[greybeard]

Nick - how about substituting a salt/crushed ice mix for your ice blocks in the bath ?
Having suggested that, I immediately realise the salt will corrode the aluminium

Have you considered aluminium/brass tube plus O-rings for a water jacket ? (Tiny Liebig condenser)
Regards
John

[nick.gilling]

Hi John,

I thought of trying to seal the arrangement I have with 'o' rings but it never occured to me to use a brass tube.

I could find some o rings that are too big to go down the slots so rest on top protruding, put one on each extreme groove then bore a tube out or find one to fit snugly over the o rings. I guess I'd need to make some large washers up for the ends then a larger outer tube with a hole in it to pour the water in and drill some radial holes in the middle section of the inner tube. That would make for a much neater arrangement than I currently have so may try that.

Thanks for the idea!

Nick

[greybeard]

Nick - if you have the o-rings, do you need the end washers and an outer tube ?
My thought was to have the water circulating in contact with the grooves, so carrying away the maximum heat. One pair of o-rings, and one tube with inlet and outlet pipes soldered to it.
John

[nick.gilling]

John,

that is a good idea but how will the water circulate though without a pump? I don't think the engine would be powerful enough to drive anything!

That's why I was thinking a jacket that could hold quite a bit of water would be better as it would take longer to heat the water?

Nick

[greybeard]

Trying to avoid this getting too complicated, but my initial idea was to have it connected to a small header tank so you'ld get a thermal siphon circulating the water.
Then I thought add a set of cooling fins to the tube, so the water is static, and only acting as a thermal bridge to the outer tube. Then you don't need the external water circuit.
Final thought - could the flywheel drive a small fan that blows cold air over the cold end of the cylinder ?
If so, you can scrap all my previous ideas

John

[nick.gilling]

I was wondering if it would generate enough heat in the water to cause a thermal siphon effect. I think that would be the best way, circulating the water around. I have seen some of Jerry Howells engines with fans on but people reckon they don't really work much in this sort of scale. Not nearly as effective as a water jacket or something. unless you had a radiator, pump and a fan that would be the ultimate! But I'm not looking to run the engine all day or anything, just for the odd 10 minute demonstration so I think the water jacket will do!

I like your idea though, I could have the narrow tube with o rings, a header tank the same height as the top of the cylinder on stilts, the bottom could feed cold water to the bottom of the jacket and the hot water should come out of the top of the jacket back into the tank.

Like I said though, want to try and keep this one simple and maybe incorporate these ideas into my next one.

Thanks

Nick

[deferr]

James R. Senft shows a water jacket setup in one version of this "Tapper" engine seen below.

The nice thing about using a water jacket is that the maximum temperature that this side of the engine can reach is 212 F. Once the water is boiling all that is needed is to keep the reservoir full. Ideally the water never reaches this level but if you design for your engine to run with the cold side at 212 F this can provide a convenient way of making sure you reach the temperature differential desired. You can use this as a sort of worst case scenario.