Quote:
Originally posted by JVN
We had this same debate.
Decision?
We decided to shift as early on in the gearbox as possible. (After all the motor combiner reductions and such). Basically, the reasoning behind this was, there is less torque applied to each shaft/gear at this end of the gearbox (higher speed = lesser torque). This means our shifter pins/dogs/whatever would be put under less load.
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She does make a nice little grinding noise as she jumps into gear, but, no damage or visible wear has occurred on our shifter dog, and the whole box seems to be functioning almost flawlessly.
*knock on wood*
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PS - The Technokitten Tranny shifts right after the motors combine (Andy has it shifting even earlier than mine does).
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this additional reduction was mounted seperate from the main gearbox, and located on their tread assembly. ... No chain.
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Bingo! John gets an "A" for the day.
When designing your shifter, do the shifting as close as you can to the motors. This means that you will be turning at a higher rpm, but more importantly, at a lower torque. This lower torque gives your dogs/teeth/hex shaft/etc. less stress and strain.
TechnoKitten... sheesh... no respect, I tell ya.
Additional reduction: *** this is BIG *** Last year, we had two gears which further reduced the rpms between our gearbox and our driven wheel. I over estimated our output speed and did not leave enough room to realistically gear down the robot. I placed the two gears at a center distance that was PAINFUL to deal with. I started out with a 32:20 gearset, thinking that if we had to slow it down, we could get a 36:16 set. We did this, and it was still too fast (no acceleration on the ramp). So, our final gearset was 40:11. There was way too much force at the gear teeth of the 11 tooth gear and we stripped that little guys a few times during the regionals.
My advice is this: the closer you get to your wheels, the more room you should leave for varying your speed. Be prepared to change your ratio so that you may have to speed up or slow down dramatically.
Andy B.