a Jerry Howell "duplex vacuum" stirling engine build

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madjackghengis:

--- Quote from: NickG on September 29, 2011, 10:40:02 PM ---Nice work Jack, I'll definitely be watching this one. I am tempted to try another stirling next as I've all but finished my other poppin.

Shipto, you've started with the most difficult type ... the LTD's are a bit of a pain to get to run. I tried making a tiny LTD which ended in tears too, need to revise the design and try again! May be better trying one with a proper burner if it's your first?

Nick

--- End quote ---
Shipto, I also want to say, I built a Duclos "flame sucker" more than twenty years ago, half an hour here and there, and spent about six months trying to get it to run, getting all kinds of noises like it wanted to, but ended up putting it in a box and on a shelf when I moved to my "retirement home". I was put onto this madmodder site by a friend, and one of the first things I saw was a high school kid who had just finished his Duclos "flame sucker" as part of a class project where more than a dozen or so were built, and I saw his first run. It was that which made me spend days looking for that little engine and find it by accident, and spend about a week considering it, seeing a few flaws, and in fixing them, getting it running for the first time. Since then, I've put about six or eight pistons in it, half a dozen cylinders, and of course, the replacement crank/cam, which was the major reason it wouldn't run, but not the only one. You may not get your LTD stirling going right off, but don't let that bother you, it's not junk until you say its junk, until then, its "just, not finished yet", but the success at getting that "lost cause" running is a large part of my motivation in making new engines and pursuing these things which feed my need to make and build. I find I do a better job working on full sized engines now, having worked in much tighter places, and more difficult problems to face, when the tiny ones are confronted. Just make sure you're smiling when you leave the shop each day, because that is what life is about. Don't ever let anyone tell you something is too complicated, or you're wasting your time, if nothing else you're learning and you're getting to use tools, what more can a man ask for? Cheers, mad jack

shipto:
Thanks I havent given up on it but its only something I have been messing with at work while we are a little slack.

madjackghengis:
Well folks, I got a bit of time to work on her and got a few small things done. The back end of the stanchions was sort of a mismatch, so I put the cylinder in a chuck on my dividing head, and rolled it around a bit with an endmill to put a nice radius on the edge.

I left a slight shoulder on it, but got a good radius, and scribed a radius between the arms, opposite, and finished it off with sawing the slight bit of material and using the die filer to finish it. Then it was time to deal with the bore. I used stud and bearing mount locktite to press and lubricate the brass tube into the aluminum cylinder, and then bored it to a fine finish. It was supposed to be .750 when done, but the tube I had was an inch o.d., so I thought I'd just go with a bigger bore, and it bored out to .965, with about a thousandth of taper.

I took a well seasoned piece of oak about an inch and a quarter, by an inch and a half, squared it up closer in the table saw, and stuck it in a four jaw, then put a nice center hole in the end, about a foot long overall.

After honing, lapping and stoning the cutter, I made about a dozen passes, bringing the oak close to size, and adjusting the tailstock for no taper and got it turned down, to the size of the big end of the hole, about .965

rubbing in a healthy dose of rouge with some of Mother's polish for lubrication, I started lapping the bore. Oak is a very open grained wood, and thus holds lapping compound well, and maintains its dimension and its profile relatively stable. About a dozen applications of rouge and Mother's, with the cylinder going on further with each application, it goes all the way on, and time to turn it around and lap from the other end, just to even things out.

Here you can see the brass the rouge picked up and left on the lap, this is almost in flakes, as the grain of the oak pulls it off, and the brass is so soft. The brass and rouge wipe right off, and fresh is applied until the cylinder slides easily on and off, with even torque on the hand held cylinder. Sorry no pictures of the cylinder, I didn't want to try to hold it and take a shot at the same time, and the battery went dead in the camera.

The lapping stick after the job is complete, still on size, and can be used again. I'd use the same if lapping an iron cylinder, but I'd start with valve lapping compound, and work my way to rouge through several grits first, but the hole is round, straight, and with a mirror polish ready for a graphite piston to be fit to it.

From a chunk of two inch stainless, I cut down to 1.2 in o.d. for the hot cap, the inside will be an inch, and the outside will be profiled thinner, to reduce heat conduction, but after drilling boring, and machining the hot end where the flame will play.

with a shoulder turned on it for a heat "gasket" so it won't be stainless hot on aluminum cold, the cap is drilled, then bored to size. I think it's 304, but that's George's guess, he left the chunk on the hood of my truck last week, when he went by. When I return, I should have the hot cap finished with heat absorbing fins on the hidden end, and an area about an inch wide thinned down from the outside to a wall thickness of fifteen thousandths or so, to minimize heat conducted toward the cool end. Thanks for watching and for the comments, :beer: cheers, mad jack

saw:
I like to see your'e picture and read read your'e description of your'e work. It's very education and I learn a lot from you.
Thgank you for posting this project :bow: :bow: :bow:

Brass_Machine:
Great thread!!!! :headbang:

Love Jerry's stuff!

You are doing a great job on this one!

Eric

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