pic: Did Somebody Say Defense Game?

[wilsonmw04]

Originally Posted by Infinity2718

Correct, current = torque. So by adding a 3rd motor to each gearbox you reduce the load on the 40amp breakers while the load on the main breaker will remain the same for the same torque, regardless of motor count.

so adding three motors doesn't increase torque? interesting.

[MooreteP]

Mad Crazy Drivetrain.

IMHO, this may be the year that Mecanums make it to Einstein.

A defensive Robot that can strafe in the Goalie zone or between two robots passing is more akin to defensive play in Hockey, Soccer, and Basketball.

Pushing or preventing is another issue, but that may not be the key to defense in Aerial Assist.

[JamesCH95]

Originally Posted by wilsonmw04

so adding three motors doesn't increase torque? interesting.

Adding an extra motor per side does increase the theoretical maximum available torque. However, traction limitations and battery limitations do not allow that torque to be fully utilized.

[Deke]

Originally Posted by JamesCH95

Adding an extra motor per side does increase the theoretical maximum available torque. However, traction limitations and battery limitations do not allow that torque to be fully utilized.

Correct, you would have to be able to feed the motor the extra current to increase the torque. So basically you increase the system stall torque by increasing motors, but can you feed it the extra current?

If two drivetrains exactly the same in traction, weight, gear ratios were in a push off/breaker cook race and the only difference is the motor count (lets say a 4 cim versus a 6 cim), the 4 cim drivetrain will pop its breakers faster. The 6 cims will have less current going through the individual 40a breakers (total flow divided by 6 instead of 4), and slightly less through the main breaker (because they should be running at a slightly higher efficiency).

My assumption why people pop breakers with 6 cims faster than 4 cims is because they think they can push while geared high, when really both systems are limited by their breakers. So you would need the correct gearing in either case to be a good pushing robot.

[JamesCH95]

I think that a brown-out and re-set of the cRIO is a very likely drivetrain induced failure. Not just the breakers blowing. I don't know which one, 6cim or 4cim, would be more likely to trigger a brown-out, though I think a brown-out or low-voltage reset is much more likely than blowing a main breaker.

Full disclosure: I have not a lot of experience blowing 40A breakers, or main breakers for that matter. I've always geared transmissions on robots a little conservatively, prioritizing robustness over ultimate performance. One robot team 95 made had issues with that, a full 4-wheel swerve in 2003, that could drain a battery down to the point of brown-out half-way through a match.

[magnets]

Originally Posted by wilsonmw04

so adding three motors doesn't increase torque? interesting.

There's a limited amount of pushing force that you can have before the wheels start slipping. So if you have two CIMs geared really slow, or 15 CIMs geared really slow, once the wheels slip, you won't see any difference. However, with more CIMs, your traction limited speed will be faster, which is useful for playing defense. If you've got a crazy high traction robot that moves really slowly, it'll be hard to catch up to somebody.

[Deke]

Originally Posted by magnets

However, with more CIMs, your traction limited speed will be faster

Can you explain this one, I don't fully understand.

[magnets]

Originally Posted by Infinity2718

Can you explain this one, I don't fully understand.

in order to get to traction limited, no matter how many CIMs you have, you need a certain amount of torque at the wheels. Let's just say for my robot, it's 16 times the torque I can get directly, with no gear reduction from a single CIM motor. So, I would have a 16:1 gear reduction with a single CIM to be traction limited.

If I had two CIMs, I would need to have 16 times the torque from one CIM, or because their torque adds together, I would need 8 times the torque from two CIMs. So, I would put these two CIMs in an 8:1 gear reduction.

The second, 8:1 gear reduction with 2 CIMs will have the same amount of torque at the wheels (16 times the torque directly from a CIM) as the 16:1 with a single CIM, but the 8:1 will go twice as fast.

What you said in your previous post was correct, you need proper gearing to take advantage of your motors.

[Deke]

Originally Posted by magnets

in order to get to traction limited, no matter how many CIMs you have, you need a certain amount of torque at the wheels. Let's just say for my robot, it's 16 times the torque I can get directly, with no gear reduction from a single CIM motor. So, I would have a 16:1 gear reduction with a single CIM to be traction limited.

If I had two CIMs, I would need to have 16 times the torque from one CIM, or because their torque adds together, I would need 8 times the torque from two CIMs. So, I would put these two CIMs in an 8:1 gear reduction.

The second, 8:1 gear reduction with 2 CIMs will have the same amount of torque at the wheels (16 times the torque directly from a CIM) as the 16:1 with a single CIM, but the 8:1 will go twice as fast.

What you said in your previous post was correct, you need proper gearing to take advantage of your motors.

Excellent, thank you! A more visual explanation helps me, I miss things when I cant visualize them.