Stirling Engine – Free Piston Engine

[Anthony SalisburyParticipant @anthonysalisbury72898]

I'm after some help. I'm really interested in the Stirling engine principles and want to learn more.

The units I'm more intrested in are the free piston versions. I would like to make a simple example; does anyone know of a good example to make and where I can get the drawings from.

Thanks,

Ant

[Anthony SalisburyParticipant @anthonysalisbury72898]

Request for drawing / help

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

Hi, try this: http://www.bekkoame.ne.jp/~khirata/english/fpse.htm

[Ian S CParticipant @iansc]

Hi Ant, your showing symptoms of hot air disease (good on you). Sorry I'v no drawings of my free piston motor, it's down for a rebuild. There is an artical in Model Engineer 1st of Dec 1995 with a diagram that could be scaled up to maybe 1" to 1 1/2" bore.

My first attempt was a BETA type, but I found it a bit of a hassle fiddling with the springs, so I put it asside and built a GAMMA one, and as it has a linear alternator I found that the surrounding structure must be non magnetic. Thinking back, this was the main problem that prevented the first motor running properly.

If you can get onto the stirlingengineforum, there is a resent thread about thermo accoustic motors, with vidio, It shows one running without a crankshaft, as a free piston motor. Ian S C

[Ian S CParticipant @iansc]

You might find the last mentioned bit by googling Resonant Stirling Engine Mk III on youtube, because when I went hunting in the Stirling Engine Forum i could'nt find it, it's there some where.

Further to motors with linear alternators, you can eliminate the springs by using opposing magnets. Ian S C

[Ian S CParticipant @iansc]

Found the thread in the stirlingengineforum, it's called "Large Lamina Flow Build", its about half way down the first page of the forum, trusting we don't get invaded again (one evening resently I went into the forum, and 4 1/2 pages had been filled with advertising rubbish, and previously the whole site was shut down, so don't complain about some minor problems ). Ian S C

[Engine BuilderParticipant @enginebuilder]

Have a look at the videos on Youtube by barumman. I don't think any plans are avilable but they is a huge range of engines he has built including free piston an ringbom types. Well worth a look.

[Ian S CParticipant @iansc]

Barumman has a series of youtube vidios on the TMG (thermo mechanical generator), I'm currently collecting stainless steel containers, in the hope I get the right pair to build a TMG. I wish I had a TIG welder of my own! Ian S C

[Jeff DaymanParticipant @jeffdayman43397]

Re TIG welders –

There really is no substitute for cubic dollars when buying a TIG set. If you can get one with the pulse timing function they are far more useful than the basic ones, especially on thin stock.

Miller Synchrowave series ($5000 up) are suberb, a friend has one. It will weld literally anything from .002" stainless up to 1/2" A36 plate to a high standard. I had a Miller Dimension 165 (about $1700) for a while last summer and found it lacking in capability. Forunately I was able to send it back under warranty. Luckily I had the foresight to specify that several particular welding ops were able to be done with this machine on the purchase order. The salesman assured me it would do those jobs, but on receiving it and testing it, the machine did not meet the requirements and I demonstrated this to the dealer. Their own welding expert also could not do the specified jobs to a decent standard on that machine. There just wasn't the heat and arc timing control that is present in the more expensive professional series welders.

JD

[Ian S CParticipant @iansc]

Hi JD, don't I know it, its the $$$s that stop me, fortunately I have a tame TIGGER, just down the road, he does'nt really like anything less than about .004", most the stuff I get him to weld are a bit thicker. I have thought of trying to do overlapping spot welds for welding ends onto the hot end of displacers, think I might be able to home brew a welder to do that. Ian S C

[Jeff DaymanParticipant @jeffdayman43397]

Years ago in industry I was involved with a type of home heat thermostat that used a gas filled "double diaphragm" bellows. It was made of two thin stainless disks about 2.5" diameter with several pressed concentric ribs. Both disks were "dished" to a convex shape. The perimeter was welded with a spot welder but the electrodes were made as two drum shaped pieces. The weld was ring shaped, and was made all around the disks' perimeter simultaneously. The weld was done in a chamber pressurized with the gas to be trapped inside the bellows. As I recall, the welder used 800A of current at 30VDC to do the weld.

Incidentally these thermostats were very expensive to make and required several tricky and sensitive operations to build. They took many more build steps to make than any other thermostats we made. The PhD MEng types said they would have a higher sensitivity than our more usual spiral rolled bimetal strip type thermostats, but this proved false in real life testing. They used several levers and joints to translate the bellows movement into a switching signal and I think mechanical losses and friction quickly overcame any increased sensitivity provided by the bellows. Dust as found in normal homes made this problem much worse when it got into the lever joints. The spiral rolled strip type with a mercury switch were the simplest and cheapest to make and worked very well, and were almost totally unaffected by house dust.

But I digress. Maybe a similar copper drum electrode as described above would work for welding the displacer cap on a tube? It would need a LOT of current though, where individual spot welds would need far less current. The lower electrode for the tube could be just a pad big enough for the tube to rest on.

JD

Edited By Jeff Dayman on 05/01/2013 15:52:04

[Ian S CParticipant @iansc]

An interesting thread has come up on the stirling engine forum, "Worlds First Downloadable Stirling Engine Kit", there's a website, Solarheatengines.com

   The rest of the site that includes this motor is worth looking at too.    Ian S C

Edited By Ian S C on 06/01/2013 09:25:05

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