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Originally Posted by zeropointbug
Simple and short, my opinion on braking.
BL motor braking: (most likely mechanics)
first: a shorted motor has incredible resistance from turning, and, the faster it spins, the more resistance it has.
- Using full motor shorting for braking would undoubtedly flip an R/C car over it's lid with ease.
- So, you need to control this shorting in order to control the motor shaft resistance, to create an average resistance or torque.
-Along came PWM... the controller sets up the FET's to unify all motor phases to create a short. So the controller will change PWM duty cycle depending on throttle position... so anywhere between say 1% to 95% (for ABS, guessing) duty cycle for proportional braking.
-These latest controllers (like the Quark) most likely have some good algorithms for braking.
This is just my simple theory on motor braking, not going into detail what happens in FET's.
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Thanks ZP. I was questioning if the motor phases, when shorted, would have enough braking force. I took a 10XL hooked to an emaxx tranny and attached a drill to the output shaft. I turned the drill on to spin the motor. The drill I used is rated for 3600rpm (assuming unloaded). Working backwards from the tranny (1.722:1) and spur/pinion (51T/14T), the motor was spinning around 23,000 rpm, which was pretty good to emulate the real-world speed of a vehicle.
Anyway, when I shorted the motor phases, the rpms of the drill dropped considerably, but didn't seem enough to support the idea that this braking force would flip a truck or provide adequate braking force for a heavier vehicle (~10lbs), let along using PWM to control the braking force, which would reduce it. That's why I was thinking that maybe the ESC was locking the rotor in a controlled fashion.
Of course, locking the rotor would probably be extremely bad for the ESC and batteries, but it was just an idea.
Also, I fully understand the theory on PWM. ;)