The failure mode turned out to be simple to detect. The key was trying to keep the planetary gears and their shafts well lubricated. Basically, the planetary gears started to bind…at best loading the 775pro, at worst stalling the motor. That then led to burning out the motor. The problem continued to cascade if we still tried to move bot during the match (which we always did early on) with one locked wheel, the other 3 swerve modules overworked and reached 775pro stall zone taking out or weakening additional motor(s).
After cooling, the gearboxes loosened up, but never 100% free.
We addressed the issue by frequent tear-down, clean and re-lube or replace gearsets, and put in a new set of 775pros when a match failure occured…not an ideal way to run a whole season, but got us through world’s.
In off-season, we replaced 775Pros and 10:1 gear sets with mini-CIM’s (due to space and weight) and 5:1 (because 4:1 were sold out). It was slower, but well suited for drive teams under development…AND…it was rock solid with zero failures even in pushing matches. Gearbox input shaft speeds were less than half, and friction heat load in gearbox reduced.
Another interesting data point on the 775pros…we had motors fail and still free wheeling and others failed rotor locked (usually shattered or melted debris). A free wheeling failure actually did not impact our match because the other 3 swerve motors could drive the bot will little performance loss…but…with a locked-rotor we learned to simply try to limp to the airship and wait for climb. So, if you have a 775pro fail locked, and have it parallel coupled with another 775pro directly or indirectly, and keep trying to power thru the match, you are going to burn up more that one motor. We have the smoking bot and e-stopped match video to prove it.
Lesson learned?..if reliability under any condition is in…775pro is out.
Can’t wait to see the new motors this season, but may just stick with drama free CIMs for one year.