How Often are Torque Arms / Axle Flats Used? Need SWXK Help

If the axle nuts on a hub motor wheel are properly torqued, will the axle ever rotate enough to make physical contact with the flats in a dropout or torque arm?

Don't get me wrong, I'm not anti-TA, just trying to figure out if they're more for insurance if they get used every ride.

I have a SWXK front hub which has a terrible axle design in which the axle flats are only on the first few mm of the axle sticking of the motor housing. This makes it hard to add washers because then you're reducing the amount of engagement between the axle flats and dropouts. Also, because of the way the housing is designed, a torque arm can only be used on one side, and the thick TA pushes the wheel off-center. If I add washers on the opposite side to center the wheel, the axle flat is not engaged with the dropout at all.

You guys think that this is a problem or should I be OK? I run the motor up to about 850w. Steel front fork.

I have never used torque arms and never had a problem. BUT, I've never used a bike with aluminum dropouts. Nor would I ever buy one to put a motor on. If I had to put a motor in aluminum dropouts, I'd use some kind of torque plate bolted to the frame or dropout instead of torque arms. I DO use torque washers on both sides of the axle and I get the axle nuts very tight. It's a good idea to check the axle nuts often, especially if you feel/hear anything unusual when taking off. So, with aluminum dropouts, torque arms/plates should be considered required. For steel dropouts consider them insurance as long as you have torque washers and have installed the wheel properly with tight axle nuts.

I use a 1000 watt PLUS modded front hubmotor mounted on a steel front fork with wesnewells dual nuts, one inside and one outside, and a 1/4 inch torgue plate.
I do not want to have the front wheel falling off due to spreading the end of the fork.
Post picture of your partial flat front axle.

I should have paid more attention to his post. I've only done one front motor, in a trike, and it was only 500W, and the dropouts where deep enough so the torque washers fit in the slot. Didn't have a problem with it either, but didn't have it long since my wife, who can't ride a regular bike, wouldn't ride it either. She can't chew gum and walk either.

Depends on how much torque you are pushing, which loosely correlates to watts.

That's not a particularly strong motor, but because the axle flats are particularly weak on the axle... i'd personally be using at least one torque arm.

You should be able to also get away with using nordlock nuts, bolted down tight though.

You're right. You can't use torque arms on that motor, so no point in discussing whether you should or shouldn't.

Whether it's OK or not depends on your forks and how well it fits. If it's an OEM bike, just be sure that you make the nuts nice and tight. If it's a conversion, there's some complications that you have to be aware of.

The most important thing is that the washer on the outside of the drop-out sits properly in any dimple without touching it, otherwise your can break your drop-outs when you tighten the nuts without ever firing up your motor. You should be OK in that respect because your axle is only 10 mm. Other motors have 12mm or 14mm diameter with two flats milled to go in the drop-outs. The larger diameter shifts the centre down. Anyway, just check that washer sits nicely.

After that, it's just a question of whether there's enough meat around your drop-out. Every fork is different, so it's not possible to comment further without seeing them.

There's literally millions of OEM bikes all over the world using 250w front hub-motors in aluminium forks without torque arms.You can see them in any ebike shops. The basic concept is strong enough if everything is done properly.

You might seriously look into welding some material to the forks if they are not already very thick and strong. Double their thickness, and they won't bend as easy, when the axle flat that does bear starts cranking on it.

Or possibly weld some material to the inside of the droput, then file down to a very very very snug fit.

And of course, keep those nuts tight. Nut pressure alone is plenty to resist the rotation, till it gets loose somehow. The suggestion to beef up the dropout was aimed mostly at preventing any distortion that could result in a loosening nut.

Thanks for the responses guys. Based on what you said I tried riding it with the TA on one side and no axle flat engagement on the other side and had no problems on my 22 mile test ride. I got the torque arm for this motor from Bike Swift (https://www.bikeswift.com), so it is possible to use one, but only on one side as the other side's axle flat sits in a recessed area, see pics below. Poor design, IMO.

My original question was more theoretical. If the axle nuts never become loose, the torque arm or axle flat is never really "used", correct? In other words, the flats (between axle and TA or between axle and dropout) never really exert a force on one another unless the axle nuts are loosened, right? I think this is correct, and in that case I will just periodically check the nuts (especially the one on the non-TA side) to make sure they're tight.