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Brent Van Arsdell Limited Edition restoration

Posted: Tue Jan 18, 2022 4:44 pm
by thomas_a_booth
I recently found this engine on eBay.

Brent Van Arsdell Stirling Engine
Brent Van Arsdell Stirling Engine
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What a beautiful engine!

I had thought it to be either a very old antique or a reproduction, but after some research found that it was an American Stirling Engine Limited Edition.

Apparently just 15 of these, with the magnetic displacer mechanism were ever made.

It appears that the connecting rod has been detached. Also, the displacer itself is misshapen, perhaps from overheating?

It is signed on the bottom: Brent Van Arsdell

It looks like it will require a bit of restoring, but I hope to get it operational.

Re: Brent Van Arsdell Limited Edition restoration

Posted: Thu Jan 20, 2022 9:36 am
by thomas_a_booth
Information about this engine from the Way back internet archive. American Stirling Company website in 2004

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Re: Brent Van Arsdell Limited Edition restoration

Posted: Thu Jan 20, 2022 9:52 am
by thomas_a_booth
Michael Crumpton's design website from about the same time period, additional screenshots from the Wayback Internet Archive:

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Re: Brent Van Arsdell Limited Edition restoration

Posted: Fri Jan 21, 2022 2:38 pm
by thomas_a_booth
The engine just arrived in the mail this afternoon, very well packaged, safe and sound. The displacer rod, which was detached in the eBay sellers photos was already reattached.

Everything seems fine, other than the foam displacer has sagged with age. Perhaps the timing could use some slight adjusting.

From what I read on the Wayback archived American Stirling website, these engines were supposed to be labeled or marked with a serial number. However, I cannot find any such label or mark. Does anyone know why that might be?

There was, I think, one original working prototype, the last engine of the series to be sold, to someone in California I think I read somewhere on one of the pages on the Wayback archived This engine came from California, so perhaps this is that engine?


Re: Brent Van Arsdell Limited Edition restoration

Posted: Mon Jan 24, 2022 1:49 pm
by thomas_a_booth
I have not had any luck getting this engine to run by simply applying heat and/or cold and adjusting the timing, so it looks like it is going to require an overhaul.

An obstacle to that end is, first of all, I don't want to damage it, and two, I don't know exactly how it was put together. Various bits could be pressed on or threaded or perhaps even pinned. The magnetic drum for example appears to have a brass plug that was pressed in, so replacing the magnet, if necessary would probably involve drilling out the plug. Thankfully though the magnet seems to be in good working condition, so that should not be necessary.

The first thing I'd like to do is take out the piston and clean the cylinder, examine the piston and check how well it seals, if at all, however, removing the arm to get the piston out has presented a problem.

There appears to be a cap nut holding the rocker arm in place. I don't know if this is threaded, reverse threaded, pressed on, glued on or what.

If there is anyone with any information on how these engines were made willing to share some tips on getting this engine apart, that would be wonderful. If not I guess I'm on my own.
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Fist of all, does anyone know, is this nut[?] threaded, pressed or glued. Whatever the case it does not want to come off easily, if it is even a cap nut at all. Perhaps the entire post is all one piece and threaded or pressed in at the other end.

Perhaps it would be better to do nothing to "restore" this engine, rather than risk breaking it.

Re: Brent Van Arsdell Limited Edition restoration

Posted: Tue Jan 25, 2022 11:49 am
by thomas_a_booth
There seemed to only be a few possibilities. Either the cap "nut" was threaded on, pressed on, soldered on, or possibly even glued on. In any case, heating it up a bit with a propane torch couldn't do any harm and should expand the metal, loosening the nut.

So as not to cause any damage, I taped some bits of wood onto the jaws of a pair of vice grips, and adjusted them so they could get a good grip and twist off the nut.
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Then applied some heat to the nut, having the vice grips ready to turn out the nut while still hot.
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As it turned out though, the pliers were not needed. Once heated, some goo bubbled out from behind the brass CAP giving off fumes and an awful odor.

The brass cap, with whatever was holding it in place; some kind of strong glue or resin, making it seem impossible to remove, virtually fell right off with the glue shortened up
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Mission accomplished!

I think it can probably be assumed various other parts may also be held together, and can be freed up in the same way.

It is a common machining trick to hold metal items together with super glue and then turn them in the lathe. They can later be easily taken apart by heating with a torch which quickly softens the glue.

I'm not sure what stuff was used to hold the parts on this engine together but it produces very nasty smelling and probably toxic fumes when heated, so this operation is best performed outdoors or in a very well ventilated area.