Spun front axle and flew over the bars @ 25mph

[totals]

I've worked on cars for years. The most important tool that is often not used by "home jobbers" that will solve this issue: A tork (torque) wrench.

Use a proper tork wrench to tighten the nuts to the proper specification !

People mistakeningly believe that if you use all of your force to tighten a nut as much as you can that it will never come lose. Wrong. Doing that, will actually stretch the bolt and weaken it. The risk is bolt failure, or the nut slowly spinning off.

Use a tork (or torque) wrench to set the nut to the maximum foot pounds of torque recommended for the nut and bolt and that nut will never come lose.

I also have tork arms on my bike, but they should be considered a back up, not a replacement for a properly tightened nut.

Finally, I would suggested testing the tightness of the nut, again using your tork wrench, regularly to make sure it is not coming lose. Because the tool tells you how tight the nut is, you can guage if something is going wrong.

I'm in Canada, but I know you can buy this tool from any auto shop. Here is the one I use: http://www.canadiantire.ca/browse/product_detail.jsp?FOLDER%3C%3Efolder_id=1408474396672989&bmUID=1230156319380&PRODUCT%3C%3Eprd_id=845524443257163&assortment=primary&fromSearch=true

This will sure take you all out of the dark in wondering if the bolts are on tight or going to spin off at any minute !

Hope this helps. I really don't like hearing about people getting hurt. These bikes are a lot of fun, and i ride over 80 km/hour regularly with a front hub motor; and do so safely knowing all the nuts and bolts are tight !

Rory

 

[gogo]

^Good explanation of the dynamics involved, totals. Part of the problem with implementation of proper torque is that specifications are hard to find. Is your fork aluminum or steel and what torque are you using?

 

[totals]

I am using steel everything.... aluminum is NEVER a good option for any parts that require fastening too. All the hype about aluminum is about weight reduction... not about increasing strength !

Steel doesn't not break in the same way as alumium. Steel also can be welded.

You need to check your bolt specification to choose the right torque. I wouldn't go over 100 foot pounds, or you will be asking that nut to stretch.

What will determine the maximum torque: the material of the axle bolt and nut. The bolt on the 5000 series hub motor is a serious bolt and nut. Torqued up to 100 foot pounds, the fork would bend before the nut will let go. And even though I have suspension forks, these steel ones aren't going to bend unless I ram into a wall at full speed.

I also put on the torque arms, but that is only as a back up. The truth is that if that bolt is going to spin free, it will rip those little arms off. That is why nothing beats a properly tightened nut.

Check your manufacturer specs !!! When they engineered the bike (or hub motor) they would have had to choose a combination accordingly.

Rory

 

[methods]

... Use a proper tork wrench to tighten the nuts to the proper specification !...
... Use a tork (or torque) wrench to set the nut to the maximum foot pounds of torque recommended for the nut and bolt and that nut will never come lose....
... Check your manufacturer specs !!! When they engineered the bike (or hub motor) they would have had to choose a combination accordingly.
Rory

Hmmm... You must not own many hub motors.
I have never seen a hub motor come with instructions, let alone torque values.
The threads are crap, cut on a lathe (not rolled), built from soft steel and different for every single motor off the line
The nuts are pulled out of some random bin.
There is no proper torque value, only good judgment

I have worked on cars for 15 years as well.
I own 3 torque wrenches, inch pounds all the way up to 180 foot lbs and they are all useless for electric bikes
Torque means nothing when you don't have pristine materials. You can "torque" something to 50 foot lbs but that is an arbitrary value. . . Was it lubricated? Dry? Clean? Dirty?

... I also have tork arms on my bike, but they should be considered a back up, not a replacement for a properly tightened nut....

Sorry totals, I think that you are sending the wrong message.
Torque arms are the correct solution, not torquing
If you want to guarantee a nut stays in place you can do something like this:



Thinking that just because you torque a nut to a specific value means that you are going to avoid an axle spinout is naive.

My axle flew out for many reasons and a properly tightened nut would be just one.
Constant torque back and forth will loosen any nut that is not secured.

I appreciate that you are trying to help but I think your single minded solution is misguided.

-methods

 

[totals]

Looking at your dropout, I can see why you and I have a difference of opinion.

Please re-read my suggestions as to how to avoid going over the handle bars. There was more than just the torque wrench. Follow those steps and you will certainly reduce the risks. In nearly 35 years of extreme riding, I have never broken a fork or dropout.

BTW, next time, tell your mechanic not to torque tighten the bolts on your car wheels and see how safe you will feel. I'm sure you understand what I am getting at.

Also, I can break and/or strip wrenches with my bare hands. I wouldn't feel any safer having them strapped to the axles of my bikes. That is clearly not a solution, especially if you question the safety of the axle bolt and nut.

I can't see why anyone would disagree with proper steps to safety....

If I were you, I would replace the bolt and nut with ones that are safe and have a higher degree of predictability... not leave a wrench tied to a questionable bolt !!!!

