Do you think my torque arms will hold 3000watts?

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EdwardNY   1 kW

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Do you think my torque arms will hold 3000watts?

Post by EdwardNY » Feb 08 2013 9:47am

I made these torque arms in a pinch to get my ebike running last year. I milled aluminum that was used in network racks in those huge lan rooms. I'm away form my bike but it is maybe 3/8" , hopefully you can see from the photos how thick it is.

I used two types with a clamping type on one side.

I also used nord lock washers. I figure these will take some stress off the dropouts?

So far these held with zero issues with my 1000watt yescomusa motor.

I am upgrading to a 45 amp, 72 volt controller, so I should be pushing around 3,000 watts with my 18s lipo pack.

So my big question is, do you think these torque arms will hold the 3000 watts? Am I putting that much more stress on the dropouts now where I should consider upgrading them?

I know that it would of course be best to upgrade them to steel. I would do that before pusing 24s. But I want to know if I can get away with these or am I taking a huge risk now?

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Last edited by EdwardNY on Feb 08 2013 7:49pm, edited 1 time in total.

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geeeyejo1   1 kW

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Re: Do you think my dropouts will hold 3000watts?

Post by geeeyejo1 » Feb 08 2013 12:30pm

These are actually torque arms, no? You have the axle in the existing dropouts of your frame and are using these in conjunction to reinforce your dropouts...
My guess is that these will suffice with the additional wattage - especially considering the clamping assembly on one side. I have the same motor and it is a speed versus torque wind. With more voltage the torque will increase along with the strain on the dropout - especially if gunned from a dead stop. If you are enabling regeneration it will also stress the dropout...
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Re: Do you think my dropouts will hold 3000watts?

Post by wesnewell » Feb 08 2013 1:06pm

If your bike has steel dropouts, those aluminum torque arms probably won't help much, but if your bikes dropouts are aluminum, they will help a lot. Aluminum of just too soft. I've never used torque arms with my steel dropouts and have never had a problem. Just make sure you keep the axle nuts tight so the axle can't rotate back and forth and you should be ok. But once it starts rotating, it will eat up aluminum dropouts and aluminum torque plates quick.
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Re: Do you think my dropouts will hold 3000watts?

Post by bowlofsalad » Feb 08 2013 1:38pm

It'd be real hard to say for sure, there are several different alloys of aluminum, and they have pretty wildly different levels of hardness. Pure aluminum is fairly soft and brittle. Personally, I'd of gone with the most heat treated steel I could have found, I still would change that if I were you concerning 3000 watts. I have knowledge in metallurgy, welding and things of that nature, but no real world knowledge in electric bicycles. I wouldn't take any chances here, it'd be cheaper to max out on torque arms than to replace a bike frame or recover from an injury.

As far was which or what drop outs to use, I couldn't say for sure, it probably wouldn't be too big of a deal to over kill on the idea. Beyond potential cost, the added weight wouldn't be much. You could probably find some carbon steel plate and do a setup with it similar to this.

If you feel doubtful of your dropout's, I'd step it up on the torque arms, 3000watts seems pretty brutal. Of course, if you accelerated moderately, you'd be radically less likely to apply enough force to the drop outs to break them. Many variables here, but the most simple course of action, or at least the safest, is to just upgrade the torque arms.

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Re: Do you think my dropouts will hold 3000watts?

Post by 999zip999 » Feb 08 2013 2:09pm

Just go buy some steel torque arms. They don't cost that much. Think if the axkle spins and the wires had rip off then what.

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Re: Do you think my dropouts will hold 3000watts?

Post by EdwardNY » Feb 08 2013 7:48pm

yeah I meant torque arms instead of dropouts.

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Re: Do you think my torque arms will hold 3000watts?

Post by 999zip999 » Feb 08 2013 7:58pm

Aluminum is not hard enough go file some aluminum and then go file steel. A steel axle next aluminum who will win with 3000 watts over time. It's a lot of work to take apart a hub to rewire when it's cut next to the axle 8 wires. it could save you time and a headache.

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Re: Do you think my torque arms will hold 3000watts?

Post by amberwolf » Feb 08 2013 8:04pm

The possible issue I see is the hose clamps. If there is *any* rocking of the axle, which *will* happen if you use regen, evne if just a teensy amount, eventually those clamps will probably develop fatigue cracks and shear thru. Like this:
http://www.endless-sphere.com/forums/vi ... 92#p545492
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I expect that once that broke, it then caused this:
Image

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Re: Do you think my torque arms will hold 3000watts?

Post by aroundqube » Feb 09 2013 12:02am

To me,the weak point is where the axle nuts tighten against the torque arms. The bolts through the dropouts,NordLock washers,and hose clamp give a false sense of security at 3000 W. If you are familiar with tightening a nut or bolt to a certain measure of foot pounds of torque, then you can understand what i am getting at. I would expect the aluminum in this set up to get stress fatigue,causing the loss of torque at the axle nuts.The extra distance that the axle nuts are away from the hub add to the leverage forces at that point.Carry a good wrench with you and check the tightness of the axle nuts while testing.

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Re: Do you think my torque arms will hold 3000watts?

