New guy's confused

[tapkoote]

I'm working on my first pop can engine,
and am on the 4th rebuild.
The displacer piston hits the side of the hot end when the crank rotates.
It needs to be rebuilt. I'm fine with that.
But some folks use a can that is sealed air tight, and some just steel wool.
What is the advantage of the sealed displacer?
thanks Pat

[fullofhotair]

The displacer does just as its name implies. It moves the hot air from bottom to top ,then back. Its not a piston so you don't want a tight seal around it. One of rev. stirlings improvements on the hot air engine was the " recuperator" this is what we now call a regenerator. It holds heat in a reserve ,usually in a steel mesh. It preheat the air ,make the engine more efficient .Making the displacer out of steel wool turns it into a regenerator. Very ingenious ,it now serves two purposes.