VersaPlanetary Friction Clutch

[wmarshall11]

VexPro/WCP's new 775pro is wildly cool. However, packing 143W into the 775 form factor seems to have come at a price, namely the allowable stall time. According to Vex's data, the 775pro burns up after ~3.9s of stall at 12V, which is faster than the other FRC legal 775 form factor motors.

One approach to avoiding stalls is a torque-limiting clutch. I designed a clutch that replaces a single stage of VersaPlanetary gearing and helps to mitigate stalls in theory. It uses a neodymium magnet and two aluminum friction plates to transmit torque through a friction interface that is sealed off from the rest of the gearbox using an O-Ring.

This design has not been verified using anything other than some back-of-envelope calculations involving the clamping force of the magnet and the friction coefficients of the plates, but should be an okay starting point for anyone deciding they want this functionality.

Imgur Album

"Pack and Go"ed Assembly

Rough BOM:
1 x 10:1 VersaPlanetary Ring Gear Kit
1 x 3/4"ODx1/4"IDx1/4"TH Ring Magnet, axially polarized, such as this
1 x Dash 123 O-Ring
1 x Custom cast Transmitting Plate
1 x Custom cast Recieving Plate