Post by EdwardNY » Feb 09 2013 3:07am

aroundqube wrote:To me,the weak point is where the axle nuts tighten against the torque arms. The bolts through the dropouts,NordLock washers,and hose clamp give a false sense of security at 3000 W. If you are familiar with tightening a nut or bolt to a certain measure of foot pounds of torque, then you can understand what i am getting at. I would expect the aluminum in this set up to get stress fatigue,causing the loss of torque at the axle nuts.The extra distance that the axle nuts are away from the hub add to the leverage forces at that point.Carry a good wrench with you and check the tightness of the axle nuts while testing.
Very true. My axle bolts were always coming loose until I bought those nord lock washers. Actually I was having lots of issues until I put those on, like one of the axles actually lowing from the dropouts. The nord lock washers have eliminated these problems and also the axle bolts have never come loose with my 1000 watts.

That is why it was a damn good thing I did a clamping torque arm for one side because that alone has probably held the entire axle stable.

I usually check the tightness of all my bolts on my bike before each ride. Including the crank or bolt where you pedal as that always comes loose.

Another good point is that pipe clamp. I am going to add another pipe clamp to that side with the increased watts.

With time I will stop being lazy and actually mill out a steel torque arms. I guess I have the time, its just that milling these things out manually to fit perfectly takes alot of time, with constant test fitting and back to the mill. however, being that I have a rough template with my aluminum ones and experience with them it should be alot easier.

I will also have to find steel plates to use.

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Re: Do you think my torque arms will hold 3000watts?

Post by amberwolf » Feb 09 2013 3:43am

EdwardNY wrote:Including the crank or bolt where you pedal as that always comes loose.
? That's not normal. Do you mean the pedals themselves unscrewing from the cranks? Or the bolts (or nuts) that secure the cranks to the BB?

If the former, I've heard of that happening when the cranks and pedals are swapped left-right, like I had them on my original CrazyBIke2 chaindrive system (although I never had any issue with that, some do), but not when they are properly tightened on the correct sides (actually even when they are only finger-tight they've never come loose on my bikes, electric or not).

If the latter, I can imagine that if the cranks are not fully mounted to the BB shaft ends, so that they can wobble a little, they could work the nuts or bolts loose, too, if those are not tight. But otherwise, even if the bolts are only fingertight (as some of mine are even now), they dont' get loose if the cranks are tightly mounted. (although I imagine if the cranks are flexible enough to cause warping when standing on them for starts or hills or whatever, and you do it a lot, it could cause them to work loose if the nuts/bolts were already loose enough to allow that, at least for square-taper types. I am not sure it *could* happen for ISIS or similar).


I will also have to find steel plates to use.
That should be easy. I've picked up quite a few bits that could make nice torque plates. The angle bracket that holds back to seat on heavy-duty office/desk/computer chairs can be easily 1/4" thick hardened steel. The bumper mount plates on trucks and some cars is thick steel with enough flat area to use. Those often get tossed with the bent up bumpers from collisions. Some steel BMX bikes, even the cheap kids' junk from Magna, Huffy, etc., have very thick rear dropouts, often large plates that can be cut entirely off the bike and bolted or welded to your regular dropouts. (that's what I made my clamping dropouts from on CB2). Lots of other potential sources for such plates, often free or very low cost.

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Re: Do you think my torque arms will hold 3000watts?

Post by NeilP » Feb 09 2013 4:49am

999zip999 wrote:Just go buy some steel torque arms. They don't cost that much. Think if the axkle spins and the wires had rip off then what.

I'd stick with those clamping torque arms over any pre made steel ones any day. You will never get an exact fit between steel axle and steel torque arm, and yo will always eventually end up with some play that only gets worse, especially if you use regen.
The weak point is possibly the pipe clamps holding them to the frame, but depends on hose clamp quality. My hose clamps held just fine,as did my stainless steel torque arms. Trouble was the soft metal of the axle.
See my thread
http://www.endless-sphere.com/forums/vi ... after+6000

Any slop/wear (if it occurs) can be constantly removed with the clamping dropouts just by tightening the clamps. Once either the axle wears or the hole in the steel torque arm wears the slop only gets worse. This results in the axle rotating a bit, then stopping suddenly, giving more twisting forces to the axle than if it were stationary and taking the forces. Resulting in, in my case, as snapped axle

I snapped my axle after 6000 miles with solid stainless steel torque arms and regen..OK so I was hitting much higher power levels ( peaks of 14kW on the CA) and continuous of 6kW). Slop built up with the axle wearing slightly with regen .

Any fixed hole style torque arm will never be as good as a clamping system just due to the fact that there is no adjustment.

My eventual solution, on a new axle

Image
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Re: Do you think my torque arms will hold 3000watts?

Post by EdwardNY » Feb 11 2013 7:10am

Very good point about the importance of clamping torque arms. I see exactly how that play will cause problems. Actually, I made a thread way back about how many of the torque arms setups I saw had play in them.

I was wondering if you should have two clamping torque arms when using regen. Technically, both of my torque arms have adjustment when riding the bike without regen or when the motor is rotating in the normal direction.

But when using regen and putting torque in the opposite direction, only one of my torque arms will be of a clamping type in that direction.

I assume the forces when using regen are much less than when driving, so will one side being only of a clamping type be enough?

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Re: Do you think my torque arms will hold 3000watts?

Post by NeilP » Feb 11 2013 7:29am

Regen forces can be just as strong. All depends on how strong regen you have set. I have locked up my back wheel ( on a wet road) from 30 mph with max regen, HVC Set at pack max voltage, while the pack is discharged. You can see 20 amps plus on regen
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