Broken drop-outs - lesson to all, fit a torque arm.

Well it finally happened, my dropouts split after 2 years of ezee motor pleasure. Maybe that torque arm I always meant to fit was a good idea after all! But luckily it happened as I pulled away from stanstill so didn't hurt myself. Down side is that it was 8 miles from home so had to walk and carry the (heavy) bike home. It happened after a massive rocky downhill section so I reckon that must have finished them off.

So John, have you still got those torque arms? I will need them for my new forks.

Dropouts are the slots at the bottom of the fork. the wheel axle slots into them. On an electric hub the axle has 2 flat surfaces that fit into the slot on the fork. The slots stop the axle from turning when the hub turns and too much torque can break open the fork slots. If a fork is made of aluminium then this is a weak point.

A torque arm is like a fork slot but it is made from thick steel so is very much stronger. I usually bolts to the fork disc brake caliper mounts but may be jubilee clamped to the fork stem.

Ouch Peter,

That must have been scary, but fortunately you are in one piece.

Regarding torque plates, we only have a couple of sets left, but we are getting new stock in tomorrow.

Just give me a shout when you want them.

Regards,

There's another important point for anybody fitting their own motor to forks:

The axle is still 10mm wide, but the height is 12mm, plus the shape at the top is now not the same - arc instead of semi-circle. This means that the centre of the axle is now about 2mm down from where it was before so that the washers no longer fit in the dimple (lawyers lips). If you don't take remedial action, when you tighten the wheel-nuts, the washer exerts a huge sideways force on the lips, which prises the drop-out apart, and it can snap before you even turn the motor.

The remedial action is either to file the drop-out deeper to re-centralise the axle, or use eccentric washers that fit neatly in the dimple. You need to check and double check that nothing will exert pressure on those lips. The Ezee motor. MAC and most DD motors have 14mm axles so the effect is even worse, and to me are better fitted in a rear wheel unless you have a large strong area around the drop-outs. Zoom forks are good in this respect.

I would advise additional strengthening (torque arms) for any motor above 250w or running at more than 15 amps. Many torque arms that I've seen fitted are as good as useless because of incorrect understanding of where torque is being applied. The arm needs to directly resist the torque and not rely on the tightness of a 5mm screw. There's nothing wrong with the design of the ready-made torque arms, but you need to think about the way they're fitted.

~Hi there

firstly, glad you are ok even if forks are totally forked

secondly - were they alu forks ? I'm interested as I've got a 250w 36v front hub that I'm running without arms...but the fork is a 29er mountain bike steel beast

I still need to dremel mine that I purchased from CYCLEZEE. Although I'm still waiting a picture of how they should look fitted, as there wasnt any instructions.

There'snot an exact way to fit them. You have to figure out what you can bolt them to. A disk mount or any other threaded hole is ideal, otherwise you have to put a jubilee clip round the fork, which is not as secure. Here's how I fitted mine if it helps. In this case the arm is pulling in a clockwise direction, but the screws are right up against the ends so it can't slip:

http://i451.photobucket.com/albums/qq236/d8veh/Rocky/frontmotor.jpg

Dave is that wheel rolling right to left in the pic and if so isn't the arm being pushed in an anti clockwise motion ?

Jerry

Dave is that wheel rolling right to left in the pic and if so isn't the arm being pushed in an anti clockwise motion ?

 

Jerry

The wheel is turning anti-clock, the spindle wants to counter that and go clockwise, so the torque arm must counter that in turn and be anchored anti-clockwise.

The wheel is turning anti-clock, the spindle wants to counter that and go clockwise, so the torque arm must counter that in turn and be anchored anti-clockwise.

Correct about the rotation. I'm not sure whether one direction is better than the other to resist the torque - I mean tension or compression. It's just a question whether anything can slip. If my wheel rotated the other way, then the arm would be in compression and relying on the friction from the tightness of that 6mm screw to stop it pushing upwards. The worst ones I've seen have had an additional link, so two screws in slots that can slip - and one of them only 5mm in a 6mm slot!.

Here's one I don't like. It looks OK, but the rotation of the arm pushes the joining bolt forwards not downwards , so only the friction in the bolt is holding it. I would have flipped it and turned it round the other way and drilled the upper piece right where the lower disk brake mounting hole is, then cut off the rest. To me that would be more secure. Only a couple of degrees of movement could break the forks.

http://i451.photobucket.com/albums/qq236/d8veh/General%20bike/Torque_arm_e-bike_FalconEV.jpg

I still need to dremel mine that I purchased from CYCLEZEE. Although I'm still waiting a picture of how they should look fitted, as there wasnt any instructions.

Hi Boyced,

Sorry about the not sending a photo:o, d8veh's one is an excellent illustration.

If someone has a question for me it is always best to send an email as I don't read every thread or post:eek:

Dave is that wheel rolling right to left in the pic and if so isn't the arm being pushed in an anti clockwise motion ?

 

Jerry

The torque goes in the opposite direction to wheel..so clockwise. The torque arm is therefore correct and pulls the axle further into the dropouts.

Edit... Sorry this was already answered.

Edited August 30, 201213 yr by benjy_a

On mine I have unfortunately had to rely on the friction of the screw in the slot due to the positioning of the only mounting hole (mudguard mount) I will post a pic later.

Sent from my GT-I9300 using Tapatalk 2

More torque arm pics - I did have to file the "slots" a little to get the arms to reach the mud

guard fittings. C washers from ebikes .ca fitted and even then i has to file a couple of mm off the "lawyer" lips.

http://img.photobucket.com/albums/v25/amigafan2003/5cd7fae1.jpg

http://img.photobucket.com/albums/v25/amigafan2003/2429597f.jpg

An yes, I'm aware the link arms are installed differently on each side - hedging my bets over the most effective way :-)

Those two, to me are good ways to install torque arms. How are they different on each side? I see both of them behind the fork leg so both in tension.

Thast cable's not right though. It shoulld goo doownwards more otherwise water will run intoo your motor as Scotty found out. I'm guessing that these photos were taken immediately after installation and before you tidied the cables, so sorted by now.

Those two, to me are good ways to install torque arms. How are they different on each side? I see both of them behind the fork leg so both in tension.

The link arm on one has the "slotted" end is fastened to the eye on the fork and on the other the "slotted" end connects to the torque plate.

Thast cable's not right though. It shoulld goo doownwards more otherwise water will run intoo your motor as Scotty found out. I'm guessing that these photos were taken immediately after installation and before you tidied the cables, so sorted by now.

I removed the zip ties, pulled of the nut cover and pulled the cable up when I took the photo so you could see the torque plate fitted more clearly :-)

This is a great post/thread for newbies fitting motors. I really struggled with this stuff when I fitted my first kit.

I have only recently started fitting my motors so the cable exits/bends underneath which makes sense when trying to keep water out of the motor,

Regards

Jerry

 

I have only recently started fitting my motors so the cable exits/bends underneath which makes sense when trying to keep water out of the motor,

 

Regards

 

Jerry

I did the same, at first. Took a little while for the penny to drop