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

Discussion on Stirling or "hot air" engines (all types)
cbstirling2
Posts: 113
Joined: Sat Dec 17, 2016 9:35 pm

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

Postby cbstirling2 » Sat Dec 17, 2016 10:45 pm

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:
https://www.youtube.com/watch?v=NnGsShW0cU0

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:
https://www.amazon.com/Lieyang-Cylinder ... ref=sr_1_1

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

Thoughts?
CBStirling2

Ian S C
Posts: 1970
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

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

Postby Ian S C » Sun Dec 18, 2016 2:27 am

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
013 (640x480).jpg
013 (640x480).jpg
013 (640x480).jpg (235.61 KiB) Viewed 955 times


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.

Aviator168
Posts: 308
Joined: Tue Feb 08, 2011 2:29 pm
Location: Brokeville, NY. USA

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

Postby Aviator168 » Sun Dec 18, 2016 9:30 am

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.

cbstirling2
Posts: 113
Joined: Sat Dec 17, 2016 9:35 pm

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

Postby cbstirling2 » Sun Dec 18, 2016 8:56 pm

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
CBStirling2

cbstirling2
Posts: 113
Joined: Sat Dec 17, 2016 9:35 pm

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

Postby cbstirling2 » Sun Dec 18, 2016 8:59 pm

I also wonder if I ran the engine upside down if that would help with shrouding protecting the cold side...
CBStirling2

Ian S C
Posts: 1970
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

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

Postby Ian S C » Mon Dec 19, 2016 1:00 am

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
[img]
DSC01049%20(640x480).jpg
[/img]
Attachments
DSC01049 (640x480).jpg
DSC01049 (640x480).jpg (161.18 KiB) Viewed 933 times

cbstirling2
Posts: 113
Joined: Sat Dec 17, 2016 9:35 pm

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

Postby cbstirling2 » Mon Dec 26, 2016 10:49 am

Ian, I wish I had a lathe!
Is there a water jacketed model out there?
CBStirling2


Return to “Stirling and "Hot Air" Engine Forum”

Who is online

Users browsing this forum: No registered users and 70 guests