Stirling engine go-kart?

Discussion on Stirling or "hot air" engines (all types)
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Stirling engine go-kart?

Post by Xaero_Vincent » Sat Jun 23, 2007 2:19 pm

I'm interested in building a go-kart powered by a Stirling engine as a project. The kart I will be using is pretty small with a 5HP gasonline engine. Trying to build a kart from scratch is a whole other project I'm not interested in doing.

I understand the disadvantages of slow start up time but that doesn't matter because it probably takes almost as long to start a carburated lownmower-type engine from cold and drive off without it conking out.

I'm curious which Stirling engine configuration produces the best power to size ratio and how I can improve upon it from there (compounding cylinders, high-temp gas flame, cold water cooling with fan & radiator, etc?). I want to avoid having to seal the cylinders with gases, such as hygrogen or helium that may leak and require a complicated pumping and storage systems, which would unlikely fit in a go-kart anyway.

Speed control and reversing will be interesting but maybe a swashplate and reverse clutch might do it? I will need to learn how those gizmos operate; the kart already has a mini CVT-like transmittion to handle small torque output at lowspeed.

I was initally planning on a building a steam engine but there are several flaws with the idea:

Boilers are potentially dangerous, especially in a go-kart configuration where the frame is constantly streesed by bumps, g-forces, and also the possibility of the kart tipping over. I would not want a boiler stressed to the point where it cracks and leaks super hot steam on my exposed limbs and face.

I'd end up having to pay thousands to buy a boiler permit, passing an exam, building the boiler, and certifying any boiler I make. I read that the exam can be $600 alone. The cost factor might be just as problematic as the safety one.

These factors combined just don't justify a steam go-kart that may be less efficent than the gasoline engine it has now. I was mainly interested in the "cho cho" sound and the insane startup torque.

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Post by Xaero_Vincent » Thu Jun 28, 2007 5:00 pm

Interesting that after a week nobody replied to this thread.

Is it impossible to use a stirling engine in any larger scale than a toy model or does it not make any sense over say an electric kart?

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Post by boydhouse » Thu Jun 28, 2007 5:35 pm

OK I'l give it a try! LOL

It is possible to use a Stirling engine to run a go Kart. They use a Stirling engine to run a submarine in Sweeden?

The problems are,
It won't be cheap.
Trottling it will be a problem
Getting it small enough will be a problem
Will it ever be as responsive as gasoline or electric???

I'm sure there are a bunch more. I would say try something a little more conventional unless you have a lot of time and money. If you have those, go for it.


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Post by Xaero_Vincent » Fri Jul 06, 2007 12:48 am

I assume by expensive you mean metal. I have a source to plenty of metal pieces and shapes and parts I might use (radiators and water pumps). I also have all sorts of equipement: welders, lathe, bench drills, powertools, so on.

I could do an electric kart but I would end up spending far more: easily hundreds for an efficent, smoth variable controller, or even more if I wanted to make the controller myself: oscilloscope, signal generator, DC/AC powersupply, components, etc; not to mention hundreds for several batteries and a motor to power it all.

People have made Stirling engines with tin cans, sticks, and balloons. I want to make a larger, more powerful version of the simple idea. I'm not too worried about responsiveness or size to a reasonable extent.

I think a basic compressed air 2-3 cylinder compounded Alpha with swashplate and very high temp differentials--hydgrocarbon/solid fuel furnace for hot side and circulated (radiator) water-cooled side should suffice. I imagine the engine will be larger (perhaps double or triple in size) but I will do what I can to make the most power out of a reasonably compact engine.

Unfortuantly for me, I wont have much time this summer to work out the concept due to summer classes. I'm guessing this project will take course of a couple years or more worth of spare time.

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Post by alpha stirling » Sat Jul 28, 2007 5:56 am

Umm... making a larger version out of the tin can concept is not enough. The only way to get the engine to produce enough power while having practical size (say 10kW) is to:

1) increase the working fluid pressure. powerfull commercial stirlings may have a operating pressure up to 200 bars (that's a little far fetch for a home built device). Increasing the pressure also increases the strain on the mechanical parts, so special material may be required

2) Building very efficient ( here "efficient"="complex") heat exchangers, simple hotcap won't do much good, as it simply can't transfer enough heat into the working medium. The engine would need both hot and cold heat exchangers, both consisting of dozens of thin pipes to keep the dead volume down and to provide a large surface area. this can easily add up complexity to the engine.

3) Building a regenerator. In it's simple form it can be a chunk of steel wool stuffed inside a tin can. The regenerator increases the engine's efficiency, but it must not bee too large not to make too much dead volume. A good regenerator is a must in any really powerfull stirling engine.

An alpha stirling would have best power to size as well as power to weight ratio. It is, however, more complicated because it has two sealed pistons instead of only one. For ease of construction a multi-cylinder gamma stirling might be an option. The most size effective engine would be double-acting four cylinder alpha with swashplate or similar power extraction...
They told me one cannot build a jet engine in garage conditions. I proved them wrong and I was only 16 :P

Don't let people's sayings discourage your creativity!

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Post by SScandizzo » Thu Aug 09, 2007 11:59 am

Hi Xaero_Vincent,

Take a look at this image: ... roduct.jpg. It's the cover of a book that describes the process of building a 5hp Stirling Engine in Bangladesh. It's a water-cooled 10 foot long behemoth. There are two significant disadvatages in using a Stirling in a small vehicle such as a go kart (or even a car). First, Stirlings are significantly larger than their IC counterparts for a given power output. Submarines are large enough to accomodate Stirlings due to the size of the vehicle and the significant advantage that there is a HUGE cooling medium available. Second, adjusting the output (throttling) a Stirling is both bad for its efficiency and very slow in responding. Once again, submarines have the advantage of using large batteries to store electricity generated by a Stirling, which can be applied on demand at the appropriate metered rate.

