Stirlingengineforum.com

Unless the shake flashlights count:

https://youtu.be/tiMz9JWMLUE


The Infinia solar Stirling, in a way, is basically just a big shake flashlight type linear generator, driven by a Stirling engine.

Well, I have to take that back

There was a time when NASA type free piston Stirling engines used one cylindrical magnet, very similar to what is found in a shake flashlight.

In my search for some commercial source for linear generators I came across some very interesting information about what I think is most likely at the hears of the Infinia Stirling engine, as well as many other linear generators, cryocoolers, heat pumps etc. utilizing the same technology.

I guess a good place to start is with this article: (or rather one of the comments after the article).

https://www.greencarcongress.com/2006/1 ... y_and.html

After the article, about the 12th comment down, someone says:

This is probably the patent holder on the linear alternator . . .

(The following links are no longer functional - Tom)

http://www.qdrive.com/index.php?page_id=33

http://www.qdrive.com/index.php?page_id=22

(Wayback archive pages available: https://web.archive.org/web/20070831061 ... .php?id=61 - Tom )

STARs™ are Qdrive’s patented linear reciprocating motors/alternators. High-Efficiency Affordable STAR™ Reciprocating Motor and Commercial STAR-Powered Acoustic Cryocooler

The STAR linear alternator is not a simple cylindrical magnet moving inside a coil, like a shake flashlight.

Rather, due to making a switch from gas bearings, which require a cylindrical rotating magnet, to planar bearings, which do not allow rotation, there was no longer any necessity to use a round, or rather, single cylinder shaped magnet that could rotate in a cylinder.

Instead, a whole array of magnets arranged in a "STAR" pattern could be used, with a corresponding multiplication of coils:
Still, frictionless, with no wear.

There is a fairly lengthy paper describing this new development that can be downloaded here:

https://www.researchgate.net/publicatio ... e-invented


Bottom line is that this new flexure bearings STAR shape linear alternator packed much more power potential than the earlier gas bearing type engines.

These kind of linear alternators are still being manufactured, apparently, mostly for military applications. (?) The patent/technology rights have been transfered a number of times and apparently split between military applications to one company and other applications, such as cryocoolers, to another company.

Apparently Ben and Jerry's ice cream freezers utilize this technology.

Basically the non-rotating flexure bearings allow multiple linear alternators to run shotgun, so to speak, on the same shaft and is not limited to cylindrical shaped magnets, as illustrated above.

Nice!

An interesting consequence is, it is not necessary to use very expensive high power magnets to get a high power output.

There is a thread on the forum from way back, with some information on these, many of the links however are dead, but at least some can be found on the internet archive.

viewtopic.php?f=1&t=1585

thank you so much again for your kindness.
I will test your engine when I receive it and I will try to rescale the dimensions and see if I can build something bigger.
I think it will help me to understand it better and also to find out how precise I should be with the dimensions.
I try the lathe and milling machines from my friend's workshop first.
or I can use 5 axis CNC to build the parts, there are some business places to provide 5 axis CNC machine services.

As far as this is a "collaboration project", maybe it could be a Kickstarter thing. The goal of a 500 to 1000 watt Stirling is, perhaps not too unreasonable.

I was going to say GoFundMe, but I've never had any luck on that platform. There are other newish platforms that might be appropriate in an emergency aid type situation, given the power outages in your region.

A review of over 45 crowdfunding platforms here:

https://blog.fundly.com/crowdfunding-websites/

At first glance I really like this:
https://warpfivefans.com/product/stirli ... generator/

A nice looking, apparently rugged, well made, portable emergency generator driven by a Stirling engine. What everybody seems to be looking for.

But, I was not able to find any specs on power output. Then further down on the page it reads:

The Stirling Engine Generator works exclusivly with the supplied Sony radio receiver for FM and AM reception.

Well,.. ok, that's great, but...

Really? For $2,000 + I can operate an AM FM radio, "exclusively". No shortwave emergency band even, and runs on liquid fuel only, apparently ?

I want to buy one, just on principle, just because the manufacture of such things, I think, maybe, should be encouraged, but I'm afraid I'd be better off in an emergency with a $20 hand crank radio, or a $50 solar powered shortwave radio.

Anyway, still a great looking little emergency generator. But not much use IMO if all it can do is run a supplied transistor radio "exclusively".

Not even a phone charger?

But, a small, portable "emergency" Stirling generator that could actually run something, and maybe use whatever is available fuel, like dry twigs, old rolled up newspapers, good old sunshine. That is something I'd sure like to see, and would like to have for an emergency, or for hiking, camping, fishing, cabin power, etc. etc.

Edit: further down it does say "any fuel", but only mentions liquids specifically:

"It’s noteworthy that the MSEEG will work with any fuel – you can use Methylated Spirits, bio ethanol, denatured alcohol or any other available fuel."

danaumer sent me a couple of videos that I've posted to my YouTube channel (with his ok)

https://m.youtube.com/playlist?list=PLp ... NGB9jK1Ko1

danaumer requested my opinion regarding materials and possible improvements or changes for up sizing the model engine

So here goes, mind you, these are my unproven, untested opinions that I'm pretty sure some others here would disagree with, so take it for what it's worth.

First, as I've already shown, in experiments, the metal (solid aluminium) displacer is an abysmal choice for material. IMO the displacer should be non-conducting so heat is not conducted through the displacer to the unheated end. All the heat should be taken in only by the working fluid as far as possible.

Also, that goes as well for every other part of the engine, except of course for the heater head which must be conductive in order to transfer heat into the engine in intermittent bursts.

So, something like this might be a good idea:
Make the hot end metal, the rest something non-conducting. danaumer had some ideas about that.

Of course the inside of the heater head, ideally, should have as much surface area as possible.
I also thought of something I think would improve air flow.

When the displacer is extended into the hot space, if possible, it should be form fitted so as to drive out all the air, but when drawn back so that the air rushes to the hot end, air flow should be as free as possible in order to allow the expanding gas to reach to piston quickly and easily without resistance.

So if the displacer we're corrugated in some way on it's outer surface, the non-conductive unheated end of the displacer chamber walls could be equipped with channels on the inner surface that would communicate with the hot space allowing the heated expanding gas to easily escape so as to deliver pressure to the piston. Something along the lines shown here:
This could be designed in such a way as to act like a valve, keeping the heat mostly away from the unheated side but opening up to allow the gas to freely expand through the channels during the power stroke.

Hey Tom, your mention up-thread of kickstarter reminded me of the Tim Sefton Stirling engine. https://seftonmotors.com/ It looks like they’re producing engines now and backed up on orders, but latest news on their site is about a year ago.
Bumpkin

I don't remember where exactly, but I saw an illustration of a large antique engine of this general design that had a flat spot on the bottom of the large heavy displacer where a roller bearing was inserted to carry the weight of the displacer, which I thought was a pretty good idea.


If I find the original illustration I'll reproduce it here and/or post a link.

Area indicated by the blue arrow.

http://hotairengines.org/closed-cycle-e ... hmann-1867


The hot air engine website is a good place to start as far as seeing how some of these old, very large heat engines were built.