 

[AussieJester]

I know i wouldn't be putting my trust in a nut on itz own if
i were using a hub motor, would definitely have some torque arms fitted.
I would look into getting some high tensile steel fixings though if they
are really that shoddy from new Methods...just to be on the safe side and i wouldnt
think it would be overly expensive...

 

[totals]

A Fox 40 RC2 is what you need:
http://cgi.ebay.ca/Fox-40-RC2-Downhill-mountain-bike-shox-shock-fork-new_W0QQitemZ250344892384QQcmdZViewItemQQptZCycling_Parts_Accessories?hash=item250344892384&_trksid=p3286.c0.m14&_trkparms=72%3A1215%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318

A fork with these type of dropouts is what you need for a higher end motor ...

 

[AussieJester]

So.... over a grand for a set of forks or a few bucks for a
torque arm...Doesn't surprise me 99% of people here use torque arms LoL

 

[totals]

which do you think is safer?

 

[pwbset]

If you want to guarantee a nut stays in place you can do something like this:

Ooo... that's badass. I'm totally stealing that for my future plug brake side... if not both sides. Hell... maybe 4 torque arms total attached to the axle and the nuts. Why the hell not... oh yeah... I'll tell you why not... getting a rear flat tire in the middle of the woods... haha... what a pain that would be... still... better than potential death I suppose. :wink:

 

[nomad85]

If I were you, I would replace the bolt and nut with ones that are safe and have a higher degree of predictability... not leave a wrench tied to a questionable bolt !!!!

I basically agree with you, but the bolts are part of the motor, and we don't really have the means to change them. I don't see the need to argue with one another about this, at least not with a negative tone. I don't think most people are going to be willing to spend 1000$ on any fork, or even a bike for that matter(500+ or - is my limit for a bike), it seems crazy to me, I am sure they are great but I am using a free bike with torque arm(I only see a need for one, if its attached well, the axle shouldn't be able to move at all right?) and tight nuts, and I feel perfectly safe (it only goes 30mph though). I would feel even safer if the ideal conditions you mentioned were able to be reproduced, but I have no idea what the proper torque level is for my motors. Maybe some day we'll have a decent quality hub motor to work with made of quality components(maybe made right here in North America 8) )

Oh and Merry Christmas!!!

 

[AussieJester]

which do you think is safer?

I would take a good set of torque arms... not that i shall ever need worry either way as i wouldn't be using a hub motor to start with ;-P

 

[methods]

BTW, next time, tell your mechanic not to torque tighten the bolts on your car wheels and see how safe you will feel.

I am my own mechanic. Thanks, I will give myself that advice. :wink:

Also, I can break and/or strip wrenches with my bare hands. I wouldn't feel any safer having them strapped to the axles of my bikes.

The wrench has zero force on it Total. It simply holds the nut tight. Same as using a "wire nut" or "castle nut" with a cotter pin.

If I were you, I would replace the bolt and nut with ones that are safe and have a higher degree of predictability... not leave a wrench tied to a questionable bolt !!!!

Are you reading the same forum I am?
We are talking about HUB MOTORS. I cant replace the bolt, the bolt is the AXLE. :|
If you look close you will see that I already replaced the nut with a lug nut from a Porsche.


Totals, I can see that you had good intentions with your original suggestion.
Leave it at that because you are not going to come out on top in this discussion.

-methods

 

[methods]

I'll tell you why not... getting a rear flat tire in the middle of the woods... haha... what a pain that would be...

That is a good point.
Problem is that it is completely impossible to remove the wheel in the woods anyway.
I would need half of a tool box:

19mm wrench the size of my arm to break torque
Full set of Alen wrenches
Screwdriver
Downhill tire lever (those tires are HARD to put on. . .)
Double thick tube
...

Just too much to carry.
If I get a flat I am walking

-methods

 

[methods]

I don't see the need to argue with one another about this, at least not with a negative tone.

I agree in principle, arguing is a waste of energy, and Merry Christmas to you!

Problem is that he got on his soap box without understanding the problem.
Everyone who can build and maintain a high powered electric bike is a skilled mechanic, we all know what a torque wrench is.
We don't need a lecture on following torque specifications that don't exist, advice on replacing "bolts" that are un-replaceable, or suggestions to buy $1k parts that are totally and completely incompatible and irrelevant.

-methods

 

[AussieJester]

What size is the axle in these hub motors Methods? I wouldn't imagine they would be 20mm diameter would they? Thats the size axle required for the downhill forks linked earlier :-S How do you manage to get a hub motor in a set of downhill forks with that size axle?

 

[methods]

How do you manage to get a hub motor in a set of downhill forks with that size axle?

Me personally?
Well, I would use half a tube of JB-Weld to epoxy the 12mm axle into the 20mm hole in that aluminum fork.

