Did I read <R32> Correctly? Six CIMs?

[DonRotolo]

It seems we can now use six CIMs, or am I reading something incorrectly?

The only motors and actuators permitted on 2013 FRC ROBOTS include the following:
Table 4-1: Legal Motors

Motor Name Part Numbers Available Max Qty Allowed
CIM        FR801-001                   6
           M4-R0062-12
           AM802-001A
<snip>

[Gregor]

Originally Posted by DonRotolo

It seems we can now use six CIMs, or am I reading something incorrectly?

Yes, 6 CIMs and up to 4 of the smaller CIM motors, an example of each is found in the black VexPro box accompanying your tote in the KoP.

[Jim Wilks]

I had trouble believing that as well. Awesome!

[Steven Donow]

Unless there was a typo, and until an update comes out, there are 6 CIMs usable, as well as 4 Bag CIMs or MiniCIMs!

[Al Skierkiewicz]

Please read the blue box following the motor list very carefully. Running many high current motors is a risky choice. CIM motors stall at 133 amps.

[cadandcookies]

Originally Posted by Al Skierkiewicz

Please read the blue box following the motor list very carefully. Running many high current motors is a risky choice. CIM motors stall at 133 amps.

Some testing may be in order...

[cgmv123]

Originally Posted by Al Skierkiewicz

Please read the blue box following the motor list very carefully. Running many high current motors is a risky choice. CIM motors stall at 133 amps.

17.2/(133*6) = 0.0215538847117794 hours or 1.293233082706767 minutes or 77.59398496240602 seconds. (You're welcome to dispute my math.)

And that's not including any of the 24 other motors you're allowed to use.

[Raul]

Originally Posted by Al Skierkiewicz

Please read the blue box following the motor list very carefully. Running many high current motors is a risky choice. CIM motors stall at 133 amps.

It is not that simple.
For example, 6 CIM motors on the drive train gives you more torque at your disposal, thus reducing the risk of stalling them. Each team has to do the math to determine what it optimal for their design.

[DampRobot]

For Al (and all you electrician magician), does appying the same torque to two CIMs or three CIMs draw more current? Although three CIMs would distribute the current over more breakers, I suspect they would draw more current over all. If teams are going to be traction limited in low gear anyway, is it worth it to go with three CIMs in the drive?

[Racer26]

My suspicion: You'll see a bunch of designed-for-6 motor drives, with 4 motors populated by the competition as teams need the weight and energy elsewhere .

[Anupam Goli]

I'm suspecting that Banebots' 256:1 CIM gearboxes may become popular in a day or two.

[Nemo]

I have an earnest desire to estimate how much our battery's voltage will drop as a result of a given amount of demand by the motors. How does one do that?

[martin417]

Originally Posted by Al Skierkiewicz

Please read the blue box following the motor list very carefully. Running many high current motors is a risky choice. CIM motors stall at 133 amps.

CIM motors stall at at 133 amps, PROVIDED that the battery can provide 133 amps. We discovered in 2010, when we had two CIMs and one FP in each transmission, that under load, the battery sags way down, and cannot provide more than about 95 amps. With a fully charged, brand new battery, we could, on very rare occasions, blow the breaker, but once a battery had a few charge/discharge cycles, it wouldn't provide enough current to blow the breaker, even with all drive motors stalled. We actually got more torque by removing the FP from the drivetrain because the battery didn't sag as much.

[apalrd]

Originally Posted by Wing

I'm suspecting that Banebots' 256:1 CIM gearboxes may become popular in a day or two.

I suspect there would be many destroyed 256:1 CIM gearboxes if that was true. The stall torque at the end of the gearbox would be ~560 newton meters.

[Trent B]

Originally Posted by apalrd

I suspect there would be many destroyed 256:1 CIM gearboxes if that was true. The stall torque at the end of the gearbox would be ~560 newton meters.

Not to mention Banebots puts a max torque spec of 85 lb-ft or 115.2 N-m of torque on their P80 gearboxes.

As for the 2 vs 3 CIM Motors, correct me if I am wrong, but based off of this http://content.vexrobotics.com/docs/...otor-specs.pdf

2 Motors at 300oz-in each will draw about 115 amps a piece. 230 amps total.
3 Motors at 200oz-in each will draw about 75 amps a piece for 225 amps total.

Because the curves are linear, total current draw shouldn't matter on number of motors. However, the motors will be rotating faster on the 3 motor setup at ~2200rpm compared to around ~700rpm because each motor has to put out less torque.