Friday, August 21, 2009

Status update, still looking for a good seal

Turns out the piston cap seals I bought are too tight. Not only do they cost too much, but they have too much friction.

I have been distracted lately and haven't done much work. I need to get bags that are made of different materials. I have been in contact with 2 plastic suppliers that promised sending me Nylon and Teflon bags, but neither of them came through.

I will be sending out requests for quotes to more suppliers for 3" wide, 6" long plastic bags made from tougher material then polyethylene.


david said...

Hello, I am thrilled to find an open sterling project, as I live in Arizona with plenty of free thermal energy. I am also a machinist, and lok forward to building my own. I do have a question. Why translate the linear movement to rotational? Why not use a linear magnet generator to avoid the wasted energy?

Dave Haun

Tom Belpasso said...
This comment has been removed by the author.
Tom Belpasso said...

Hi David,

Thanks for the comment, I didn't know anybody was watching.

One of the goals of my design, is simplicity. True you could use the linear motion to generated electricity. The Stirling cycle needs a 90 degree phase difference between the hot and cold pistons. I am not sure how to make this work without a cam or crank shaft.

The cam has several advantages, especially when ganging several engines along the main shaft. If any of the engine piston pairs leak, the pistons of that engine would be pushed up out of the way.

As compared with a crankshaft, to make the cam is very easy, just cut a slice off round stock and drill an offset hole. Then attach the cam to a straight shaft.

To add more sets of 2 piston pairs, just extend the shaft, the length of case side pieces and added shaft supports between each section.

I have tried to make many pieces from extruded material to reduce the amount of precision cutting.

I do have to "turn" the piston down to a smaller diameter, but I do that using a dremel drill press and a cutting wheel. I have a jig to hold tube while I rotate it under a cutting wheel. The do come out rough, but that is why I am using the bag material as a seal.

I still need to find a better bag material. I have given up talking with plastics suppliers, they say they are going to send me samples, but don't follow through. It is sad, because I am so close to finishing the prototype.

Toke said...

Hello, this is an interesting project.
Is the project still active?