Back Driving a Versa planetary gearbox

[Drew_trak]

Does anyone know the amount of force it would take to back drive a Versa planetary gearbox 100:1 attached to a MiniCim? Thanks!

[piersklein]

Are you running current through the motor?

[Drew_trak]

Yes - u have any advice on how much?

[asid61]

Download the JVN calculator, go to the "Rotary mechanism" tab and input your stuff there if you haven't already.
A minicim has a stall torque of 12.4 in*lbs, so on a 100:1 reduction that's about 1240 in*lbs (minus efficiency losses). I personally don't like running motors with current for extended periods of time except on the drivetrain, and even then not really. I would try to get maybe a quarter of that stall torque max, but I have no basis other than experience for that recommendation. If you wanted to figure out exactly how long you can put a current on a motor, Vex has graphs for motor power and heating.

[Joe Johnson]

Originally Posted by Drew_trak

Does anyone know the amount of force it would take to back drive a Versa planetary gearbox 100:1 attached to a MiniCim? Thanks!

Not sure what you are getting at. Are you asking, are you asking how much torque it would take to backdrive the MiniCIM through the 100:1 Versa Planetary when the robot is disabled?

For example you might be trying to winch your robot up and then not have anything other than the motor's cogging torque to keep the robot from falling?

If this is the case, I urge you to think again. My experience is that without something more than this you will have a difficult time preventing the system from backdriving. It is the kind of thing you can get to work... ...almost but that you'll be sorry about in the end.

It is not that hard to make a latch or a catch that prevents backdriving.

Dr. Joe J.

[Ty Tremblay]

The root of the issue here is that you're running a mini cim through a 100:1 planetary, which is not recommended by VEXpro.
http://link.vex.com/vexpro/pdf/Versa...ry-LoadRatings

[asid61]

Originally Posted by Ty Tremblay

The root of the issue here is that you're running a mini cim through a 100:1 planetary, which is not recommended by VEXpro.
http://link.vex.com/vexpro/pdf/Versa...ry-LoadRatings

It only means that you can't stall the minicim without breaking the VP. You can still run them together.

[kitare102]

Originally Posted by Ty Tremblay

The root of the issue here is that you're running a mini cim through a 100:1 planetary, which is not recommended by VEXpro.
http://link.vex.com/vexpro/pdf/Versa...ry-LoadRatings

Look in the 3-stage section of the simple load ratings charts. Using more structurally stable stages, VEX greenlights gearing a miniCIM up to 108:1, so you can still use a legitimate configuration to reach that 100:1 reduction. That's what we'll likely be doing for one of our manipulators.