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What is inside a NuVinci N360?
#1
The following 3 posts is an entire topic copied from the discontinued NuVinci Forum. Some posts are written by members of the old forum and not by me.

by Oran on Fri Mar 30, 2012 10:39 pm

Well here's the answer. In some ways the design of the N360 is the same as the N17X as would be expected. It's no surprise that it contains balls and traction rings, what the following photos show is just how much Fallbrook have simplified the design. Simple means better and more reliable "Perfection is not the state where nothing further can be added, but rather where nothing further can be taken away” Hugh Piggott.
This is what you find when the hub is opened. The large diameter ball bearing allows the input and output rings to rotate at different speeds.

Inside of lid [Image: Insideoflid_zps58dd1b70.jpg]

Inside of hub[Image: Insideofhub_zps819eab6f.jpg]

The clamping pressure adjuster assembly can then be lifted out of the hub.

Clamping pressure adjuster assembly [Image: Clampingpressureadjusterassembly_zps4f78a70d.jpg]

The balls and traction fluid are then visible inside the hub.

Traction fluid inside hub [Image: Tractionfluidinsidehub_zps19ce49cf.jpg]

When the traction fluid has been drained the non drive side axle lock nut can be removed allowing the axle and ball tilting mechanism to be lifted out.

Ball tilting mechanism [Image: Balltiltingmechanism_zps61d1fc61.jpg]
- Oran
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#2
The output traction ring and clamping pressure adjuster can also be lift out of the hubs case .The photo below shows them left in place.

Output traction ring [Image: Outputtractionring_zps5b648716.jpg]

The balls are on spindles which are simply placed in their slots and can easily be removed.

Some balls removed [Image: Someballsremoved_zps475e1175.jpg]

Balls [Image: Balls_zps22584de6.jpg]

That is all that can easily be taken apart. The final photo shows all the internal parts.

All the internal parts of an N360 [Image: AlltheinternalpartsofanN360_zps1c2f1df4.jpg]

In case anyone is wondering whether it is possible to put it back together and make it work again, the answer is yes. Due to the simplicity of the design there are only two things to tighten, the axle lock nut and the lid, so it is hard to go wrong. Since I reassembled the hub I have given it some hard usage for over 100 miles with no problems apart from the traction fluid leak. Sadly its life is limited while it continues to leak.

Re: What is inside an N360?
by CadenceKing on Sat Mar 31, 2012 12:21 am

Thank you so much for posting these captioned photographs!

Best regards,

CadenceKing
He's a smooth operator,
smooth operator,
smooth operator,
smooth operator. . .

Re: What is inside an N360?
by mwjh on Sat Mar 31, 2012 1:14 pm

Very well done, thanks for sharing.
mwjh

Re: What is inside an N360?
by FransM on Thu Apr 05, 2012 3:43 pm

Thanks a lot, very interesting.
Do you reckon you could fix the leak by replacing the seal(s) if NuVinci would provide those?

Re: What is inside an N360?
by Oran on Thu Apr 05, 2012 10:51 pm

I’m glad to see my photos are generating some interest.
If NuVinci would provide a new seal I’m sure I could replace it. Not sure whether it will fix the leak as I think there is another problem with the hub that made the seal fail. The seal that failed is the one clearly visible in the centre of the first photo.
Getting NuVinci to provide spare parts and more traction fluid will be the hard part. They don’t want the hub to be opened by anyone so prefer to replace the whole hub which is what they did with mine. It seems a pity with something that is so well built to choose to throw away and replace rather than repair. As you can see from the photos it is quite simple and should be easy to service or repair. Not sure why they have decided the hub should be sealed for life, things usually work better if serviced occasionally and there life extended if parts can be replaced.

Re: What is inside an N360?
by FransM on Fri Apr 06, 2012 7:44 am

Thanks, Oran, for your reply.
I heard from someone who has spoken with NuVinci Europe that they want the leaking hubs back for repair.
Something may have changed there.
What do you think the problem is that is causing the seals to fail? Any clue?

