RC-Monster Forums - View Single Post - F/R gear ratio for 1/8 on-road conversion

BrianG · 11.17.2010, 02:14 PM

I look at this in two ways:

1) Spiral vs straight cut. Spiral cut gears have more contact area to reduce stress on individual teeth and are quieter, but they do place more thrust load on the bearing (under heavy load, tends to "push" against the inner race of the bearing). Personally, the reduced tooth stress of spiral cut is offset by the fact your bearing may wear out faster, which loosens the mesh. If there was a way to use a thrust bearing to keep the pinion gear from stressing a normal bearing, I would choose spiral cut style.

2) There are a couple considerations for the gear ratio. First is the size of the pinion. Smaller pinions have more wear since they turn more. But since both pinions above are the same size, this doesn't matter. The ring gear with fewer teeth will technically have more wear than the other, but I don't think the difference is worth considering.

The second consideration is how much gearing you have with the spur/pinion and/or transmission (none for buggies). If you find you are limited in spur/pinion gearing choices (maybe due to motor size or spur availability), then you choose the F/R diff that complements those limitations.

Other than that, I would say the choice is arbitrary.

	(#2)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	11.17.2010, 02:14 PM I look at this in two ways: 1) Spiral vs straight cut. Spiral cut gears have more contact area to reduce stress on individual teeth and are quieter, but they do place more thrust load on the bearing (under heavy load, tends to "push" against the inner race of the bearing). Personally, the reduced tooth stress of spiral cut is offset by the fact your bearing may wear out faster, which loosens the mesh. If there was a way to use a thrust bearing to keep the pinion gear from stressing a normal bearing, I would choose spiral cut style. 2) There are a couple considerations for the gear ratio. First is the size of the pinion. Smaller pinions have more wear since they turn more. But since both pinions above are the same size, this doesn't matter. The ring gear with fewer teeth will technically have more wear than the other, but I don't think the difference is worth considering. The second consideration is how much gearing you have with the spur/pinion and/or transmission (none for buggies). If you find you are limited in spur/pinion gearing choices (maybe due to motor size or spur availability), then you choose the F/R diff that complements those limitations. Other than that, I would say the choice is arbitrary.