Correct positioning of a front torque arm?

[Cackalacka]

Hey gang-

Quick question: what is the correct positioning of a set of front-fork mounted torque arms, in front or behind the fork? Does one want it to exert a pull force or a push force to counteract the force of the hub?

Many thanks,
Cackalaka

 

[Link]

It shouldn't theoretically matter, but having tension between the end of the arm and the fork is generally easier when it comes to keeping everything in place then with compression.

Assuming something like an Ampedbikes torque arm. I think it has to be tension with the C'lyte ones (which I hear aren't all that good, anyway).

 

[Cackalacka]

Thanks Link,

Funny you should mention AmpedBikes torque arm as well as the Clyte; I'm installing a recently received AmpedBike arm on a front-mounted 4-series Clyte (I think the crap-tastic torque arms usually come stock with the 5 series.)

My bikes front drop-outs are fairly thick, but it is still appearrs to be an aluminum alloy. From what the Clyte vendor's install guide tells me, as well as many of the threads on the forum indicate, I prolly won't need the arm.

But that said, as I'd like to ride the hell out of this thing once its complete. $20 bucks for a little piece of mind is $20 well spent.

So I'm guessing mounting the arm to the rear of the fork would provide tensile reinforcement, whereas mounting to the front of the fork would provide compressive reinforcement, correct?

May be a moot point, as now that I have the arm to play with, it appears the shape of the dropout would prevent me from having a robust rear-mounted arm without filing down some of the areas of the fork around the dropout. I may rely on compression-oriented torque arm support after all.

Ciao,
Cackalacka

 

[Link]

Yah. The axle is trying to spin the opposite direction of the wheel, so behind the fork = tension; in front of the fork = compression.

Probably won't be doing much on only a 4XX, but still worth the money. Lot easier to make $25 than to replace your fork or face.

 

[Cackalacka]

Yeah, I may attempt to do something similar to what I believe you did Link (after starting this thread I figured I might as well do some more vigorous homework.) I may hook a strap up to the disk break slot, and run it to one of the torque arm's holes, and have the torque arm 'flat' (i.e. parallel to the ground) so the bulbuous part of the "P" of the torque arm will square with the rest of my dropout.

Have you had a lot of success with your strapping the ampedbikes TA on the rear axel? Does it ever jiggle or vibrate out of position on the strapped side?

 

[John in CR]

Cackalacka,

Don't let the thickness of those front dropouts lead you into any sense of security. Mine snapped right off in the first 10ft, and that was with torque arms on both. Luckily the torque arms held the front wheel on, but they just weren't thick enough themselves and they cut right into the soft steel axle allowing it to spin and break the wiring harness. With front AL alloy dropouts I believe you have to treat your torque arms from the standpoint that you want them to also hold the wheel in place. Imagine sitting on the saddle and the front wheel coming off regardless of speed. It's something you don't want to happen, period.

I've gone to steel sleeves with 12mm thick steel dropouts welded at the bottom. I just cut the existing dropouts off and slide the sleeves right over the shocks and clamp them on. It may be overkill, but at least I don't have to worry about a face plant into the road from the front wheel coming off.

John

 

[dogman dan]

What no pics of the trick fork mods. Please post a pic of it. Pretty please. In fact, it deserves it's own thread.

 

[Cackalacka]

Whoah, John!

You peeled through the dropouts AND torque arms in the first ten feet? What were you pushing down there, a 5-series on some cracked-out fusion-powered controller? That's insane!

I do share you and Links caution, though. After witnessing a friend of mine spend a lot of time and effort strapping on a small combustion-engine on his bike, only to toss the bike (before it tossed him), purely for safety concerns, I'm all about having a functional vehicle. An unsafe one is, imho, non-functional. I really can't afford a new hub, to say nothing of a new face.

The bike passed the 10ft test; after I rigged it up, I and a friend from down the street rode it up and down my flat street for a total of around two miles. I really (somehow) had to tap into the adult in me to pack it up, unplug it, and wait for the arms to ship. It was tough, particularly after waiting two months for the hub itself to ship.

I've subsequently stripped the batteries off to take my dog for some runs, it freewheels excellently.

But yeah, the dropouts do have a little beef to them, even if they aren't the right matierial. In fact, they are so thick (and the axels so narrow) that getting the nut locked on after putting the new arms in place may present a challenge of their own.

This weekend though... this weekend.

 

[John in CR]

No X5 just a no-name 500W hubbie with 80V on an original E-crazyman, but my start is uphill and the bike and I are about 300lbs, so at such a small radius the torque is tremendous. The tire spun on a bit of gravel, so when it got traction on the pavement they snapped. The torque arms were what the machine shopped talked me into, 2mm very strong stainless, but they had about as much play as an open end wrench, so the axle started to move fracturing the dropouts and had some momentum for the torque arms to just cut right through the threaded part of the axle. I think the main culprit to snapping so quickly (in addition to a bit of tire spin on some loose gravel) was the odd shape of the dropouts themselves, which I may have weakened when I tightened the larger than standard nut.

Since I didn't eat it, the biggest issue was the broken harness, which is a major pain in the butt, especially when you try to push the limit on new phase wire size. Works like a charm now, and I just installed the torque sleeves on a new and better suspension fork after hacking the dropouts off of the new fork.

John

 

[Link]

Have you had a lot of success with your strapping the ampedbikes TA on the rear axel? Does it ever jiggle or vibrate out of position on the strapped side?

Works good for me. The way I have it mounted, it couldn't come loose if it tried. It's pinned between the drop and the hub.

I should be okay, because there's no play in the arm at all. Actually, I had to grind it out a bit to make the GM's axle fit. :?

Pics for anyone who cares:

 

[Cackalacka]

Bah-

Can't position my arm inside the dropouts; everything is pretty flush right now, and I'm afraid of putting additional lateral tension on the front forks. Trying to slide a couple milimeters of stainless steel inside the span appears to be a no-go. That said, I think the nut & washers will do a pretty solid job keeping the arm positioned.

I think your strap that you are using is a bullseye for what I want to secure my arm with. Care to divulge where you procured it?

 

[Link]

It's just a strip of brake line soldered to itself to make a loop and a small 40lb turnbuckle from Home Depot. I was originally going to strap it down differently, but seeing the turnbuckle made me realize I could use it to actually put a bit of torque against the axle. A torque arm that's just held in place still forces the drops to take most or all of the torque from the motor unless you have a super stiff (read: like diamond) torque arm and there is no play in its mount whatsoever. Torqueing it backwards means you can take a lot of the torque off the drops.

 

[Cackalacka]

Brilliant, thanks Link.

 

[StevenR]

I run a 5 series C'lyte and have two torque arms because I have regen enabled. The C'lyte arm has a substantial amount of play and needs to be run out to the end of the play then fastened down. The other arm is from hipowercycles@gmail.com. It is set up to handle the regen which, on the C'lyte system, is on/off and can come on HARD at high speeds and low battery voltages. With a single C'lyte arm the axle worked back and forth loosening the bolts - bad thing. I had to get both tight against the fork with no play. Now I can hammer on/off throttle on/off regen with no problem. The C'lyte arms are tough enough they just have play that is unacceptable if regen is used.

 

[Link]

A note on the brake cable thing: crimp AND solder. It seems that while a soldered joint can take a lot of stress, it weakens up really quick. The thing's gone missing twice now. The first time I thought it was a fluke, but it looks like it's not. :?