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.