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How I built a hot air engine almost entirely from junk. I've wanted to build one of these ever since discovering stirling engines in about 2003. Spending the weekend making things in Steveastrouk's workshop gave me the opportunity to make the precision parts I'd need, and I knew most of the engine was going to be made of improvised materials, so decided to see if I could make the entire thing out of scrap or unwanted materials.
If you aren't familiar with how Stirling engines work, there are plenty of resources online- the Wikipedia page is a good place to start.
If you aren't familiar with how Stirling engines work, there are plenty of resources online- the Wikipedia page is a good place to start.
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The "core" of a gamma stirling engine of this design is a large cylinder that holds the displacer, connected to a smaller power cylinder providing the power strokes. I decided to follow Darryl Boyd's "walking beam" design, where the power cylinder sticks out of the side of the dis[placer cylinder, because it suited the materials I had and it looks cool :)
I found that an aluminium drinks can would fit neatly inside a steel soup can, so decided to use that for the displacer on the grounds of being cheap, light and easy to work with. The steel soup can provides a sturdy body for the engine and also meant I could ake the bottom removable to allow maintenance.
I found some decking to use as the base, some 1" x 1/2" pine to use as supports for the moving parts, and a piece of 3/4" aluminium strip to use as the beam. The engine is a messy combination of metric and imperial units- that's what happens when you use scrap materials!
I found that an aluminium drinks can would fit neatly inside a steel soup can, so decided to use that for the displacer on the grounds of being cheap, light and easy to work with. The steel soup can provides a sturdy body for the engine and also meant I could ake the bottom removable to allow maintenance.
I found some decking to use as the base, some 1" x 1/2" pine to use as supports for the moving parts, and a piece of 3/4" aluminium strip to use as the beam. The engine is a messy combination of metric and imperial units- that's what happens when you use scrap materials!
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thanks for ur response! This is the only thing thats bothering me, otherwise i'm really looking forward to making this!!!
Unless you can make the cylinder and piston perfectly smooth you are aiming for the best compromise between it being too loose (and leaking air) and too tight (and friction taking power away from the engine). I believe loose is generally better for a hand-made first engine. How you do this is entirely up to you, there are a number of possible approaches- check out the many other Instructables on stirling engines.
The displacer pushes the air in the engine to the hot end, where it heats up and expands. This expansion pushes the power piston outwards, because it's the only part of the engine that can move to let the air inside expand. The power piston moving outwards turns the rotating parts around, which moves the displacer and so moves the air inside the engine to the cold end. The air cools down and contracts, and so sucks the power piston back inwards.
The power piston itself needs to be able to move in the cylinder freely, but also to move in the cylinder with a change of air pressure. The simple way to do this is to just glue a cut-out circle of balloon rubber over a hole in the engine, so it will move in and out with changing air pressure. I did it by making a smooth brass tube and a piston to fit very closely in that tube. That way is more fun and can make a more powerful/efficient engine but needs workshop tools whereas the balloon method might only need a knife and some pliers. Check out reukpower's instructables for more on how you can build stirling engines without precision engineering tools.
I picked up some at a camping store
Ideally the displacer should be light, so if you can find one an aluminium drinks can might be better than a thicker steel soup can, but I don't see any reason the soup can wouldn't work.
I can't seem to find any drink cans around, so I'm going to use these cans instead, now that I know that it should work. I shall inform you on how well it runs.
I think it was overheating at the time- with better cooling and a more suitable generator I figure I could get perhaps one or two hundred milliwatts out of it.
Efficiency is pretty poor, I think an average candle puts out something like a hundred watts of heat so we are talking about something like 0.1%. Not great!
That was only running on one candle, though. Heating it with a small cup of meths, it will run at several revolutions per second- it might go faster but I'm afraid to let it run that fast in case something gets damaged in the process. I'll take a video of it running fast and post it in the comments when I have time.
I do oil the crank bearings and the sliding displacer rod- it's possible I hadn't done that when I recorded the video, but it doesn't squeak as much now.
just go to YouTube and search for KS90 and you will see some nice examples!
They also start running when the upper surface of the displacer cylinder is being heated by just letting the sun shine on it!
But they are a bit difficult to align and when building one, you have to avoid everthing which could cause some unneeded friction.