Re: What is inside an N360?
by NuVinciSupport on Fri Apr 06, 2012 3:56 pm

Hi Guys,

The short answer is due to the tight manufacturing tolerances that are used when the hubs are constructed. We have seen the occasional failure of a seal at production, but get missed at the QC checkpoint before they go out to the public. When this happens, it is usually a small batch that sneaks through the system as opposed to one or two with just some inherent problem. When this does happen, we ask for the hubs back to cross-check the batch numbers, and either track down any remaining hubs that might potentially have a problem, or just to be ready when the others come back (if they come back at all as they may never experience a problem). In these situations, it is a not a user error that has caused this particular problem and that is why we are quick to replace the hub with a new unit rather than a repaired one. Usually we can replace the seals and re-use the hubs, but then those hubs are converted into test units or for some other project. We do not send repaired hubs back to the public. Only new units.

As for the actual problem itself, the seals on the hub are lip seals, and sometimes it is possible that a very small gap (we are talking micrometers) is created if the 2 seals are not properly aligned at construction. As such, this defect is not noticed until it makes it way onto a bike and the centrifugal force of the spinning hub starts whipping the fluid around and forcing it out through this small hole.

The reason the hubs are sealed for life is so they can have as long a lifespan as possible. We have customers who have been using their N171 hubs for over 30K miles with no service intervals. This is due to the seals working properly and no contaminants getting into the hub or fluid leaking out. If the hubs were able to be opened and serviced, it is very likely contamination would get into the hub at some point and the life expectancy of the hub would rapidly diminish.

Frankly speaking, if you know you have a part that is designed to last for over 30K miles with no service, why would you want to service it in the first place if nothing is wrong?

I do like the pictures that have been posted and glad everyone is getting a good look at them. If any of you have visited us at shows, we usually have a cutout of the hub on display for people to see and touch, but this is definitely nice as well.

Keep On Smooth Cruising
NuVinci Support
- Oran
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#3
Re: What is inside an N360?
by Oran on Sat Apr 07, 2012 10:32 pm

I believe I have worked out why the seal has failed but it is only a theory. I would be interested if anyone believes my theory is correct. When I first saw the traction fluid I noticed it was full of fragments of metal. I investigated where they had come from and discovered that the ball axles had scraped grooves in the ball tilting mechanism, see attached photos. On the ends of the ball axles are O-rings which I presume are meant to prevent metal to metal contact.

N360 24 [Image: N36024_zpsffc07915.jpg]

N360 28 [Image: N36028_zps683724d4.jpg]

The traction fluid is meant to have metal particles in it but it is a very fine powder not the larger fragments I found. My theory is that the fragments of metal are getting under the seal and causing it to leak. It must be the geometry of this seal that means the particles get forced under the seal rather than repelled.

Therefore I think the true cause of the leak is the O-rings on the ball axles are too soft. Does this sound like a plausible explanation?

Shifting under load would seem like the most likely time that the ball axles are going to scrape against their guide slots. As far as I am aware it is OK to shift under load.

The N170 has a totally different mechanism for tilting the balls and so far I haven’t seen any proof that anyone has done any significant trouble free mileage with an N360.

Fallbrook’s CVT’s are in general very well designed and made and I would definitely recommend them. This is just a small issue that is to be expected with any new design.

Re: What is inside an N360?
by NuVinciSupport on Mon Apr 09, 2012 5:36 am

You are correct in that the N360 is designed to be shifted under load where as the N171 cannot (or, was not designed to). It is perfectly fine for you to shift the N360 under load at any point in time.

As for your theory.... interesting. I'm sure our product team would be interested in taking a read of this thread.....
Keep On Smooth Cruising
NuVinci Support

Re: What is inside an N360?
by FransM on Mon Apr 09, 2012 6:34 pm

I have already had 5 hubs fitted, one of which has been replaced almost immediately because of extremely high resistance (in high and low gears), all of the others have started leaking within 1000km.
All but one on the right-hand drive side, and the one on the left-hand side.
Once the leaking starts, it continues to drip after every ride.
As I do not have the impression it is an occasional failure, I think it would be a good idea to look into it further and maybe Oran's investigations and theory helps.
Oran, thanks again for your brilliant photo's.

