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Unread 16-01-2017, 02:36
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asid61 asid61 is offline
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AKA: Anand Rajamani
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Re: Machining precision required to make custom gearboxes

Quote:
Originally Posted by mman1506 View Post
Your probably going to be fine, the 24DP gears commonly used in FIRST are purposely larger than necessary so they can handle being abused in low precision gearboxes and high sudden torque situations. Usually the failures of gears in FIRST are either due to gears being too small and cracking at propagated stress points of the hex shaft or flexing and allowing the gear mesh to become far too loose (the VEX Ball shifter 3rd stage seems to have this issue). In the scheme of things the amount of time FIRST robots run is very short and wearing your gears to the point of failure is very unusual unless something is really wrong like the mesh being too tight. This why its common to add .002" to the C-C mesh of gears in FIRST.
Quick correction: gears in FRC are 20DP (which is actually a very odd pitch for some reason, most sites only sell 16p or 24p) and are actually way undersized. If you compared the tooth of a Vex gear to that of a Boston Gear gear, you'll notice that the Vex teeth are slightly thinner and have large sections of the root of the tooth taken out.

I second that you need .002" precision at the minimum. Personally I prefer .001". If you do not have a mill, please don't attempt this mid-season- there is almost a saturation of gearboxes available from WCP, Vex, and Andymark.
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