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LTD Stirling Hard to Find Materials

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Bogstandard:
Sorry Nick, I should have worded it differently.
The photo was sent by Jan, and it is his egg cup Stirling on there. My three do in fact have built up crankshafts, but are about to be modded because I am fitting ball races onto the crank ends rather than a needle point, which I find very difficult to adjust correctly.






The problem with these tiny engines is that the size of the hot water reservoir, even a coffee cup, very quickly goes cold. So Jan shows in the picture a stand, holding a glass shot glass being kept warm by a tealight, giving at least an hours running.

K&S tube is a seamless brass tube that you can normally buy in short lengths from model shops.

John

cidrontmg:
There´s also Bengs Modellbau (in Germany), that sells many hard-to-find things, graphite and test tubes (just one, if you want just one) among them. Several sizes at http://www.bengs-modellbau.com/material/buildingmaterials/index.php
That´s a Google-translated page... I´ve bought several times of them, they send very fast. Everything high quality.
Just noticed that the English site is only a small part of the German site, graphite can be found here
http://www.bengs-modellbau.de/material/halbzeuge/
And there´s quite a lot of other interesting stuff in the German pages.
Like craynerd said, test tubes work fine for displacer cylinders, but they´re too leaky for a power cyl. They don´t need to be true, inside or out, so they have largish tolerances. Like Bogs suggested, brass (or aluminium) would be far better.
But I guess you are already covered...  :)
 :wave: 

NickG:
Thanks Olli,

Your egg cup stirlings look great John, did Jan put water in the shot glass when running or just rely on the heat it absorbs?
Come to think of it, I have seen yours before, I remember the different flywheel designs.

Does the K&S tube have an accurate bore or would it need boring & lapping? I was looking in the metal place's catalogue that I use and looking for seamless tube but wasn't sure what the finish and roundness would be like. Then I thought I could use ground steel for the piston but the graphite Ade has kindly donated will be just the job for that now.

Thanks,

Nick

Stilldrillin:
Nick.
I've used K&S 3/8" bore tube for steam loco cyls. It measured .002" oversize, and no measurable ovality. The pistons I made fit beautifully.....

http://madmodder.net/index.php?topic=3325.0

Found some in a local Craft Shop, now.  :thumbup:

David D

Bogstandard:
Yes Nick, you fill the glass with water, and top up when necessary.

As Dave has said, K&S tubing is very acceptable and should be fine for what you want to achieve, in fact they nestle very nicely inside each other, if ever you want to make something that telescopes.

No need to worry about getting it spot on internal size, somewhere near should be fine, and make the power piston to fit.

BTW, I do like the other one you showed, that lends itself for scaling down to something a little smaller because of the block on top of the displacer cylinder rather than using tubes.


John

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