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I am working on a new displacer.What does the group think of directional air flow? My displacer is flanged in the middle to isolate hot end from cold end. I have a port in the middle of the top and the middle of the bottom. The displacer is ridged under the ports for a loose slip. The top port will open at about tdc and the bottom port will open at about bottom of stroke. If I run an air line from the top to the power piston and one from the power piston to the bottom would the air be hotter to the power piston and colder to the cold end of the displacer? The addition of a dwell would seem to help this cycle.

All I can say for now is, the power piston is at the cold end, and the displacer is there to alternately have a hot space and a cold space at the appropriate timing, you really should build a motor(if you have not all ready done so). In the usual sealed cylindrical displacer the air is directed down the gap between it and the hot cap, this works as a regenerator. Another type is the one made from metal gauze, and steel wool, the air passes through this on its way to the cold end and return, the trick with this one is to get the density correct.
Ian S C

Clarification... The top port will open at tdc of the power piston and the bottom port will open at bottom of stroke of the power piston since the displacer is 90 degrees ahead.

Directional flow might have some advantage, but it loses the Stirling advantage of simple regeneration that comes from the air passing forth and back through the same route. Ericsson incorporated regeneration with his directional flow design, but it was more complicated. It might be worth looking up the Ericsson engine for some reference/inspiration, but I think it's noteworthy that he eventually went back to manufacturing Stirling engines.

Bumpkin

Thanks for the reference Bumpkin. At least if it doesn't work I'm in good company.

Preliminary observation is that the directional air flow does work. Don't know yet if its better comparatively. I measured the temperatures of the piping going into the power piston from the hot end of the displacer and the temperature of the cold end of the displacer and the temperature at the power piston was always 10-15 degrees hotter. 160 compared to 145. The hot end runs 450-500.Still not getting much power for the temperature difference. Best I've done is .75 volts at about 200 rpms.