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i have made an engine with diaphragm that ran. And felt why i failed with metal piston as it was heavy and the power this generates is low . I plan to make a light piston. I will get a cylinder plastic syringe and use a paper to make the piston. I will use a 1 cm wide paper strip to make a roll that will tightly sit in the cylinder due to its recoil. I will fill the space with silicone sealent . And thats it. Any advice

asiminations, I feel that paper on plastic woul have a fairly high coefficient of friction, when syringes are talked of in hot air circles, they mean glass, and graphite is the best for the piston. A bit of brass tube (new), and if you have no machinery (lathe) you can make quite a good piston with JB Weld, there is instruction some where on the net.
It is possible to make a LTD motor with a cast iron piston and cylinder, thats what my one has, if you have a lathe, the cast iron piston can be made very light weight. Ian S C

you are right about the materials but hard to get for me so trying somethig simple the feather weight of these might help

my first attempt is not very bad but i am planning to change the materials from paper to aluminium foil and glass tube

Sound worth trying. Ian S C

I saw some videos online once of someone's paper pistons. They were folded like a bellows and worked very well.

Hi
How to make a billow :http://www.groeg.de/puzzles/rocket.html
Jan

Here is a video of a Stirling engine with a bellows drive.

http://www.youtube.com/watch?v=BvxPJ2ypjP8

well all my tries to make paper and plastic piston and cylinder to work failed as high resistance did not allow the engine to run though it moves a bit

jimlarsen wrote:Here is a video of a Stirling engine with a bellows drive.

http://www.youtube.com/watch?v=BvxPJ2ypjP8

That must be the piston with the least friction.

I think the paper bellows might offer quite a bit of drag, depending on the materials used and how it is made. But it is an interesting approach.

As for the paper piston, this is how we learn! My Dad always tells me I can learn more from my mistakes than I can from my successes.