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RepairmanSki
06-18-2006, 01:00 AM
I get that Stirlings aren't IC engines but for lack of a more appropriate place...anyone building them?

jans123
06-18-2006, 01:30 AM
You are right, Stirlings are not IC (Internal Combustion) since the heatsource is outside the engine it selves. Neither are they to put into the category of steam engines since they don't invoke a phase change vapor <> liquid. If to be categorized I would put them among “hot air engines”, sealed devices that work trough the Carnough cycle without having the media (air, helium, whatever) to go trough a phase shift (liquid <> gas).
But I guess that cnczone isn’t the right forum for this. Try Model Engineer.
Best regards from Sweden, the country of the midnight sun
/jan

Kiwi
06-18-2006, 05:57 AM
Are the CNCZONE rules really that narrow?
I would think that the Stirling Engine would be of interest on this forum.

epineh
06-18-2006, 07:36 AM
Interesting read, never heard of the Stirling Engine until now, still a little confused on how it works, little too late at night for me right now...

As for someone building one, I would like to give it a go, I just have to finish my 3 axis router first, oh yeah and get through the house building process, then probably a boat shed, but after that I'll get straight on it.

Interesting how they make such good cooling units under outside power.

Thanks for something to add to the "to do" list.

Russell.

rippersoft
06-18-2006, 09:02 AM
If you use CAD to design and CNC machines to cut the parts, why wouldn't this site be an appropriate place to discuss Stirling engine builds? Just add a new forum for threads..... Anyone interested in discussing how to make one?

RipperSoftware

strat
06-18-2006, 02:08 PM
http://www.bekkoame.ne.jp/~khirata/english/make.htm
heres a site for building a simple one out of a can ..... i haven;t built one yet myself the guy that got me started in the machining built one you could set it on your hand and it would run from the heat of your hand

pminmo
06-18-2006, 02:18 PM
A Sterling Engine is a temperature differential engine that rely's on a closed system of gas. It's motive force comes from expansion and contraction of the gas. Even though the Sterling cycle has been around for a LONG time, it's not been much more than a novelity even though there have been some very powerfull Sterlings built. Part of my leasure reading over the last year has been on producing electricity and if it was feasable for me to build something to generate power in a suburban setting. It' isn't real feasable for a DIY'er to build photovoltiac cells, I live in a region that wind isn't real practicle, so in looking for other possibilities, a Sterling engine(s) might be the most practicle for me. Utilizing the Sun's IR heating, and the earths underground 53 degree constant as temperature differential sources. Still reading and thinking though. There is a lot of interest across the world on Sterlings as an energy source. And when you consider that depending on where you live relative to the equator, on sunny days, there is nearly a kilowatt of IR energy per square meter from the sun, seems like we should be harnessing more of it to produce motive energy.

pminmo
06-18-2006, 02:22 PM
http://www.emachineshop.com/engine/ has a simple rotary sterling

Mcgyver
06-18-2006, 04:33 PM
Here's a link that shows how they work - simply two pistons, 90 degrees apart. the displacement piston alternately moves the air from a hot space to a cold one, power comes from the expansion and contraction of the air.

http://www.keveney.com/Stirling.html

They are low power/low efficiency and can therefor be a pain to get a model running properly. you have to hit that optimal balance of the piston sealing well enough to take advantage of the pressure changes, but have minimal drag/friction because its so low power. While low power, their advantage was that they did not the danger and complexity of steam (because there's no boiler) here's some pics of one i made, a 1/4 scale model. this particular one is water pump, using the water it pumps as the cooling force via a water jacket around the upper half of this cylinder. it runs on camp stove fuel and pumps water beautifully, but only after a lot of fine fitting and bore lapping (with homemade adjustable copper laps)

jans123
06-18-2006, 05:02 PM
Are the CNCZONE rules really that narrow?
I would think that the Stirling Engine would be of interest on this forum.
Sorry if I stepped on someone’s toes - not my intention. Promise :-)
What I was thinking of was that I have seen forums and pages dedicated to Stirlings. One of my friends built one after getting hints from such a page a few years ago. Rather simple they are and some types can be built with material easily machined by simple cnc’s, materials like aluminums and plastics
:cheers:
/jan

Kiwi
06-18-2006, 05:41 PM
jan
They don't have to be simple.
A NZ company is making them for generating electicity.
http://www.whispergen.com/
Also one of the Scandinavian countries are using them to drive submarines. (I believe they are very hard to detect with sound equipment.)

