Group project - is there interest?

[RonT]

As I've only been on the list for a short time, this may have been brought up before. I'm here because I'm interested in a small power producing engine, more than a toy, less than an industrial power plant.
Is there enough interest and talent in the group to come up with a group design and prototype? The proposal is to work on collaborative project between the various talents and skills in the forum and come up with something that approaches a practical working model.
The great majority of kits I've seen online are toys or small models to demonstrate Stirling engine principles, there seems to be so much room for improvement.
On another point, I'm wondering how much talent is still participating in the forum and reading the posts?
Ron - in Yellowknife (current outdoor temp. is -27C, its warmed up quite a bit)

[Chriske]

Ron,

I'd love to see a project like this get started. I'm interested to in make a more powerfull stirlingengine.
In fact I'm in the middle of a learning process right now. Built myself a few small engines powerfull enough to drive a small train on gauge 1.
Me, only building stirlingengines for about two years now, I'm eagre to learn...but...
Among stirlingenginebuilders there is a tendency to protect there project/drawings.
In my search to find plans/drawings to make that more powerfull engines I got always stuck with replies like :
- No replies at all
- I've build this one without plans..
- You first have to send me ... $
- Ones you build a few smaller engines you have to find out for yourself because there are few plans of béta and alpha engines to be found on the net
- ...
To be clear on the matter I'm talking here about the more powerfull Alpha and Béta type engines. The smaller types, gamma and LTD there are tons of drawings and plans to be found on the internet, I know.

I teach making telescopes for almost 35 years now. I'ts a small community and we all share our knowledge worldwide. I expected this would be just the same in this stirlingenginecommunity. I found out this is not the case and still do not understand this rather strange attitude at all.
I'm almost 60 years of age and, you guessed it, shared everyting I've knew all my life. Together is my motto.

Ron, I hope you'll find a few other people like yourself working together on a project like this one.
And if you find the crew to do this, I hope you'll share this project among the Stirlingenginecommunity.

Thanks

Chris

[RonT]

It didn't take long after joining this forum to see that it wasn't what I'd expected. I was hoping to find a mix of learners like myself, and some experienced designers and builders sharing their projects, experiences, and mentoring skills. The help from the group has been useful, but I lack direction and skill to make wise choices as to how to start building.
In other areas of personal interest that include astronomy, amateur radio, Linux, and recently, metal machining, it hasn't been hard to find "enthusiasts" eager to help. A couple of days ago I posted a question on a mini-lathe users group asking how to cut circlip, or E-clip, grooves on a shaft using a lathe and I was overwhelmed with useful information. That doesn't seem to be the case with Stirling engines in general as I've observed so far. And hours of searching the web for information revealed that maybe 25% of links are dead, and that there are zero active links to any practical designs.
Has interest in home built Stirling engines dropped off over the last few years?
Ron (in Yellowknife)

[Bumpkin]

RonT, a shaft with a groove in it existed before you asked "How do you do that?" I've never seen a Stirling engine that does what I want so there is no "proven design" to follow. The question has to be a more theoretical, "What might work?" But we tend to see what we're looking for and random inspiration sometimes leads to focused vision. That's happened here for me numerous times. Give us a chance. Bumpkin

[RonT]

No problem giving the group a chance. My post was about the lack of information and designs of Stirling engines in the low power experimental (versus models, toys, and commercial high end) range in general, anywhere on internet. I'm looking for inspiration, and examples of other peoples work that they're able share some insight and detail on. For an idea thats almost 200 years old I thought I'd find more practical examples at the hobbyist level. Perhaps I should subscribe to some of the magazines.

[bobshau]

Hi, I am new here. This is my first post.

I haven't searched the archives yet so I don't know what topics have been discussed in the past. Is there anyone working on the following?

My goal is to upgrade my analytical model of a free piston stirling engine then build a test unit capable of about .5 horsepower. Plan to use 10" diameter silicone rubber diaphrams for the displacer and power piston. 4ooF source and 180F sink. The power piston will have about +/- 1.5 inches of linear motion and drive a linear alternator.
Has anyone done anything like this?
Bobshau

[Ian S C]

bobshau, Yes I'v built a small free piston engine, it's in bits at the moment for a rebuild, it's a GAMMA design, this makes working on the individual cylinders much easier. My one has a power cylinder with 1 1/4" bore, and uses the magnets from a microwave ovenfor the linear alternator, and below this is a 4"dia magnet from a speaker, this is arranged to have a like pole opposing the magnet on the alternator, there by acting as a spring. Hope to get it running again early in the new year. Ian S C

[RonT]

If you do this project Bob, I hope that you'll be able to share some of the details on the forum. Did you have in mind water or air cooling? 180 degree F water is somewhat warmer than the water in a home hot water heater, or it could be used to heat water for home (hot water convective) heating.
Ron

[Tom Booth]

I think the problem, as far as building a medium power Stirling is that it is much more costly in terms of R&D. A hobbyist can build a small model relatively inexpensively but to tool up to build a real engine that produces usable power would take some capital. Since a Stirling engine is probably not patentable there is little incentive for a company with the means of producing it to invest the money that would be necessary to develop it. At least that is my general impression.

