As I mentioned in my previous post I've been working an a whole bunch more wagons one of which will require the upper part to be made by hand as it is too fine to 3D print. Specifically I'm working on a Rhosydd slate quarry rubbish wagon using a drawing from the Lewis and Denton book. This wagon has a wooden underframe very similar to the slab wagons with a three sided iron body to hold the waste. Unfortunately I can't find a photo that I can show you of a complete Rhosydd rubbish wagon, but you can get the general idea from this photo, while a photo part way down this page shows a rusting upper body.
same was as the slab wagon using axle retaining clips.
I haven't ordered a test print yet as I'm going to wait and order prints of all the wagons I'm currently working on at once, but I'm not expecting any issues given how similar to the slab wagon the model is. Having said that I'm not as confident about producing the upper body, although I have now made the first prototype.
The reason I can't print the entire model is that the minimum wall thickness for the material I'm using is 0.3mm. Walls that thin though are quite brittle, and as 0.3mm represents approximately an inch at 4mm to the foot scale, it would obviously produce walls that were too thick to represent sheet metal. I'm intending to solve this problem by modelling the sheet metal using ... sheet metal.
The photos show the progression from raw materials to the assembled prototype. Essentially I draw out a pattern on the computer based on how I wanted to fold up a single piece of metal to form the body (minus the rivet details). A printed copy of the pattern was then stuck to a sheet of 0.12mm brass before being carefully cut out using scissors; the tin snips unfortunately have serrated blades meaning that they aren't any use as they leave crinkled edges on the metal, although they are good for cutting sheet sections etc. a cheap non-serrated set are now on order. The fold lines were then scored using a scalpel and then any remaining paper was peeled off and the metal cleaned to remove the glue.
The upper body was then formed using my hold-and-fold. I was going to simply glue the corners but I'd not taken the thickness of the sheet into account when designing the pattern so had to resort to soldering to keep the corners together. Soldering was fairly straight forward; I tinned one side then held the joint closed with a bulldog clip before applying the soldering iron. As the solder in the gap melted the clip pulled the corner tight and once cool left me with a nice join that just need a little filing.
The result is pretty good. It isn't an exact replica as the original is made of angle iron with separate sheets for each face but once I've added rivet detail and filled the body with some rubbish it should look pretty good. I'll tweak the pattern slightly to take the material thickness into account and make up another one and then add some rivets before painting. When I eventuall get the underframe printed I should just be able to stick the two halves together.
For my first attempt at designing and building my own model from sheet brass, and my first ever attempt at soldering brass sheet I'm really happy with how it's gone so far.