Europe has a lot of CHPs (Combined Heat and Power plants) installed, using biomass to generate heat and electrical energy in housing areas, based on stirling engines. Of course these engines by no way can be compared to the ones you will find at instructables.com, but these are real hitech products, running 30,000 hours and more needing only a small amount of maintenance.
There are small CHPs (15 kW heat and 3 kW electrical energy), just take a look at http://ec.europa.eu/environment/life/project/Projects/index.cfm?fuseaction=home.showFile&rep=laymanReport&fil=LIFE99_ENV_D_000452_LAYMAN.pdf
Hungary based FlexEnergy is builing a generator (38 kW output) running on landfill gas (methane) only.
Now you can continue to state "...Stirling engines are at best a curiosity though..."
A 40kW diesel generator isn't newsworthy, its a pallet item.
http://www.google.com/images?um=1&hl=en&safe=off&tbs=isch:1&&sa=X&ei=s7FrTY7PPIO88gaU4LyQCw&ved=0CC8QBSgA&q=40+kW+diesel+generator
About 153,000 results ...
I think we need to distinguish between fantasy and reality but that's just me.
Yes, it most certainly does. It's called proof, and it's not an opinion. You have been proven wrong.
[pfred2: There is likely more steam piston engines still in operation than Stirling engines today.]
Of course there is. Steam is still one of the most efficient and most powerful systems there is. If there wasn't a problem with steam production and storage we'd still be using them in our cars. You're not making a case for yourself. How exactly do you think nuclear power plants work? That's right...steam...
[pfred2: I think we need to distinguish between fantasy and reality but that's just me.]
I guess the sources that Hebinho mentioned are fantasy and not reality? I don't think "we" need to distinquish between fantasy and reality, I think just "you" do.
You may now continue to post opinion...
No I'm not making a case with you! Because you are an unreasonable individual.
I'm supposed to accept a few sources but it is OK for you to ignore the overwhelming number I present? At this point I really don't care what you think.
Fusion isn't even done at a stable level yet. Once fusion reactors are perfected it will be extremely practical and will take the place of current nuclear reactors. You're still wrong in your example.
[I'm supposed to accept a few sources but it is OK for you to ignore the overwhelming number I present?]
Overwhelming number of what? You have produced zero evidence that "stirling engines are at best a curiosity".
Here are 153,000 examples
http://www.google.com/images?um=1&hl=en&safe=off&tbs=isch:1&&sa=X&ei=s7FrTY7PPIO88gaU4LyQCw&ved=0CC8QBSgA&q=40+kW+diesel+generator
That took all of a tenth of a second for our favorite search engine to cough up but you conveniently choose to ignore. Go argue something you've a chance with like extra terrestrials or the Easter Bunny. That ought to be a good one, least you'll have baskets pretty soon as proof!
& Don't argue the stupid position of proposing ethanol, that would require energy to make energy, wasting time & power.
No, it's not. You're basically saying so in the latter part of your statement. Will you ever stop being wrong(Apparently not)? It's not supposed to take a continual energy feed to keep the reaction going. It's only supposed to take energy to start the reaction, and it should keep going for as long as it's stable. You understand what stable means right? ITER is expected to produce a minimum stable reaction of 480 seconds but could be as much as 1,000 seconds, producing 5(on the low end) to 10(on the high end) times as much energy as was needed to start the reaction.
[pfred2: That took all of a tenth of a second for our favorite search engine to cough up but you conveniently choose to ignore.]
You posted the same exact useless link again? That's proving that stirling engines are a curiosity how?(I'll give you a hint: it's not) With the national average for diesel being $3.716 per gallon and some places as high as $3.964, tell me again which one you think is actually more practical? Do you have to keep paying the sun to receive and convert it's energy? A link to diesel generators proves nothing about stirling engines. You'd have to be delusional to think the diesel generator is more practical.
You just choose not to see the relationship. They pointed out one example of a 37kW generator I pointed out 153,000 of similar in just one other technology. Now if diesel wasn't more practical then how come there are so many more examples?
By the same example 100 years ago you would be saying coal powered steam engines were the only solution earth ever needs, claiming petrol engines were a fad.
100 years before that, you would be mocking anyone even thinking anything but a horse could move a cart.
You would probably also be saying that since 90% of carts were drawn by horses, that those carrying heavier loads which required bullocks to pull them should be regarded as imaginary?