Re: tranny

[Frank Pittelli <frank-at-rctankcombat.com>]

chris barthelson wrote:
> hello everyone
> Just a couple of questions. What size shaft should I use for my 
> transmission?

Depends on the bearings that you are using.  It is sometimes cheaper to 
use 5/8" shafts, because that's a fairly common shaft size for garden 
equipment, which means that cheap bearings are plentiful.  But, if you 
may find some bearings for 1/2" that are cheaper, so you'd go with that 
shaft size.  For example, Steve Tyng found some inexpensive 1/2" 
bearings recently, so we'll be using them for our next tranny. 
Basically, any shaft that is 3/8" or bigger will work fine.

> And I want a duel stage 9:1 reduction what is the cheapest 
> way to achive this???

If you're using chain, you can get 4 pairs of 10-tooth and 30-tooth 
sprockets for the tranny.  We've used #35 chain because McMaster-Carr 
carries a complete line of sprockets, but that's heavier than necessary. 
  Joe Sommer found a place to order #25 chain, which is more compact and 
lighter, but will do the job fine.   I'm not sure if there is a price 
difference.

Chain is a good solution, but is more expensive than using a two-stage 
belt reduction, which is the first tranny we built.  When using belts, 
we used 4 pairs of 1.5" and 4.5" pulleys to achieve the 9:1 reduction. 
Keep in mind, belt trannys need a more complicated mounting system, 
because you have to be able to put tension on the belts.  Also, because 
they are under constant tension, they make the motor work harder and 
they need to be adjusted periodically.  Finally, belt trannys aren't as 
compact as a chain tranny.  As always, you've got to tradeoff some 
performance to save money upfront.

 > And I'm using tts tracks so I dont need any slipage right??

That's correct.

        Frank P.