Torque arms

[Thecaptain115]

It looks like my kickstand functions as a type of torque arm, not sure how strong it is though since its not welded.

Here is the other side. I was going to mount an aftermarket one here.

Bike is a Mongoose Maxim 26". I know its a dept store bike blah blah blah. I'm just wanting to know if I should run dual aftermarket torque arms, and if so, what brand would fit my application the best. Or can I get away with just one and leave my kickstand be. I'm trying to get all of these things done before I order the big stuff. I want to be 100% sure everything will work before I spend the big $$$. WIll be running a geared rear setup on 12S LiPo.

 

[rojitor]

I don't think that kickstand can handle a motorhub, definitely i recommend you dual torque arms.
I use these http://www.methtek.com/2012/04/26/g...rm-thick-14-inch-stainless-steel-made-in-usa/

 

[dogman dan]

No, it won't work as a torque arm. Too thin and weak.

It would be cool though, to build a beefy torque plate, and then weld the kick stand to it. I find those rear axle attached stands work well with heavy bikes.

It's what I use on the commuter.

If my eye for the welds is correct, that's a steel rear dropout. So that makes doing this easy.

 

[Thecaptain115]

Yeah I figured it wouldnt work. Guess I will just run dual torque arms.

 

[dogman dan]

You still have a very nice, big flat plate for a rear dropout. It will make bolting on a torque arm easy most likely. No hose clamps, just drill a hole where you need to, and bolt it to the frame.

 

[Thecaptain115]

Anyone know where I can get just the small part of the torque arm? Id like them to be stainless. It looks like thats the only part I would need. Going to run one on each side.

I know this is a dumb question, but could I make these from carbon fiber sheets? If so, how thick?

 

[wesnewell]

Check the dropouts with a magnet. If they're steel, you likely don't need torque arms. I've built 4 bikes with steel dropouts and no torque arms and none have ever had a problem. Currently running 24s lipo on 1000W rear hub motor up to 4000W and no torque arms. Was running 18s with regen for 8 months prior.

 

[d8veh]

I bought a couple of those kick stands in our local £1 shop with the same idea. If you've got a relatively low powered motor -say something like a BPM at 25A max, one of those stands would probably give enough extra strength to an aluminium frame to get by provided that you did the nuts up tight and used the anti-rotation washers. However, now that decent torque arms are commercially available fairly cheaply, for me they'd be a safer option.

 

[Chalo]

Check the dropouts with a magnet. If they're steel, you likely don't need torque arms. I've built 4 bikes with steel dropouts and no torque arms and none have ever had a problem. Currently running 24s lipo on 1000W rear hub motor up to 4000W and no torque arms. Was running 18s with regen for 8 months prior.

That's definitely playing Russian roulette with dumpster quality bikes like the one in your sig and the one in the original post. Have you measured or even visually checked your dropouts for spreading?

When I first got a hub motor, I thought I could get away without a torque arm too. I was only running 36V/35A, no regen, and I had nice thick chromoly tips on both of the good quality forks I used (one Tange, one Surly).

I never spun an axle, but I spread open the fork tips on both those forks. All I can think is you must be using a motor with a very speedy winding, or else you are ignoring some warning signs. Maybe both.

Chalo

 

[Thecaptain115]

They are steel. I figure the extra support can't hurt thats why I'm going to run two. Probably end up just making something myself.

 

[wesnewell]

I checked them every day for the first week or so, Now I check them maybe once a month. At first the freewheel side nut would need tightening, but the other side, where I installed a jam nut on the inside instead of that weak spacer, has never loosened once. After 7-8 months;View attachment 2

 

[dogman dan]

Well, Wes, you must have some pretty good threads on that axle then. The washers look good and flat, so you got that right. No lawyer lips to tilt the washers and force the axle out of the droputs. Some of the old x5 motors had axle threads so shitty you'd never get enough pressure on those nuts for more than 1000w.

But in any case, you basicly have nothing securing the axle but a bendy cheap steel dropout, and nut pressure. When I read Justins fork failure experiments thread, I was quite impressed by how much torque nut pressure alone could resist. That is, till the nut loosens a teeny tiny bit. Or the threads strip. So check those nuts often.

 

[Thecaptain115]

Opinions on making some from carbon fiber plate? I'm concerned about the contact area from the spindle.

 

[Chalo]

Opinions on making some from carbon fiber plate? I'm concerned about the contact area from the spindle.

That would be trying to carry the load perpendicularly to the way CFRP board has strength. Also CFRP has no toughness to speak of; it doesn't absorb much energy in becoming distorted, and most definitely does not become stronger as it deforms, the way many metals do. Mostly it just fractures as soon as it reaches its limit. I can hardly think of a less suitable material for the job. Maybe porcelain? Balsa wood? Duct tape?

For this job, you want a tough and ductile but strong material. That means steel or stainless steel if you want to make it easy on yourself. Titanium or some kind of nickel superalloy if you want to get all fetishistic about it.

Chalo

 

[Thecaptain115]

Yeah I didn't think cf would work, figured I'd ask though.

Any good recommendations on a torque arm/plate I can buy? I have the resources to make my own, but would rather just buy a good quality piece and be done with it. Doc doesn't have any in stock right now, and he didn't say when they would be again. I do have several weeks to wait though.

 

[dogman dan]

Grin Cyclery.

 

[Thecaptain115]

Here is a question: the rear drop out has a little flange that is offset for mounting the rear shifting mechanism. Should I just grind this off when 'mounting a torque plate lke dr bass'?

 

[cal3thousand]

Here is a question: the rear drop out has a little flange that is offset for mounting the rear shifting mechanism. Should I just grind this off when 'mounting a torque plate lke dr bass'?

Are you riding without a rear derailleur?

 

[Thecaptain115]

No, I took it off for the pic. I'm hoping I can just cut that part off and use the torque plate to mount the derailer to.

 

[cal3thousand]

No, I took it off for the pic. I'm hoping I can just cut that part off and use the torque plate to mount the derailer to.

Couple things come to mind:

1) alignment of the derailleur. I'm not sure if this can be compensated, but most likely able to using the adjustment screws if the thickness is not too much to adjust for (especially since it is already offset in design)
2) threading. You will need to tap and thread the torque plate to match.

BTW, can you post and share details to how you got the torque plates made including sourcing materials, measuring and cutting?