Sterlin Engine not working

[Fool]

Disconnect the piston from the crank. Operate the displacer by hand. The piston should pop in and out as the displacer pushes the gas from hot to cold. Adjust the piston stroke to that distance.

[Kayjas]

The piston housing is aluminium and the piston is also aluminium and a bit loose. So I've made a new one out of brass and a slightly better fit. I will finish it off in the week but is ally and brass a good combo?

[Kayjas]

Brass was better and it almost got running but the friction of the piston is still too much.
Now going to try a delrin piston.

[Fool]

Try putting ice on the displacer cooling fins.

[Kayjas]

I think I'm nearly there now.
I made a piston out of some PTFE and to my delight it started running. However the piston is still dragging and producing friction. What is the ideal material for the block with the bore a d the piston?

[VincentG]

An aluminum bore is not ideal, but in that case you would want the piston material to be much harder than the bore. So something like steel or cast iron would be best.

[Kayjas]

Thanks to everyone on here for the tips and advice.
I now have a fully working Sterlin Engine that was made by my late father. I ended up with a delrin piston and during the heat up I spay some fine oil onto the piston and the cranks. It runs so fast I thought it was going to take off. Thanks again

[Tom Booth]

... during the heat up I spay some fine oil onto the piston and the cranks. ...

Often a problem with small models without expanding piston rings and seals. Due to thermal expansion there needs to be excess play which closes up giving ideal clearance once the engine is running. A bit of oil at start up helps close the gaps until the parts get warm enough to expand.

Congratulations!

[Kayjas]

My Stirling run's a treat when I heat the end with a mini cooking blow torch but if I use a candle wick with lamp oil it won't get hot enough and run.
Any ideas?

[Tom Booth]

My Stirling run's a treat when I heat the end with a mini cooking blow torch but if I use a candle wick with lamp oil it won't get hot enough and run.
Any ideas?

You might try putting a shroud over the candle, and displacer chamber, possibly with a chimney to retain more heat.

Especially if you could make it out of ceramic or firebrick or refractory, like a forge type lining inside.

A lot of the old models had shrouds and/or chimneys

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Maybe also banding the displacer chamber with a copper band from a copper pipe can help distribute the heat around the full circumference. Otherwise the heat from a flame underneath can tend to warm the bottom only. The copper conducts more heat around and over the top. Theoretically anyway, if it doesn't block heat.

Probably electroplating a thin layer of copper onto the outside end, like a copper bottom pot would be ideal.

Don't know what your using for lamp oil, but you might be able to find a hotter burning fuel.

[Kayjas]

Thank you for your reply. I will Make a shroud and a copper sleeve. Plus I can try paraffin instead of the lamp oil. Thanks again for the advice.