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 normally another piece of metal attached to the axle that may consider this axle torque and transfer it further up the frame, thus relieving the dropout itself from bringing all of the stresses.
Tighten the 1/4″ bolt between the axle plate and the arm as snug as possible. If this nut is normally loose, then axle can rotate some quantity and the bolt will slide in the slot. Though it is going to bottom out preventing further rotation, by enough time this occurs your dropout may previously 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 tiny amount of filing may be essential for the plate to slide on. In conditions where in fact the axle flats are a bit narrower than 10mm and you are feeling play, it isn’t much of an issue, nevertheless, you can “preload” the axle plate in a clockwise way as you tighten everything up.
Many dropouts have speedy release “lawyer lips” which come out sideways and prevent the torque plate from sitting down Torque Arm china smooth against the dropout. If this is actually the case, you should be sure to get a washer that suits inside the lip place. We make customized “spacer ‘C’ washer” for this job, although lock washer that is included with a large number of hub motors is often about the right 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 more discrete and protect the paint job from getting scratched. We contain several bits of shrink tube with each torque arm offer.
However, in high electricity systems that generate a lot of torque, or in setups with weak dropouts, the forces present can 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 leading to the wheel to fall right from the 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. Oftentimes this is sufficient.