Frans

Re: What is inside an N360?
by Oran on Tue Apr 10, 2012 12:03 am

I’m very interested to learn that I’m not the only one who has had more than one leaking hub. 5 hubs ! I am currently waiting on my third hub. Both have leaked on the drive side so that the freewheel fills up with traction fluid. The first one started leaking at about 300miles (500km). The second one at about the same mileage but the leak is not bad so I am still using it and have now done 700miles (1100km). From what I was told and can see without taking it apart the second hub has different supposedly better seals which is probably why the leak isn’t too bad.

I was hoping my next hub, which should be a 2012 model, has had this issue fixed but it doesn’t sound like it. Surely Fallbrook haven’t made a mistake and blamed the seal for the leak rather than doing a proper investigation and found the real fault. Clearly something needs to be done about the leaking issue and the wear that is occurring whether it is the course of the leak or not. I’ve been thinking about how I would fix the wear issue and it is quite a difficult problem to solve without using expensive bearing. If the O-rings were hard enough to prevent contact they will probably be too hard and wear out instead.

As for shifting under load the N360 may be designed to shift under load and does shift under load but doing so seems to be damaging the hub. As can be seen in the photos in my previous post most of the wear has occurred on the left of the top slot and right of the bottom. This would suggest that it is happening under load as these are the sides the ball axles will be pushed against. There has to be a change in the position of the ball axles or change in ratio for any wear to occur. So the wear must be occurring while shifting under load.
........__o
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......()/()

Re: What is inside an N360?
by NuVinciSupport on Tue Apr 10, 2012 4:20 pm

FransM and Oran-

Please send emails directly to support@fallbrooktech.com.
FransM- If you still have these leaking hubs and have not warrantied them, then let us get that taken care of you for you.
Oran- If the new hub is leaking, the same applies to you as well. Please send these hubs back so we can see what is going on and get any potential problems rectified as fast as we can with you.

As for my comment about the lip seals, etc., I am not saying that it is the only reason there could be a leak, just something we have seen in the past that can cause the leak and something we have worked to rectify. The reason we ask for the hubs back is so that we can inspect the damaged hubs and see if there is a common thread that needs to be addressed in either the design or the production of the hubs. We have made quite a few improvements to the 2012 model (from stronger snap rings, tighter seals, upgraded cassette bodies, shifter interface improvements, and a few more).

While we do recognize that the N360 is a revolutionary product, there are always going to be things we can continue to improve to give you the best possible riding experience that we can give you.

Like I said, please contact our support group as soon as you can so we can get your hubs taken care of as fast as we can.
Keep On Smooth Cruising
NuVinci Support

Re: What is inside an N360?
by FransM on Tue Apr 10, 2012 8:31 pm

@NuVincisupport,

Thank you, I'm getting excellent support from NuVinci Europe.
It's just that I'm also interested in the root of this problem because it seems to be a general one, and I was glad to see that someone (Oran) is taking a thorough look at it.
I hope that this issue has been resolved in the 2012 series.

Frans

Re: What is inside an N360?
by Oran on Tue Apr 10, 2012 11:35 pm

NuVinciSupport,

Thanks for your advice but I have already requested a replacement hub and I’m currently waiting to be contacted when the 2012 model becomes available. I’m having no trouble getting replacement hubs but what I’m not getting is any answers. I’ve been e-mailing about what I think is the true cause of the leaks for months now and all I’m ever told is that the seals are to blame. If the wear is part of the normal breaking in process then just say so. The fact that nothing has been said about it makes me think you know it is a problem. Am I really the first person to discover this fault?
What other modifications have been made to the 2012 model? Is tightening the seals the only thing that has been done about the leaking issue? As far as I can tell this isn’t going to work and will only result in a lower efficiency. The seals have been improved once before without success.
How long will it be until the important issues are resolved rather than modifying parts that worked perfectly well as they were?

I’m happy to send my current leaking hub back to you so your product team can see what I’m talking about.

We both know the routine for getting new hubs what we want is some answers please.
........__o
........\<,
......()/()

Re: What is inside an N360?
by NuVinciSupport on Wed Apr 11, 2012 5:17 pm

Hi Oran,

I'm sorry you have had to go through this process more than once. We have many customers that never experience these sorts of problems... ever. Thus, your situation is slightly unique to say the least.

