Thread: Cim breakers tripping?
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Unread 28-03-2008, 12:33
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M. Mellott M. Mellott is offline
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AKA: Mike Mellott
FRC #3193 (Falco Tech), FRC #48 (Delphi E.L.I.T.E.), FTC #9980 (FMF)
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Re: Cim breakers tripping?
When we changed out the final pair of gears in our transmissions to increase our speed, we had issues with the breakers popping on our right-side gearbox CIM motors, and it did seem to happen more frequently as the playoffs progressed. Running 4" wheels (4.5" with the tread), we also noticed that the right-side motors were running hotter than those on the left. We analyzed the issue, and after testing showed us the issue was not in the servo-shifters and was in fact the breakers, we came up with several correctable fixes:
  1. Frictional losses: upon inspection, we noticed more "slop" in the spacing of the gears in the problem gearbox, which allowed the gears to potentially rub. We disassembled the gearbox and added shims to tighten up the gear spacing. We also notice the bearing support of the direct-drive output axle was not as firm as we would have liked. A space was designed in for an additional roller bearing at the inner wheel support and the , but it wasn't installed due to redundancy. Despite the rule-of-thumb (do not support a shaft at more than 2 points due to potential binding), we added the bearing to better support the drive shaft. These changes added up to an improved drive train.
  2. Driving style: our driver was used to running both joysticks full forward (tank steering) down the straight-aways, then throwing both stick backward for a half-second to power brake. We believe this jacked up the amps with the backdriving (brief as it was) and helped to incur the breakers popping. We had him concentrate on his approach to each corner, driving smoother through the corner, and less "back-braking".
  3. Motor temperature: despite a reduction in the drive motor temp after matches with the other changes, we added the use of a clip-on fan aimed directly at the drive motors as a precaution (better safe than sorry) to help cool the motors between matches. If possible, get one that's battery-powered--always safer when there's no cords to get tangled, and a power strip may not be available to plug into during the playoffs.
Perhaps one or more of these ideas could help with your situation.
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