Torque arm shim

[E-HP]

I got anxious about getting my bike back up and running so instead of fabricating the torque arms at this time, I bought one from Grin. I also have one of those generic arms with the hose clamps. Not a surprise that generic one has some play, but I notice last night that even though the Grin arm goes on pretty snugly, it too has some play (hole to axle fit). My question is, has anybody used shims to eliminate play in the torque are due to the arm to axle fit?

My thought is to buy a cheap set of feeler gauges and find the right size that can fit tightly between the axle and inner flat portion of the torque arm hole as a shim. I think between the two arms, I can avoid disaster, but I'd like to get the one as tight as possible to avoid even minor damage to the dropouts, since I plan to up my regen levels.

 

[eee291]

You are using the wrong kind of torque arms for regen man.
I always go with the clamping type.
They are not that expensive and you can even find a few people selling different designs on here.

If you have a weak setup maybe you can get away with the cheap ones too.
My brother took them to bench vice and hammered on the sides to make it squeeze onto the axle more tightly, you might be able to do something similar

 

[amberwolf]

My question is, has anybody used shims to eliminate play in the torque are due to the arm to axle fit?

Not in a torque arm, per-se, but yes, I have, on SB Cruiser. However, they tend to work loose over time due to the pushing from regen / acceleration toggling.

Then, when it loosens on only one axle end and not the other, the repetitive twisting along the tight axle weakens it, and has snapped at least two of the axles I've had break (possibly three).

 

[E-HP]

My brother took them to bench vice and hammered on the sides to make it squeeze onto the axle more tightly, you might be able to do something similar

Hmm, maybe I'll try this on the cheap one and see if it makes a difference. I was running a medium level of regen when I had the motor on my steel bike, using the cheap torque arm, which did the trick there; but this frame is aluminum, so not confident that one generic arm will be enough. Thanks.

 

[E-HP]

However, they tend to work loose over time due to the pushing from regen / acceleration toggling.

This is another issue that I just realized myself when taking the wheel off of my old frame. I noticed on lug nut was pretty easy to unbolt. They were tightened down before the last ride. Have you ever tried something like blue Loctite on them?

 

[amberwolf]

No, but the nuts loosening is a sign of rocking, which is a problem with teh torque arms (or dropouts, or clamps) that has to be corrected.

The nuts won't stop the rocking even if they are super tight and locked down, if the flats of the dropouts aren't properly secured in position by whatever method, and alternating acceleration / regen is of sufficient torque against the axle.

YOu could even weld the nuts to the axle after tightening them down, and the axle will still rock if the flats are not flat against parallel surfaces.

Basically the nuts work loose when the axle rocks in the direction that causes that, while the surface the nut presses against does not move, so ti forces the nut to turn. If it loosens it enough, then vibration can take over and loosen it further (or even make it fall off, over a long enough time period).

 

[E-HP]

I ended up snapping off a piece of razor blade (0.12 mm) and was able to tap it in between the Grin torque arm and axle flat. The sharp edge of the razor allowed me to get it started and then tapped it in with a punch. There's no movement at all with the shim. I put the cheap torque are on the other size and was able to tension it in the direction opposed to the regen force. I'll try this for a few rides, then disassemble it for inspection.

 

[dogman dan]

Fabricate your own TA, for the best fit without going to clamp type.



Sure, the razor shim was a good idea, and it worked. But its not too hard with some basic tools to fabricate a TA. When I do that, I make the hole a tad small to begin with, then file wider to that perfect fit. Gotta have it real tight for regen, one way or another.

I found the grin TA a nice enough fit for most DD motors, but not so great for the smaller geared ones, with 12mm axles.


With a steel frame, its easy to make a clamp TA. Weld on a big piece of metal, aligned to the dropout. Then bolt on a matching piece for the other side of the drop.

 

[E-HP]

Fabricate your own TA, for the best fit without going to clamp type. PA220038.JPG

Yup, definitely a future project since I have about 30 inches of the 1/4" steel flat bar left to experiment with. The cheapo generic arm will get replaced next. :thumb: