Ideal front fork drop outs for electric motor?

[Green Machine]

HI guys,

I am getting a custom steel front fork made for a front drive hub motor bike.

I was wondering if anyone could provide any insight on what the ideal front drop out would be for a mountain bike style front fork with no suspension. It seems that most front drop outs were designed to be used with a quick release. Does anyone know of a design that would work well with a hub motor? Or is the traditional quick release type design all that is necessary strength wise on a steel fork?

 

[hjns]

Get some of DocBass' Torque Arms, weld them onto your custom fork, and be done with it.

 

[MadRhino]

Anything previous to the invention of the quick release.
Large, flat, thick, open dropouts.

Better, since you have it built custom: Strong pinch dropouts

Even better: Build on the rear

 

[dogman dan]

Custom made, Just make em 3/8 thick, big and flat. Then you'd need no torque arms at all.

Another option would be what I did with my racing bike. To support 3-4000w on a front motor, I welded tabs to the fork arms so I could bolt the torque arms on instead of relying on a hose clamp. Worked great. I'm going to make you dig for a pic. Seach pics and vids, for Dogmans race bike, deathrace bike, something like that. You should be able to find the old build thread from about a year and a half ago.

 

[bionx 1954]

I am using Kona Project 2 steel forks, they do have QR but are super strong. I have 9c 2807 runing 72v @ 2000 plus watts with torque arms both sides.with no problems. The Kona P2 forks are about 70.00 US

 

[Green Machine]

ok thanks for all the advice guys...i will look into all the things you said.

 

[Green Machine]

This is what i have so far...do these look thick enough for a 2000w motor set up?

Made in steel.

 

[dnmun]

you can use the front forks with the lawyers lips around the dropout recess if you use a C washer in the recess to absorb the force of torquing the motor down. steel dropouts, no worry, but you have to use the C washer in aluminum dropouts to prevent the nut from twisting the dropout and fracturing the aluminum when it is first tightened.

justin invented them, and stocks them, and jason at ebikekit.com sells them too.

 

[dogman dan]

Looks good to me. 2000w is just under 3hp, so not that bad. Any more and it will get too hard to controll the wheel anyway.

 

[howbeit]

Get some of DocBass' Torque Arms, weld them onto your custom fork, and be done with it.

While testing my ebike over this past weekend, it looks like either the lawyers lips on my front fork is too weak or I did not properly attach the motor. I did use all of the washers provided, but who knows. Basically the lip has been bent on both, and the bike shop says that there is just too much torque.

Do you think it would be possible for me to salvage the front fork I have by welding on the TA that you referred to? If so, what is the best way? The Doc's TA looks hard core!

 

[icecube57]

Surly instigator steel fork for non suspension builds

 

[dogman dan]

Depends on the fork, if steel you can weld on it, weld new droputs on it, or whatever. I ran nearly 4000w through a front hub by using regular torque arms, but I welded tabs to the forks so that I could bolt the arms in place, no damn hose clamps.

Most likely your problem was primarily caused by not using C washers, since they almost never come with a kit. Your kit washers are too large for the lawyer lips on most forks.

See this thread.

http://endless-sphere.com/forums/viewtopic.php?f=4&t=15163&hilit=Ebikes+ca+c+washers

You must have the washers bearing flat, on the surface designed into the fork that was intended for normal size washers. The c washer fills that gap. Once you fix the washer problem, add torque arms and you shoud be ok.

 

[howbeit]

You were right. After researching for a few hours last night, I discovered the C washer problem. Instead of dealing with welding this mangled fork, I will probably just pick up another fork, some C washers, and another torque arm.

It would be great if someone made a special fork just for ebikes. I'd rather not take any chances at all.

*EDIT: Does anyone know where I can find good C washers? Ebikes.ca indicates that theirs are custom made. Do they have to be custom made?

 

[aroundqube]

I just realized that there are 2 different bikes and forks in this thread . howbeit -keep it simple. Since you are replacing the front fork, get one for a bolt on wheel without lawyers lips,and made of good steel.