Pinions

[lewist]

what is the smallest sized 48 pitch pinion you can get.. i need between a 7 and a 10 tooth pinion

(is just about mod motor related.. i am gearing an 11 turn motor!)

[Mark Stiles]

can't you go up on the spur? The smallest pinion I've got is a 12.

[lewist]

no i have an 87 tooth spur which is the largest traxxas do for the stampede, i don't know weather an aftermarket spur would fit/do the trick, but i would probably have to go to 100 teeth.. about 3 teeth on the spur is one tooth on a pinion or something like that so if i need to go down 5 or 6 teeth on the pinion then i would need 15 - 18 teeth on the spur!!

can i borrow that 12 tooth??

[Mark Stiles]

yep, but I'll want it back at some stage!

[lewist]

yeah course.. hence borrow :P

if it is better i will buy one...!!

[Chrisyc]

why wpuld you want a 12 tooth pinion ??? even with a 65 tooth spur on an mr4 (2.2) has a final drive ratio of around 12!!!

12 is ridiculous!!!!! :-

[Mark Stiles]

Not sure what the internal ratio of lewis's sst '99 is, although the track he races it on is very small for touring cars. We can do low 8 second laps with 1/12th circuit cars, and thats without additive! :o

[PDW]

Apart from the fact that not many people use them, one reason you cannot get these small pinions is that, from an engineering standpoint, it would be bad design practice.

When the tooth numbers get down to this level, the correct involute tooth form causes an excessive undercut at the root of the tooth, making it weak. At the same time, there are too few teeth to ensure proper engagement, increasing the risk of breakage.

If the 12 toth pinion doesn't work for you, call RW Racing and see if they would make you an 11 tooth - but beware the design issues above. HTH :)

[lewist]

its not for my sst nobby... its for my monster truck

i have re-fitted it with larger wheels and tyres and now i am a bit stuck on the gearing...

i am aware that when they get that small its difficult to make them, and they become a bit inefficient but i would need a 110 tooth spur or more!!

[lewist]

why wpuld you want a 12 tooth pinion ??? even with a 65 tooth spur on an mr4 (2.2) has a final drive ratio of around 12!!!

12 is ridiculous!!!!! :-


not rediculous when you have rear tyres the diameter of dinner plates!!!

[Chrisyc]

right ;D
no need to get violent ;D i thought it was for your touring car! ::)

[Chrisyc]

yeah with monster trucks you need a silly ratio, i used to have a tamiya blackfoot, and it came with a 9tooth pinion (although i think it was 32pitch ;D)
and tamiyas have wierd gears!