Overdriving Worm Gear & Brake Options
Overdriving Worm Gear & Brake Options
(OP)
Hi,
We are experiencing a problem with an overdriving worm gear box. The worm gear ratio is 100:1 which would suggest that it should (ideally) self-lock. However probably due to the high loads and vibration it is overdriving. It is probably also a function of gear teeth wear as the overdriving is being experienced only after time in service.
Anyway my question is what brake options/configurations are available particularly keeping in mind the drive train is used intermittently with very short drive periods. Ideally I would like a soft stop, if that makes sense. Any recommendations on suppliers would be greatly appreciated.
As a side-bar question do double enveloping worm gears increase self-locking characteristics?
Cheers,
Rich (Mech Eng)
We are experiencing a problem with an overdriving worm gear box. The worm gear ratio is 100:1 which would suggest that it should (ideally) self-lock. However probably due to the high loads and vibration it is overdriving. It is probably also a function of gear teeth wear as the overdriving is being experienced only after time in service.
Anyway my question is what brake options/configurations are available particularly keeping in mind the drive train is used intermittently with very short drive periods. Ideally I would like a soft stop, if that makes sense. Any recommendations on suppliers would be greatly appreciated.
As a side-bar question do double enveloping worm gears increase self-locking characteristics?
Cheers,
Rich (Mech Eng)





RE: Overdriving Worm Gear & Brake Options
It will surely void any remaining warranty, and it may kill the gears; the stuff makes wet clutches grab like crazy, but automatic transmissions don't have many sliding surfaces that aren't clutches or brakes ... unlike a worm gear box.
Of course, if there's a life safety issue even remotely involved, I am prepared to retract the above statement, and to deny ever having made it or thought about it.
A magnetic particle brake on the input shaft should lock it up nicely, and with some electronic bits you can ramp the current to get a 'soft stop' as you want. Of course you need to power (and probably cool) the brake to keep it stopped, so a spring-set brake might be a better choice. If it's released by air, you can figure out how to make it apply softly.
Mike Halloran
Pembroke Pines, FL, USA
RE: Overdriving Worm Gear & Brake Options
RE: Overdriving Worm Gear & Brake Options
RE: Overdriving Worm Gear & Brake Options
RE: Overdriving Worm Gear & Brake Options
"Generally speaking, if the worm lead angle is less than 5°,
there is reasonable expectation of self-locking. Again, no guarantee should be made and customer should be advised. If
safety is involved, a positive brake should be used."
RE: Overdriving Worm Gear & Brake Options
A standard belleville spring has a linear behavior therefore, as long as it wears the braking force will change. For this to work you need a belleville spring with a range of constant force which is not standard. One more problem is that the ends of the spring will cut into the gear if not wide enough and grinded. The belleville spring hardnesss is usually ~50RC.
RE: Overdriving Worm Gear & Brake Options
Full details could include wear washers to protect the gear side and ID interface, a thin scallopped belleville spring with curled fingers, etc.
Maybe this is not a std belleville washer.