Originally Posted by
Rick
Quote:
I just realized that I can offer a little advice on this subject. It just so happens I'm currently servicing an old Counterpoint semi-recumbent tandem for a friend. One of her relatives installed an electric front 20" wheel, which quickly bent, rotated and twised the fork blades and dropouts.
There is a lack of pertinent info in your advice. There are some reasons that this could happen. The main one that happens to come to mind. is due to poor fitment of the hub motor axle it was allowed to spin in the fork and twist the power cable and pull itself from the fork. poor fitment of hub motor axles is common. Most front hub motor axles are 12mm diameter with 10mm flats ground in them. There usually needs to be some filing of the openings in the stays so the axles will fit. The smaller hub motors use the stay opening with a type of tabbed washer as the torque arm. If the axle bolts work loose or the filing is not done properly or both. The force can cause the opening in the stays to spread and the axle to rotate. The power going through the motor can be excessive enough for this to be a problem. Even with a torque arm that mounts off of the axle and straps to the fork. Careful attention needs to be made to assure everything fits, is properly tightened and there are no signs of the fork blades spreading or the flats rounding. The Grin All Axle Hub Motor Is made so there is no spreading force on the fork blades. There is a 20mm hole through the axle which you use the axle end caps that match your setup. 9mm quick release is what I will use. You can go to the info page I posted in a previous post in this thread. I believe that the torque created by the system I am building is less than the hard breaking of my disk brakes. The direct drive motor will be setup with regen also.
Unless I was running a motor with low torque and knew the capability of the dropouts to resist torque, I would not rely on the dropout or the little tabbed washer to provide torque relief. Grin, as well as others, sell several different torque arms. I see them as cheap insurance as I am sure LV2TNDM's friend now knows. (Picture below of my set up, I used a section of old radiator hose to protect the paint). (The Grin all axel motor has a superior design for torque mitigation (IMHO).)
Also, you state:
Originally Posted by
Rick
I believe that the torque created by the system I am building is less than the hard breaking of my disk brakes.
The torque resulting from the disc brakes are between the tire/rim and the hub flange. The torque resulting from the motor is between the tire/rim and axle. You won't be able twist the axle and spread the drop outs via the disc unless the brake calipers were attached directly to the axle.
