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Powder keg

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What are you going to use for a gasket for the hot cap?

Wes
 

shred

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Powder keg said:
What are you going to use for a gasket for the hot cap?

Wes
The instructions call for some auto exhaust gasket material, but the drawings call out fiberfrax. I checked a couple auto parts stores and they only had pre-cut gaskets, which I could cut them from, but there would be a lot of waste. I happen to have some 1/8" fiberfrax (aka: kiln fiber paper) in my glass fusing supplies, so I'm going to try that. It's good to 1900'F, so that should be enough :D

We'll see today.. I started final assembly last night.

 

Powder keg

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Where can you get Fiberfrax?

Good luck on your engine:O) I can't wait to see it run.

Wes
 

shred

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Update: It's all together, but it doesn't run :mad:. Time to go chase down air leaks and friction points. Meh.

I ended up using auto gasket material because the Fiberfrax didn't stay together where I needed it. Mr Gasket "ultra" is a royal PITA to work-- it's got a layer of steel mesh through it, so scissors and X-acto knife are out. The drill press grabs and rips it apart. Small drills get knocked off alignment by the mesh.. I finally had to resort to the mill and a 1/16" end mill at 10K RPM just to get some half-decent gaskets, and they still look like a 2-year old hacked them out with blunt scissors.

 

Powder keg

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It'll Run Shred!!! Keep after it:O) Maybe a punch of some sort would make a nicer gasket? Just a thought.

Good luck, Wes
 

shred

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It runs now! Needs some tuning and break in still, but it's going. Pictures and video will be along.

I had most of the problems in the book-- too much friction (those blasted gaskets again.. moving around), an air leak around the cold cap and I went ahead and re-made the piston in graphite, which helped a lot (I found some solid graphite 12mm pencils at an art store last week... after I'd made the piston from Al), as well as reducing the internal volume a little and pretty much tweaking on most every part. I'm on my 3rd or 4th crank pin by now-- I keep losing the things and making new ones is quicker than searching the muck under my bench.

If you had a big hydraulic setup a punch would be the way to go on the gaskets, but it'll take a lot of push. Either that or get the kind which isn't steel-reinforced to begin with.
 

shred

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Here ya go..

I should get some better ones soon, once it gets cleaned up some.



 

Powder keg

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That looks super!!! I can't wait to see the video:O)

Later, Wes
 

BobWarfield

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Yay, Shred, glad you got it running!

I'm wondering whether nicely machined surfaces and something like Permatex Ultra Copper High Temp RTV would have gotten you there for the gasket? It would seal, but perhaps would conduct too much heat across the gap.

Best,

BW
 

shred

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The main gasket issue in this design they're expected to add 1/8" or so of height to the displacer cylinder while keeping dead airspace to a minimum plus block heat from the hot cap sneaking around in the metal versus doing work; thus the fiberfrax wasn't strong enough to be used as a structural element. Were I to build another of these, I'd look hard at something different for heat-blocking-- either different gasket material, or a different design with thinner gasketing-- maybe a sandwich of stainless steel and thin fiber paper or something (Senft likes compressed asbestos material in the Moriya design, but I'm thinking that's a little hard to come by as well these days)






 

Brass_Machine

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Shred,

Still waiting for the video.... Get on with it! ;D

J/K

Eric
 

shred

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Yeah, it needs some cleanup and a proper lamp and stand, but it'll do for the time being ;)
 
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