After a very disappointing day trying to use hand twisted wire crankshafts and bottle cap piston tops, we shifted over to 3d printing to make a well dimensioned soda can Stirling engine. We found that the crankshaft sizes has to be really surprisingly small. Remember that things more twice that radial distance over a full revolution.
Things that may have helped: We got those Sterno heat things. Actually it was too aggressive. The steel wool displacer was nearly the width of the.
We kept the floss hole pretty tight, by poking it with a small object and threading the floss through with a needle and running it back and forth until the steel wool weight is enough. It is basically air tight and a little too sticky, but it works.
The files can be found here https://cad.onshape.com/documents/65e85cdc777333555f580b5a/w/e8a82a796b8d794bd914d077/e/82b3f39011e3b6223a8eb6be
Mostly everything is 3d printed, with some 3mm screws and 1/8in home depot steel rod for axles.
Currently we hot glued the crankshaft together. A better idea possibly is to print them a little tight and then head the shaft with a lighter and sort of melt it through a bit. Might make for easier assembly.
The free wheeling floss pulley is clutch. We had a lot of problems with binding on our crappy version.
The displacer and piston rod are 90 degrees out of phase. Checkout the assembly in the Onshape document to see.
We do have difficulty with melting parts. The stand in particular keeps melting. We’re thinking about it.