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jonhjames___9698
Posts: 3
Joined: Sun Jul 30, 2006 7:49 pm
First Name: Jon
Last Name: James

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Post by jonhjames___9698 »

Dear Mr. Hornbaker & others,

I am attempting to build a power producing Stirling of the beta
type, single cylinder. I have built 3 model stirlings in the past, 2
of wich were successful.


I need advice in a few areas, as follows:


The design I am working on will have a 5" stroke and 5.5" bore. The
displacer length will be 2X the bore, = 11". Does this sond workable
to you?


Is it reasonable to have the same bore and stroke for both the
displacer and the power piston?


What is your thought on the actual diameter of the displacer running
in a 5.5" bore, in order to provide for air flow around the
displacer?


I am planning to use a portion of the 11" long displacer as a
regenerator, by wrapping metal mesh around the displacer rod. I
thought I would devote 8" of the length of the displacer to the
regenerator and 3" would be a "can" to form the hot end of the
displacer. What are your thoughts on this arrangement?


I am also considering sealing the crankcase. Would the pressure
buildup in the crankcase on the backside of the power piston provide
some amount of "flywheel effect"?


Do you feel it would be significantly beneficial to groove
or "thread" the inside and outside of the displacer cylinder in
order to create more surface area?


Thanks in advance for your help.


Jon James

rtopf
Posts: 21
Joined: Fri Jun 28, 2002 6:49 am
First Name: Richard
Last Name: Topf

Response to Repost

Post by rtopf »

Jon,

The engine you propose has a very large swept volume for a Stirling engine. The large pumping engines of the 19th century were in the same size range. The biggest problem you will encounter will be the lack of sufficient surface area for heat transfer. It is very likely not to run at all without some modification to smooth surfaces. Putting a thread form would help but probably not enough for a pressurized engine.

You would be wise to look at old patents from Ericsson, Rider, and others from about 1850 to 1900 for ideas. Google has a new patent search feature that will find the old ones.

Also you could learn much from the experiences of Merric Lockwood who authored the book "How I build the 5 HP Stirling Engine". That engine is also big, around 6 inch bore.

You should also be aware that the piston phase angle is different in a beta than a alpha or gamma. Most alpha and gamma engines put the power piston crank pin 90 degrees behind the displacer. Since a beta engine puts power piston in the same bore, the actual volume phase angle is determined with one piston in relation to the other. In other words, the power piston should still fol ow the displacer by 90 degrees, but the distance to the displacer is moving, so the actual volume phase is the difference in there combined positions.

Rick
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