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So You Want to Build a Stirling Engine ?

PostPosted: Tue Apr 14, 2009 6:00 pm
by stan.hornbaker
The following arrived in my email this AM.

"Subject: Seeking your advice

Hi there. I understand that you are a Stirling engine expert.

I'm trying to create a Stirling engine powered generator to be
manufactured using recycled material in developing nations as part of
a microenterprise development program I am working on. If you don't
mind, I have a few questions I need your help with:

1. How do you size the engine?
2. How do you determine its power output?
3. How do you determine the number of RPMs it makes from its design
4. How do you determine its power input requirements?

I hope I'm not imposing on you. If I am, I want to apologize for it in
advance and hope you can help me with my problem.

Thanks & best regards."

My Reply follows:

"I offer you a one word piece of advice. D O N ' T . Not flippant but
serious advice.

Designing a power producing Stirling engine from the starting line is
a long and arduous task frought with a steep learning curve and much
time devoted to preparation and knowledge acquisition.

Even the experts (very few and far between) have to build a prototype
and then modify it to reach a really good engine. This requires more
R&D financing than is likely to be available.

To find more information go the < > and look at
some of bottom of list topics on the Power Producing, Waste Heat, &
Model Engine Forums.

A CD with items of interest is available for the cost of mailing & a
blank CD.

Also many links are to be found at < >

Engineering Thermodynamics < > Is
required understanding of the subject of Stirling engines. Dr. Izzy
published this jr-sr level web site for his engineering students to
make it available to anyone interested. It is a quite complete
treatment of the subject as well as providing the necessary background
for any attempt at construction of a real Stirling engine. Note that
is is quite long and has many more pages linked to one another.

There are may sources on the web with plans and instructions to build
Model Stirling engines.

This has been presented to provide the best advice and information
that I can think of at present. While not a designer but having
followed the progress or lack thereof of the topic of Stirling engines
the last 15 or so years and being a retired mechanical engineer I have
a well rounded knowledge of what is involved in the design and
production of Stirling engines. Anyone with even modest skills can
build a low temperature (LTD) engine from plans and/or design one from
observing what others have done. When you want real power output you
have a different "Kettle of Fish."

Here is an additional email message from another person's email to me.

"...have to build a prototype and then modify it to reach a really
good engine. This requires more R&D financing than is likely to be

There's the answer you might reconsider giving this individual. Ask
him/her if they have the money required to complete the above process.
If so, recommend that they spend it on an already experienced "expert"
who's in the R&D stages already. If, by some strange chance, the reply
comes back that the money can be spent in this manner, then inform
them that they must offer the money in the same manner as if they were
designing it themselves. In other words, high risk, no guarantees, no
set goal timeframes or deadlines, no outside (or entrenched) 'expert'
advice and no bean-counters.