New Stirling scaled of GPU 3 first testrun

Discussion on Stirling or "hot air" engines (all types)
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tom-rock
Posts: 18
Joined: Tue Feb 25, 2014 1:24 pm

New Stirling scaled of GPU 3 first testrun

Post by tom-rock » Sun Feb 21, 2016 1:10 pm

Hi,

as discussed in an earlier topic I modified my Stirling engine a lot.
The heat exchangers are now scaled of the famous GPU 3 with the methods of Dr. Allan J Organ.

I hadn´t much time the last month so it took much longer to complete the Engine.
A first testrun with a lot of provisionals and by far not the best setup gave
a very promising 108 Watt @ 7 bar air charge.

I think this engine has a lot more potential.


Here is the Link to a small Youtube video:



(If the link does not work just search for ralf tom-rock)


I am always happy for comments and suggestions.

Greetings

Ralf
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Ian S C
Posts: 2221
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: New Stirling scaled of GPU 3 first testrun

Post by Ian S C » Mon Feb 22, 2016 1:33 am

That looks good Ralf, havn't looked at the video yet. One place you might get another Watt or two is if you degrease the bearing in the pillow block, and just use oil.
Ian S C

PlaniTechic
Posts: 29
Joined: Sat Mar 21, 2015 11:38 pm

Re: New Stirling scaled of GPU 3 first testrun

Post by PlaniTechic » Mon Feb 22, 2016 8:28 am

Ralf, this is awesome!!
The new heater head seems to really pay off. Also the shaping head you made for your mill is pretty cool. I was thinking about building something like that too, but it will be a while till I get there.
What are the modifications you are doing next? And would you also share some details on how you went on with the scaling from the GPU 3 engine?
Keep up the good work!

Plani

tom-rock
Posts: 18
Joined: Tue Feb 25, 2014 1:24 pm

Re: New Stirling scaled of GPU 3 first testrun

Post by tom-rock » Tue Feb 23, 2016 1:47 pm

Hi,

thanks for you kind comments.

Ian you are right the big bearings have to much fricton I will fix this in the future, thanks.

After fixing countless provisionals my main focus is on finding the right balance between
friction and tightness in all seals. (Piston rings and displacer rod seals).

I also have a problem with the alignment which causes massive scraping of the pistons
on the cylinder walls, they have to be turned out and honed again :-((( .
I was to keen on testing the new Engine to early.

I scaled the heat exchangers of the GPU 3 (do you all know this engine?) using FastTrack, FlexiScale
and ReScale by Dr. A. Organ.

In his Book "Stirling Cycle Engines" (2014) he discribes the process in Detail.
You don´t need to understand heavy math, most parameters are derived using graphical design charts.
If you don´t have it you must buy it.

Nevertheless it is a very time consuming process, it took me about 2-3 month of much work until
the new heat exchangers were designed and I was satisfied with the theory.
(And I have a good mathematical Background).

I asked some professional experts and even Dr. Organ gave me kind support
but not all coud be clarified, e. g. I couldn´t make the heating slots as long as required and there
is still no way deriving this properly.

Best wishes

Ralf

Ian S C
Posts: 2221
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: New Stirling scaled of GPU 3 first testrun

Post by Ian S C » Wed Feb 24, 2016 2:56 am

Ralf, I seem to remember that Andy Ross made the finned inside of his hot cap on a flat piece of metal, then rolled it, pushed it into the hot cap, and brazed it in place, but I like your method of making it in one piece.
Ian S C

PlaniTechic
Posts: 29
Joined: Sat Mar 21, 2015 11:38 pm

Re: New Stirling scaled of GPU 3 first testrun

Post by PlaniTechic » Wed Feb 24, 2016 8:02 am

Actually, I have Dr. Organ's book too :smile: , and so it comes that I have read about the GPU-3 engine.
But it looks a tiny bit intimidating to me, to say the least. And therefore I didn't dig any deeper into the matter as of yet, that's still to come.

Good luck with the refit of the cylinder and keep us posted. It's always very interesting to see the progress you make on your engine.

Plani

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