Friday, March 16, 2007


Darwin's X-axis toothed pulley

The last gear problem for Darwin, casting a 12 mm gear to fit on a 6.35 mm motor shaft. A flat was needed to ensure no slippage on such a thin shaft. Final solution was to use the same kit used to make the Y gears (see previous post). The collar was prepacked again, but this time, becasue there was a bit more wall thickness, the hole was simply started by working a screwdriver into the capa. The collar was then put into the pot with a new blade part which fitted the motor shaft profile. The motor shaft was then poked in from the back. Worked first time.

This was then complemented with Vik's superb idea of a washer + bit of capa for the second lip.

Next: a repeatabiltiy test for the X. Though I need to solder up a universal PCB first...

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Nice one, Ed. What's the belt gear looking like at the other end?

Vik :v)
There is no gear at the other end - it free-wheels, so it just goes over a smooth pully of the same diameter. That's quite easy to make.
Riiight. That simplifies things a bit.

Vik :v)
I thought he was kidding at first... but it's in the picture annnnnnd in the diagram.. Idlers. They are so smoooooth.
it might be interesting to try putting gears on both ends... perhaps that might improve accuracy. then again i'm no MechE so who knows!
Yeah gears on both ends was the first thought, but actually because the idler gear has no rotational constraint, there's no mechanical advantage in giving it any teeth... and it's much simpler not to.

Funny how the path of least resistance, which sometimes has connotations with laziness, is usually the best?
I think it's similar to the way mature wisdom resembles being tired :)

Vik :v)
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