torque arm mandatory on 12s30amp 9c?

1KW

1 kW
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Jul 24, 2013
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have a nice stinky, can't get any tq arms to fit without waiting 2 weeks to get em.

is It fine if I just make sure the nut is tight and I made sure to sandwich the 2 spacers with the ridge that comes out against the steel deraiuler hanger.. only running 44v*30 amps.. it did fine on a one mile stretch.

worst comes to worst is will round out swingarm wheel hole?
 
The worst case is that when it rounds out the drop-outs, the axle starts spinning and it rips the wires out by the roots. This would require a dis-assembly of the motor, identify which wire goes where, re-solder, etc...also have to track down any shorts that resulted, and hope the shorts didn't do any damage.

Perhaps make a dogman style TA for now?

"Torque arm picture thread"
http://endless-sphere.com/forums/viewtopic.php?f=2&t=26444&start=25#p424343
 
Torque arms are mandatory for use with any hubmotor that isn't mounted in dropouts designed or modified specifically to take the extreme forces at the axle of a hubmotor. This is especially true with aluminum bikes because of the way aluminum fails. ie Without any warning it can just snap. Imagine your wheel falling off just as you start to pull out in traffic.

Torque arms are just too cheap and easy to DIY for a permanent solution custom fit to your bike.
 
If you have steel dropouts, you don't need torque arms as long as you get the motor mounted right. If the dropouts are aluminum, I get/make some steel torque plates (not arms). I've used 5 bikes with steel dropouts and never used a torque arm or plate up to 4KW with regen braking without a problem. I'll never buy a bike with aluminum dropouts to put a hub motor on.
 
Just don't use full power. Though I have an alloy frame with no torque plates and the same torque and have done so for thousands of miles. A quick look on ebay for electric bikes will show non of the 9c kits supply any torque arms and non of the pre-built bikes use them either. I guess if you look long enough you might find some, but on the whole it is far from mandatory.
 
You can get away without one, but sooner or later your bolts may come loose and this will cause damage to your AL dropouts and subsequent damages as described above.
30A can be a lot if your controller is set to 2.5x phase current multiplication, especially if you use regen braking.
 
My nuts are quite loose. I won't put undue pressure on my axle.

Where are the results of Justins testing? He bolted a few motors in a few different front forks to find their limits. That is a lot more use than opinions.


edit: Regen is a huge issue. Even a 50w motor would need careful mounting if you use regen.
 
I found it :)
http://endless-sphere.com/forums/viewtopic.php?f=2&t=14195&hilit=forks+torque

I think it says 3mm of steel would hold without nuts. Nuts can easily double that. I'm sure we can all compare alloy to steel. A proper read instead on just scanning page one would likely be very informative. For a couple of weeks you should be fine in any drop-out with reduced power.
 
I would say it will work, but be a risk. Would be better if you had something steel on both sides. But the steel hanger will help. File your dropouts a few mm deeper, till the axle center of a 14 mm axle is in the same spot as the original 10mm one.

Get your nuts nice and tight, Justins experiment did show that tight nuts do hold a lot of torque. But here's the rub, they could loosen.

What I like to do is tighten up, then wait 15 min. any kind of washer bending you may get will happen then. Then tighten up again. At this point, with no regen, you are very likely to have the nuts stay tight. Even so, ride 50 feet, then check. Make sure the axle is not working it's way out of a shallow dropout.

DO get the torque arm on it asap, and go easy on the starts meanwhile. Give it half throttle for 5 feet, then a smooth ramp up to 100%. Avoid harsh throttle changes till you get the TA's.
 
Probably would work, as long as you have teh right washers to spread the pressure of the nuts/locking washers onto the dropouts correctly.


Just remember, if it doesn't work....:
http://endless-sphere.com/forums/viewtopic.php?f=4&t=64279&hilit=+broke%2A&p=965702#p964426

file.php
 
For sure you'd need torque arms for the example in that picture. Alloy suspension forks, with a 5000 series crystalyte. Potentially double the torque of a 9 continent at 1500w.

I still think a lot of the alloy fork spinouts were due to lack of a c washer. Once an alloy fork gets a micro crack, it's doomed.
 
Hi, on my stinky set up (13s 50A ~2,2kW) rear hub, no regen, I just filed carefully the original drop out to have a proper fit.
I do regular NDT like dye penetrant check to monitor crack appearence
But still haven't seen any crack yet... some days, i think about making some TA from 10mm wrenches but less and less
 
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