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Fixing N360 guide slot wear.
#21
If it happens to be a good fix, I am sure that guys at Fallbrook are going to consider a desing change since it involves almost nothing!

As some say, the best solutions are often the simplest ones!
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#22
If I've read the Intellectual property notice correctly Fallbrook own all rights to any improvements I make to their hubs. Fallbrook probably wish I had payed more attention to it at the start, I've clearly not followed their Ts & Cs. As far as I'm concerned there is no such thing as maintenance free. From my experience the things that resist being taken apart are the ones that contain bad design and poor construction.

I strongly believe that simple is always better. If a part doesn't exist it can't go wrong. I like this quote by Albert Einstein
Citation :Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction
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- Oran
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#23
I do not believe that this hub can possibly be maintenance free... Even more with intensive users as we are!

I am a professional mecanics in the industrial business and I have seen hundreds upon hundreds of gearbox systems including CVTs and they all need at least a little bit of maintenance once in a while to keep them from defects. The minimum maintenance has to be fluid flush once in a while... In ideal conditions and even if a machine is not running much, oil has to be changed because of oxidation and particles have to be removed from the insides.... Oxidation occures even if the oil has additives to prevent this... these additives only extend the life of the fluid but they are the first to deplete.

Just imagine what the fluid looks like in a far from ideal system such as a bicycle! Intense vibrations, constantly varying torque, dust, water, mud, sand, snow etc... The fluid must look like /$?%$/% after only a couple of thousands of kilometers!

I think that it is a shame that Fallbrook won't let handy entusiasts like us put their hands on maintenance parts and fluid for their hubs... It could even be a secondary market for them!

Anyways, I love the feeling of the ride, but I am starting to feel some resistance when pedaling and if the hub gives away, I don't think I will be replacing it with another NuVinci unless Falbrooks changes their ways!
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Si ça n`a jamais été fait, donnez-moi juste le temps de trouver comment !


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#24
I'm glad you think the same way I do and I didn't realize you had lots of experience with transmissions. I hate using something that is on the road to a scrap heap and I know how long the road is. Ultimately everything will end up as scrap but if I feel there are things I can do to lengthen that road I’m much happier.

I’ve learnt something new about oil, I didn't know about oxidation. If particles are a factor that speeds up the process of oxidation, then oil that looks like metallic paint isn't going to last very long. I don't think outside contamination is an issue as the hubs tend to bleed oil. I have never seen any evidence of dust, dirt or water in any of my hubs.

I'm half way with the milage now. Its different to do many miles on a 16 square mile island. I can't do more than about 8 miles without ending up back were I started or turning back the way I came. I'll see how far I've done in another 2 weeks if its more than 400 miles I'll open the hub.
- Oran
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#25
I've got bad news about the new modified hub it's started to leak. I know some people will think its because I've taken it apart and that's damaged a seal. Whilst I can't rule it out as a cause I think it is far more likely to be due to the wheel bearing that has for some reason become loose. The same thing happened to another hub and its not the bearing that has failed it has just become loose on the axle. No idea at the moment what can be done about this.

As I had the hub off the bicycle I couldn't resist opening it to see how the bushings are doing. And this is another disappointment because it looks like they are wearing out faster than I would have liked. I've done 275 miles and there is a noticeable amount off both the I.D and O.D. They seem to be wearing unevenly as the O.D has lost 0.1mm on the planet side and 0.2mm nearest the end of the axle. The I.D has increased by a similar amount and has also worn less at the planet side.

[Image: P1010141_zpsd4fcabaf.jpg]

The good thing is that they do seem to be saving the output side of the stator. Unfortunately the stator has worn slightly on the input side instead. I need to do more miles to know if things will settle down or continue. I was hoping the traction fluid would remain free of metal particles as I think its a major contributor to the seal failure's.

[Image: P1010153_zpsf0206066.jpg]

Some people might be thinking why does a bit of wear on the stator matter. I think it matters because if there is even the smallest amount of wear the planet axles will not be aligned correctly and this will reduce the efficiency. Its similar to having the wrong tracking on the wheel of a car, the friction will reduce fuel efficiency and eventually wear the tyre.

My conclusion from all this is that the N360s stator design is a complete failure. It might be a cheaper option to manufacture and is fine for the majority of occasional bike users but for long term serious use it's never going to work. A complete redesign is now the only option and I'm going to leave that to Fallbrook. I remember one of the selling points was no metal to metal contact which results in a long maintenance free life, sadly it turns out to be the complete opposite.

