TangoOscarMike

My 3D printed tender chassis has arrived. The four protrusions are intended to tuck in the corners, and I deliberately left some vertical clearance to be filled with shims. Unfortunately, I enormously overestimated the amount of clearance needed, so the first order of business was to build up these corner pieces by two additional millimetres.

Meanwhile, I have ordered a print of this, for the tender chassis:

Well, I've just had three weeks without Internet (Vodafone and Telecom blaming each other for the outage), followed by two weeks on holiday. A strange experience altogether. But now I'm back. The printed surface is rough and a little bit porous - it takes paint well, without any need to prime. I apply many coats of (tapwater) thinned acrylic, and the build-up of paint removes some of the roughness. Here are some examples (although these are examples of Shapeways' "smoothed" version of this plastic, whereas the Crampton parts are not smoothed): Some people achieve much smoother finishes with several coats of primer and sanding. But as well as being hard work, this approach requires careful handling of the fine detail (or removal of fine detail altogether, with subsequent replacement needed). So I am almost certainly going to take my usual simple approach.

Thank you, that sounds like good advice. Possibly a sturdy plastic strip running up the middle would be appropriate. Perhaps held in place with a machine screw that mates with an epoxied-in nut, because I like to make things that I can dismantle. Hmmm... I'm also thinking of having pickups on the front wheels because (I suppose) the more's the merrier when it comes to electrical contact.

I've made a bearing and support, for the front set of wheels, out of brass tube and channel. The tube has cutouts where the axle touches the frames, to prevent sideways movement of this brazen contrivance and to put the axle at the right height. The channel prevents rotation. The tube sticks out past the inner frames, to prevent the sideways movement of the axle. It's a slightly loose fit, but I hope that with thin shims it will be a tight fit and hold itself in place. I'm making two more for the other carrying axles - these will have shorter tubes to permit sideways movement.

An experimental lining technique. Four holes drilled in a piece of plasticard. Cut out, and attached using the masking tape and superglue trick. Drawn round with a marker pen. As usual, it's worse than I'd hoped but better than I feared, and the camera is cruel. I'll see if I can tidy it up with some paint.

I had a little struggle with this. In case anyone else did: That the splashers were not lined My conviction thereof reduced (to an unpalatable degree) By the photos, few in number It actually makes perfect sense if you take a deep breath and read through steadily without pauses. But that's a risky business for an asthmatic like me. You're welcome! Tom

Definitely worth consideration. I'll be having the same set of questions again with the tender, as well.

The whole locomotive is a single piece of plastic, so the axle boxes make it impossible to get a file in. There is probably an alternative way of abrading away the tops of the slots - perhaps a grinding tool attached to the very motor that I have bought for the tender. But I will avoid that particular rabbit hole for now, while I think about contrivances of brass tube, channel and strip.

Thank you both. My initial reaction was that this won't work so well because the axles, bearing against the tops of their slots, are at the right height, and the tube would put them half a millimetre lower. But on reflection, the tube could be cut away where these supports are, or could be wholly inside the inner frames. So I think this might indeed be the right approach. I might already have some suitable tube, but if not my local model shop does.

Instead of the recommended Alan Gibson wheels, I've bought Hornby tender spare wheels - 4 pairs in each case, although that's more than I need. The tender wheels have pin-point axles, which will have to be filed off. The locomotive carrying wheels seem to be about right. Fitted loosely like this they (and the drivers) all roll properly when I push it along the track. But the axles are 2mm diameter, whereas these slots would accommodate 3mm axles. So there is a bit too much freedom of movement. I think that I will: Restrict the fore-and-aft movement with shims inside the slots. I suppose maybe I could try plasticard. I'm not sure. Restrict the side movement of the front pair of wheels, either with shims outside the wheel supports ("dummy frames" perhaps?) or with shims inside the axle boxes. Not restrict the side-play of the other two pairs of carrying wheels. But I would be most grateful for comments or advice. Meanwhile, I'm having a little trouble finding a suppler of gear wheels for the tender mechanism. There are plenty of on-line shops with a huge variety of things that seem almost right. It's a bit of a wearing situation for a procrastinator.

I've reached the iterative phase of painting, in which each session serves mainly to correct the errors from the previous session. I've also started mutilating Dapol/Airfix figures for the crew.

https://www.youtube.com/watch?v=pH37Dep0cvU

Is there an opportunity here for some dual-gauge track?

