6 775 pro vs 6 mini CIM drive train

With all the recent discussion regarding 4 CIM vs 6 miniCIM drive trains, I was wondering how the pros and cons of using 775 pros or miniCIMs. Thoughts?

Take a good look at VEX’s motor tests, particularly the locked-rotor test.

If you run a 6 775Pro drivetrain into a wall, or get into a pushing war, and it happens to be torque-limited instead of traction-limited, you’ve got limited time to back it off before something starts smoking. And by something, I mean I’m not sure how many motors will release the magic smoke…if you don’t find them all you could get drive issues in the next match. I’m not saying that 775Pro drives are necessarily bad, but they MUST be properly designed to avoid situations that involve your robot sitting out for one or more matches to swap motors.

But if you run 6 miniCIMs into a wall or a pushing war, chances are you’ll be just fine as far as motors frying. CIMs use a different method of heat dissipation than 775s that just happens to be more tolerant of stalling.

I think the general consensus is that you want at least 8 775pros in a drivetrain (to share the load and keep current draw per motor down).

I’m surprised how little people are discussing robot weight and size as factors here. The tiny gear shuttler off season robots we’ve seen pop up on CD recently could probably perform great with a much more lightweight motor setup.

OP, what are YOUR thoughts on this topic?

at most FTFY

more then 8 motors will most likely see a diminishing return in drivetrain performance, as you already begin to have overall current limitations with 8 motors.

2451 prototyped a 5x 775pro gearbox last season (search CD, I’m too lazy to link) but ultimately decided that it wasn’t worth running 10x 775pros and kept it to 8 on the competition robot for 2017.

https://www.chiefdelphi.com/forums/showthread.php?t=157311&highlight=2451

Teams used 8 775 pros so they could lower the maximum voltage / current allowed but still maintain similar torque to CIM’s. This helped mitigate the 775 pros burning out.

I hate to sound like a broken record, but questions like the OP’s are why so many experienced folks are a little tentative to suggest 775 drivetrains. Teams that don’t realize what they’re getting into will smoke the motors quickly and be dead on the field. Of course, I’d rather see the questions asked right now so that the word can get out to many people. Hopefully we can avoid having a ton of teams saying ‘let’s run 775s!’ because they read the first or second post of a thread here on Delphi without understanding all the engineering that goes into running 775’s successfully.

“Exactly” is probably best then… My impression has been that 6 775pro DTs are more likely to heat up / burn out, 8 is optimal, and 10 is unnecessary (a high level description based on synthesis of all the more technical comments I’ve read)