Worm Gearbox

[tnkayaker]

I'm in need of compact gearbox and the only thing I can come up with is a worm gear type. I don't have any experience with this type of gearbox so I was looking for suppliers and gear cost and began to notice that the worms would have a description of RH on them. Now I'm begining to think that worm gears are directional. My question is are they directional?

TIA
Erik

 

[BobM3]

RH would be Right Hand (like most screw fasteners). It just determines the direction the gear rotates when the worm is turned in one direction. The teeth on the gear would have to match the "handedness" of the thread on the worm.

 

[Warpspeed]

Some worms and helical gears can be directional, the classic automotive differential gears being a common example.

The teeth are often not cut symmetrically for very high torque applications. The pressure face will be nearly vertical, and the trailing side of the tooth will be cut at a steeply sloping angle for clearance to the next passing tooth.

This may or may not be relevant to a particular gearbox, but for the higher torque rated gearboxes it is not uncommon.

 

[Spurs]

Try looking at this website to answer some quetions on what you are defining as crossed axis helical gears

http://www.webgearservices.com

 

[tnkayaker]

Thanks for the info everyone.

Here's my next question...can the worm be driven with the worm gear? The worm would have no load. Basically free-wheeling.

 

[BobM3]

It can if it is not self-locking. If the lead angle on the worm is below a certain value (theta < invtan (friction coeff)) then it won't backdrive.