Would you pay $80 for a torque arm?

[LewTwo]

Maybe.

My local cutter offers 0.2mm tolerance on laser, 0.3mm on water.

But. The cut surface is rough, and they say if I want to smooth it after, I should allow 0.5mm material removal to attain a uniform surface.

I'm thinking of the faces that contact the axle flats. A loose fit there will mean rocking under the drive-regen cycle. For that matter, the star contact faces are also a concern.

Maybe they're just cowboys.

Every manufacturing process (and to some extent, every shop) has limits to the tolerances that they can obtain. This is something the designer has to account for. If one needs closer tolerance than one might obtain from water/laser cutting then one might have the axle flats water/laser cut undersized and finish machined to size. Of course another option is to have all the bits done on a CNC milling machine.

For one or two units (i.e. DIY) a 6 inch mill file should suffice for finish machining.

 

[offGridDownUnder]

Of course another option is to have all the bits done on a CNC milling machine.

Yes.

A bit of local color. There don't appear to be any small shops here any more - only big ones. I was told at least half a day to set up, at $1000/day.

 

[LewTwo]

Yes.

A bit of local color. There don't appear to be any small shops here any more - only big ones. I was told at least half a day to set up, at $1000/day.

The OP mentioned a quantity of 10K in his first post.

 

[marka-ee]

Instead of the star cut out thing, it might as well just be a circle because you can always find somebody with a cheapo welder that can tack it in a few places and it will never turn on you. It doesn't take any welding skills at all. Even a beginner could do it.

 

[Chalo]

One of my friends, also an experimenter DIY has been running the arm ahead of the fork. Looks funny to me - I'm really aware of
looks. His garden hose clamp is nicer visually than other I've seen:

.View attachment 359747

Trouble with that arrangement is, the torque on the arm is reverse from the torque on the wheel. So the multi piece chingadera is easily articulated in that orientation, which makes it much less effective.

It's pretty easy to visualize-- comma shaped piece rotates "backwards", smiley cyclops worm shaped piece rotates around the clamp bolt, and the hose clamp on the other end pushes up the fork leg (or allows the worm to inch up the fork leg).

It would augment a hokey setup like that hugely to weld the comma to the worm.

 

[LewTwo]

For folks in the UK that might be interested in torque arms with star inserts and do not want to pay shipping from the 'new world' or 'import fees': you might try
Hammer-ebikes
Ian Hammon, hammer-ebikes@outlook.com

Home

www.hammer-ebikes.com

Phone: 07754032024

I believe they may have originated this concept as well.
https://endless-sphere.com/sphere/attachments/torque-arm-star-version-1024-jpg.299167/

 

[spinningmagnets]

...chingadera...

I've heard this before, it must be an engineering development term.

 

[LewTwo]

I've heard this before, it must be an engineering development term.

According to my bilingual friends, it is a vulgar term that might be politely translated from Spanish to P.O.S. in English