That being said, the only place where fluid can exit the hub is through the seals. Granted, there may be something else going on that is contributing to the problem, but ultimately it is a seal issue. Also, it is not a case of just tightening the seals as there are manufacturing tolerances to consider, so again, there are other factors at play.

As for answers not getting back to you fast enough, it is entirely possible that the question is still hanging out there and is still being looked into. Engineers take their work down to the Nth degree and if it means going through something with a microscope, then that is what they will do.
Keep On Smooth Cruising
NuVinci Support

Re: What is inside an N360?
by Minkball on Fri Jun 29, 2012 6:02 am

Oran, Frans - great discussion and pics. From your experience, do you think the N171 avoids this leaking problem with its heavier and different internals?

Oran, have you ever opened up an N171?

Can the 'different ball shift mechanism' be deduced from the NuVinci N171 manuals?

The reason I ask is that there are still quite a few heavily discounted Cadillacs around with the N171. I'd rather accept an extra 5 lbs in the hub than risk losing that critical 100ml of green fluid on my 11 mile daily commute, as things stand.

Re: What is inside an N360?
by Oran on Fri Jun 29, 2012 10:30 pm

Hi Minkball,

I don’t really know enough about the N171 to give a definite answer. From what I can remember when I looked through some old posts on this forum a while ago the N170s had suffered some leaking issues which could be easily fixed by replacing the shift rod. The N171s have an extra O-ring which apparently fixed the problem.

I have never opened an N171 but you can come across photos of the internal workings by searching the internet. http://motorbicycling.com/showthread.php?t=21827&page=3

The N170/ 171 ball shift mechanism is completely different and a lot more complicated compared to the N360. This is one reason why an N360 may be better because a good way of increasing the reliability of something is to simplify it.

Have a look at the topic “How Reliable over long distance rides?” as there are some posts you might find interesting like a recent one by Rob_E. I have also written about what happens if you were to lose all the traction fluid.

The 2012 model of the N360 which I am currently testing does seem to shift differently and I have been told that something has been done about the issue I describe earlier in this topic.

The N171 is more robust, it has a higher torque rating than the N360 but the N360 is still very well engineered. I would probably recommend an N360 as it is more refined and I think you will find this an advantage if you are going to use it every day for commuting. The N171 can’t be shifted under load whereas the N360 can. Being able to shift under load is one of the things I like about my N360 because you can maintain a perfect cadence even when accelerating hard or going up a steep hill.

Hope this helps.
........__o
........\<,
......()/()

Re: What is inside an N360?
by kilou on Sat Feb 16, 2013 7:25 am

Any news about this leak issue as of february 2013? Has the 2012 model solved the problem?
Re: What is inside an N360?
by Oran on Sat Feb 16, 2013 8:22 pm
At the moment I would say yes as mine is leak free and I have done nearly 1700 miles since I installed it back in May last year. The first two hubs I had started leaking at 400 – 500 miles so I’m well past that.
I was never told exactly what was done to fix the leaking problem, perhaps it was just the seals. I still think there is something in my theory and there was some mention of the shift mechanism having been modified. I do think the 2012 model is harder to shift but I’m not sure. When the hub develops a fault hopefully not in the near future I will open it up and find out.
........__o
........\<,
......()/()

Re: What is inside an N360?
by kilou on Sat Feb 16, 2013 10:39 pm

Thanks for the feedback Oran. I'm interested in getting one of these hubs but the leaking issue was putting me off. I'm happy to read your new hub appears to be reliable so far. The only weak point left is the lack of spare parts and impossibility to get friction fluid from Nuvinci. So called sealed for life units still makes me uncomfortable to buy this thing though. I've never trusted sealed for life units and probably never will. I wonder whether other friction oils may be used in the N360.

