paper: 4 CIM versus 6 CIM theoretical calculations

[asid61]

Originally Posted by InFlight

I would caution against using the 775 Pro motor in a drivetrain application. This is an air cooled motor with an internal fan. There is no effective cooling at low speed near stall current conditions. One defensive pushing match will let the smoke out of these motors. The much higher speed output would require additional gear stages as well.

The Mini-CIMs is really the equivalent to 1/2 a CIM in terms of torque and current. If a team wanted a competive advantage of running a three motor gearbox per side; the combination of two CIMs and one Mini CIM would be a better choice. It would provide 125% the performance of a 2 CIM drive, with more brownout margin than a 3 CIM drive.

Actually, I know of a few teams that did 775pro drivetrains without problems this year (and a few that did have problems). 3310 is one example of a 775pro drivetrain done well, I believe.
1296 had a super light and compact robot, but ran only 4 775pros in their drivetrain which caused numerous burnt motors. They upgraded to 4 CIMs for champs.

[GeeTwo]

Originally Posted by InFlight

I would caution against using the 775 Pro motor in a drivetrain application. This is an air cooled motor with an internal fan. There is no effective cooling at low speed near stall current conditions. One defensive pushing match will let the smoke out of these motors. The much higher speed output would require additional gear stages as well.

I explicitly said that this was worth considering if you're going to do proper speed and thermal monitoring. As I recall, the 775 Pro has better efficiency and far lower weight than the CIM, though by the time you gear down it will be reduced or possibly dissapear. My point here was simply that WITH MONITORING, it is worth looking at these motors. Oh - I also seem to recall an inverse differential based gearbox a few months ago that might make air cooled motors more viable for drive trains (though I was never convinced).

Originally Posted by InFlight

The Mini-CIMs is really the equivalent to 1/2 a CIM in terms of torque and current. If a team wanted a competive advantage of running a three motor gearbox per side; the combination of two CIMs and one Mini CIM would be a better choice. It would provide 125% the performance of a 2 CIM drive, with more brownout margin than a 3 CIM drive.

Looking at the numbers a year or two ago, I came up with 2/3, based (IIRC) on the peak power and stall torque. The free speed is also a bit faster.

Edit: Wow - sniped on both points, by different posters.