pic: 3CIM Ball Shifter

[Cory]

Originally Posted by Lil' Lavery

I have another question. Why bother with a 6-CIM, 2-speed drivetrain at all? It seems like a lot of resources to invest in only marginal gains over either a 4-CIM, 2-speed or 6-CIM single speed.

For us it came down to the fact that we wanted to utilize our drive motors to hang (we set our initial goal at less than 10s) and we also wanted to maintain the responsiveness and acceleration of our 2011 robot, except 30 lbs heavier. To do that we needed the extra CIMs.

[Gregor]

Originally Posted by Cory

For us it came down to the fact that we wanted to utilize our drive motors to hang (we set our initial goal at less than 10s)...

PTO's are an entire different ballgame, and negate some (most?) of the issues Karthik was trying to bring to light with looking at the opportunity cost.

[Tom Ore]

Originally Posted by Aren_Hill

Quick bit of advice, it is probably good form (on both the ball shifter and dog gear setups), to put your third reduction after the shifting shaft.

To generalize what Aren is saying, always try to put your mechanical advantage as close to where you need it as possible. (That is, pass the big forces or big torques through as few components as possible.)

[MichaelBick]

I agree that 6 CIMs are overkill if you aren't using a PTO. 4 CIMs + 2 550s seems like a good compromise and additionally makes it harder to blow the main breaker(our 6 motor drive was geared for 19.2 FPS @ 100% efficiency and never blew the main breaker). I agree with karthik though: if you can't find an easy way to add the extra motors, it isn't really worth the effort of completely repackaging the gearbox.