jans123
06-19-2006, 01:34 AM
jan
They don't have to be simple.
A NZ company is making them for generating electicity.
http://www.whispergen.com/
Also one of the Scandinavian countries are using them to drive submarines. (I believe they are very hard to detect with sound equipment.)
They sure don't need to be simple. Our Swedish navy use them in their submarines and those engines are very complex, but the original sterling engine is very simple as is e.g. the more complex "kalorik" engine by John Ericsson" (the guy with the propeller an who also build the "Monitor". I also once found an hot air engine in an American history book. The engine was put to the market i guess around year 1850 with the advertised by Cammeyer and Sayer as "An engine simpler than a stove" or something like that. A simple device it was and it was a "Stirling clone". You can make them complex if you want. I like nice engineering, but I also admire simplicity. For a beginer it would be more simple to start with a "simple" Stiling than an IC engine.
/jan

nick.gilling
06-19-2006, 07:03 AM
Hello,

I am currently designing a simple stirling engine and will post up some pics soon. Not sure where I'll put them but probably in here! If they get removed, so-be-it but I'm sure it'll be of some interest to somebody.

In the past I've only made model steam engines but want to try a stirling engine before I attempt an IC engine.

Nick

balsaman
06-19-2006, 07:09 AM
A great idea. I am working on adding a Stirling Engines section to the forums...Won't be long.

Eric

epineh
06-19-2006, 08:48 AM
Send those pics Nick, I for one am quite interested in seeing a working engine, but I must resist the temptation to have a go myself, I found I get more achieved if I limit myself to 100 unfinished projects at a time... once I get my router made then that will be a different story, can't have only 99 things going at once hehe

I get the theory of the engine now but still find it hard to believe it actually works

Russell.

nick.gilling
06-19-2006, 09:40 AM
I know what you mean, I still have a problem seeing how the air is cooled and heated so fast! What's even more baffling is the low temperature differential ones, they only need a delta T of a few degrees to work.

I have to confess to actually buying one of these from e-bay, just to get an idea of dimensions used etc. It works from the heat absorbed from your hand.

The first one I am going to attempt though, will hopefully run off a tea light. I presume it will be easier to get a hot air engine to run if it's got a bigger temperature differential.

No doubt we will soon find out!

Good idea Eric to add a Stirling section, there are whole societies for Stirling engines and I'm sure people will find it interesting.

Nick

RepairmanSki
06-20-2006, 02:15 AM
I'm glad there is interest. I for one am certainly interested, obviously since i posted =)

I have found these forums as a whole to be full of useful information and even more packed with interesting, helpful members. I am also quite glad to hear about a new subforum being created for the Stirling, thanks Eric!

pminmo
06-20-2006, 08:47 PM
If you start running though Sterlings and heat differential engines, there are some amazing configurations. The one thing that has me stumped, I kind of thought there would be some references to utilizing R134 or R22, ammonia, etc for gas, and thus helping the heat/cool cycle.

"Liquid ammonia boils at any temperature greater than -28°F and will expand to 850 times its liquid volume. One gallon of liquid will expand to 850 gallons or 113 cubic feet of gas."

Look up "icy ball".......

Geof
06-20-2006, 09:05 PM
If you start running though Sterlings and heat differential engines, there are some amazing configurations. The one thing that has me stumped, I kind of thought there would be some references to utilizing R134 or R22, ammonia, etc for gas, and thus helping the heat/cool cycle.

"Liquid ammonia boils at any temperature greater than -28°F and will expand to 850 times its liquid volume. One gallon of liquid will expand to 850 gallons or 113 cubic feet of gas."

Look up "icy ball".......

Did you not find anything about using helium. I seem to remember reading something a long time ago about the idea of using helium because it has a high heat conductivity so the gas can cool and warm quicker.

jans123
06-22-2006, 04:08 PM
Did you not find anything about using helium. I seem to remember reading something a long time ago about the idea of using helium because it has a high heat conductivity so the gas can cool and warm quicker.
You are right about helium and it is used in the most efficient Stirlings. Helium is also a very small gas molecule that has a low mass and moves very fast. The other heavier gases mentioned in the beginning of this line of the thread (like the coolant media in refrigerators) are less suitable in a Stirling engine. They have a high weight and change easily phase and might be better of(???) in a sealed steam engine. By the way, I experimented with propane in a low temperature sealed steam engine… let’s say that that experiment will not go any further… and please all of you, avoid such adventures.
/jan

pminmo
06-22-2006, 04:55 PM
Can't say I looked into helium, never thought about gas weight.

Jan
I've wondered about low temp sealed steam engines, can you give me some insite?

One of Many
06-22-2006, 10:32 PM
You know something has potential when military applications people take notice and further the progress that will eventually trickle down. For the length of time these have been a limited viable resource, not much change has taken place to eek out every last ounce of efficiency they can muster.

One tidbit article that mentions these advances. (http://www.memagazine.org/backissues/may99/features/stirling/stirling.html)

DC

40fordcoupe
07-04-2006, 08:40 AM
Our Swedish navy use them in their submarines and those engines are very complex, /jan

Here are a couple of links that tell more about these amazing submarines.
http://www.kockums.se/Submarines/aipconversion.html
http://www.kockums.se/ :cheers:

jderou
07-05-2006, 07:21 AM
They are low power/low efficiency and can therefor be a pain to get a model running properly.

Had to point this out because I don't want newcomers getting the wrong idea. They are actually much more efficient than any ic engine.

Mcgyver
07-05-2006, 09:42 AM
jd, you are right, I stand corrected. my paradigm was the historical engines where, lacking helium, heat exchangers etc, the efficiency was a fraction of steam

Geof
07-05-2006, 10:17 AM
Had to point this out because I don't want newcomers getting the wrong idea. They are actually much more efficient than any ic engine.

I think it is the theoretical Carnot efficiency is higher; whether you can actually attain it is another matter entirely.

pminmo
07-05-2006, 10:17 AM
I think Stirlings can be best described as a unique engine. Applications where rpm control is necessary, Stirlings wouldn't fit as well as IC engines, and probably where the interest fell off in the late 1800's. The last 30 or 40 years should have been different, and today especially. Mechanical storage and direct utlization of the sun's energy via Stirlings is so practicle, it's hard to understand why they aren't out in the masses. My interest is DIY electric generation. I can't reasonably build PV arrays's, but I believe I could build Sterlings and PM Generators for much less than what PV's cost. But I'm not a engine designer, and I'm struggling to find a usefull set of plans that are practicle and of a usable size.

jderou
07-05-2006, 01:12 PM
Stirlings have been able to reach around 50% efficiency (I think the theoretical carnot cycle would be 100%). IC engines are low 30's at best. Its a shame they are not being utilized more, seems like it would be great for electric hybrid cars.

Geof
07-05-2006, 01:25 PM
Stirlings have been able to reach around 50% efficiency (I think the theoretical carnot cycle would be 100%). IC engines are low 30's at best. Its a shame they are not being utilized more, seems like it would be great for electric hybrid cars.

If I remember my Physics correctly Carnot efficiency can never be 100%; that implies your heat source has an infinitely high temperature and your sink is as zero absolute. The thing about Stirlings is that they are essentially a constant speed constant load device which for many applications is impractical also they are bulky for the power developed. The bulk probably makes them impractical for hybrid autos however for stationary cogeneration units they would probably beat gas turbine units for efficiency except for the inability to vary the output. What would be interesting to see is the efficiency that could be obtained using a gas turbine for the variable power output and have a Stirling running on the turbine waste heat as a base output. It would probably be necessary to have some system to keep enough heat going to the Stirling when the turbine was throttled way back so this would detract from the overall efficiency.

40fordcoupe
07-05-2006, 06:58 PM
But I'm not a engine designer, and I'm struggling to find a usefull set of plans that are practicle and of a usable size.

http://www.innerlodge.com/TechLine/Harry&ElaineDiers/index.htm
Here is a site describing a Stirling engine outboard a man in Australia has built, this might give you some inspiration. :cheers:

Rhodan
09-03-2006, 05:51 PM
Part of the Canadian Navy's machinest training program (TQ5) is to make a sterling engine. Its configured like a 3 foot tall windmill and we powered them with a plain old propane torch. I got mine up over 700 RPM turning a 2 foot fan made of 1/8th aluminium sheet. Of course, for the speed tests we all flatened our fans to give the least amount of load - I got about 400 RPM with the blades bent normally (around 20 degrees).

I least thats the speeds I remember - I built mine back in 1986 or 87 when I was at Fleet School.

nick.gilling
09-04-2006, 10:48 AM
Cool, you can get kits for the type of engine you describe but on a smaller scale.

Did you get to keep your engine or has it long gone?!

Rhodan
09-04-2006, 12:56 PM
Cool, you can get kits for the type of engine you describe but on a smaller scale.

Did you get to keep your engine or has it long gone?!

I ended up donating it to an Antique boat society. I did some volunteer work on a 1918 tugboat and they really like the engine while I was having nothing but troubles moving and finding storage for it. Too darned big lol.

debogus
09-04-2007, 01:46 AM
I just made a tin can gamma type and it actually works .
Far from efficient ,takes a small butane torch to run it.

But hey it was just a experiment to see if I could do it.
Next I'm going to tackle the low temp variety