anyone tried worm gears?

[Vitamin_J]

i always used to fool around with Lego's and make trucks and whatnot. the most useful lego reduction was the worm gear.

i was just wondering if anyone has ever tried to use one. if i were to build an axle, there would be a worm gear in place of the differential, much better reduction, and easier than bevel gears.

 

[JasonInAugusta]

http://www.rccrawler.com/forum/showthread.php?t=1563&highlight=worm+gear

 

[Grizzly4x4]

Ace did this a long time ago, he will be at the next get together.

He machined his own axles with a 20:1 gear reduction. It werks awesome but has short run times. He thinks it is due to the low efficiency of the worm gears.

http://www.rccrawler.com/forum/showthread.php?t=450&page=2&pp=10&highlight=pimping

 

[Vitamin_J]

nice, thanks

 

[Ace]

Worms are really attractive because they self lock and have really high reduction in a single stage.

Problem I found is efficency. The chart sez about 70% at 20:1 and even that I think is low. Those ratings are for worms running at higher rpm with lower loads. A crawler puts relatively high loads are low rpms and the friction losses are high.

My worm crawler runs about 5-7 minutes under hard climbing conditions. I remember having to change batteries 3 times on the 1st section at the UTRCRC comp!

That truck is the most manoverable rig I have, and it's only 2WS. Partly because the worms lock the axles, kiney like having brakes on the steep stuff. I can back up 1/2" stop move forward 1/2" when doing a 20 point turn... Even on a real steep slope it won't roll.

Worms at 4:1 are more efficent but they don't lock. Next axles I build will have bevel gears with compound spur/pinion to get about 20:1 ratio in the axles again.

 

[Vitamin_J]

thats cool, but those runtimes are horrible.