Whoo-hoo  – I seem to be getting the hang of 3D modelling, at least for simple shapes like carriages and wagons.  Whereas I had some infuriating moments when designing my first cattle wagon model, its open-top cousin has proceeded with scarcely a hitch.

 

I decided to follow exactly the same procedure that I used for my first wagon : floor and ends as one ‘body’ and individual sides as two separate ‘bodies’. After printing these separately, I used a soldering iron, set to 200°C, to ‘weld’ the parts together. In the current case, I had no roof to consider and the chassis has the same wheelbase as the closed wagon, so I could re-use the same design.

 

I found that reducing the printer nozzle temperate to 190°C from my previous 200°C resulted in a considerable improvement in print quality, with crisper details and no stringing of filament between window apertures, for example. It also prevented excessive adhesion to the work-bed, which is unheated on my printer.

 

I’m sure that there are many other ‘tweaks’ that I could make, to improve print quality further., but for the moment I am happy with the results I am getting. I find it quite remarkable how much easier the whole process seems, now that I’m past the teething problems that I recorded in earlier posts.

 

Open-Top Cattle Wagon

 

After building a model of a ‘closed’ wagon, described in previous posts, I now turn my attention to the ‘open’ type. One of these appears near the foreground of one of the photos taken at the Swindon dump, around 1892. (my colouring added) :

 

 

Open Cattle Wagon at Swindon dump

 

This photo shows the end-profile very clearly, while the sides can be seen to be similar in appearance to the ‘open’ type. The ‘hoops’, which are presumably intended to carry a tarpaulin in wet weather, rose somewhat higher than the end walls, well above the bracing timber that runs along the length of the wagon. The lime-washed interior also shows clearly. The tops of the door-posts appear to be rounded, which I have reproduced in my model.

 

In another photo of the Swindon dump, there is a very distant view of two similar wagons between a closed cattle wagon and a tilt wagon. Although blurred, this is useful in showing the relative heights of the side apertures on these different types. There is no sign of a lengthwise bracing rail on these distant photos. They also appear to be somewhat narrower than the adjacent tilt wagon (which is not lime-washed). Since an early drawing of a GWR Tilt Wagon (National Railway Museum no.4832) indicates an overall width of around 9’ 6” for this type, the photo evidence is compatible with a width of 8’ 6” for the cattle wagons, as I have used already for my closed wagon.

 

 

Line of Cattle Wagons at Swindon dump

 

I based my design on a sketch in the Broad Gauge Society magazine ‘Broadsheet’ v. 52, which states that it is ‘not to scale’. I checked this sketch against the Swindon dump photos and made some minor adjustments. The sketch shows only 10 bars across each window opening, compared to 11 on the closed wagons, while the overall proportions of the sketch suggest a length of about 15’ 9”, against 16’ 6” for the closed form. This is largely conjectural on my part but helps to provide some variety in my proposed train.

 

As before, I prepared my own drawings to these dimensions, using ‘Autosketch’ software, as shown below:

 

 

My ‘Autosketch’ drawings of Open Wagon

 

I imported the end profile, as a DXF file, into ‘Fusion 360’ and extruded this to the required length of 63 mm, to form a solid wagon body. As before, I drew a rectangle at the top of the body and extruded this downwards to within 1mm of the bottom, which left me with a floor and two ends. I added end detail by using the ‘push-pull’ tool on relevant parts of the DXF drawing. This formed a complete body, which I exported to my ‘Cura’ software as an STL file.

 

Similarly, I imported the wagon side as a separate DXF file and added details to represent the framing, planking, bolt-heads, etc., by using the ‘push-pull tools’, as described previously for my closed wagon.

 

After exporting all these ‘bodies’ to ‘Cura’, I used this slicing software to prepared the ‘gcode’ files for my E180 printer. One advantage of printing the sides separately is that, by laying them flat on the bed, they print relatively rapidly – only around 18 minutes for each side (at an estimated filament cost of 3p)

 

It proved very simple to shorten my existing chassis from 66 mm to 63 mm length, without affecting other features, such as the wheelbase.. The new version of the chassis was re-printed, exactly as described in previous posts.

 

The printed components looked as shown in the following photo. These are exactly as they came from the printer, with no ‘clean-up’ of any excess material being needed – an advantage of the reduced temperature.

 

 

Open Cattle Wagon - Components

 

After printing the parts, it was a simple matter to assemble the complete wagon, using my soldering iron to make the joints, as described in a previous post.

 

As ‘extras’, I 3D-printed the two hoops, mainly as an experiment but they turned out to be remarkable tough and they hold their shape well. Again, I used the low-temperature soldering iron to fix them in place.  I also included a notch (0.5mm wide) at the top of each end in the 3D drawing.  I cut a length of 20 thou plasticard, which slotted neatly into the notches and formed the longitudinal bracing spar. The final appearance (re-coloured to brown in Photoshop) without any ‘fettling’ after printing is shown below:

 

 

Side view of my Open Model

 

 

 

End view of my model, intended to mimic the Swindon dump photo

 

As I gain confidence with the software, I feel it is possible to add finer details.  There’s a lot still needs to be added to these models but, perhaps, my next attempt will include more fittings.

 

Mike