Author Topic: Head cold from Hell and maybe a Stirling engine.  (Read 23033 times)

Offline Brian Rupnow

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #15 on: January 21, 2018, 12:52:52 PM »
Hugh--see that brown colored part between the "hot cylinder" and the frame of the engine.-That is a 3/16" thick piece of asbestos to insulate the hot end from the cold end and the machine frame. Of course I will source some other type of insulating material than asbestos, but that is there to accomplish what your post was talking about. :pinkelephant: :pinkelephant:

Offline Brian Rupnow

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #16 on: January 21, 2018, 12:56:09 PM »
Ian--That motor doesn't have a power take-off as you point out. Since these are a rather weak engine anyways, I don't plan on running anything from it. It is just another type of engine to have "under my belt'.---Brian

Offline Brian Rupnow

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #17 on: January 21, 2018, 02:29:34 PM »
So there we have it---Pretty as a new pup!!! I can't say I'm really enthusiastic about the studs called for in the Moriya fan drawings, but I will probably change them up to socket head capscrews when I actually get to building it. The entire top end including both diffuser and power cylinders and pistons are taken directly from the Moriya fan drawings, and if you take a look on YouTube there are literally dozens of videos showing Moriya fans a operating.  The offset on both power piston crank-throw and diffuser piston crank throw match that of Moriya's. The distance from the bottom of the cylinders to the centerline of the crankshaft again matches the Moriya fan.  The main base, flywheel, and crankshaft are more along the lines of what Tubal Cain shows in his videos. The only "exotic" material on the entire engine is that brownish colored piece of insulation between the hot end of the diffuser cylinder and the 1/2' plate it bolts to--It is called up as being asbestos, but I will try and source an insulating material that is a bit more health conscious.

Offline crueby

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #18 on: January 21, 2018, 02:34:50 PM »
Very neat package, can't wait till you are feeling better and can dive in on this one in the shop.

 :popcorn:

Offline Brian Rupnow

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #19 on: January 21, 2018, 04:41:22 PM »
The good news is that after scrounging around in my "left over pieces" bin, I've found enough material to build everything for this model. The bad news is that my printer just ran out of ink.

Offline Brian Rupnow

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #20 on: January 21, 2018, 09:06:41 PM »
I wouldn't want you guys to think my life is dull or boring in any way---But it is winter. I had nothing to do today, so I started making parts. Todays work yielded the engine base. The eagle eyed among you may notice that the base looks a bit thicker than it does in the solid model. It is. I had a piece of 2" x 1" material, and decided not to spend any time making it 3/4" thick. This will ultimately work to my advantage because it gives a little more room to slide a can of Sterno under the hot end of the displacer cylinder. Today is my 29th wedding anniversary so me and good wife are off to a fancy restaurant for dinner.

Offline b.lindsey

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #21 on: January 21, 2018, 09:10:50 PM »
Congrats on the anniversary Brian. Enjoy your celebratory dinner  :)

Bill

Offline NickG

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #22 on: January 21, 2018, 09:12:49 PM »
Nice design Brian, great to see you doing a Stirling . Don’t be fooled into thinking they are forgiving to machine though, any binding , tightness or excess friction could prevent it from running. I designed and made my own Stirling too after similar research to what you have done. I had the advantage that my power cylinder and displaced cylinder were detached completely with a  rubber tube connecting them. Even then I still had to change my displaced to a larger diameter and go water cooled! Mine was a ‘gamma’ type run off the same crank but that means two things - timing not adjustable and stroke is the same for both cylinders. You have the option to play with those. As others have said, it’s important to prevent heat transfer from
One end of the displaced to the other as well as between the cylinders. So very thin stainless tube is good for the hot cap ( thin as you dare make it) and displaced. I used aluminium for my displaced hollowed out.  Of course the thinner you make it and the longer you make it, the less heat transfer there will be from
One end to the other so it’s worth bearing in mind.

The ratio of swept volumes has a large bearing on how easily the engine will run. So making your displacer swept volume larger generally means a lower temperature differential can be used to create the pressure difference. That is why LTD engines have relatively huge diameter displacers ( easier to increase swept volume with bore rather than stroke)

Having a smaller ratio of swept volumes apparently (what I’ve read) makes for a more efficient engine in terms of power, but you’ll have to put more heat into it and hence cooling, insulation etc will need to be better.

So if I was making another I think I’d be generous with both displacer length and swept volume as I would just want a reliable runner without needing a blow torch!

The other thing to minimise is dead space, which your design seems to do quite nicely (1/16” clearance sounds just enough without causing any drag but minimising dead space (unswept volume) . Again, the ports don’t want to be too large but enough not to give any undue pressure to overcome. Because your cylinders are back to back, this minimises dead space. Just ensure that the pistons sweep as much of the bore as possible. Looking forward to the next steps.


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Offline Brian Rupnow

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #23 on: January 22, 2018, 01:43:58 AM »
What an ignorant wee piggy that gusset plate is turning out to be!! The piece of stock I have to make that from is just slightly larger than the finished part will be. My largest drill is 1" and the radius on the gusset is 1". There is really no good way to hold it in the mill vice to use my boring head. It looks like it will be a faceplate job. I will have to think about this one some more, and see if I have some scrap to make the brown colored fixture from.

Offline Brian Rupnow

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #24 on: January 23, 2018, 01:29:45 AM »
And here's an update on whats happening today. I trimmed my over-thick piece of material for the gusset down to 0.742" (that is the width my once sharpened 3/4" endmill cuts to.) The layout lines on the piece show the cut lines. The base is finished, setting in the background, with two likely candidates for the fixture which will be made to mount the gusset plate onto the faceplate for boring. There is no work at my across town office tomorrow, so I should be able to finish the gusset and maybe the last piece of frame plate that the cylinders mount to.

Offline Brian Rupnow

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #25 on: January 23, 2018, 02:34:53 PM »
And for those of you who like to see set-up pictures---Here we have the 2" diameter hole bored thru the gusset plate. I used my longer boring bar to clear the bolts which are holding the gusset fixture to the faceplate.

Offline Brian Rupnow

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #26 on: January 23, 2018, 06:34:33 PM »
All of the aluminum frame pieces are finished. Even though there was a fair bit of extra work carving the radius in the gusset, I like it.  Faceplate work is something I do very little of, so it was kind of fun.

Offline crueby

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #27 on: January 23, 2018, 07:23:00 PM »
That gusset plate looks great - lots of the early metal frames had parts that looked more like wooden knees and joints, this harks back to those.

 :popcorn:

Offline Brian Rupnow

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #28 on: January 23, 2018, 10:38:46 PM »
After spending most of the day standing at the mill or lathe I feel Like I've got wooden knees and joints!! Nothing that being 50 pounds lighter or 50 years younger wouldn't fix. I scrounged around in my brass drawer, looking for enough brass to make the bearing stands from. All I had that was big enough to get two pieces out of was the last of an aluminum bronze bar I've been using up. Damn, that's miserable stuff!! It's as hard to machine as mild steel. I'm glad that these two stands will be the end of it. I can't even remembered why I had it, but I will make it a point to not buy any more.

Offline Steamer5

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Re: Head cold from Hell and maybe a Stirling engine.
« Reply #29 on: January 24, 2018, 05:55:06 AM »
Hi Brian,
 Looking good.

Here’s a link for maybe your next one......

<a href="https://www.youtube.com/watch?v=nSE3GmUdxoQ" target="_blank">http://www.youtube.com/watch?v=nSE3GmUdxoQ</a>

Cheers Kerrin
Get excited and make something!

 

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