Dummy inside motion

[barhamd]

As an experiment I had a go at 3D printing some dummy inside motion for my J17. The absence of anything between the frames was quite noticeable even though there are splashers and sandboxes in the way. The 3D modelling was quite fun, making a rod and a cam, repeating the part and then rotating them around the axle to give different relative positions. The sizes were based on the GERS drawings but I'm not trying to claim any degree of real accuracy, just trying to 'make something which looks right enough'. I've deliberately left off the outside parts of the drive cranks so that the part will fit between the High Level bearings and CSB components.

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The 3D print came out ok and shows I should be able to thin down the rods slightly, I'd erred on the side of strength for the first attempt. Sitting between the frames I think the part gives a reasonable impression.

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Once the body is in place you can't really see a lot but you can at least see there isn't just a massive void.

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The loco is now pretty much complete, there are still a few things left to do but it begins to look the part.

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David

[steve howe]

Looking good David,
Time was when we would never have given the space between the frames a second thought, its amazing how much of a difference some bits of machinery make to the overall look of the thing. I don't know if it was common practice accross the regions, but the GWR painted theirs red (various theories as to why have been floated - I suspect it was to draw attention to dangerous areas) but when this is done it really looks the part. Perhaps some enterprising manufacturer might consider bringing out a range?

Steve

[Suffolk Dave]

Nice work and an excellent use of 3D printing.

[DougN]

Seriously nice work. I would like to install something in my G6... It is making me want to learn how to use the 3d packages.... I have a mate that will print things for me! Once upon a time it was only very skilled, high value semi inaccessible technology is now becoming easily accessible.

[davebradwell]

I believe red paint between the frames was widespread - live steamers do it and they're led on by drivers and other railway professionals. As to how much red showed after a few weeks in the vicinity of a total loss lubrication system is anyone's guess. Perhaps a few red corners where the grime has been rubbed off by passing overalls.

Might I appeal for a back face for the cylinders so that the smokebox isn't hanging in space, it makes a good frame stretcher anyway. This will lead to slidebars, of course! Another prominent bit is the top of the motion bracket which is usually a hefty casting and sometimes carries the weighshaft - another prominent bit. You're lucky with this loco as it has so much junk on the platforms it's difficult to see in.

DaveB

[barhamd]

I printed a slightly modified version of the cranks and also tried to model the slide bars, piston and valve rods and cylinders as a block to go under the front. Whether anyone will notice is a moot point but I think the chuck of cylinder/valve under the front end might be quite visible from a low angle.

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I'm not sure about the colour, I really don't think red is a good idea, on most of the photographs I have of J17s it is hard to even work out which BR totem was on the tender. I don't think by the mid to late 50's the motion would be anything other than dirty black, perhaps with a hint of oiled steel.

David

[davebradwell]

Yes, that finishes the job. Slidebars would, of course, be shiny where the crosshead moves but you might just dry-brush darkish red on exposed corners of the rest to give the bits some shape in the gloom.

DaveB