I've sloshed some black paint onto the cylinders, and I'll try to avoid removing this part from the chassis again. If I keep taking it on and off I'll end up breaking it. This is how it looks with a coat of primer. From this particular angle the dome and funnel look a little small, but to my eye not too small. The original locomotive is German - black with red wheels. The only way for red wheels to make sense in my locomotive is if the whole thing is red, so that's that for the choice of livery. In any case, according to my childhood reference material, most narrow gauge tank engines are red.

Well. There were times when I thought that I would have to modify the design and discard this first attempt. But in the end, with some filing and a shim, the body fits properly. The bracket+cylinders piece was perhaps sound in concept, but the detailed design was no good - there was no way of getting it in place without breaking it. After reconstruction with bits of plasticard, and in a workable arrangement this time, the part is now usable. The roof, on the other hand, is fine - no modification required! The next step will be a coat of primer, after which it will actually be possible to see what it looks like!

After months of procrastination, I've scuttled back to my comfort zone and designed a 3D-printed locomotive body (printed by Shapeways). Its vestigial structural running plate sits on the chassis as before, with a cosmetic running plate and footplate 3mm lower. The attachment plate now includes an elaborate bracket that holds two cylinder enlargement wrappers. I'm not entirely pleased with this. The proportions of the details aren't quite right (dome too small, perhaps), the body will need some filing, and the plate/bracket requires lots of fettling. I might have to detach or even abandon the cylinders. But I'm going to press on with it anyway.

That could well be a good idea, although maybe to be useful for this purpose it would have to have more smallness. In any case, if/when I finally manage to make a layout, it will probably be a minimum 009 and too small for any optical shenanigans. I would also want it to be viewable from all sides.

Well, I'm not going say it's finished - that's pretty intemperate language. But I have stopped, for the time being. I decided not to deal with the gap between thatch and chimney. The cure might be worse than the disease. I had a horror of people looking in through an upstairs window and out through a downstairs window, so I was planning to install card baffles inside. That turned out not to be necessary. If this was a brick building it would clearly be an H0 model - hopelessly small for 1/76. But it's alright for an old timber framed house to be small and have low ceilings. This elegant Andrew Stadden lady would have to duck to get in even without her hat. But in fact she wouldn't dream of entering such a nasty little hovel. She's only here to deliver religious tracts and pamphlets about the evils of drink. She's wasting her time. Druids have been operating a still in here for 9 generations. My next piece of model building nostalgia will involve Linka moulds.

I'll just stick my oar in with a mention of OpenSCAD. It's not for everybody, but I like it.

Here is an arrangement that I think will fit. The gear wheels are of a type stocked in my local model shop. They have rather large bosses, but I don't think this will be a problem. I've bought an N20 motor (it's so tiny!) so now I must get my act together and buy the railway wheels and the gears.

And now it's assembled. I found that both roof halves were rather warped, so I heated them in the oven and straightened them with my fingers. And with that done the parts were a pretty good fit. There was still an unsightly seam at each corner... Rather than use filler, I flooded the gap with liquid cement and then put a strip of plasticard into it. When the plastic was soft, I pushed it further into the gap with a sculpting tool, taking advantage of an effect that normally spoils models. Once it was set I filed, sanded and painted the corners. In spite of the general good fit, there are gaps on both sides between the chimney and the thatch: I've managed to get brown paint onto the unpainted plastic, so these gaps are now much less visible. I'm procrastinating about what to do next. Firstly, I don't know what would actually be realistic in this case (although I'm sure the internet can help!). Secondly, there is a risk that anything I do will actually be more conspicuous than the gaps.

I'm considering it now!

On reflection, I have a bit more freedom with the motor's position. I'll try a few more variations on this concept to see if I can get it to fit. In fact, if the motor's gear acts on the idler instead of the central wheel, then I'm pretty sure it'll be fine. I'm also pretty sure that I'm mis-using gear wheel terminology.

I'm starting with a plan to put a motor in the tender. On the Shapeways site, @Rudititanic suggests (and provides a chassis structure for) a Tenshodo motor bogie, but also lists drawbacks: The wheelbase is slightly wrong Limited haulage capacity But in any case the bogie in question is out of stock at motorbogies.com. So I've been considering other ways to motorise it. Plan A was to use an N20 motor+gearbox with two right-angle shafts, and put the central wheels directly on those shafts. The motor would have to be tilted to clear the axle behind. Plan A wouldn't work because it would bring the motor too low. This is a sketch of Plan B, again with an N20 motor. This doesn't work either because the motor is too long to fit in the tender. And I can't find any other orientation that fits. So now I'm thinking of a shaft with worm wheels (driving all three axles) and connected via gear wheels to a motor above it (without the built-in gearbox). I would very much welcome suggestions!