sufficient dimensional information to start to create a model.
     
    I gather that some of my readers like to read my ‘blow by blow’ accounts of how I build my models, so I shall record my progress in ‘diary’ form.
     
    My first step was to copy a couple of drawings from the ‘Engineering’ article and insert them as ‘canvasses’ into my ‘Fusion 360’ 3D-modelling software. This article also provided some key dimensions, including wheelbase of 5 feet and overall length of 12’ 11”.  I used the overall length, plus the width of 5’ 3”, to ‘calibrate’ the images in ‘Fusion 360’.
     
    My next step was to use the ‘sketch’ mode in ‘Fusion 360’ to create a rectangle over the entire outside valance. I followed this by using the line and arc drawing tools to mark out the shape of the valance, where it curves over the wheels, and selected the enclosed area of the valance, after which I used the ‘push-pull’ tool (press ‘Q’), to extrude this by 1 mm above the canvas plane. The result of these operations is shown below:
     

    Creating valances in Fusion 360 from a ‘canvas’
     
    I created a buffer beam in exactly he same way, by drawing a rectangle over the head-on image of the engine. I rounded off the corners of the buffer beam by using the ‘Fillet’ tool to reproduce the appearance of the prototype.  After extruding the drawing by 1 mm, I now had all the parts necessary to create the outside members of the chassis.
     
    To do this, I used the 'Move' tool to rotate the parts into the appropriate orientations, followed by the 'Copy' tool (which is an option within the 'Move' tool) to provide duplicate frames for both sides and buffer beams for both ends, as shown below:
     

    Creating the Frame in Fusion 360
     
    I like to keep all the parts as separate bodies at this stage, so that I can easily re-position them later if necessary. I think this approach is analogous to using ‘layers’ in Photoshop, to keep options open for making alterations later.
     
    The article in ‘Engineering’ gives the boiler diameter (inside) as 2’ 8” and the length from smoke-box tube-plate to back plate of the firebox casing as 7’ 6”. I checked these dimension on the drawing (they were correct) and drew circles over the drawing to represent the inside and outside diameters of the boiler and then extruded this to a length of 30 mm, to create my model boiler.
     
    On the prototype, the firebox can be seen to be located within the back end of the boiler. I added lines to my boiler sketch to represent the outer faces of the firebox and extruded these to a length of 14 mm (equivalent to 3’ 6” on the prototype). Since the grate slopes down towards the front of the firebox, I drew a triangle on one side of the box and then used the push-pull tool to Cut the lower part to the correct profile, as shown below.
     

    Creating the Boiler and Firebox in Fusion 360
     
    None of the illustrations that I have of ‘Edith’ shows the front of the smokebox, so I had had to make informed guesses. I simply extruded another body from the front end of the boiler, to create a cylindrical smoke box of length 4.67 mm, in accordance with the drawing and equivalent to a prototype length of 1’ 2”.
     
    The ‘Engineering’ article describes the cylinders as: “outside cylinders 8 in. in diameter with 15 in. stroke, these cylinders being placed at an inclination of 1 in 5, and being situated at a distance apart transversely of 4ft. 2 in. from centre to centre.”  I decided to create these cylinders as separate components, so that they can be positioned on my model as required.  I started by creating a simple ‘box’, then drew a circle on one end face, which I extruded to represent the cylinder end-plate.. In exactly the same way as I did for the firebox, I cut away part of the side of the box so that it would fit against the outside frame at the desired 20° (1 in 5) angle.
     
    (as a note to self: it’s good to write up like this, because I suddenly realised, while writing, that I had wrongly set the angle to 5° through a hasty mis-reading of the above description)
     
    After placing these various bodies in their appropriate locations on the overall model, the assembly now looked as below. Note that I have still kept all the parts as separate bodies, so that I can re-adjust them if necessary and also so that I can print them individually.
     

    Creating the Smokebox and Cylinders in Fusion 360
     
    The remaining, most obvious parts are the two coal bins at the sides and the back-tank, so I drew these next, following my standard method of extruding from the drawings. These are simply extruded rectangles, with a few radiussed corners. The outline of the side bunkers was marked by a very faint dotted line on the ‘canvas’ but the main body of the back-tank was obvious.
     
    I initially extruded these parts as simple cuboids and then rounded the vertical corners of the back-tank by using the ‘Fillet’ tool to create the rounded appearance shown in the illustrations of the engine.  I placed the three items in their locations on the frame and then tackled adding the flare around the top of the back-tank.
     
    I’ve tried various methods for creating such flares, of varying degrees of complexity, but since I found the ‘Sweep’ tool in the ‘Create’ menu of Fusion 360, it’s become very simple!  I simply sketch the end profile of the flange and then click on the ‘path’, which is the line around the top of the tank body. The profile is then automatically turned into a solid body, as shown below:
     

    Creating the flange around the Back Tank in Fusion 360
     
    With a few minor additions, such as the tank filler, the assembly was now beginning to look very much more like a locomotive!
     

    My 3D-model assembly in Fusion 360
     
    I have now reached the point of adding the boiler fittings, where I can adopt my tried and tested method of using the ‘Rotate’ command on a profile sketch. I made the chimney and dome in two parts, the lower of which I ‘Joined’ to the top of the boiler, leaving a flat surface on which to attach the upper part, after printing.
     
    Normally, I would now start on the design of the chassis but, since I want this to be a working replacement for ‘Jeanette’ on my layout, I shall have to make some modifications, to enable the body to fit onto my Arnold chassis. I shall keep the parts designed so far, so as to leave open the option to create a true scale model but shall now take a break , to consider what ‘distortions’ I shall have to make.
     
    Meanwhile, a colourised view of model ‘Edith’ so far:
     

     
     
     
    Mike
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