Wednesday, December 3, 2008


  • The biggest difficulty in making something like a Stirling engine without access to a machine shop is how to make the power piston. The piston has to be precisely sized to fit inside the cylinder. However, via a YouTube video, I have discovered that it is possible to use a pair of PVC pipes to get the same effect. I made one and under breath power it worked so well it nearly knocked my teeth out. I haven't done any real testing yet, so I don't have all the construction details worked out, but basically you just get two sizes that differ by 1/4" and sand down the smaller until it fits in the larger.

  • The way I'm going to test the piston is to build another Stirling. Need a bigger displacement chamber for a piston this big. Should be metal, not too thick-walled, largish, easy to make air-tight. A paint can would be perfect, except you don't want to combined leftover fumes and high heat. Turns out Lowe's sells empty paint cans! Quart- and pint-sized. That means you can even remove the lid to work on the innards and then reseal it.

  • What with one thing and another, the flywheel on the new engine has to be mounted differently. I need a whole crankshaft dealie (which is something else it would be easier to make with a machine shop). Once I realized this, I realized I'd also need some kind of bearing. Idly reading something completely unrelated, I came across a mention of "skate bearings". I was thinking inline skates, but skateboards have the same thing. They are only like $1 each! And I even had an unused skateboard at home, from which I harvested 8 of them. ID ~8mm, OD ~22mm. Cute as a bug's bearing.

  • I've had these drawing pencils for a while now. The leads are 2H, HB, 2B and then some high B one, I dunno what. The problem is you have to keep sharpening them like every 15 minutes. The other day I realized this is already a solved problem: mechanical pencils. The only question was, do they sell mechanical pencil leads in hardnesses other than HB? Answer: Yes. So now I have 3 mechanical pencils, each with a different lead. Makes drawing so much less of a hassle. Can't shade with the side of the lead, of course, but I never did that anyway.

  • I'm not going to meet my Xmas diet goal. Scale is still going down, but too slowly to make it in time. Maybe I should aim for the secondary goal (an additional 10 lbs) at the 2 year mark (March?).

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