[theprgramerdude]

Originally Posted by artdutra04

2.5" CIM motors, followed closely by the Banebot RS775-18. While much praise has already been espoused about the versatility and durability of the CIM motors, we've found that the Banebot RS775-18 motors are close runners up. Unlike the other BB motors, the RS775's are champs and won't give up the ghost just because you told them to run at stall for a few seconds. During testing, we learned they'll trip out the Jaguars or circuit breakers long before they'll suffer any harm.

Putting 8 CIMs in a FRC drivetrain won't really accomplish anything other than to deplete one's battery faster. This is because of the major difference between your example of cars and FRC robots: Most FRC robots are traction limited, while cars are usually torque limited. Adding more powerful engines to cars yields better results because torque-limited cars have a large capacity void between what the stock engine puts out and the maximum power than can be utilized by the wheels to make the car go.

On the other hand, adding more power to an FRC drivetrain may actually lower a team's effective pushing power, as dynamic friction is almost always lower than static friction. (Think back to Lunacy). Thus, by having more motors in a drivetrain, they will increase the odds that the motors will be able to overcome the maximum static friction with the ground and start spinning their wheels, thus lowering their ability to push other robots.

Now even if they can overcome the traction limitations, they still have to deal with the relatively small field size. How likely is it that robots will have the room to accelerate to speeds beyond the top speeds of 15-16 ft/sec already seen on many FRC robots? Why do you think teams don't currently use three or four speed gearboxes that can theoretically take their robot to 20, 25, or 30 ft/sec? It's because the field is small enough such that gearing for that speed would never be useful.

Don't forget the huge voltage drop that can occur if the CIM's change their input voltage to fast; it's pretty easy as-is with 4 CIM's to brown out the system if you go from stop to full power. With 8, or even 6, the current limit starts to become a major factor too.