Thread: Worm Gear Gearbox
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Unread 04-01-2005, 13:27
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Re: Worm Gear Gearbox
Back Drive-ability is a function of surface finish, lubricity, and worm lead angle. Using a bronze worm gear and a hardened steel worm (the small screw looking one), the max lead angle is 5 degrees to insure self locking. This is not a guarantee! What is a guarantee is that above 5 degrees, the worm gear set will not lock. The lead angle is the reason the window motor locks and the van door motor does not lock. It really has nothing to do with the gear ratio. A gear ratio of 50:1 with a lead angle of 15 degrees will not lock.

However, the more thread starts on the worm, the higher the lead angle and the lower the gear ratio is. Remember, gear ratio for a worm gear is # of teeth on the gear divided by number of thread starts on the worm.

-Paul