To give a sense of the magnitude of the forces, a hub electric motor with a 12mm axle generating 40 N-m of Torque Arm china torque will exert a spreading force of just under 1000lb on each dropout. A torque arm is certainly another piece of metal attached to the axle which can have this axle torque and transfer it even more up the frame, therefore relieving the dropout itself from choosing all of the stresses.
Tighten the 1/4″ bolt between your axle plate and the arm as snug as possible. If this nut is certainly loose, in that case 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 enough time this takes place your dropout may already be damaged.
The tolerances on engine axles may differ from the nominal 10mm. The plate may slide on freely with somewhat of play, it could go on correctly snug, or sometimes a small amount of filing could be necessary for the plate to slide on. In situations where in fact the axle flats happen to be a bit narrower than 10mm and you are feeling play, it isn’t much of a concern, but you can “preload” the axle plate in a clockwise route as you tighten everything up.
Many dropouts have speedy release “lawyer lips” which come out sideways and stop the torque plate from sitting flat against the dropout. If this is actually the case, you will want to be sure to possess a washer that fits inside the lip location. We make customized “spacer ‘C’ washer” for this job, although lock washer that is included with various hub motors is often about the proper width and diameter.
For the hose-clamp unit, a small length of heat-shrink tubing over the stainless steel band can help to make the final installation look even more discrete and protect the paint job from getting scratched. We involve several bits of shrink tube with each torque arm package deal.

However, in high electric power systems that generate a lot of torque, or in setups with weak dropouts, the forces present can 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 creating the wheel to fall correct from 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. In many cases this is sufficient.