Re: What is inside an N360?
by Oran on Sun Feb 17, 2013 1:40 am

I know what you mean about sealed units. I also believe that things should be maintained and repaired but this is seen increasingly as old fashioned, nowadays it’s throwaway and replace.
Fallbrook are very good at replacing hubs if you have a problem, there’s no hesitation they just send out another hub. However if you have to pay to have a wheel built it can be an extra unexpected expense.
As far as other traction fluids that can be used Fallbrook say that theirs is the only one. It is a very important part of the hub and their fluid has been designed to maximize efficiency an important factor when a CVT is used on a bicycle.
I did come across a very similar transmission called the Cleveland Speed Variator and this company sells traction fluid for it. I’m should think it will work but there will probably be a loss of efficiency. It is recommended for this type of transmission that the fluid is replaced every 1000 hours which for a bicycle is roughly every 10,000 miles. One day I might get some of this traction fluid and try it in one of my leaking hubs.
........__o
........\<,
......()/()
- Oran
Répondre
#4
I recently made an attempt to stop one of my hubs leaking. This was because after examining the leaking seal in more detail I discovered hidden within it is a garter spring. This meant the seal could be tightened by simply shortening the spring.

After 188 miles and having shortened the garter spring three times (which reduced its circumference from 86mm to 74mm) I was unable to stop the leak. So it seems there is something else going on.

Possible explanations for the leak now are that the seal is made of the wrong rubber. The seal is not aligned with the shaft or the metal particles are interfering as I said they were.

The only way I see of fixing it now is to experiment with new seals which will get a bit complicated as there are many different types and materials. If the shaft is misaligned or has imperfections I don’t think there is much I can do.
- Oran
Répondre
#5
Thanks for that thread Oran! As always your inputs are so appreciated and I think you must be the 2nd most knowlegable person on the N360 after Fallbrook themselves!
-
Si ça a déjà été fait, je peux le faire
Si ça n'a jamais été fait, donnez-moi juste le temps de trouver comment !


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#6
In mid September my hubs warranty will expire and I’m considering opening it up as it is a 2012 model. If I do then the photos will be posted here. It will be a chance to find out when was actually done to solve the leaking issue.
- Oran
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#7
Sure you want to break appart a perfectly working hub?...
-
Si ça a déjà été fait, je peux le faire
Si ça n'a jamais été fait, donnez-moi juste le temps de trouver comment !


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#8
No I just want to carefully open it up have a look inside and then put it back together. I’ve had these hubs apart before and they have continued to work fine afterward.

If anyone is interested in drawings of Fallbrook’s CVT have a look at patent US8360917, I found it will searching for information on CVT efficiency. There are drawings of a different ball axle tilting mechanism. Also a shifter that appears to operate with one cable.
- Oran
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#9
Wow! those images are interesting... Seems like there are images of the 1st generation in the lot... They probably have abandonned the idea of a 1 cable shifter for stability reason... (Shifter moving by itself)
-
Si ça a déjà été fait, je peux le faire
Si ça n'a jamais été fait, donnez-moi juste le temps de trouver comment !


Répondre
#10
Interestingly the drawings are not of an early model they are certainly not the N170 or N171 but do appear to be a bicycle transmission apart from figures 49 -54. I’ve had a more detailed look at the patent and I believe it may contain information about a new model of the hub. The patent was filed at the end of January this year. I will try to summarize what I have read.

I won’t know until I open my 2012 model N360 but I think figures 23 and 26 show modifications made to the ball axle tilting mechanism. There are different ends on the ball axles so I wonder if I was right when I posted back in Apr 2012?

Now it gets very interesting as I think Fig 3 shows the next generation hub.

The method used to tilt the ball axles is very different as figures 4, 5 and 14 – 16 show. Figures 6 – 9 and the paragraphs that go with them explain the current method. This seems to allow a different type of shifter to be used. Various designs are shown in figures 28 – 48. A single cable operated one is shown in figures 62 – 64, the current shifter is 67 – 70. Figure 48 looks like an interesting concept, the ratio is partly varied by the chain tension, not sure what that’s about.

The other noticeable difference is that there doesn’t appear to be a freewheel, the current design of freewheel is shown in fig 65. I know that torque can’t be transferred backwards through a hub so in theory a freewheel is not needed and it would improve the reliability.
- Oran
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