To give a feeling of the magnitude of these forces, a hub electric motor with a 12mm axle creating 40 N-m of torque will exert a spreading force of slightly below 1000lb on every single dropout. A torque arm is certainly another piece of metal attached to the axle which can consider this axle torque and transfer it further up the frame, therefore relieving the dropout itself from choosing all the stresses.
Tighten the 1/4″ bolt between your axle plate and the arm as snug as possible. If this nut is certainly loose, after that axle can rotate some amount and the bolt will slide in the slot. Though it will eventually bottom out and prevent further rotation, by enough time this occurs your dropout may currently be Torque Arm china damaged.
The tolerances on motor axles may differ from the nominal 10mm. The plate may slide on freely with a lttle bit of play, it could go on correctly snug, or sometimes a tiny amount of filing may be necessary for the plate to slide on. In conditions where in fact the axle flats are somewhat narrower than 10mm and you feel play, it isn’t much of an issue, nevertheless, you can “preload” the axle plate in a clockwise direction as you tighten everything up.
Many dropouts have speedy release “lawyer lips” which come out sideways and stop the torque plate from relaxing toned against the dropout. If this is the case, you should be sure to have a washer that fits inside the lip area. We make custom “spacer ‘C’ washer” because of this job, although lock washer that comes with many hub motors is often about the proper width and diameter.
For the hose-clamp style, a small length of heat-shrink tubing over the stainless steel band can generate the ultimate installation look more discrete and protect the paint job from getting scratched. We contain several pieces of shrink tube with each torque arm program.

However, in high electrical power devices that generate a whole lot of torque, or in setups with weak dropouts, the forces present may exceed the material durability and pry the dropout open. When that happens, the axle will spin freely, wrapping and severing off the motor cables and potentially creating the wheel to fall correct out of your bike.

In most electrical bicycle hub motors, the axle is machined with flats on either side which key in to the dropout slot and offer some way of measuring support against rotation. In many cases this is sufficient.