Thanks @Jodel ill have a read throughOn the 'Endless Sphere' web-site, torque arms have been / are discussed to quite a depth. If you want to gain additional knowledge, have a look at these threads:
Dropout Failure Experiments, and a call for Fork Donations
The strength of bicycle forks, their ability to handle the torque of hub motor axles, and the importance or non-importance of torque arms, has been a heavily debated topic in the ebike community. And rightly so, since failures that result in a wheel falling out of a vehicle can be more than a...endless-sphere.com2018 Torque Arm Tests, Splined Interface Design and Tabbed Washers
In some sense this is a decades old follow up to our initial torque arm experiments from this thread https://endless-sphere.com/forums/viewtopic.php?p=211356#p211356 The standard for imported ebike hubs back then was M12 or M14 axles that were ground flat to 10mm in order to use the dropout...endless-sphere.com