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GNRi JT 2-4-2 tank locomotive

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Richard EH

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Given the interest on another thread in my 3d printed JT tank, I thought I’d start a specific thread detailing the approach to creating this model.


I should say at the outset that it is available to buy, if you’re interested – however, I know there are diverging views on the suitability of 3d printing, currently, for modelling. I think I’ve found a way here which makes the best of the technology, and mitigates some of the problems – surface texture being the key one. I have to say there doesn’t seem to be much demand for it, however I could do with a couple at least for my own layout – I plan to model Ballyhaise at some point…. So clearly it’ll be a great loco for me to model.


This project was actually started around 3 years ago. I wanted a JT tank, and having the opportunity of some time whilst ‘between jobs’ I taught myself how to use google sketchup. At the time, I couldn’t find a proper set of drawings for the JT, only outline side elevations in a couple of books – plenty of pictures though of them in their final years on the Belturbet branch. Clearly, there’s a preserved one, and Mark Kennedy kindly took a tape measure to it, to provide an overall width – most helpful!


Supplied with that information was enough to draw it up. <Photo>. Given that it is quite a simple 2-4-2 tank, I split the frames so that the driving wheels are supported on quite a thick short chassis for strength which is printed in White Detail which is very rigid and works well so long as it’s thick enough – it can be a bit brittle so thickness here is essential. I designed in some holes for supporting the brake gear, and a between wheel bracket to support the pick ups <Photo>.


The front and rear fames, both bogies and chassis are printed in white strong and flexible, which gives reasonable support, wall thickness and is relatively cheap. I designed the body to omit the smokebox, chimney, dome, whistle etc – these are all best done, certainly in my view, by using existing brass or whitemetal castings. To get around the texture issue, which I don’t find a huge problem (it’s all in the finishing – see below), I clad the running plate, bunker sides, boiler and smokebox in 10 thou plasticard embossed with rivet detail. It’s not easy or really possible to do the curve of the cab roof so I’ve lived with that.


The final piece of 3d printed detail is the most interesting one – these are the 3d printed brass connecting rods. Given that it’s my own chassis and wheelbase that I was using, I drew up the two rods, joined them with a sprue and printed them via imaterialise in brass. I’ve bushed them, and they’re fitted onto standard Romford wheels and crankpins. So far, they’ve proved robust.


The build was quite straightforward really, detail the body with the plasticard, add the chimney etc. For the chassis, I used a mashima motor and a branchlines 40:1 gearbox. Romford wheels and crankpins. The brakes are alan Gibson plastic parts with wire for the brake rigging.


The finishing was interesting, a blast of Halfords car primer, and the secret with the WSF is to give it a good scrub with a toothbrush and water to remove any loose bits and get it as smooth as possible before the final coats are applied. I managed to source some transfers from <<>>> but then when I applied the varnish, found that it had got cold and when sprayed on resulted in a snow like appearance. Luckily a wash and partial repaint meant it was rescued, so 91 is now ready for service.


93 isn’t far behind now!


Anyhow, I hope that is of interest, and gives some background to the build process. I can post more on the 3d printed GNRi passenger brake vans if there is interest.








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]Hi David,


Thanks for that!


No, the boiler is a plasticard overlay, and the bands are plastic strip overlaid on top.


My website has further details :http://www.glr3dmodeldesign.co.uk


Attached are a couple more photos taken at the weekend, wonderful light on sunday, always nice to get in the garden and get some nice natural light photos!







JT painted 1.JPG

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