2-cylinder Gamma - project

[Ian S C]

Remember that the diaphragm must be loose enough so its not trying to stretch at the end of the stroke. Good to see a start to your work. Ian S C

[Triangle.Stirling]

Thank you for your interest Ian SC, you seem to be the only one who is reading this

The 3D model is almost finished now, and we're a bit further with the actual build.

first a few pics of the 3D-model:

Sideview:


from above:


And then the actual build:




Next week we hope we can get a great bit further with the build!
Let us hear what you think! All comments will be very appreciated.

[vamoose]

I've been watching with interest, as i'm sure many other forum members are..
Am impressed with your progress so far, and It seems you guys are heading in the right direction.
Sometimes its easy to get ahead of one's self with theses engine's, but you seem to have things in check.

I'm guessing youve seen this recent video by approtechie

[youtube]http://www.youtube.com/watch?v=HqdoCzNAzHM[/youtube]

seems like great minds think alike..

u r 's

vamoose

[Triangle.Stirling]

Thank you Vamoose, it's only my second Stirling-engine, my first one was a tin can version, the one from Specallez.
It costed me quite a bit of time to make it, and then wouldn't work. I spent about 10 hours on that one to get it running. That brought me into Stirling Engines.
Most knowledge comes from youtube-videos. We've seen so many of them, and combined the parts that we thought are the best.

The only thing we still don't know, is about the cooling.
In my opinion, a water jacket is the best way to ensure cooling, but i don't like to put rusting tins on my stainless steel bottles, so i don't have a solution for that right now.
I thougt about running a pvc tube round the upper part of the cylinder, and pumping water through it. It's easy to do, and i think it will cool reasonably good.

Any opinions on cooling the engine?

also, stay tuned, next saturday we're going to spent the whole day building, so i think we can make a bit progress then...

[Triangle.Stirling]

Is it a big problem if we reduce the displacer-stroke to 24 mm, instead of 40 mm.

We made a mistake in calculating the diaphragm displacement, so we have to change the displacement of the displacer cylinder.
If we make the stroke of the displacer 24 mm, we still have the 1:1,5 ratio, so that shouldn't be a problem.

[Bumpkin]

I can see how predicting exact diaphragm displacement could be difficult. Anyway, I don't think having a higher ratio of displacer volume would necessarily be a bad thing unless you're running very high temperatures. You could give it a try before changing it.

Bumpkin

[Triangle.Stirling]

Yeah, predicting that is not simple. We just made a diaphragm with random size and tested how much water will fit in it. Multiply that with 2, and that is the displacement.
So i calculated the exact dimensions, but i made a mistake by calculating the displacement of the displacer. I calculated less than it should be, so we had to change someting.

We want to be as close to the 1:1,5 ratio, because we want a powerful engine. We just set it at 1.7, and ended up with 17 mm diaphragm stroke, and 26 mm displacer stroke.

I hope 26 mm is not too short? I read that short strokes give a fast engine, with lower torque, but what is a 'short stroke' ?
It's not a problem when it's a fast engine, that's just cool, and we can gear it down when we find a useful thing to power. The maximum power will be equal, only at a higher engine speed i guess?

although, experimenting is not that easy, we have to made another crank, displacer and housing for the diaphragm then...
Settled the displacement as mentioned above and worked a day on the engine, with our 2. Also made the bits and pieces that will make up the crank. Precision is very important there, but i believe we managed very well.

More updates to be coming soon !

[Triangle.Stirling]

updates not coming as soon as hoped...

We had to finish our final assignment and hand it in. That was a lot of paperwork, but we managed it.



We already got it back, and we got a 9,5 for the content, and a 9,0 for the design/appearance of the paper.

For our assignment we also had to put the engine together. We finished it, but it was not ready for working:


we 'finished' the engine, but then we had a problem. We first thought we could glue some rods to bearings, but that didn't work.
We had to think of something else, but couldn't come up with something. At least we found a solution:



The bearing clicks in the holder, and the connecting rod can be threaded in the plastic. There is a 6 mm thread already there. De 'clamping force' for the bearing is more than enough, but we have to test that.

In the meantime i decided to seal the edges of the wood. Its more beatiful, and it keeps the moisture out.


We also realised, we had no support for the connecting rod of the diaphragm. We decided to make a support for that also:



Everything is now sealed, and support is made. Now it's time to build it up again, this time right. Busy with school, so i don't have that much time. Hope to build the bottom up the coming week, and then have to make a few rods the right length. Then it must be tuned right, and then it's time for a test-run.

