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Curious about the Willstead model engine (vs Bohm vs others)

Posted: Sat Dec 17, 2016 10:45 pm
by cbstirling2
A few years I got a Bohm Stirling model and was not happy with its performance. It ran but after a while it would heat up and quit running in short order. It seems like a bad design (an older version of http://www.en.boehm-stirling.com/hb26.html ). To my newbie eyes, it appears that the hot side conducts too much heat to the cool side and robs power.

I recently saw a video of a Willstead engine driving a lot of toy equipment:


Looking at the engine: http://www.willstead.com/img/home_engine.jpg It appears to be of the gamma type.
Does it lack a regenerator? Or does the copper tube act as a regenerator?

On Amazon, I saw this 4 in 1 engine:


Would that be able to drive as much equipment as the Willstead? Any idea on its quality?

Thoughts?

Re: Curious about the Willstead model engine (vs Bohm vs others)

Posted: Sun Dec 18, 2016 2:27 am
by Ian S C
I have a Bohm HB7-A02 in my collection of hot air motors, There isn't enough thermal separation between the hot and cold ends, but it will run a tank full of spirits. It's not designed to power anything more than it's self.
The Willstead is a similar design to my first motor, depending on it's size it should be able to turn a small electric motor as a generator. If you have a lathe, you could scale that design up so that the power cylinder could be between 1" and 2", and say 1" stroke, and you would be sure of having enough power to run a transistor radio.
The Lieyang motor looks complex, and interesting.
In general these kit motors, and built up ones are designed and built to run as toys, the materials used are not always the ideal for the best efficiency, the only way that will occur is to build your own to best engineering standards, it all depends on what you want. Ian S C
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This little motor based on one in "Model Engineer" has a power cylinder bore of 5/8" and a stroke of 1/2", and it will power a 3V transistor radio.

Re: Curious about the Willstead model engine (vs Bohm vs others)

Posted: Sun Dec 18, 2016 9:30 am
by Aviator168
To my newbie eyes, it appears that the hot side conducts too much heat to the cool side and robs power.
Thermal short.

The gamma engines look very much like alpha riders.

Re: Curious about the Willstead model engine (vs Bohm vs others)

Posted: Sun Dec 18, 2016 8:56 pm
by cbstirling2
I wonder if the Böhm engine can be improved by electrically insulating the stainless heat head from the brass cooling tower? A thin wafer washer? Only the bolts would conduct heat

Re: Curious about the Willstead model engine (vs Bohm vs others)

Posted: Sun Dec 18, 2016 8:59 pm
by cbstirling2
I also wonder if I ran the engine upside down if that would help with shrouding protecting the cold side...

Re: Curious about the Willstead model engine (vs Bohm vs others)

Posted: Mon Dec 19, 2016 1:00 am
by Ian S C
Some redesign of the cooling fins would be a good start, it's designed as an ornament. Better to start with a scratch built motor that to try and modify the commercial one.
Another modification, the fly wheels, keep the same/or similar weight but increase the diameter, maybe by an inch.
Ian S C
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Re: Curious about the Willstead model engine (vs Bohm vs others)

Posted: Mon Dec 26, 2016 10:49 am
by cbstirling2
Ian, I wish I had a lathe!
Is there a water jacketed model out there?