Help? Axle Popping Out

[mancuz28]

Newb here...Rear wheel, 26" Magic Pie 4 + 36V lifepo4 installed and run wonderfully for about 50 miles, mixed gravel and paved roads. Was feeling good and purchased a bike trailer to haul my kid, installed and rode around with him for 15 minutes having a great time when...rear axle popped out and locked up.

The failure occurred on a moderate downhill, under regen braking. Tried to re-install, but now when I try to tighten the nuts, the opposite-side axle will pop out. I can't get them both tight. I managed to get them both around 40 lb-ft without popping out, but then I rode it and had another failure (again, under braking), so obviously I'm in need of repair / reinforcement.

I'm able to run the wheel while the bike is stationary...nothing wobbling or vibrating. Just can't get things tight enough to ride...

Frame and dropouts are aluminum. No cracks or noticeable bends in the frame/stays as far as I can tell, but it does look like the dropouts are getting worn.

I probably overtightened the nuts on initial install. All instructions I saw said to tighten "as much as possible" so that's what I did. Probably around 100 ft-lbs. In retrospect I'm guessing this was too much as it looks like it dug into the dropouts.

Will a torque arm fix this situation? If so, do you have recommendations for a seller (I'd like adjustable if possible)?

Could my axle or stays be bent? They didn't seem to be, but I didn't to a close inspection. If so, is there any way to fix this?

I'm a bit heart-broken that I can't ride right now...any help is greatly appreciated.

This is the axle resting in the non-chain-side dropout. Seems there is a bit of a gap, but this is as far as it goes down. The other side seems better.
http://i.imgur.com/y3jNegc.jpg

Non-chain-side dropout with axle out:
http://i.imgur.com/ilN0yPt.jpg
http://i.imgur.com/Z8p5fAh.jpg

Chain-side dropout with axle out:
http://i.imgur.com/ymQYvI3.jpg

Chain-side, axle resting in dropout:
http://i.imgur.com/3Q8uRGR.jpg

 

[mark5]

This is the axle resting in the non-chain-side dropout. Seems there is a bit of a gap, but this is as far as it goes down. The other side seems better.
http://i.imgur.com/y3jNegc.jpg
...
Non-chain-side dropout with axle out:
http://i.imgur.com/ilN0yPt.jpg

Is there a slight dimple or cup in the non-chain side dropout meant to hold a quick release? Can't be certain from your pictures. If there is you could use a C-washer to fill the dimpled space. Otherwise the washer under the axle nut may not be able to put tightening pressure laterally and evenly against the dropout or part of the washer could fall into the cup like pictured below. In that picture the axle nut is only applying pressure to the tabbed half of the washer because the other side of the washer fell into the cup. Apart from that you might have to file the dropouts a little bit deeper to make the axle go in further. In the below picture the tab doesn't even go into the dropout like it should because the dropout could use some deepening. Also, you should install a torque arm if you don't already have one.

Dogman Dan and d8veh explain it better: http://endless-sphere.com/forums/viewtopic.php?f=2&t=43786#p638454, http://endless-sphere.com/forums/viewtopic.php?f=2&t=43786#p639052, http://endless-sphere.com/forums/viewtopic.php?f=2&t=43786#p645655.

 

[mancuz28]

Thanks, I think this may be what's happening. I'll do a little more tinkering tonight tonight to confirm that's the case but I suspect you're right about the cupping of the dropout.

And I do think filing the dropout will help. The anti-turn washers are not seating in the dropout, so a few more mm might do the trick.

 

[arkmundi]

Its just a matter of time before you destroy those aluminium dropouts. I have the Grin torque arm, enhanced with U-bolt, on both sides. So the dropouts and bolts are secondary to holding the axle in place on the frame.

See more at http://endless-sphere.com/forums/viewtopic.php?f=2&t=63524&p=1033357#p1033357

 

[dogman dan]

One thing we can be certain of, you absolutely must have a good tight torque arm, if not two of them, to control a hub motor that uses regen.

You have damaged your frame some, so now when you tighten the nut and run the motor, it wants to shove it right out of the notch. As the axle starts to rotate a bit, instead of cracking your frame, it's just shoving it out now that your notch is looser.

In the first picture, you can clearly see how the nut and washer have been grinding back and forth, filing away at the dropout.

Look at some torque arm threads, and pick out something. File your dropouts a bit deeper, getting the center of your motor axle in the same spot a regular skinny bike axle center would be. Then secure them with two torque arms.

The good news is that you have a nice flat dropout plate. It should be easy to get a torque arm, and either remove half of it, or cut it down to a smaller plate. Then drill a bolt hole in the frame, and bolt on the torque arm. Something like this.

 

[mancuz28]

Thanks all. OK, I'm sold on the torque arms! Will be ordering a pair later today. Hopefully, combined with some dropout filing that will solve my issues.

