What’s inside a 2012 model NuVinci N360?

[Oran]

I have removed content from this post because I have chosen to support Fallbrook. It is important to understand that Fallbrook are at the difficult development stage of an exciting new technology in the bicycle world. If this means restricting information provided to the general public and protecting their design from competition, then it had to be done.

I can assure you that customer satisfaction is at the heart of what Fallbrook does. Without the support of customers they could not do what they are doing.

If you have a problem with a hub Fallbrook will be happy to replace it for you, let them worry about what went wrong.

Warning contains information fans of NuVinci hubs may find disturbing.

I thought it was finally time to open up my 2012 model hub which has now done 2800 miles (4500km). I noticed recently that the wheel bearing was loose and made a knocking noise when pushing the wheel from side to side. Also having ridden another hub recently I realised how much resistance there is when shifting and that the efficiency isn’t as good is I think it should be.

I decided to take the hub out of service and dismantled the wheel. With a bit more effort than expected I unscrewed the lid.

So what was done to fix the leaking of the drive side seal, well it turned out to be just a different seal installed the wrong way round see photo. This has proved to be very successful at retaining the traction fluid not a drop had leaked out.

The bearing visible under the seal (the loose one) is completely free of traction fluid.

Sadly this is not the end of the story and there is a lot more wrong than just a loose wheel bearing. Further investigation of the hub revealed a catalogue of other issues. I’m glad I stopped using it.

Shifter resistance
I have tried everything to reduce the shifter resistance but had no success. I have now discovered what was contributing to the problem. The seal has had all its numbers rubbed off by the three eccentric gears that move the shifter. The seals rubber is designed to be resistant to wear so there must have been a lot of friction.

Non drive side leak
As I continued to dismantle the hub I discovered a small amount of leakage from the non drive side seal. Nothing sufficient to worry about but not ideal.

Wear on ball (planet) axle guides slots.
I wrote about wear on the shifter mechanism (stator) in a post on the old forum (What is inside a NuVinci N360?). Well this wear is not a good thing and does continue and after 2800 miles it is really quite severe. Interestingly most of the wear has occurred on the output side guide slots. The slots that tilt the planet axles have hardly worn at all.

Damaged O-ring on ball (planet) axle
The wear mentioned above is now so bad that it has almost destroyed one of the O-rings on a planet axle. A second O-ring is also looking badly damaged. This really can’t be doing the efficiency much good having plant axles tilted at odd angles.

Contaminated traction fluid
When pouring the traction fluid back into the hub I noticed just how contaminated it is. There’s now so much ground up metal in it that it resembles metallic paint. When new it is more transparent and has a greenish colour.

Loose wheel bearing
And finally the reason I had a look at the hub. The bearing itself is fine, it has just become a loose fit on the axle. I think that forces from the balls and traction rings are acting on the hubs case causing the bearing to move in ways it wouldn’t normally. If it was a simple wheel the bearing would just roll around the axle and wouldn’t wear.

So what does all this mean? Well realistically with my kind of usage the life of one of these hubs is at best 2000 - 3000miles (3200 - 4800km) without a major overhaul. I don’t think I have given the hub a particularly hard time and I have always kept to the minimum sprocket ratio rule. I wouldn’t won’t to keep riding a hub in this state. I built my other leaking hub into a wheel and really noticed the increase in efficiency as its only done 900miles.

[FransS]

Warning contains information fans of NuVinci hubs may find disturbing.

Indeed it does!

On the other hand, all of my hubs got replaced long before getting to that mileage. If that continues one can ride forever.

Thanks for sharing your findings with great pictures.

[Oran]

As long as poor efficiency is considered worthy of a warranty replacement we’ll be OK.
I’ll let you know if I get a new hub from the European service centre.

[Normand_Nadon]

That is some sad news... NuVinci will have to do something about those design flaws! There seems to be a missmatch between the hardeness of the two materials.

For now mine seems to perform well after only 1000kms or so... Of course my bike is light in the "NuVinci standards" but I can sure put a lot of power on those pedals when needed so I can't say if my usage vs. your's will make a difference.

When you say poor efficiency, what exactly do you experience?

I’ll let you know if I get a new hub from the European service centre.

The fact that you stripped down the hub should make any warranty exchange impossible... shouldn't it?

I think I should start saving my money for an over-expensive Rohloff hub before it's to late!


P.S.: Please excuse the multiple grammar/typo error in the previous text... I am completely dead tired have problems making a
decent sentence in my own language (french)...just imagine what it looks like in my head to try to make a readable one in english!!!

[Oran]

My experience of poor efficiency is simply that it requires more effect to achieve the same speed or I end up going slower for the same effort. I ride the same few miles of road almost daily. This gives me a very good sense of how fast I should be going for the effort I put in. So I can get a sense of the efficiency.

I bought my original hub over two years ago now so the warranty has expired on that one. I’m not sure if warranty replacement hubs are coved by another warranty.

[Normand_Nadon]

Here in Canada, by the law, if a product is under warranty for 2 years, you can have as many replacements as needed during those 2 years but the new part does not "reset" the warranty.

[Oran]

Thanks for clarifying this, I thought that was most likely to be the case.

[Normand_Nadon]

As I said, this is the law around here... I don't know for your country.

[Oran]

I’ve been thinking about how I would attempt to fix the guide slot wear issue. My initial thought was that ball bearings are what’s needed. Then I thought, why should this be necessary when there is already a bearing between the axles and the planets? The axles can roll along the guide slots if they want to. So why aren’t they doing so and instead scraping along the slots? Well it’s because the axles and planets pivot on their centres which means that one end of the axles want to rotate in one direction and the other ends in the opposite. It then depends on which ends have the highest load as to which direction they rotate in. Ball bearings are what’s needed but are only required on one end of each axle.

The catch is that a bearing so small is unlikely to be able to withstand the load. Maybe a complete redesign of the shifting mechanism such as that shown in fig 4 below from Fallbrook’s patent is the only way to fix it.

[Normand_Nadon]

Oh.. the way I see it, the seal is not reversed as it seal against the axle in the middle but since I don't see the complete assembly, maybe I am missing something.

The traction fluid looks a lot like the one we have found for kopps style CVT !