The plan now is to continue adding up the miles until the bushings fail or I get feed up with the reduced efficiency. I've modified the new planets being very careful to fit the bushings the same way so they can continue wearing in the same way. There has possibly been issues with axle ends coming off because they were much harder to remove. I had to modify a nail punch and use thicker metal as a support before I could knock them out.

The old set of planets have been returned to their original state and have been put back in to the test hub. Well 5 of them, I'll write about it in a different post under the test hub thread.
- Oran
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#26
Even if the raceways were made of "adamantium" (fictional metal of wolverines claws), they would wear of in contact with another material rubbing on it... even if it is platic!

It is just that the "softest" material wears faster but the effect of floating particles makes a grinding effect between the two surfaces.

I honestly was expecting the oillite to wear faster in traction fluid.... it is far from an ideal lubricant for this kind of material!

I think one of the upgrades Fallbrook should be considering is electroplating hard chrome on the raceways.
what material is it made of? If it's aluminium, it needs a layer of electroless nickle then chrome... if it is steel, sulfamate nickle first then chrome. ( I worked two years in a plating factorie!)
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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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#27
Your right about it wearing regardless of how hard the material is. A rough calculation gives an idea of how many times any motion will be repeated . If we said the average cadence is 50 rpm which will allow for times without pedaling. This will result in the load changing from 0 to some value 6000 times in an hour. A topical average speed is 12 mph which means 500 oscillations per mile and half a million after 1000 miles.

That's an interesting point you mentioned about the particles helping the wear. Once a small amount of initial wear has occurred the process can escalate.

The stator is made of an aluminium alloy but I can't remember what the other metal is that's been added. Some sort of bearing is really the only option because if the axles are ever going to be low in friction the ends must be able to rotate in opposite directions. I was wondering if needle bearings might be an option, if I can find the right size.
- Oran
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#28
I know its been a long time since I have posted anything so I thought it was time for an update. I have recently achieved 1000 miles with the hub I modified with bushings. The experiment has been very successful and I'm happy with the way it's performing. I have been in contact with Fallbrook and their Chief Engineer is very interested. However they currently have the situation very much under control. The bushings can't be made to work on the production line and there are a few minor issues with using them.

I now have a better understanding of the problem thanks to Fallbrooks Chief Engineer. It appears that I completely overlooked the fact that the planet axles ends are on different sides of the slots and therefore don't need to rotate in different directions as I had thought. It really does appear to be simply a metal hardness issue. The bushings are working because they increase the contact area and so reduce the stresses. The increase in area is not much which makes me think that this problem is only affecting a small minority of people like myself who can really crank serious torque though a hub. How many people ride a bike that weighs nearly 20kg (44lbs) and then uses it to tow a trailer weighing more than myself. Or the other day on my way to work I was going uphill against 40mph winds.

The bushings have so far prevented any wear on the output guide slots.
[Image: P1010228_zpsc7909a52.jpg]

The bushings don't seem to have worn since I last checked them which means things have settled down nicely.
[Image: P1010245_zps792478f2.jpg]

The input guide slots have worn a bit but I'm hoping this will be like with the bushings just a part of the settling in process.
[Image: P1010207_zps3dbfcf6d.jpg]

The traction fluid is still reasonably clean and there are very few large particles of aluminium. Most of the contamination is a very fine dust and the hub feels noticeably smoother to ride a low speeds than any of my other hubs.
[Image: P1010251_zps52a557ba.jpg]

One of the problems with using the bushings is that they are a smaller diameter and this reduces the overdrive ratio. For me with my setup this isn't much of a problem because I can still get over 100 gear inches instead of the 130 I used to have.

So far I think the bushing solve the problem for me even if they are not the ideal solution.
- Oran
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#29
Wow... that is an impressive update I have to say!

And don't be to hard on yourself about not posting in a long time... it is my own website and I have no time to create new conversations these days!

Since you are in toutch with the engineer at fallbrook... can you suggest them to sell the traction fluid (in unidentifiable packaging if needed) so we can minimize the wear of our hub.... metal particles floating in a gearing system is just a good way to accelerate deterioration!

I too put a lot more stress on my hub than the average user and I am starting to get nervous about long term reliability...
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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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#30
Thanks, posting on this forum has always been an extra thing I do when I have time. However I don’t feel like I’ve got very far with things recently but maybe one day I’ll restart the efficiency test project.

Asking Fallbrook for traction fluid is probably the best option as I have had no success with any other companies. Apparently hubs that contain fluid looking like metallic paint still pass the tests. The particles are soft metals like magnesium and a small amount of aluminium which have no affect on the steel traction parts. This may be true but I think the seals must be suffering because of the particles.
- Oran
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