To give a sense of the magnitude of the 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 a separate piece of metal mounted on the axle which can take this axle torque and transfer it further up the frame, therefore relieving the dropout itself from choosing each 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, after that axle can rotate some sum and the bolt will slide in the slot. Though it will eventually bottom out and prevent further rotation, by the time this takes place your dropout may already be damaged.
The tolerances on engine axles can vary from the nominal 10mm. The plate may slide on freely with a bit of play, it could go on correctly snug, or occasionally a tiny amount of filing could be essential for the plate to slide on. In scenarios where 
in fact the axle flats are a lttle bit narrower than 10mm and you are feeling play, it isn’t much of a concern, nevertheless, you can “preload” the axle plate in a clockwise course as you tighten everything up.
Many dropouts have quick release “lawyer lips” which come out sideways and stop the torque plate from sitting toned against the dropout. If this is actually the case, you will want to be sure to get a washer that meets inside the lip area. We make custom “spacer ‘C’ washer” because of this job, although lock washer that is included with a large number of hub motors can often be about the right width and diameter.
For the hose-clamp unit, a small amount of heat-shrink tubing over the stainless band can generate the ultimate installation look even more discrete and protect the paint job from getting scratched. We consist of several bits 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 can Torque Arm china exceed the material strength and pry the dropout open. When that occurs, the axle will spin freely, wrapping and severing off the motor cables and potentially creating the wheel to fall correct out of the bike.
In most electric 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. Oftentimes this is sufficient.