-methods

 

[Russell]

Hmmm... You must not own many hub motors.
I have never seen a hub motor come with instructions, let alone torque values.

I have! the Ezee kit manual gives a torque spec of 100Nm or 800in-lb (page 5) for their kit.

http://www.ebikes.ca/store/ezee_manual_V20.pdf


One thing I noticed when I installed my motor kit was that the washers were rather large and required me to file down the "lawyer lips" to get them to fit flush and the nuts properly tightened down. The Ezee kit by contrast includes what looks like smaller spacer washers to fill the gap before a larger washer and lock washer are installed. I very much doubt an experienced ebiker would overlook this but someone installing their first kit just might not take the time to deal with the protrusions one way or the other with filing or a "filler" washer which could result in a spin-out of the motor.

BTW Methods I read this thread with interest and wondered if you have reached any final conclusions about the cause of the accident and the high regen currents you saw.

 

[totals]

I can't see why anyone would argue with good parts and safety. I haven't argued against torque arms, just made the point that using them as a means of adding to safety, not replacing properly setting up a bike and maintaining it. No need to continue this discussion. I'm sure all who read this will see that it is not worth arguing. I really do think your intentions are good, and that a lot of people are trying their best to work with a limited budget.

With that said... Final words of wisdom:
1. Get a good fork, if not a $500 to $1000 high end one, then one made of thick steel with larger dropouts (not like the little ones shown previously in this thread). The high end types that I have suggested, I have never seen break - even after serious off road and extreme use.
2. Attach proper torque arms; as your fail safe.
3. Torque the nut, so not to over or under tighten.
4. Check the torque of the nut with the torque wrench regularly to make sure it is not coming loose.
5. Replace the fork if any noticable damage, or after any hard collisions or wear has occurred.
6. Consider a new fork after a few years or after 10 to 20kms of use to that you are not riding on weakened dropouts from the pull from the motor.

I do respect all your comments, and do appreciate your knowledge, otherwise I wouldn't be out here reading and learning from you all. I was just giving my thoughts I how I safely run a 5303 on a front suspension fork. I ride between 400 and 600 kms per week. With the CA I installed, I will be sure to report back by fall 2009 on how things have gone after 15,000kms. Once I break my dropouts, I will post back here .... otherwise....

Thanks, and Merry Christmas.

Rory

 

[swbluto]

I can't see why anyone would argue with good parts and safety.

Some will argue against anything if it's in the justification of their own choices and actions.

 

[AussieJester]

I can't see why anyone would argue with good parts and safety.

I don't see that 'they' have. I know i was simply questioning spending 1000 bucks on a set of aluminum forks that a hub motor wouldnt even fit in to start with (without modification) When a simple torque arm will suffice. If a new member came here clicked that link you posted and bought those forks what would you say to him when he comes asking how do i make the hub motor fit the axle it's waaaay to small for the forks...? Not sure JB Weld would cut it Methods (as fantastic a product it is) Might have to splurge for some Devcon

 

[slayer]

Hmmm... You must not own many hub motors.
I have never seen a hub motor come with instructions, let alone torque values.

I have! the Ezee kit manual gives a torque spec of 100Nm or 800in-lb (page 5) for their kit.

http://www.ebikes.ca/store/ezee_manual_V20.pdf


One thing I noticed when I installed my motor kit was that the washers were rather large and required me to file down the "lawyer lips" to get them to fit flush and the nuts properly tightened down. The Ezee kit by contrast includes what looks like smaller spacer washers to fill the gap before a larger washer and lock washer are installed. I very much doubt an experienced ebiker would overlook this but someone installing their first kit just might not take the time to deal with the protrusions one way or the other with filing or a "filler" washer which could result in a spin-out of the motor.

BTW Methods I read this thread with interest and wondered if you have reached any final conclusions about the cause of the accident and the high regen currents you saw.

Thats a good thing that one manufacturer finally gives a value of torque forces...
and by the way 800 inche lbs is about 66 foot lb

(edit) i am not suggesting anything or approving 66ft lb ... as i just had a quick read on this threads i am just comenting...it is just a good thing they advance numbers then we could say, i did it according to the specs and ...

 

[docnjoj]

That torque value sounds reasonable, as auto hub bolts average 90-100 lb/ft! Of course, there are 5 of them per wheel!
otherDoc

 

[Miles]

To have to rely on the nut to maintain structural integrity, in this way, is absolutely crass engineering design i.m.o. None of these powerful hub motor kits should be sold without a torque arm and instructions to fit it (even this is the mother of all kludges).

 

[Toshi]

I have to weigh in with the biker's perspective: a Fox 40 would be a horrible choice for a hub motor. As others have noted it uses a 20 mm axle. This is a 20 mm round axle that slides freely in and out of the hub. Plus the lowers are all magnesium iirc (or aluminum failing that -- certainly not steel).

The best option would be something like a Surly steel fork, or what I have, a GT cromo fork with milled steel torque arms bilaterally: