Four Little Motors

[Megamanx736]

we have four drive motors all CIM motors, but when we go be beyond Three Drive motors,our robot Seizes up, we started using Talon, Swapped to jaguar still the Seizing happens we have disconnected our compressor but to no anvil.
Please its getting close to the last days, Thanks in advance for any help

Are your motors going in the same direction? The seizing could be caused be two motors in the same gearbox turning opposite of each other, fighting in opposite directions. As always, a picture of the setup would be helpful for us to diagnose, but checking the direction of the motors would be one of the first things I'd suggest doing.

[CalTran]

A picture would be nice. What drive train are you running? Is the forth motor running the correct direction? Could you describe "seizing up" in some more detail?

[Grim Tuesday]

I can't exactly figure out what you're trying to say.

Are you running all the motors in the right directions? What gearbox are they in? if it's a Toughbox they have to be running in opposite directions.

[Chris is me]

Originally Posted by Grim Tuesday

Are you running all the motors in the right directions? What gearbox are they in? if it's a Toughbox they have to be running in opposite directions.

No they don't? The gears should be running in the same direction.

Remember, opposite sides of the pinion are doing work on the intermediate gear. Draw this out and you'll see what I mean.

[billbo911]

This sounds familiar. I'll guess that you are using PWMs to command the speed controls, correct?

It is possible to drive a couple speed controls via PWM w/o powering the DSC. But, once you get more than a couple PWMs going out of the DSC w/o powering it, you begin to have trouble.

Make sure you have +12vdc going the the DSC from the PDB. Then also verify that you have 3 green lights lit up on the DSC. That should do it.

[kevin.li.rit]

Originally Posted by Grim Tuesday

What gearbox are they in? if it's a Toughbox they have to be running in opposite directions.

Originally Posted by Chris is me

No they don't? The gears should be running in the same direction.

I think by "they" he was referring to the 2 toughbox gearboxes that are normally placed in opposite directions. In this case, as previously stated, it sounds like one of the 3 motors in both gearboxes is running in the wrong direction.

[Andy A.]

I suspect that at least one motor is turning the wrong way. However, we do know of at least one CIM motor this year that was clearly a manufacturing defect. It's possible there was more then one.

Removing each motor from the gearboxes and watching them spin in air would be a pretty reasonable way to check that they're all turning, and turning the correct direction.

[kevin.li.rit]

Originally Posted by Andy A.

I suspect that at least one motor is turning the wrong way. However, we do know of at least one CIM motor this year that was clearly a manufacturing defect. It's possible there was more then one.

Removing each motor from the gearboxes and watching them spin in air would be a pretty reasonable way to check that they're all turning, and turning the correct direction.

Would it be preferable to unplug all but one motor from the gearbox?

I would also check the speed controller or driverstation to see if the speed controllers are receiving all the same PWM signals for one gearbox.

[Orion.DeYoe]

Originally Posted by Megamanx736

we have four drive motors all CIM motors, but when we go be beyond Three Drive motors,our robot Seizes up, we started using Talon, Swapped to jaguar still the Seizing happens we have disconnected our compressor but to no anvil.
Please its getting close to the last days, Thanks in advance for any help

First thing I would check is that the motors are all going the correct direction (and not fighting each other). I seem to always get one motor turning the wrong way when I set up our drive base code. It takes like 5 seconds to change so I would try that first.

[thmeans06]

Make sure they each motor on your gearbox is turning the wheels in the same direction manually: one motor at a time, touch the black to back and red to red on a battery. If they are not turning the wheels in the same direction then reverse one of the polarities on your speed controller.

Also, we had a weird stalling issue with our drive train this year when we tried to move them at more than a slow turning pace (with the robot on blocks). Turned out it was caused from a bad battery.

Also, if you are using 2 motors on each gearbox, I recommend using one motor output for each side and making the PWM cable into a Y cable so you know that both motors are always being driven at the same speed.

Hope it helps.

[Andy A.]

Originally Posted by Coffeeism

Would it be preferable to unplug all but one motor from the gearbox?

I would also check the speed controller or driverstation to see if the speed controllers are receiving all the same PWM signals for one gearbox.

If I had no doubts about the CIM's this year, I'd say just disable one motor from each drive train by pulling the PWM cable and setting the controller to coast and attempt to drive. If the wheels turn the correct direction, test the other two motors the same way. If they don't turn correctly, swap motor leads or programmed commands to get things turning right, then test the other two.

The catch here is that I have a tiny sliver of doubt about the CIM motors now. The thread showing a 'seized' motor fresh out of the box details such an alarming QC issue that I still don't understand what went wrong. It's possible that other teams may have gotten a seized motor. Removing them all from the gearboxes gives you a chance to very quickly identify which motors are/aren't turning, and a chance to see if they turn by hand.

*Shrug* there are a couple ways to skin this cat. I like the 'take it apart and see each thing do a thing' approach right from the start.

[thmeans06]

Originally Posted by Andy A.

If I had no doubts about the CIM's this year, I'd say just disable one motor from each drive train by pulling the PWM cable and setting the controller to coast and attempt to drive. If the wheels turn the correct direction, test the other two motors the same way. If they don't turn correctly, swap motor leads or programmed commands to get things turning right, then test the other two.

The catch here is that I have a tiny sliver of doubt about the CIM motors now. The thread showing a 'seized' motor fresh out of the box details such an alarming QC issue that I still don't understand what went wrong. It's possible that other teams may have gotten a seized motor. Removing them all from the gearboxes gives you a chance to very quickly identify which motors are/aren't turning, and a chance to see if they turn by hand.

*Shrug* there are a couple ways to skin this cat. I like the 'take it apart and see each thing do a thing' approach right from the start.

I agree completely. We always test our motors before we ever mount them to a gear box. Then during assembly we test as we go as well. Having a simple process like that will help avoid mechanical issues... Then you get to make mean faces at your programmers when something doesn't work...