[DFTF] Motors... ...Drive Motors...

[Brandon Holley]

Originally Posted by JamesCH95

How were the motors setup? Transmissions, loads, control, etc. Like I said my team had a 100% positive experience with them, so I'm curious as to why your experience was 100% negative.

We used 2 to run our elevator winch. The winch was close to the bottom of the robot, and powered a ~12" long aluminum drum that would wrap up the sailing line in our elevator.

The winch itself had each 775 powered through a "CIM-U-LATOR" and then further reduction inside a gearbox where the motors were paired. I'm not sure of the overall ratio off the top of my head, I can report back later. We did quite a bit of math to make sure we would be geared for an appropriate speed. Additionally about 75% of the weight of the elevator (and claw system) was offset by spring force. To say this thing was overpowered would be an understatement.

When we had functioning 775s, the elevator ran up and down with few issues. Unfortunately we never had one 775 that functioned flawlessly. Even if we confirmed there was no case short when installed, the motors tended to develop them over time. It wouldn't take long either. We checked the case short after each and every match to basically gauge how long we could continue running that set of 775s before needing a different pair. After each match we would watch the resistance drop until finally we would have issues with the minibot deployment which signified an end of life for the motor.

We tried to isolate the motor from the robot by placing dielectric sheet between the face of the motor and the gearbox plate. We also tried wrapping screws in teflon and then installing them. The short went through the motor pinion, into the CIMULATOR gearbox, through the CIMULATOR output shaft into our custom secondary gearbox, through the output shaft, through the bearings pressed in the plate that the shaft ran through, into the gearbox plate and the gearbox plate mounting screws, and finally into the frame of the robot. It was a nasty problem to have.

"Zapping" the motors was a common practice teams used to fix this issue, and we did so as well. On some motors it would definitely enhance their lifetime, on others it didn't do much of anything. It was almost kind of sad how good we got at pulling the motor off the robot, "zapping" it, and then replacing it. We often did this process, or a full replacement of the motors in-between matches.

If Banebots can show us that this isn't going to be a reoccurring issue, then I would say we'd be open to using the motors again. Like I said, when they worked, they worked perfectly fine. However, it was my understanding that Banebots essentially said the issue was minor and recommended the "zapping" process.

I will add that we used a pretty well tuned PID loop to control our elevator. We did a pretty good job about handling stall though. There were several timeouts built in that would cut power to the motors after a couple seconds of stall and ensure we weren't just driving around with the motors humming.

Just our experience with them. I know others who have had success with them, and I know others who dealt with the same issues we did. It seemed to be luck of the draw this past year.

-Brando