Stirlingengineforum.com

I think your first pic, of the contact strips, is possibly the best, but I would put them on opposite sides of the displacer, and use a metal wheel as the other side of the connection.

I'm worried about the weight that all of this would add to the displacer though.

Looks a bit like someone has seen a diagram of a "Steam injector" (as used to top up steam engine boilers) and failed to understand the magic involved.

Jack - do you have any diagrams of what you propose?

That final paragraph seems to involve a major mis-understanding on somebody's part (possibly mine) - it certainly seems to describe an 'over-unity' machine.

Charles law states V1/T1 = V2/T2 So if we have a 1cm^2 tube with 100cc of air under the piston, then we need to double its volume to lift our piston by 1m. If we start with 300K air then 100/300 = 200/T2 = 600K 3.65 Joules are needed to raise 100cc of air from 300K to 600K We used 1J raising the 10...

Here's my contention with the absolute zero thing, the best we can do on earth is exhaust down to 1atm at 300k or so. So chasing "100%" efficiency is like a baseball player chasing a 1.0 batting average, when .300 is considered excellent, and .400 is unheard. Instead, re-framing "100...

Fool,
My supposition regarding Tom's observations is that we shouldn't consider it to be an engine at all, rather it is a self-powered heat-pump, since it doesn't drive a load, and therefore the only work it can do is 'internal'.

Tom, The "absolute zero" thing is a core part of the definition of efficiency for a fuel-powered engine - if the exhaust is at any temperature above absolute zero then there is energy being wasted. It's a particularly poor definition for Stirlings, with the many possible energy sources, bu...

I think the difference in temperature in a Stirling engine is largely time dependent. (What part of the cycle). I'm quite happy to accept that that is true, but only if someone can point me at some science that says how fast temperature equalises / quantifies a temperature gradient in the working f...

Atmospheric pressure across the entire globe varies very little from 14.7 psi Good point. However that is exactly why we have wind - air mass "moving itself" in order to equalise _pressure_ differences caused (largely/entirely?) by temperature differences. Which rather brings me back to t...

If that is truly the case, then the gas laws imply that the temperature of the fluid must also be equal, everywhere. This is another case where it helps to think of energy flow into the engine, rather than heat. Glad when you chime in Mike B. I think this ties in nicely with your thoughts on "...

It's just one wishy-washy sequence in essentially an open chamber. The gas is free to move around. Even with the displacer fully raised, convection causes the cold gas to sink and be replaced by hot gas, which in turn is cooled, and again sinks. I know I mentioned the speed of sound before, but as ...

"Pretty obviously the elevated heat signature appearing around the power piston could only be from "work"."

Why is that?
Could the heat not come from the working fluid?

If you do want to have the two faces have matching grooves, then think about using casting for one or both.

Tom, IIRC you were the first to mention fridge's. We seem to be in agreement that they have little relevance to this discussion. Average <anything> is ALWAYS a thing, and while it may not be entirely easy to predict, the average temperature of the working fluid of a hot-air engine is definitely a th...