Question

Do Stirling engines' air containers need to be connected with air?

Answer 1

Two plastic plugs contain water (allowing for curved piping). That whole segment can move back and forth along the pipe connecting the two pistons. The pressure of the gas is therefore transferred between the pistons as if they were connected directly. Yet, convection is now blocked, or at least greatly reduced.

Alternative to my solution would be any kind of mechanical connection, like additional pistons.

Now, I have not seen this design which means it probably won't work. Why wouldn't this work?

Reminders:

the rest of the design is a normal alpha Stirling engine (so the pistons are moving in a controlled manner)

The blockage in the pipe can move freely to both ends of the pipe

Answer 2

so it should not be connected with air