5000 watt torque arm? :)))

[fluid2150]

Hey guys,

After my last torque arm chewed into my axle i got
Paranoid. So i viewed alot of your guys ideas and have come up with this design. I think its safe to say mega over kill )) better to be safe than sorry



View attachment 2






Well time to make the other side

 

[fluid2150]

 

[Philistine]

That is not overkill, that is just awesome, and is what all hubmotor axles deserve. Well done sir.

Sure, your torque arm looks all Mandingo like and totally cruel, but hubmotor axles are like Sasha Grey. They look all small and harmless, but always somehow end up sending most "beefy" torque arms into exhausted collapse, whilst they just sit there begging for more.

I once spun a HS3540 axle a full 360 rotation inside a brand new double pair of Ebikes.ca torque arms.

Now I only use clamping style torque arms when possible.

 

[John in CR]

What is the purpose of the bolt in the first picture? The axle should fit between the closed end of the slot and the clamping bolt.

 

[rp3]

I once spun a HS3540 axle a full 360 rotation inside a brand new double pair of Ebikes.ca torque arms.

At what power level did this happen? And what model arms where they?

 

[dogman dan]

I think he's using the bolt much like the allen screw in a notched axle keyway, like you see on swamp cooler pulley.

I DONT like it. all the pressure is concentrated on the tip of that bolt, and it's theading into presumably softer metal. The axles are notoriously soft, and it will just cut away that point just like a thin torque arm does.

My pinch dropout design, (you've seen the pics) spreads the force of the pinch across a full one inch of the length of the axle. The force is produced by two grade 8 bolts and locknuts.

Like the rest of it, the long bar with the footpeg mounts is neat. I need to do something similar to my longtail bike, but the mounts will accommodate a trailer hitch.

 

[fluid2150]

Sorry its been so long, but dogman you were right!

They started to widen and slowly the rocking was happening,
So i did what you said. Ive drilled and tapped it and clamping
Style achived. So much better! Ive pumped, get this 116amps
At 65 volts! 7500watts! Regen is around 15amps at 80volts.
I actualy blew two 50amp fuses.

But it held beautifuly )) but now ive snapped two axles. I really
Am begining to think crystalyte arnt the best quality when comes
To axles. And snapping in the same location!




View attachment 1

 

[dogman dan]

Well there's the rub. I'm not sure which motor you are using, but others have proved 100 amps can twist off a 14mm axle with 10mm flats.

 

[hydro-one]

you are likely tightning the outside nut too tight (in fruitless paranoia). this will lead to failure of that spot. i only tighten the freewheel side really tight, the wire side i leave "looser" . the constant stress combines with pulling and creates the stress riser leading to the crack. or something. its a poor design. but yeah nice arm! except what dog said. i agree the pinch is in the wrong spot: edit i see youve resolved that issue great work. now call kenny or get to the shop and design a new axle for all of us. and sell it cheap.

 

[parajared]

I bet Doctorbass torque arms could handle 5000 watts without any issues. http://endless-sphere.com/forums/viewtopic.php?f=31&t=29129

 

[Doctorbass]

Problem like showed in that thread occur when people think ONE torque arm is enough...

That's why i'm selling DUAL torque arm kit ( one left and one right) That is by far the best solution to share the load and to not have any deformation of the axel and T-A

I sold more than 400 of these kit and never got any complaint or reported failure of axel or T-A :wink:

Life is good when things are engineered properly 8)

Doc

 

[fluid2150]

For sure bass, well as ive said the most ive pulled was7.5kw
With no issue. As this is the second axle i can only assume
Poor material. Have dropped it back at stealth bikes yesterday
And he even addmitted could be a bad batch. Well he showed
Me a "stealth axle" which looked like it was made from hi tensil
Steel. Black colour. This it deffenitly not. Poor choice on crystalyte
On going this way :/

Thanx for the compliments guys, i love my t.a it holds like crazy!

And i have drbass ta just was to sure on my bike to use them
Thus i made custom ones but did use them as a template

 

[captain387]

Did this axle fail with one TA or two TA?

 

[fluid2150]

Did this axle fail with one TA or two TA?

Two t.a's

 

[Bluefang]

Just putting it out there but isn't there another thread that talks about how these overkill torque arms with clamping bolts are the actual cause for the axles snapping due to been slightly out of alignment. They are absolutely not needed FFS.

Alloy drop-outs will not handle a high powered hub motor, bolt/epoxy some 5mm steel around the drop-out and you will be golden. Thick steel dropouts like on BMXs will probably handle up to 5kw. I would suggest bolt on dropouts so you can have it as a slip on tight fit onto the axle and just bolt it in place so it cannot allow the axle to fall out of the drop-out. I generally use bolt on torque arms out of some scrap metal with a M6 bolt holding it in place about 1" away from the axle.

 

[Tench]

I pressed a broken axle out of a Crystalyte motor last week, the axle material (I wont call it metal) was so soft the threaded section bent, so I chopped that section off and pressed onto the 17mm dia main axle section which mushroomed under the moderate force needed to press it out. This was under a pushing force not an impact. They seem to be made of chocolate!!

