worm gears

[gunder463]

so whats this i hear all the time about worm gears overheating and getting hot? do they just make them improperly or are they being applied improperly because i know they have high speed worm gear saws that dont over heat. was just wanting some info before i try some losi axles or rock force axles.

[StomperCrawler]

They're not made for speed or long trail runs, they're made for competition crawling which only takes a few minutes per "heat" (no pun intended). If you want speed, don't choose a LNC. If you want longer trail runs, you could either choose a shafty or else figure out a heat-sink solution to use with really sticky grease in the gears.

[gunder463]

Originally Posted by StomperCrawler

They're not made for speed or long trail runs, they're made for competition crawling which only takes a few minutes per "heat" (no pun intended). If you want speed, don't choose a LNC. If you want longer trail runs, you could either choose a shafty or else figure out a heat-sink solution to use with really sticky grease in the gears.

do rock force axles have the same problem with over heating as LNC?

[Olle P]

You get all the answers in this thread.
The reason saws don't overheat is basically "efficient cooling" which a crawler can't have.

[EeePee]

Originally Posted by gunder463

do rock force axles have the same problem with over heating as LNC?

I have them both and I'd say they are the same in this regard. They are built and sized a bit differently from each other, but the same thing is happening. The worm screwing the spool causing some heat. They don't "overheat" though, they just get slightly warm unless you peel out in a driveway for entire battery pack wearing in new tires. Then they're kinda hot.

[meatmonkey]

By design a worm gear axle is going to generate more friction from the worm gear sliding across the teeth of the lower spool gear. Friction generates heat, and both contribute to wearing out grease.

This design also puts much more lateral load on the worm gears' bearings compared to a bevel gear arrangement.

The upsides to the worm gears are improved driveshaft angles and clearance, virtually no detectable torque twist due to the greater gear reduction, increased ground clearance under the housing, and ussually an instant drag brake (except on some "high-speed" spools with less gear reduction)

The downsides are limited maximum RPM and the need for frequent regreasing.

What is best worm gear grease? I know that typical NLGI#2 parts store wheelbearing grease is not adequate.

[gunder463]

Originally Posted by meatmonkey

By design a worm gear axle is going to generate more friction from the worm gear sliding across the teeth of the lower spool gear. Friction generates heat, and both contribute to wearing out grease.

This design also puts much more lateral load on the worm gears' bearings compared to a bevel gear arrangement.

The upsides to the worm gears are improved driveshaft angles and clearance, virtually no detectable torque twist due to the greater gear reduction, increased ground clearance under the housing, and ussually an instant drag brake (except on some "high-speed" spools with less gear reduction)

The downsides are limited maximum RPM and the need for frequent regreasing.

What is best worm gear grease? I know that typical NLGI#2 parts store wheelbearing grease is not adequate.

well ill have to see what im going to do, i suppose the heat isnt really an isssue, plus i take my stuff apart frequently enough that i dont mind changing the greas alot and i dont normally use automotive grease, i have a company called ECL (engineered custom lubricants) down the street from my work and they make me small batches of grease's for my rc's plus i get experimental grease some times haha, but ill talk with them and see what they say about lubricant,

[Olle P]

Originally Posted by meatmonkey

The downsides are limited maximum RPM...

Could you elaborate on this? The only reference I've found to pinion speed is that the more speed the less friction, so any absolute upper limit (other than those imposed by outer factors such as motor power, friction and cooling needs) doesn't seem to exist.
Hitting a very high speed over a very short period while starting with a cool and well balanced worm drive should be doable.

As for good grease, I use a cheap grease based on Lithium, PTFE and MoS2 which has very good thermal and mechanical properties.
In general the best lubrication for worm drives is an oil bath, but we can't have that in our crawlers.