Front Torque Arm Installation Feedback.

Look up :) the video doesn't work. And why bother posting the video when the first sentence of my first post already did that. In one sentence.
Because "lawyer lips" isn't confusing enough. If you search the failed video(I edited), you will see why I posted it for the OP.
 
Yeah I read it. I've seen them slide down. On my own miserable failure of a first bike build, and repeatedly over on the DIY FB groups where there are plenty of boneheads who don't do careful work.

This illustration is similar to the one on the Grin page but its different enough to make the issue easier to grasp.

The chief difference is the direction of torque on the axle. The arrow shows it acts on the torque arm down and forward. Using the lever that is the axle-mounted arm, That lever is pulling straight down on that blade-attached torque arm. When it fails, (i.e. the dropout snaps) the unrestricted torque of the motor pulls that blade mounted arm straight down. Especially if its loosely attached as you say. But since many forks have decreasing diameters leading down to the dropouts, even a tight fit can give way with a hard tug.

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The Grin V3 arm addressed this weakness in design by giving the blade-mounted arm two or even three different locking points. But its the wrong tool for the job for the OP's situation.

View attachment 93981
I think I understand what you are trying to say.
However if you notice in the pic of the broken dropouts, the torque arm piece that holds the axle, is NOT rounded or distorted in any way, which to me means the material of the fork simply broke due to excessive weight or other factors unrelated to torque ! Could be that the fork is aluminum, which is a no no when using front wheel motors.
 
Are you saying that your front wheel shot straight down and off of the axle???
There are so many issues with that scenario, first being your axle nuts must have been barley on and you must have been doing some sort of wheelie with a front motor??? It's to confusing to contemplate.
Keeping the wheel on the axle is a side benefit, but not the major purpose of a torque arm, which is to prevent axle rotation IN the drop out, which is what causes the drop outs to shear away from the fork , as shown in your pic.
No :) . The torque arm allowed enough fudge (fit on a quality piece should be tight and precise) that the axle was able to move when it shouldn't - again a common feature of these pot-metal cheapie arms. I had a fairly powerful motor on as I said. The dropouts spread (not a snap). The now-released axle spun. A spinning axle with that axle arm still attached pulled straight down on the blade arm and that whole arm shot straight down until the dropout arrested the hose clamp that was still intact. Exactly like in the picture I posted of the other guy's fork from today's latest catastrophe.

On an unrelated note: as the axle arm spun, it wrapped the motor cord that WAS running up the fork around the other side of the axle. Luckily it just released from the plug and no damage.
I think I understand what you are trying to say.
However if you notice in the pic of the broken dropouts, the torque arm piece that holds the axle, is NOT rounded or distorted in any way, which to me means the material of the fork simply broke due to excessive weight or other factors unrelated to torque ! Could be that the fork is aluminum, which is a no no when using front wheel motors.
Look at the pic more closely. It may not be so obvious because I sized the pic so open it up in a new window. Look closely at the dropout's internal profile. The builder hasn't copped to it last I checked, but I think its pretty clear he filed the dropouts to match the axle profile and this guaranteed failure. As I said when I posted that picture, "there are other reasons this setup failed" but I posted the pic to display how the arms slip down when they are pulled upon.

Worth mentioning @hulk is to be commended for taking the step of doing torque arms in the first place, and to ask whether he got it right. I'll say again this low torque motor can live with one of these torque arms put on properly on the non-drive side (assuming its fit to the axle is *snug* with zero play). I would only change the parts on the drive side, and that is assuming he can't get the one he has to work once the brakes get mounted, since it should go behind not forward of the fork blade. The alternate parts I mentioned will work around the brake calipers being there once installed.
 
No :) . The torque arm allowed enough fudge (fit on a quality piece should be tight and precise) that the axle was able to move when it shouldn't - again a common feature of these pot-metal cheapie arms. I had a fairly powerful motor on as I said. The dropouts spread (not a snap). The now-released axle spun. A spinning axle with that axle arm still attached pulled straight down on the blade arm and that whole arm shot straight down until the dropout arrested the hose clamp that was still intact. Exactly like in the picture I posted of the other guy's fork from today's latest catastrophe.

On an unrelated note: as the axle arm spun, it wrapped the motor cord that WAS running up the fork around the other side of the axle. Luckily it just released from the plug and no damage.

Look at the pic more closely. It may not be so obvious because I sized the pic so open it up in a new window. Look closely at the dropout's internal profile. The builder hasn't copped to it last I checked, but I think its pretty clear he filed the dropouts to match the axle profile and this guaranteed failure. As I said when I posted that picture, "there are other reasons this setup failed" but I posted the pic to display how the arms slip down when they are pulled upon.

Worth mentioning @hulk is to be commended for taking the step of doing torque arms in the first place, and to ask whether he got it right. I'll say again this low torque motor can live with one of these torque arms put on properly on the non-drive side (assuming its fit to the axle is *snug* with zero play). I would only change the parts on the drive side, and that is assuming he can't get the one he has to work once the brakes get mounted, since it should go behind not forward of the fork blade. The alternate parts I mentioned will work around the brake calipers being there once installed.
Two points, where is the "drive side" on the front fork?
Are you suggesting that he only needs ONE torque arm on a front install?
Because that would be a reckless suggestion, serving no purpose except to add to the possibility of a major malfunction.

I expanded the pic you posted and I say again the axle piece shows NO signs of distortion.
 
Thank you for the advice, gentlemen. The front motor is a Bafang 500w motor and the bike is a Yuba Mundo Classico.

If I am reading this correctly, the lawyer u-clip is the first thing that goes on the axle? Right now I have a washer and then the u-clip.

Now that I look at it the two front torque arms are kinda thin. I'm ready to buy some real torque arms and a member was nice enough to post two different links to two different torque arms, but I am not sure which one to go with? They are both expensive and I want to make the right choice the first time.

Also, in a couple of days I will be posting my thoughts on my first e-bike build on here.
 
Thank you for the advice, gentlemen. The front motor is a Bafang 500w motor and the bike is a Yuba Mundo Classico.

If I am reading this correctly, the lawyer u-clip is the first thing that goes on the axle? Right now I have a washer and then the u-clip.

Now that I look at it the two front torque arms are kinda thin. I'm ready to buy some real torque arms and a member was nice enough to post two different links to two different torque arms, but I am not sure which one to go with? They are both expensive and I want to make the right choice the first time.

Also, in a couple of days I will be posting my thoughts on my first e-bike build on here.
Well it's your money, but I think you should ask around on endless spear about the effectivness of the torque arms you have, but install two not one.
My suggestion is if you are that worried, next time you should install a rear motor as the fronts are much more susceptible to failure.
Also If you search the name I posted for the video it would be clear what the u shaped washer is for.
Good luck
 
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