New member with torque arm question

[BillysMagicBikeShanty]

Hi, posting this to become a confirmed member. My question is, besides hose clamps, are there any torque arms which secure directly into fork and frame fender bosses? Thanks!

[Bikemad]

Hi andto the forum.

ebikes.ca produce a torque arm that is designed to use existing eyelet mounts on either the rear frame or the front fork.

Check out the TorqArm V5 on their website or watch the YouTube video here.

You can even download a full scale drawing to enable you to print and cut out the pieces to test the fit on your bike before purchasing.

I think the V6 or V7 TorqArms would be a much better choice as they transfer the torsional force much further away from the dropouts, which should greatly reduce any chance of the dropout breaking due to metal fatigue from the bidirectional axle torque being constantly applied directly to it during both power and regen, which the dropouts were never designed to withstand. 

Alan
 

[BillysMagicBikeShanty]

Thanks Alan!

[e-lmer]

Alternately you can make a custom one that fits over the nut,
then bends around to screw to the fender mounting holes.

I used a Dremel to cut through the hex shape, then a chisel to
bend the resulting triangles up and around the nut hatch.

I have attached a drawing, but I may be able to attach
a photo next time.

[Bikemad]

Elmer,
What you have proposed is basically a locking tab/plate for the axle nut, but this will not directly resist any torque from the axle itself.

A torque arm is used to resist axle movement by acting directly upon the flats of the axle and preventing it from rotating in either direction (under power and under regen).

Simply locking the axle nuts in relation to the dropouts is unlikely to prevent rotational movement of the axle itself, and therefore should not be used instead of suitable torque arms.
I don't see a problem with using your nut locking tabs/plates in addition to torque arms if you are concerned about the axle nuts working loose over time.

If the axle nuts were able to be torqued up tight enough to prevent the axle from rotating (without stripping the threads), the nuts should not require locking tabs as they could not work loose over time if there was no rotational movement of the axle.

Alan
 

[e-lmer]

Hi Alan.  You are correct except the axle spinning is not the root cause.  The problem is the repeated accelerate/decelerate cycle listen the nut. This not only allows the axle to spin, but eventually drop out.  Keeping the nut captive and tight has eliminated this risk. 
Have you seen this:

https://www.reddit.com/r/ebikes/comments/ucjgnr/diy_torque_arm/

[Bikemad]

Have you seen this:
https://www.reddit.com/r/ebikes/comments/ucjgnr/diy_torque_arm/

A spanner can make a crude but effective torque arm when secured properly, unfortunately the one in that photo would not be very effective if regen were used, as the axle would simply twist the spanner away from the bolt being used as a stop.

Of all the torque arms I have seen, I think these are the best torque arms currently available for hubmotors with 14mm solid axles:



Click on the above picture, or watch the excellent video here for further information.

However, with a price tag of $55 (USD) this quality item isn't cheap.

Alan