Hope to post a little more often in the future. There will be a Youtube movie when it's running, that's a promise!

[Ian S C]

Thanks for your posting, you are doing a great job, your motor looks good, and with the work that's gone into it, that should get 10 out of 10. I think you'll find that there are quite a lot of people watching this build, maybe some of them will be encouraged to build one of their own. Ian S C

[Triangle.Stirling]

I've been busy yesterday.
I went to the shed to fix the light on my bicycle and ended up working on the stirling engine.
Even cleaned up a bit of workspace so we can put the engine clean together.


Already had assembled the diaphragm-support:



Decided to make the crankshaft and connection rod ready. I made all the connecting rods the correct length and assembled it.




Glued the support for the displacer rod, and have to wait for the glue to cure.
I've planned to put everything together on monday (end of testweek) and do the testrun on tuesday.
Hope I can show you more in the near future!

[bladeattila]

Pretty nice engine!
I need to see run this engine! :)
Congratulation!

One question : what was that plastic peace around the bearings originally? That is a great solution for rod connection!
Thanks for your answer!
Kind regards:
Blade

[Triangle.Stirling]

Thank you blade! Hopefully we're able to get the engine running soon.

About the plastic piece around the bearing:
In Dutch it is called a 'klembeugel'
Translated into English you get 'clamp' or 'clamp bracket'

In the Netherlands you can find it in hardware stores. It is used to mount a water pipe to the wall.
There is a bit of threaded rod in the wall, the bracket is then put on the threaded rod, and the water pipe can be clicked in place.

For the small bearings (outside diameter 12 mm) they had the right size at the hardware store. Just the size for 12 mm water pipes.
For the larger bearings (outside diameter 19 mm) they had not the right size. I went to a 'dedicated shop' that sells plumbing stuff and pvc etc. I don't know the right name, but it is mainly intended for plumbers and construction workers to buy their stuff. I could get the clamps for 20 mm pipe, and the 19 mm bearings fit in nice, and strong.
The clamps are available in many sizes, there's always a size that will fit. They are really strong, you have to push hard to click the bearing in place.
I hope this helps you.

When you discover the right name of this sort of clamp, or find where you can buy them, please share.
I think i'm going to make a Youtube video soon, to help other people.

Regards,

Krijn

[Triangle.Stirling]

So, as told earlier i assembled the engine on monday. All went according to plan.

Tuesday we (I and my friend) started to try and get the engine to run. We started with small tea lights. That didn't work, so we moved to something that gives more heat, alcohol burnpaste.
At least we even tried with a camping cooking burner, but it would'nt start.

We thought hard about the reasons why it wouldn't start, and now we know.

The top plate (aluminium) presses down to the other plates. The top plate presses directly on to the diaphragms.
It turns out, that all the air leaks out from under the top aluminium plate.
It is mounted with 6 nuts on the threaded nuts. The nuts are fastened as firm as i can, and as firm as the threaded rods can handle.

Problem is that the aluminium plate bends a little. It is pressed down at 6 points, and between these points the pressure is less firm, giving the air leaks.

Does anybody know a solution to solve this? I don't really fancy making a new plate out of steel or something.
Does anybody have a good idea so that the middel of the plate is also thigthly closed?
We thought of adding more layers of rubbers. When the rubber is compressed at the sides, the middle will also be compressed.
We also thought about adding a bit of vaseline, the rubbers are dry now, this will provide a slightly better seal.

Another question: The displacer rods are 4 mm stainless steel. They slide through a tube that is also 4 mm inside diamter, lubricated with graphite powder. Is this enough of a seal, or are there other ways to seal moving rods?

We hope you can give us good ideas. Your collaboration is really appreciated!

As a bonus, a photo of the 'finished' engine, we want to get it running, now it's finally complete, so feel free to post your ideas!

[bladeattila]

Thanks very much!
That's awesome! I hoped it existed in smaller size too... but it's just a dream about it!
But the 12 mm is Ok!
In Hungary I found it some agriculture or heating system shop, so thanks very much again!
Best regards!
Blade

[tomostre]

Did you consider automotive silicone gasket? Get a tube at autoparts store, i think it is usually red. I wouldnt worry about the displacer rod too much. I think you gain a good understanding of your engine if you try parts without the axle first, i.e. If i raise displacer by hand, does the diaphragm move? Cheers. Post a video when you get it working.