Even with very snug fitting TA's you are up against it as the dimensional difference between the 10mm flats and the core dia of the 1/2" UNF thread is very little so only a very small deformation of the chocolate thread is needed to allow the axle to spin, as soon as one side spins the other shears off.

Adding width to the torque arms is a good idea as more deformation is required for a failure but remember your setup is only as good as the worst torque arm, thinking one is good and the other just ok is not good enough, it will twist the good side off as the poor one spins.

If one of these axles was mounted in a round hole with no torque arms and the axle nuts dogged up as tight as possible (without stripping or breaking the axle) it would still spin as soon as power was applied, so make it strong enough to run without nuts, consider them a bonus not a method to prevent spin.

Personally I change the axle before I even use the motor as this is less work than repairing a failure and all the associated possible damage to wiring, halls fets etc not to mention possible injury.

I don't buy miss-alignment of TA's as a reason for failure, these axles are so soft they will not be stressed by slight bending.

 

[Punx0r]

I recall that previous thread and could not understand how missaligned torque arms would supposedly cyclically stress the axle and induce failure.

Just to throw in my own experience. I started off with 3mm steel dropouts and added non-clamping 8mm torque arms (tight fit, required taping onto the axle). After 2000 miles of 1000W, then 2000W use I noticed slight rounding of both the axle and (to a much lesser exent) the arms. I immediately converted one arm to clamping type and will remake the other soon also make it clamping. It's the regen that causes the damage.

I agree that for modest and up powers clamping arms are nothing but good. I also agree that the clamped area should be as large as possible, some of these 3mm stainless steel arms you see are worrying - "like a knife through butter" springs to mind

 

[torker]

I think you hit it when mentioning using regen. I think that is key . Also 7500 watts How much torque is at the axle ? I don't know math :? sorry.. It seems like a lot maybe several hundred ft.lbs ??

 

[Ykick]

I think you hit it when mentioning using regen. I think that is key . Also 7500 watts How much torque is at the axle ? I don't know math :? sorry.. It seems like a lot maybe several hundred ft.lbs ??

Wise words. Makes me think about relatively heavy weight bike, minimal axle size and too often low-carb steel. Then applying 4-7kW in one direction and who knows what in the other regen direction? Multiple all that action by 100's - 1000's constantly twisting back/forth. 'few jumps and/or hop off a curb or two - 'suppose it's an inevitable conclusion?

 

[izeman]

+1. running 7.5kw through a motor that was NEVER designed to be handled like this can NOT be called bad engineering or bad quality. i would call it EXCELLENT engineering. as much as needed and as little as possible. these motors are made for 1000w. and i never heard of anyone that snapped and axle at that power. at least if we're talking about HS3540 or something like that. you didn't answer the question about model yet i think.

so if you want to take it to the limit build your own parts or buy a different motor. i guess that's more or less it.

and yes: regen kills axles and dropout really fast. i quit it after the nuts got loose even when tighten really well and the axle hold in two clamping 10mm hard steel dropouts. 4.5kw max this was on a HS3540.

 

[Punx0r]

It does make me think about doing away with regen. It's pointless as energy recovery, but a very useful brake. I just worry a little every time I feel it smartly tug the bike backwards ang think about that amount of torque on soft 10mm axle flats.

 

[electr0n]

I spun my HS3540 axle in ebikes.ca torque arms a while back and ruined my drop outs. I switch to another bike frame for a while and the axle nuts would come loose eventually and I could feel the axle wiggle a bit between regen and acceleration with 5 to 7kw.

I have not had a single problem since using angle iron to hold my axle. I like that it's wide and holds more of the axle and it's also much easier to get the motorized wheel off for maintenance.

 

[Ykick]

It does make me think about doing away with regen. It's pointless as energy recovery, but a very useful brake. I just worry a little every time I feel it smartly tug the bike backwards ang think about that amount of torque on soft 10mm axle flats.

Replacement brake pads are much cheaper and easier to replace than motor axles.

I get that it's cool to prove regen concept but as a practical application to most eBikes it almost always proves to be more trouble and expense than it's worth.

 

[Doctorbass]

Breaking hub motor axel is very frustrating because of all repair it involve as well.

I remain convinced that the design, material and the use have something to with.

Curiously guys, there is no or very rare reported issue with broken axel with the use of The Ultimate T-A 8)
http://www.endless-sphere.com/forums/viewtopic.php?f=31&t=29129&start=300

Using TWO T-A and a strong material is one of the key for success.
They don't need to look uggly, they can weight just as low as 245g per set to take 10kW easy.
One desing that cover most of the ebikes frame easy also help reducing the cost and price as well.

Over 350 set sold ( I have stop counting...) Next batch is being prepared for spring 2014. I have few left from the last batch of 75.

Doc

 

[mvly]

I am on doctorbass on this. I have a wider axle on the TC-80. 5KW on startup without a problem. Regen up to 2.5KW going fast downhill. No problem. I doc's torque arm on both side bolted to the dropout. With epoxy. So far so good. I am careful though. I try to limit my acceleration and maintain 2-3KW of power during my ride. At those power I am going 40+mph so I think that is plenty fast for me. After some point it just doesn't feel safe anymore. If you really want to go faster than 50mph continuous, then I recommend you custom build everything or as much as possible.