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Unread 03-05-2012, 10:31
Thad House Thad House is offline
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Re: Dual CIMs and #25 Chain

Quote:
Originally Posted by Dad1279 View Post
Explain the drive being jumpy?

For demos, you could switch to a less grippy wheel, so the drivetrain won't be stressed.

I don't believe you want to drive two motors that are connected together with different values. That will stress the driven motor more. We also had a situation where we tried to calibrate one of the victors on a drivetrain with the other disconnected, and blew out the disconnected victor, but I'm not sure that's related, but given the price of victors it's an experiment I don't want to repeat.

If you really want to try driving just one motor, I would either drive the second at a 'reduced' PWM value so it will be coasting, or make sure the brake jumper is not set on the coasting motor.

Can you post a picture of the chassis? Is it possible with the cantilevered axles there is flexing that is causing the mis-alignment? Are the chains near the frame, or on the other side of the frame/bearings?
The jumpiness is when we go to move, the robot lurches forward and sometimes the front wheels come off of the ground. Also when reversing directions the robot almost always goes onto the 2 back wheels.

When in the 1 CIM mode, the other CIM is set to coast mode via CAN, and receives a 0 output. so it is just freespinning.

We have a pillow block in the middle with a bearing on both sides. There is 2 inches of axle coming out of both sides. On 1 side is the wheel, and the other side are the 3 sprockets. The sprocket connected to the transmission is the one closest to the bearing, with the sprocket actually touching the bearing.

The only time it could become misaligned is if the transmission bend and torque down, which would move the output shaft slightly.

And the reason we are thinking 1 CIM vs 2 is that last year we used the exact same drive setup except only 1 CIM per side, and never had any issues at all. As driver I loved the 2 CIMs per side, but the chain breaking caused so many issues that i want to figure out what caused it. And everyone on my team is thinking overtorqueing the chain.
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