6 CIM Drivetrains... What's Your Experience?

[Nathan Streeter]

Our team is nearing design completion on an off-season drivebase project... We'd decided to use a sheet metal drivebase a while back, but have been toying with different gearbox/transmission ideas. We've used Super Shifters for the past 4 years... and while we did consider trying the new Sonic Shifter and the Ball Shifter, we decided to broaden our experience by trying a single-speed 6 CIM drivetrain.

So, have you tried using 6 CIMs on your drivetrain? Do you know of other teams that have? What top speed have you geared for? Did you struggle with too much current-draw/voltage-drop in a pushing match and/or in acceleration? If so, did you use any software limits to minimize it (i.e. a voltage ramp, mentioned here, or a cut-off if the robot detects a voltage drop)? Also, what did your robot weigh?

We're currently planning to gear for about 10.5 fps (about a 10.5:1 reduction), but are primarily concerned about drawing too much current in a pushing match. If we have current draw issues we can either try software limits/overrides and/or try removing the two "extra" CIMs or swap them for miniCIMs or RS550s, which each draw around 2/3 the current of a CIM.

So far, I only know of 254 using 6 CIMs in 2013 with their 2-speed+PTO gearbox and of 610 using them this year in their 1-speed+PTO gearbox. I heard though that when 610 set aside their climber mechanism they also removed the 2 "extra" CIMs... according to their website they designed for a top speed of about 9fps.

Any recommendations, cautions, or further information?