 

[mancuz28]

Any opinions on these rear torque arm options?

http://www.amazon.com/dp/B00UM3ZYIS?psc=1
(The cheapest option for a set of 2...any concerns with quality/strength? A)

http://www.amazon.com/Crystalyte-Torque-Arm-Universal-Motors/dp/B00BF092EY/
(Apparently these are very large and maybe overkill?)

http://www.amazon.com/Grin-Technologies-Universal-Electric-ebikes/dp/B00K60C67Y/
I'm guessing these are the best quality, but of course most expensive.

 

[wesnewell]

What you really need is steel torque plates, mounted solidly to both dropouts using at least 2 bolts along with epoxy on each. Or a bike with steel dropouts.Torque arms will help, but they aren't near as good as torque plates. I think someone on es sells good torque plates, or you can make your own.

 

[mark5]

Any opinions on these rear torque arm options?
http://www.amazon.com/Grin-Technologies-Universal-Electric-ebikes/dp/B00K60C67Y
I'm guessing these are the best quality, but of course most expensive.

This is a good product. I have one and it fits closely on my axle. One of the Amazon reviews was apparently by E-S member snellemin using it on his Magic Pie. arkmundi has a good idea of using a U-bolt to secure it if you can fit one on your bike.

Doctorbass has torque plates you can attach using epoxy:

Doc's ULTIMATE TORQUE ARMS fit most of the frame UPDATE 2013
http://endless-sphere.com/forums/viewtopic.php?f=31&t=29129

 

[999zip999]

Forget regen and it's 4% gain. To small gain 4% for all it's trouble. Don't do it.

 

[mancuz28]

I like the regen not so much for energy savings, but for brake pad savings. I do quite a bit of hills and my old pads got glazed and worn pretty quickly. I do think I'm going to turn down the regen though, it's pretty strong at the factory settings. about half of what it is now will still let me ride down at a safe speed without brakes.

 

[Ykick]

There is no "safe speed" with dropouts like that. Even if you do somehow manage to clamp the axle into the frame well enough, give it enough miles and time, strong regen will ultimately twist the axle in half. Just get better brakes and get over the "regen ideas" you've talked yourself into.

But of course what the hell have we learned with over 10,000's of miles and dozens of ebike assemblies/installations?

 

[mancuz28]

Did not mean to dismiss the experience on this board! By "safe speed" I meant in feeling I could control the bike under regen alone, not regarding the integrity of the frame / dropouts / axle. Obviously you all know more than that about me!

So, you'd advise, even with torque arms + filed dropouts + lower to 50% regen, it would still be an unsafe risk to the axle and dropouts? I definitely would rather be safe than sorry, so I will take your word.

 

[amberwolf]

If you want to use that frame for a motor, regen or not, you should make torque *plates* that cover the entire dropout area and extend the dropouts below the frame, becuase you simply don't have enough surface for your axle nuts to clamp to.

No matter how tight you think they are, they are not pressing flat against a surface (as only half of each at best has a surfac to press against!), so tey will come loose. Even Nordlocks wouldn't help you.

Without regen at least you wouldnt' have the axle rocking back and forth, but even without it I don't think it'll stay in there.


With a stiff steel plate on each side of each dropout, connected/filled between them on the underside of the dropouts so they cant be crushed together with space between them, and the plates all bolted to the frame itself, then you would probably be just fine with full regen/power levels.



If you look at my CrazyBike2 thread, I took thicker dropouts off a BMX bike and welded them to my originals (which were thin steel of an old 10speed bike). Originally I made them clamping types but had issues with my construction of that and eventually went with just being deep regular dropouts--that depth means there is so much metal past htem that the accel/regen torque has to pry against too much metal to work it's way loose, so I don't have problems even though the braking and accel forces are strong and go on longer because it's such a big heavy bike.

 

[mancuz28]

Because I'm an impatient bastard I ordered two grin torque arms from amazon prime to get my bike back up and running over the weekend. I filed the dropouts 2mm, the axles are fitting nicely in there now. Took a test ride with the torque arms and everything is feeling pretty solid, everything still snug, but I understand this is not the best long term solution.

I will look into fitting some proper torque plates and hope to make that conversion in the near future...will take it easy on her for now (no regen, reduced acceleration, no towing, avoid hills).

 

[Ykick]

With regen OFF, Grin TA's and the hardware (nuts, washers) fitting squarely and flush to the dropouts while decently torqued, I wouldn't be too concerned.

IMO, it's mostly regen which seems to cause hardware to loosen. That constant twisting back & forth is nearly impossible to wrangle in without serious clamping action. And as mentioned, even if you accomplish that, give it enough time and strong regen - relatively soft axles will eventually fail.

 

[dogman dan]

For the ultimate grab, a torqe plate, or whatever, that actually clamps down on the flat part of the dropout.

If you get a bike with a really large flat area around the axle, you could do like I did on one of my bikes a few years back.

Nothing like a clamping torque control device, for regen. Then for sure, what will eventually give out is the axle.