Michael Sexton's ball millMichael Sexton sent me some pictures of the ball mill that he built using wooden gears drawn with the gear template generator
"This design has turned out rather well. Those are steel bearings in the center of each gear. They are held in by a press fit (forstner bit with a bit of tape around the bearing). They hold up to wear pretty well. I have had this on running for a total of about 4 hours, so it is just getting broken in. The gears exhibit no signs of wear unless the mass inside the ball mill container is too great."
I love this application. This is the first time I have seen this type of plywood gears seen in a real power application. So far, I have only used plywood gears for hand-cranked applications, such as this router lift, where wear has never been a factor.
"The reason for the wire around the ball mill
container is to keep the ring gear from slipping. I couldn't believe the amount of
force that the steel balls exerted on the container. I had the ring gear on rather tight,
and the rolling/banging action of the balls still managed to make the gear slip.
The wire is wrapped around in a spiral pattern so as to exert force in the opposite
direction of the slip. This way, when the ring gear attempts to slip, it is like
tightening a knot."
"I probably could have used fewer gears had I used the pin type gears from your gear program.
All of the gears in the box are 1 of three sizes. Anyway, so far it works quite well,
I have powderized glass for use in re-melting (pulverised using 1 inch diameter steel
balls - about 40 of them). The gears prevent slippage of the ball mill container,
which I had problems with earlier. I will talk to you later!"
I think Mike did well sticking to involute gears. I don't think the pinwheel type gears are that good for power transmission.
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