Garden Railway Forum

Here's another photo showing more clearly what I think I mean
Rik

Thanks.
That is exactly what I thought when I posed the question.
Also, following the trail your picture above I followed the thought and ended up up this page:
https://resurgamrollingstock.co.uk/prod ... ad-wagons/

It appears that that type of coupling was used on RNAD wagons.

Armed with that info, the A-D drawing now makes complete sense. Thanks Rik.

philipy wrote: ↑Fri Oct 14, 2022 8:31 am Armed with that info, the A-D drawing now makes complete sense.

It's called a link and pin coupler and there are numerous design variants going back a long way. US railroads used them in preference to the British 3 link coupling, although both are at the same barn door level of technology. https://en.wikipedia.org/wiki/Railway_c ... nk_and_pin

Very dangerous to use in full size and claimed to be the reason why the Janney coupler (knuckle, buckeye, MCB, etc. etc.) was invented in the US. It was said you could recognise a railroad worker by how many fingers he had missing.

My timber tram models use a variety of the things, some commercial, some scratchbuilt and they are as big a pain to use in model form as the common SM32 centre buffer and chain coupling.

Graeme

OKey Doke, thanks guys.
Well it's drawn up and I think is pretty close to the drawings /pictures. Getting the double curve on the face was abit ofa mare though! Also the helical spring... it is possible in Sketchup but I decided the learning curve was too steep for what it is. I'll print them without the link, obviously.

Would it be possible to print a hexagonal recess, in the base of the 'cone', with a hole at the back?
You could fit a bolt, a threaded spacer behind, and then a spring and washer/nut.
Hey-presto! A sprung link and pin coupling..

Or would it be just too fragile to be practical?

Phil.P

Certainly possible to draw and print, Phil. Not sure about the strength though. The diameter of the cone at the small end is 2.5mm and the diameter of the shank to the head is also 2.5mm, all as drawn, ( but could be a wee bit flexible I guess).
That means that your rod would need to be only about 1.5 dia to allow enough 'meat' around it and that might look bit skinny where it is visible.
It's an interesting thought though, thanks, but I have enough on my plate atm!

philipy wrote: ↑Fri Oct 14, 2022 1:42 pm Also the helical spring... it is possible in Sketchup but I decided the learning curve was too steep for what it is. I'll print them without the link, obviously.

The technical term for that type of spring is a volute spring. Used a bit in railway work, such as buffers, as they have a longer compression range than a garden variety helical coil spring, due to the coils telescoping, instead of just closing up.

In this size, you could get a reasonable simulation by stacking four cylinders of decreasing size. Once it's painted dirty black it won't be obvious it isn't really a volute.

I suppose you aren't planning on pulling heavy loads with this thing, so plastic might be strong enough.

Graeme

GTB wrote: ↑Sat Oct 15, 2022 2:09 am
The technical term for that type of spring is a volute spring. Used a bit in railway work, such as buffers, as they have a longer compression range than a garden variety helical coil spring, due to the coils telescoping, instead of just closing up.

In this size, you could get a reasonable simulation by stacking four cylinders of decreasing size. Once it's painted dirty black it won't be obvious it isn't really a volute.

I suppose you aren't planning on pulling heavy loads with this thing, so plastic might be strong enough.

Graeme

Thanks Graeme.
I knew that was the wrong spring name when I wrote it, but I couldn't for the life of me think what it was actually called.

I tried stacking decreasing cylinders, but it just didn't look right which was why I originally settled for a simple cone. However your comment prodded me to think about it again and I realised that a set of decreasing cylinders with angled joins would look much closer to the real thing, and this is the result: It looks fine from the top but the apparent twist goes the wrong way underneath, of course, but thatdoesn't really matter, and it can't be seen from the sides. Don't know how well it will print, but will find that out later this afternoon.!

That's a really impressive bit of 3D drawing - even more so when its size is taken into consideration. I hope it prints OK

Rik

ge_rik wrote: ↑Sat Oct 15, 2022 7:42 pm I hope it prints OK

It seems to have done. I haven't had chance to clean all the supports off yet but it looks pretty good, if I do say so myself. I'll try to get a pic in the morning.

philipy wrote: ↑Sat Oct 15, 2022 11:33 am I knew that was the wrong spring name when I wrote it, but I couldn't for the life of me think what it was actually called.

It looks fine from the top but the apparent twist goes the wrong way underneath, of course, but that doesn't really matter, and it can't be seen from the sides.

Took me a while to remember the name of the spring as well........

No-one except you will ever know that it is 'not quite right'. I'm not sure I could even see the 'spring' without my workshop glasses (custom prescribed safety reading glasses with a 1.5x magnification)

Graeme

Yep, I'm really pleased with the way the buffer/coupling has printed.

Graeme, the spring cone is 8mm long so I'd guess you'd be able to see it!

Wow! That has turned out well. I like the old glass bottle effect.

Rik

ge_rik wrote: ↑Sun Oct 16, 2022 8:55 am I like the old glass bottle effect.

Anycubic 'Tough' Translucent Green resin!



However, finally getting somewhere overall.
The body now complete and in all over works grey. Don't worry about the roof being wonky, its only temporarily in place until I've fixed the engine and driver inside and I don't want to do that until after I've finished spraying.

Looks very tidy, Philip. It seems tiny there against the track width.

That is a nice piece of printing!

Trevor

philipy wrote: ↑Sun Oct 16, 2022 7:32 am Graeme, the spring cone is 8mm long so I'd guess you'd be able to see it!

I could probably recognise that it was a link and pin coupler, but without my modelling glasses I'd be hard pressed to tell whether the spring was a volute or a stepped cone.......

The model has come up well. Just how big is that thing, I'm guessing about the size of a 20 HP Simplex?

Graeme

Thanks chaps.
Graeme, the body is 125 x 69mm

My bent frame Simplex measures 130 x 78mm, so very close.