To give a sense of the magnitude of the forces, a hub engine with a 12mm axle producing 40 N-m of Torque Arm china torque will exert a spreading force of slightly below 1000lb on every single dropout. A torque arm can be another piece of metal attached to the axle which can consider this axle torque and transfer it further up the frame, thus relieving the dropout itself from currently taking all of the stresses.
Tighten the 1/4″ bolt between the axle plate and the arm as snug as possible. If this nut is usually loose, then axle can rotate some volume and the bolt will slide in the slot. Though it is going to bottom out and stop further rotation, by the time this takes place your dropout may previously be damaged.
The tolerances on motor axles may differ from the nominal 10mm. The plate may slide on freely with a bit of play, it may go on perfectly snug, or in some instances a little amount of filing could be necessary for the plate to slide on. In situations where the axle flats will be a little narrower than 10mm and you are feeling play, it is not much of a concern, nevertheless, you can “preload” the axle plate in a clockwise path as you tighten everything up.
Many dropouts have quick release “lawyer lips” that come out sideways and stop the torque plate from relaxing toned against the dropout. If this is actually the case, you should be sure to possess a washer that suits inside the lip place. We make custom “spacer ‘C’ washer” for this job, though the lock washer that is included with various hub motors can often be about the proper width and diameter.
For the hose-clamp model, a small length of heat-shrink tubing over the stainless steel band can make the ultimate installation look even more discrete and protect the paint job from getting scratched. We include several bits of shrink tube with each torque arm offer.

However, in high vitality systems that generate a whole lot of torque, or in setups with weak dropouts, the forces present may exceed the material strength and pry the dropout open. When that occurs, the axle will spin freely, wrapping and severing off the engine cables and potentially triggering the wheel to fall proper out of your bike.

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