When hubs impode.

[mickle]

I rode the bakfiets onto town yesterday to run an errand. On the way back i went to pull away from some traffic lights, there was a big bang and the back wheel locked up. The RH chain tug had split wide open and the right side of the NuVinci hub had turned in the drop-out (alignment washer and all) spreading the drop-out slot wide open. These are all super duty parts and ive often put a lot more force via the pedals than i did in that moment. I guess it was it's allotted time to go. The whole wheel seized solid (and its not jammed against the frame anywhere) and its a non-user serviceable part. So. Bugger.

The worst part is the damage to the frame. It feels like a wound. It may return to its original shape but it'll be forever weaker. And if it fails in the straightening its new drop-out time. Which is a strip down and rebuild and a bunch of paint ruination. Its proper gutting. I love that bike.

A van had to come out to collect me and it and I havent found the courage to inspect it in any detail.

Ho hum.

 

[Davidc]

Is that the new NuVinci 360 or the older one? Are you going to challenge them over it?

 

[mickle]

Older one. And yes.

 

[Rickshaw Phil]

I was going to ask how you were getting on with the Nuvinci. I really liked the idea of one of those hubs. Not so sure now.

 

[simon.r]

...I havent found the courage to inspect it in any detail.

Ho hum.

Be interesting to see photos as and when you do. Of the drop-out as well.

 

[Rickshaw Phil]

Is there any further news on this?

 

[mickle]

Is there any further news on this?

Yes indeed!

Its not as bad as i feared thank goodness. The drop-out went back in shape with very little persuading and there appears to be nothing at all with the hub. Phew. Pics to follow when i get in front of a computer.

 

[Norm]

What happened then? Why did it lock? And what's to stop it locking again?

 

[mrandmrspoves]

I assume the Title should have read implode (or have I misunderstood?)
I would have used the term seize or a very vulgar descriptor!
Still, could have been worse - could have exploded....

 

[Rickshaw Phil]

Yes indeed!

Its not as bad as i feared thank goodness. The drop-out went back in shape with very little persuading and there appears to be nothing at all with the hub. Phew. Pics to follow when i get in front of a computer.

I'm very glad the damage wasn't as bad as you first thought, but like Norm I'm wondering what caused it all to lock if the hub seems okay now.

 

[mickle]

So then. For some reason I neglected to snap any images of the drop-out at its bentest. The first image is as far as I'd got before remembering that Ricky Phil wanted pics.

The drop-outs are surprisingly soft - hence the damage done to the face of the drop-out by 10+ years of wheel nut tightening.

The rear wheel seizure was caused - at least partly - by my slackness. The chain had become slack because I was relying too heavily on the chain tensioner, a chain tensioner, I should mention, which had been heavily drilled out to accept the oversized NuVinci axle. In the pic above you can see how the former LH side tensioner does not yet fit.

Many geared hubs, including the NuVinci have to 'push off' against something. The anchor for the torque generated by the gearing down is provided by a tab on the wheel nut washers - which prevent the axle from turning in the drops. Shi**no's ones fior example, are bright yellow - I presume so that you don't forget to fit them...

In an inspired move I removed the left hand washer in order to fit a trailer bracket. Genius. So my hub was operating on just 50% of the required anti-spin washers. When I then failed to tighten up the RH wheel nut it was an accident waiting to happen. Once the axle started turning the wheel nut instantly unwound itself from the axle, providing no further impedance. The (heavily drilled out) chain tensioner was then expected to shoulder 100% of the weight of a 60lb cargo bike + my 17stone kicking away from the lights. Pop.
I don't know why it seized at this point, but it wouldn't turn so I couldn't even wheel it along and I had to call for back up. But it turns now! Yay.

nb I reckon it's probably best to place the anti-turn washers behind the axle (if space permits) as it's less likely to spread the drop-out if it happens again - less leverage.
The middle 'gear' is - as far as I can tell - somewhere in the middle of the range. So working up and down the gears exerts forces on the axle in both directions. Wind - unwind - wind - unwind. It's no wonder the wheel nut came loose. (Note to self: keep an eye on that RH nut.)

 

[mickle]

bang

 

[Davidc]

Interesting. An unfortunate sequence of events, as is often the case.

 

[Rickshaw Phil]

View attachment 15062

bang

There's been a bit of force through that. As Davidc says, an unfortunate sequence of events!

So, apart from this little incident, what is the NuVinci like to use?

 

[mickle]

... what is the NuVinci like to use?

Bloody lovely. Mine's the original which is significantly less light, less easy to fit and less easy to shift under load than its replacement. I still love it though. It's a fantastic thing.