Notch in Bionx axle

`sandorszabo,
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sandorszabo,

I don't know why you think your post would be moderated because our moderators are here to help, the only reason you get moderated on this site is for inappropriate language or graphics in a post.

Now for your question.

I think the following image is the one you are talking about-

It seems to me that you can only turn the axle to vertical if you have vertical dropouts on your bike. After thinking about this a while and studying the image it seems they want to be sure the the axle is turned so it has no play in it. If the axle has any slop or play it may spin and destroy the dropout. Here is a picture that may help-

As you can see the axle wants to spin in the opposite direction of the wheel so if you make sure it is already as tight to the dropout as possible it should minimize the ability of the axle to tare out the dropout. Hopefully there will not be as much slop in the real dropout, I enlarged the slop factor so it could be seen. I would say if you turn the axle so it matches this image you should have no problems.

Chas S.
My Bicycle Pages

Moderator Captain

Well hello Everyone!

Sandorszabo, that was a good question. I've been searching around for some info on the very same thing. Chas, great diagram! I've owned an E-vox 140 with a BionX PL350 installed for about a year. It was installed by the BionX rep himself. It worked fine until not so long ago, when I started to notice some extra drag on the bike. Funny I missed it, but I found that the wheel was crooked. I straightened it out again (failing to realize the position of the axle notch) and thus, quickly became crooked again. As I have fiddled with it again and again, the axle threads and frame around them have become worn, and I haven't checked the spoke tension in a while. Finally I've got the wheel on as straight as I can get it, and the axle notch is propped up to keep everything solid from the torque.

The questions I have are as such: Has anyone had any problems keeping nuts tight on the bionx axle? Because of the weight and torque of the motor, do the spokes require semi-constant check-ups? Will these things ultimately affect the position of the wheel? And of course, any ideas on how I might rectify a crooked wheel?

Thanks everyone, glad there's a site out there for questions like these! (Of course, this is V for voltage, not B for Bionx axle nuts!)

Gus

Gus

The notch must be located in the six o'clock position. The torque sensing mechanism within the hub motor requires this. If the notch is rotated 90 degrees to 3 or 9 o'clock, it will not sense your pedal effort. This is not important if you only use a throttle. It is critical if you use the pedal assist modes.

In order to adjust the position you must pull the metal part with the dropout key off of the axle. This can be done with a custom puller from Bionx. All dealers should have this puller for their own use. When installing on a hybrid the dropouts are more horizontal, on a mountain bike they are more vertical. Dealers must adjust for this variation when installing Bionx kits.

You can also do this yourself with a tool from most auto parts stores. Google "3 jaw puller" look for a smaller one. The puller must be kept vertical. I have done this with a puller from Advance Auto Parts. It was slightly tricky to position the wheel and the puller, having a friend help would make it easier, but with some care it will work. Striking the center plunger bolt end with a mallet when the puller is fully tensioned also helps to loosen the part. It will come off with a sharp "pop." Then position everything on the bike. When you retighten the axle nut, the part with the key will seat itself automatically.
En szeretlek Budapest.

Hi Silentflight,

Welcome to the V-is-for-Voltage Forums!

That sounds like some very helpful advise.
Perhaps we can get one of our Collaborative Handbook gurus to add this to the Bionx Kit section.

We can use all the the helpful tips we can get here.
Your input is appreciated! Thanks

Regards,
VT-01
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Thanks Chas S for your effort. However, reasoning from the installation guide alone has compromised your analysis. You really need to see an actual Bionx wheel setup to picture the problem. For example, the Bionx axle does not sit directly in the dropout. It's embedded in the key/lug device. And it's perfectly round.

Silentflight: Thank you, thank you, thank you. Not only doesn't the Bionx guide explain the function of the notch ("torque sensing mechanism", I get it!), it says nothing about your explanation of tapping on the axle to release it so that it can be rotated. No wonder it wouldn't budge. One thing though: You mention that the angle of the dropout varies from bike to bike and that the dealer needs to "adjust for this variation." Other than keeping the notch verticle, what else needs to be adjusted?

Mike Lewis

After reading the post from Silentflight I retract my previous information but it was the best I could gather from the manual. I think Bionx needs to be told their manual needs to be updated to include how this operation is accomplished.

Special thanks to Silentflight for your help.

Chas S.
My Bicycle Pages

Moderator Captain

Just in case there is any miscommunication, the tapping with a mallet should be done on the end of the central plunging bolt of the 3 jaw puller once you have already brought it to a high tension, assuming that has not already released the part. If you haven't, try a google image search for "3 jaw puller" once you see one, you'll know exactly how to use it.

The dealers need to adjust for the variation in the angle of the rear dropouts on different bikes. As described, the notch is kept vertical by loosening the piece with the key, then it is possible to freely rotate the axle within such that the notch is at the 6 o'clock position, that's all there is to it, but it's critical to making the torque sensor work. It will otherwise underestimate torque by cos(angle) where the angle is measured between a vertical line and the position of the notch. At + or - 90 degrees it essentially loses all ability to sense torque.

V Kerulet

Yes, having the notch in the correct position helps the Bionx mechansim differentiate the torque you apply through the pedals versus the bumps you hit on the road. That's what the Bionx engineer said when i asked him about it.

I have recently fitted BionX 350pl. Initially worked well but now experiencing motor going on and off every second or so on all levels of assist (but OK with accelerator). Seems this may be because notch in axle has somehow moved 60 deg away from 6 oclock. The instructions show use of special puller to pull off the 'blocker' (which fits in the dropout) but not much use if you don't have one! I was therefore very interested to read the above and the suggestion of using a 3-jaw puller instead. I have found some via Google but they are not cheap! Anyone managed to find inexpensive tool or found other way of (safely) loosening the blocker so it can be twisted back into alignment with the notch?

PS I'm located in the UK.

Steve

I believe all Bionix dealers are supplied with the "Bionx tool kit" mentioned in the instructions - which includes the specified puller. Alignment of the notch is maintained by a tapered shaft (it says "conique" in the instructions)which is why it "pops" during the loosening process. It's held in alignment by the friction of the shaft. So for yours to have become misaligned means - I think - that your axle wasn't tightened enough. The Bionx axle nut must be tightened with much more torque than your average bicycle, otherwise the motor can actually twist the lug out of the dropout slot (as I soon found out).

Thanks for your suggestions - i will look in tool stores in UK to see what I can find (we don't have the ones you mention). Also, no BionX dealer in UK (I imported mine from Nycewheels in NY). Hence the problem.

Steve

There is a good video on youtube regarding installation. http://www.youtube.com/watch?v=M5evWA1yIDk

This pretty much nails it. I borrowed one such tool from a local BionX dealer and it really makes the job easier. You're right about getting it tight. Really tight!

I just want to add that the key needs to fit snugly into the drop-out slot. If the drop-out slot is wider than the key it will inevitably move at some point, and a few degrees is enough to make the assist and generate actions noticeably less smooth. Also, diagrams elsewhere in this thread show the "correct position" of the loose key in the slot, but realize that hitting full generation mode going down a steep hill puts significant, opposite torque on the shaft. The key can turn backwards by however much slack is in the slot. The back-and-forth action will eventually loosen the wheel.

I installed a sheet metal shim on the inside of the drop-out slot so the key won't budge.