Wednesday, August 15, 2012

Working In The Wild West

In my previous post I showed you one modification that had been made to the L&YR 0-4-0ST, aka the "Pug", in order for it to work under the Liverpool Overhead Railway. Well today I'm going to cover the other modification, one which was needed to allow the pug to work in the Wild West Aintree.

In 1916 one of the places the pugs were being used was the munitions factory in Aintree. Now the last thing you want in a munitions factory would be rogue sparks from the chimney of a steam engine. The solution was to fit wild west style spark arrestors. Given that I have a model of a pug with a smoke deflector I thought I'd try and produce one with a spark arrestor as well.

I found two photos of the engines with spark arrestors fitted and used these to build a model version in 4mm to the foot scale to match the Hornby model I already owned. Here you can see the photos I used for inspiration as well as similar shots of the completed model.

It's not a perfect model but as a first attempt I'm happy with how it turned out especially as it involved something I've never tried before: 3D printing. I used Blender (a free, open-source 3D modelling application) to create a 3D model based upon the two photos. I then uploaded the model to Shapeways, and ordered a printed copy which I then painted. Here you can see the step-by-step photos: a computer rendering, the printed object, primed ready for painting, and the final painted item.

While I'm happy with the shape, there are a number of things wrong with the final model. Firstly as you can probably tell from the second and third images the sides of the model are very rough. This is an unfortunate side effect of the printing process. Because of the fine detail (remember the whole model is just 15mm tall and 12mm at it's widest) I had to print it using the Frosted Ultra Detail material. The printing process essentially creates the object in layers by depositing small amounts of material which are then hardened before the next layer is printed. Where there is an overhang, a wax substance is deposited to provide support. This is then melted away after printing has finished to leave the final model. The problem is that this can cause slight pitting to the surface of the model. If you look closely enough you can see that the top of the model is smoother (it's almost see through in the second image) because it didn't require support material. So as the top covers a smaller area what I'll do when I print it again is flip the 3D model upside down so that the large sides don't require any support material.

The main problem though is that I badly messed up painting it and actually broke off some of the finer detail. Everything was going well to start with. I'd washed it in some strong washing up water to remove the last traces of the wax and then primed it using an aerosol (the same as I did the wagon I built recently). This worked well and allowed me to see the finer detail better than on the plain model. Unfortunately i then made the mistake of trying to spray paint it black and ended up with way too much paint, so much so that I obscured all the detail. I stripped the paint back (neat detol works well for this even if it does stink), but in the process the clasps on either side broke of. Now given how tiny they are I'm not really surprised. I then re-painted the model by hand but then compounded the problem by trying to spray on some satin varnish only for lots of white dots to appear (this happened with the black wagon as well, although not the red one so I'm wondering if it's the black paint that's the problem not the varnish). So in the end I've repainted it by hand and forgone the varnish, which means it's gloss instead of matt. So I will at some point have another copy printed and will try again to paint it properly.

Even with the painting disaster I'm happy with how it turned out. I'm sure I'll show you it again when I've had it re-printed but as the postage costs mean you really need to order multiple items (or much larger items) it will have to wait until I have something else I want to print -- I have some other models that I'm working on but some of them are proving a little tricky to finish.


  1. Have you tried airbrushes. use acrylic paint and a thin varnish to finish.

    1. Yeah I'm guessing an airbrush would give me much better control, but I was hoping to avoid the cost of buying one, at least initially. The aerosol cans were fine for the larger models but not for this tiny little thing.

    2. This is a pointless thing to tell you but if you'd started this before I sold the pottery you could have had a choice of airbrushes. They really are good for that sort of thing.

    3. It could of course just be that I'm a little heavy handed with the spray can. Mind you I think I'll start looking around for an cheap/reasonable airbrush. Although apparently it's not the airbrush that's necessarily expensive, but the compressor to generate a reliable air flow. While I know you can use cans of compressed air or even an inflated tyre, apparently they tend to be just as awkward to use well as an aerosol can.

  2. I never would have guessed what it was when you mentioned it on another blog. As you said size wouldn't have mattered in the decision making process.