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Is the power piston cylinder considered "dead space" and should it be kept to a minimum? This can be shortened considerably. Should I expect any improvement?



This has a steel wool displacer and works very well. I tried loosely packed steel wool inside the power cylinder but couldn't see any improvement using a digital tachometer. 200RPMs with and without. Is it doing anything?

Bidwell, I would not worry too much about dead space, although it should be kept to a minimum.
I have an article from Model Engineer 18th Feb 1977 "Stirling Engines", More research and development by W. D. Urwick. There is an interesting part of this where he conected the two cylinders with 6ft of rubber hose, and found that the extra dead space so formed had little or no effect on the performance of the motor. In regard of stuffing the cylinder with steel wool, that could to some extent work as a regenerator, and may not be a waist of time, and if you get it right it may improve the ecconomy, you would have to reduce the heating, and keep the same revs. 200 rpm is proberbly the speed it runs regardless, although the revs on these motors often increases as it gets run in, and frees up. Ian S C

Thanks Ian. I cut about an inch off the cylinder and gained 10 RPMs. I've switched to an alcohol lamp with a small flame to keep tests constant.

When adjusting the displacer's travel, is it better to favor the top? I figure favoring the top would keep the displacer cooler.

Bidwell, I tend to try and keep it fairly even. Congrats on the rev increase, thats the idea of these things as far a I am concerned, experiment, change one thing at a time, see the effect, with a tin can motor, make two, keep one as control, modify the other one. Just out of interest, what is the stroke of the motor, looking at the photo it appears very long, maybe about 4", a short stroke would be better for higher revs. Ian S C