So, in general, hot air engines are big and function best at one speed. I'm with alpha on this one, though. Give it a shot and suprise us all!


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Post by Xaero_Vincent » Thu Aug 09, 2007 5:02 pm

Thanks a lot for the information!

10 kW would be like 13.5 horsepower and quite a lot of power for a go-kart. But what about an old tractor with no engine?

I might be able to get an old tractor with no engine for cheap; my grandfather may have connections. I imagine it would be safer to work with a pressurized engine when you're further away from the engine compartment thats also in-closed. My go-kart is a small one for kids with a little lawnmower-type engine behind the seat; there wont be no room for a 10 ft. Stirling engine. :P

If the working medium was air, how much pressure would you estimate an Alpha Stirling engine might require to match the power-to-size ratio of a typical gasoline engine? 200+ Bar (3,000 PSI)?

I think there are 200+ Bar hand pumps used for paint ball guns. It looks like I can pick one up for about $200. I imagine it being possible to adopt the pump to pressurize the cylinder compartments of a Stirling engine.

Another thought...

Besides a gas engine (would have to make or buy for no cheaper), would a steam engine be more practical for a heavy old tractor?

After all a Stirling engine becomes just as dangerous--if not more so--than a steam engine if the pressure inside the engine had to be hundreds of Bars and hundreds of degrees in temperature to produce enough power.

A steam engine would not need nearly as high of pressure; 150+ ton steam locomotives moved with only 200 PSI boilers in direct drive. A steam engine will not have any trouble adjusting power output or cutoff with a simple valve gear and throttle, nor would it need a transmission to run. A strong, monotube boiler with proper safety valves is very unlikely to explode and a steam leak from the coils (after years of use) would merely rise steam up the exhaust chimney, prompting for service.

If I were to design a well insulated, high-pressure (perhaps 40 Bar) quadruple expansion steam engine that exhausts into a condenser, I may be able to reach 30% efficiency or better.

Reciprocating steam engines are generally very poor in terms of efficiency but only because very few steam engines were designed for maximum efficiency. A steam engine with 5% thermal efficiency faired well against the new gasoline contender back in the beginning of 20th century.

A diesel engine is another option but not very unique when I could just get a tractor with one. If I'm going to spend time on this, I want it to be cool and different; something I can work on when I'm not working with computers.

Yes, I'm a computer guy and have no girlfriend, so its possible that way! :razz:

Anyway, just my two cents.

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Post by SScandizzo » Fri Aug 10, 2007 1:52 pm

I really don't know much about pressure values, so I will leave that information to someone else more qualified. What I can comment about is the steam versus Sterling issues. Two of the reasons that hot air engines "lost" the battle with steam engines was their size and the materials required to make them reliable. Stirlings, for the most part, are larger per unit output than steam engines even though they are far more efficient. Also, in the nineteenth century, material sciences were just not advanced enough to develop metals that could withstand the constant high heats that Stirling engines demanded. In essence, failure due to high pressures (in steam engines) was traded for failure due to high temperatures. Sure you could run the Stirling at a lower temp, but then you also get lower output.

Ultimately, IC engines trumped them both because of the smaller size per unit output. They are (relatively) terribly inefficient, but they are very compact and quite forgiving in terms of manufacturing tolerances.

So, if you have you heart set on a Stirling powered vehicle, I bet a tractor is a much more realistic target. You'll probably have to gear it down quite a bit (if we use the 5hp = a few hundred pounds paradigm), but if you're not in any great hurry to get places, it might be a really cool project!


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Post by Stevedigiboy » Wed Nov 28, 2007 7:39 pm

I think the west is pretty behind on this stuff, time to get building your go cart! just try.
441rider on youtube
I am already at 400psi on my component stirling and have calculated the upper limit with high grade bolts 1500 on a 38mm o.d. hot cap! 1 peice with a shere end i am going to test first before January. I make precision parts for corporations so this is my Christmas present to myself. LOL!

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Post by ToddW_00 » Thu Nov 29, 2007 3:38 pm

How about a stirling generator/electric go-kart? Could have a battery and solar panel for buffering and quicker starts.

Have never posted here that I can remember??? 4 posts??? but I admire everyones enthusiasm so I thought I'd say Hi :smile:

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Post by Mountain Stirling » Mon Dec 03, 2007 4:25 pm

You may want to do a little research. It is my understanding that General Motors (USA) actually committed quite a bit of research to this issue and did develop working models for automobiles. I think they backed off of it due to costs associated with mass production (at that time), I also understand that they are reinitiating this program. IF they can do it for a car (of course they have millions for R and D) then I am sure it could be replicated. It can be done. Just like putting a guy on the moon. It really is a matter of resources and research (or sweat and ingenuity). Just my two cents. Good luck. I hope to see the working model soon.

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Post by spinningmagnets » Sun Aug 03, 2008 10:32 am

Stirlings are safer than steam engines, and were invented because of steam boiler explosions in the early days. The problem is that that at a lower pressure, you must have a bigger engine to achieve the same power.

Dustin made a 2-1/2 HP Gamma Stirling, which is roughly equal to the power of a gasoline scooter engine. The problem is that Dustins Gamma is the size of a small sofa, and he is happy to get 150 PSI. Also you must carry a lot of fuel in both weight and volume. Diesel/kerosene would have the smallest bulk and weight per BTU.

I think Stirlings are wonderful, but you must be realistic about the power/size ratio.

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Post by MOLTOV » Wed Nov 19, 2008 5:06 pm


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