No excuses for not fitting a torque arm or two!

[Fordulike]

For the majority of the higher powered hub motor conversion kits, omitting to fit at least one torque arm is like wrestling daily with a crocodile. One day it'll bite you in the arse
In the past few years, I've read so many threads over on the Endless Sphere forum, where someone has face planted the deck coz they didn't fit a torque arm.
The bottom line is, ordinary pedal bike dropouts, front and rear, were never designed to resist the rotational forces that a hub motor axle exerts on them.

If you're using a powerful front hub motor, then you must use a torque arm.
Even with a rear setup, it's advisable to use at least one torque arm.
There's a few different types about, so there should be no problem finding one that fits most bikes.

I can personally vouch for Cyclezee's torque arms and I fitted two on the rear of my bike with no problems.
It gives you peace of mind that the wheel is not going to spin out of the dropout

Selection of Torque Arms

I know a few of the more seasoned kit fitters will argue the fact that you don't really need to fit torque arms if the dropouts are made of steel etc..
Call me a bit of a girl, but I've always over engineered and checked, checked and checked again when it comes to anything safety wise.
Even if I was fitting a hub motor kit to an all steel bike today, I would still fit one torque arm.
Over engineered?..... maybe.... Safe from face plants?..... definitely

 

[Cyclezee]

Hi Fordulike,

Thank you for that endorsement

 

[Deleted member 4366]

If you get a torque arm, there's a couple of important points:
1. You must get the correct size slot for your axle. 12 x 10mm for Bafang, small MXUS and Q100/Q128 motors. and 14 x 10 for Ezee and the big direct drive motors. A 12 x 10 axle will fit in a 14 x 10 torque arm, but it'll twist in it..
2. You have to anchor the tie bar properly. There's normally two pieces or more: the motor piece and one or two tie bars. The tie bars need to be at right angles to the motor piece to resist the torque. This one here is relying on the tightness of a small screw on slippery metal since the pivot point is trying to move from side to side, not up and down.



If you can, anchor the tie bar to a disc mount, which normally gives a decent angle for the tie bar. You'll probably need to drill a hole in the tie bar for which you need a 5% cobalt drill, or you can make your own tie bar out of a piece of mild steel, which drills more easily.



Home-made tie bar:



If you're lucky, you can drill your frame and not need the tie bar.

And finally, one piece torque arms don't have the problem with the pivot:

 

[eHomer]

I took Dave's advice with my torque arms.

When I fitted the MXUS cassette motor to the rear of my Giant Trance, I shortened the BMS torque arm link plate and put two bends in it to fix it to the nearest disc brake mounting point.




..and when I fitted the Q100H front motor to my Alubike, I found that the standard BMS torque arm lined up perfectly with the mudguard mounting lug cast into the forks, giving a very neat installation.