K Eilander wrote:
I've heard of/seen those, but how do you diy your own!?? That would be super interesting! Do you have links?
No links, I'm afraid, but I did make one myself for a
greenhouse at my university when I was going to school up in Maine. The campus
greenhouse was 50+ years old, all steam-heated and single-pane glass, and used wax motors for the vents. One busted, and I was able to make a jury-rigged replacement.
I bought two copper pipes, where the inside diameter of one was roughly equal to the outside diameter of the other. I crimped and folded over one end on each, so they were both sealed on one end. I then used a mandrel to expand the smaller pipe very slightly while it was inside the larger pipe, so it was an extremely tight fit between the two.
For the interior wax, I used a mixture of parrafin and mineral wax, that liquified about 85*F. That took a little trial and error, but I imagine if you were better at chemistry than I am you could find a way to calculate the right ratio for an arbitrary temperature. I painted a small amount of silicone sealant around the outside of the interior pipe, to act as a kind of 'piston ring' and keep the wax mixture from leaking too badly.
It worked pretty well, but was eventually replaced. I wish I still had it, or had some photos to share, but I do not.
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