Hi,
We are using a single Falcon with a 16:1 gearbox to climb similar to IUPUI’s RI3D robot. After climbing, we are relying on the falcon’s braking mode to stay up there. However, there is a slight back drive that takes around 15-20 seconds for the robot to completely touch the ground. However, we are concerned if the back drive while the Falcon is braking causes any internal damage to the motor over a long time period. Is it safe to keep using the Falcon like this?
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TL;DR: it’s fine
Per the manual:
[Brake mode] is accomplished by essentially shorting the motor leads, which causes a Back Electromotive Force (Back-EMF) to resist the rotation of the motor.
This is an expected function of brake mode. It doesn’t resist all motion. It just slows it down, especially at higher speeds. To get a feel for this, compare pushing a robot that’s off to pushing one that’s on and has the drive motors in brake mode.
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Within reason, no it’s not an issue. The speed you’ve described of the fall for a typical FRC climb means you’re well within the intended use.
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Brake mode in a brushed motor and a brushless motor can be two different operational modes. In the brushed motor, a short is put across the motor wires essentially using the motors magnetic system to produce a force that resists turning. Brushless motors can simulate this effect with control. The description for the Sparkmax controller is that it shorts all motor wires together for brake mode and implies that is for both brushed and brushless configurations. Check your operation to confirm that the motor acts as you wish when the robot is disabled.
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I can confirm that the SparkMax brake mode behaves -exactly- like a well done short between all three phases. Merely plugging TWO Andersons together doesn’t deliver as much braking torque. Actual testing cause, enquiring minds wanna know!
Yes, this can deliver more braking torque than the rated running torque, especially if the motor is turning FAST. BUT, it only works when the motor is turning.
Yes, it heats the motor up -really- fast. All that energy is going into the resistance of the windings.
Active braking on SparkMax, where the commanded motion is the opposite direction from the actual motor rotation, is also very strong. In fact, it does not respect the current limit you set in firmware…
One could imagine some programming fun on the SparkMax where it detected that the motor was turning the wrong way or faster than desired and applied the maximum braking ability of either the “brake mode” or reverse drive. Slide into the goal anyone? 
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