vermicular engineering

[travis]

Does anyone have something bad to say about worm gears? Or good actually, good is what I am looking for. I want to experiment with drive shafts this year and worm gears look to be a great way to do it, especially with multiple things running on a common drive shaft (say like 3 wheels).

My thoughts so far:

They can have poor efficiency, but you can do similar reductions with fewer steps (and weight and volume). Maybe one hardened and polished worm on a polished phosphor bronze gear is equally lossy as the 3 stage rolled steel on steel spur gear transmission it replaces. Ideally anyhow, this is the case.

Even in ideal situations, they do generate heat. I'd like to run them "open" which is to say with HD grease rather than in an enclosed oil filled housing. 1800rpm is the maximum Boston Gear lists them at, but that is for all day every day industrial work. The easiest thing to do would be to run them straight from a CIM at closer to 5KRPM. Extrapolating from the BG tables, I am still OK on power ratings, but I don't want to weld them together.

At sufficient pitch angles they cannot be back driven, so you have built in position holding, which saves oodles of complexity.

Motion Industries seems to be the only e-commerce supplier for Boston Gear and have a 6WD suite of worm gears for ~$800; a touch pricey. Anybody have a cheaper supplier, or manufacturer? Mcmaster only has CI gears, which is not ideal, though their 6WD suite would be more like $600.

So who has used worm gears and what nightmares/wonderful dreams have they wrought? Oh, and anybody ever licorice a drive shaft a much lower than expected torque values?

Travis