I'd love to be involved in such a project, but about all I could contribute is ideas. If I had the resources to build a large engine I would. I do know of a guy in California who was working on such a project but did not have a good design so was using trial and error. It was costing about $300 for each "trial" just to get cylinders cast. I think he finally gave up.

Perhaps if there was more demand for such an engine. An IC engine isn't exactly new either. That is, no one company has exclusive rights to market such an engine but the demand is high enough that that really doesn't matter.

[bobshau]

Hi all,

Ron T. I will be glad to share details and progress on this forum. So far, my preliminary analysis shows that the 10" diameter displacer should have a mass of about 7 pounds and a spring constant of 300 pound inches. The 10" diameter power piston should have a mass of 30 pounds and a spring constant of 30 pound inches. The air passage through the cooler, regenerative heat exchanger, and heater should have a permeability of about 1.4x10^-5 in^2. Air pressure=115 psia.

You asked about the cold air temperature of 180F: The heat sink is my house hot water heating system which normally runs around 140F. This gives me a 40F temperature difference between the heat sink and displacer cold air.

Tom Booth. You are correct that cost is a major driver for a do-it-yourself project. I'm hoping that costs will be lower using diaphrams instead of pistons. We will see. Also, I'm planning to use schedule 40 pipe and flat plate for cylinders and and end caps, respectively. Cutting will be done with a right angle grinder and welding will be done with ac stick.

Ian S.C: Thanks for the tip of using an opposing magnet as a spring.

Blessings,
Bob

[RonT]

I'm also interested in the project and hope to hear updates. Providing heating and some electrical power for an off grid cabin / cottage with little waste heat as the cooling system heats water for other uses, thats sounds like a good idea. Thanks for sharing!

[Geoff V]

Ron

I do not believe for one moment that SE enthusiasts are not willing to share their designs, the problem is, nobody has produced a design which can be made with rudementary equipment, limited skills and is capable of producing 'usefull power', the reason, pressurisation.

Because the surface to volume ratio reduces as one increases the size of a SE, the power (unpressurised) per cc of swept volume decreases and limits the output to a few hundred watts. The only example of an unpressurised engine that I have seen so far, with a claimed output over 1Kw, has a piston 4ft in diameter, quite impractical for all but a few applications.

On the other hand, the 5cc, yes 5cc engine built by Eddie Chapman in the 90's produces 95watts at 2000rpm on helium at 80bar, eight times the maximum working pressure of most air compressors!

The long and short of it is, if you want power, pressurise it, no if's or but's.

So there is the problem, designing a machine to operate safely at very elevated pressures on expensive gases using tools found in the garden shed.

GeoffV

[Ian S C]

I quie agree with you Geoff, I'm quite happy with just a bit over 5W out put from a small unpressurised motor. If more power is required from this type of motor, proberbly the best way is to build another one or however many are required to give the out put wanted. Ian S C

[RonT]

Hi Geoff, my appologies, I may have worded things poorly and shouldn't have come across as suggesting that group members were unwilling to share ideas and projects. If I read things correctly, there is little available in that power range that is practical to build; hence little to share. Steam then would seem to be the practical alternative for an external combustion power source in the power range I'm looking for. Other than dead internet links, an odd youtube video of the Philips generator, and an unsupported reference to Stirling powered battery chargers being air dropped to the resistance in France during WWII, I didn't find much online for Stirling power.

[Chriske]

Hi guys,

I did not say : nobody's willing to share at all.
I wrote : only in the high power range engines amateurs ar not willing to share. In the smaller engines ranges there are tons of plans to be found, please reread my first post in this topic..!
Someone wrote in another post : there are'nt that many engines available in the high power range.
My question is now : what is available amongst amateurs and is willing to share his drawings.
The only one I found so far is Mr. Ross from whom I purshased plans to build his 'B-20' kit.
Maybe he got some more drawings/plans, I'll ask him. It's in that range btw and even more powerfull i'd want to start building engines. Purpose is to drive a small train with it (gauge 5"), and maybe, just maybe a bicycle... (yes, I just started reading is book... )

To be clear on the matter, when I asked through forums about these engines I asked in :
3 english forums
1 dutch forum
1 german forum
1 french forum
So maybe now you understand my point of view about not sharing drawings. Beeing new in this hobby it is(was?) very hard to believe nobody has plans to build somewhat larger engines.

I hope you'll understand my point of view..

Thanks,

Chris