Roller Clutch + Silicone Lube = Fail?

[StudEbiker]

I blew out a 1/2" roller bearing on my modified Currie setup yesterday. The bearing was only 300 miles old. Now due to some difficulties setting up the Nuvinci, I have probably been running the set up in too high of a gear and putting extra stress on the bearing. However, in the last week I felt I may have finally got it dialed in to a place I'm happy with and feel that the stress on the system has done down significantly.

Because I've been doing more riding, I have been lubricating more. I have been using a spray silicone lube. This week was the first time I lubed twice in one week. And yesterday (about five miles after spraying it with the lube) I blew out the roller bearing. It no longer grips. So of course I started running through the possible causes.

One is that I just stressed this bearing too much and caused it to fail early.

But then I realized that it might have something to do with the lube.

I tried searching about lube for one way bearings and didn't come up with much other than oil seems to be the recommended lube. I didn't find anything specifically against using silicone though.

Anyone have any experiences or thoughts on this?

[Spicerack]

I personally don't rate the spray silicone lube at all. It doesnt seem to work well for long. I used it on a motorcycle throttle for example and it made virtually no difference. A bit of spray oil and it worked straight away. I can't explain in technical terms why the spray silicone doesn't work but from my experience I don't use it at all.

Hope you can get your bike fixed up!

[bigmoose]

Rolling element bearings use the hydrodynamic properties of oil to lift the metal surfaces apart from each other. There is never metal to metal contact in ball, roller or needle bearings... ideally. IIRC, in applications like you mention there is a "special" oil that gets extremely thick under high shear forces. That is the optimum for power transmission applications using rolling elements.

Silicon spray I do not believe will build a hydrodynamic wedge or support a hydrodynamic film. The only thing I found silicon spray good for is to keep power windows slippery and fast.

[Hillhater]

.... I blew out the roller bearing. It no longer grips. ......

Are you talking of a bearing ..or a roller clutch. ???

[StudEbiker]

roller clutch.

[liveforphysics]

You're talking about a 1-way bearing I assume?

The correct lube in these things is CRITICAL to the function. If you add non 1-way bearing lube, you've destroyed it.

Also, if you just use them you're generally going to destroy it anyways, unless you get the type that has a roller bearing on each side of it to support and keep the 1-way bearing always centered and never getting thrust axis loading while it's locked up. Those types tend to last decently if you never use them for more than about half the torque they are rated to carry.

[StudEbiker]

So what exactly is the "correct" lube?

[liveforphysics]

So what exactly is the "correct" lube?

The lube it came pre-lubed with. If you can see the clutch section itself, it's not supported correctly and it is doomed to fail. If you lose or replace or even water down the factory lube with anything else, it's doomed.

Do you know how they work? It's little oval shaped pieces with a little flap of spring steel behind them, the ovals are sized so the shaft can fit through, but once the ovals try to roll, they are too larger on the long-axis of the roller to fit the shaft and rollers in the outside housing, so it binds and pushes the rollers against the shaft surface, and it's only the friction of that hardened steel roller pushing against the shaft surface that transmits all the torque. Anything that reduces that friction between the oval roller face and the shaft directly alters the torque holding of the clutch, and no lube means they gall to the surface and fail. This is why they have extremely specific lubes for this application.

More importantly, if you have it exposed so you can just add lube in the side of the oval clutch rollers, it's doomed from the start, as they can not function as a bearing, they can only function as a clutch that needs to be supported by bearings.

The smart option if you want to give one the best chance of surviving is to get the type Miles used on his bike, a sealed package with an inside sleeve and a roller being for support on each side, then NEVER LUBE IT.

[liveforphysics]

In fact, never lube any sealed bearing, and on open bearings, strongly avoid ever lubing a factory lubed bearing, unless it's some extreme situation where water or solvent or something got in there and wiped out the factory grease.

[StudEbiker]

Okay, I got it.

So it seems likely that what happened was that I sprayed the silicone up all over the chain and sprockets and some of it got into the the 1-way bearing area and caused it to lose it's grip. This is basically what I figured might have happened though I didn't know exactly how the one way bearing worked.

The bearing is not exposed. If you look at my avatar, the bearing is inside the black housing. It is inserted into a 19t #25 sprocket which goes on a shaft that is in between a bronze bushing on one side and a planetary reduction on the other side. The planetary is heavily lubricated with moly grease as I was advised to do by Knoxie. It seems like the spray lube probably just penetrated a little more than it should have, so in the future I will focus a more viscous lube only on the chain. Hopefully this will solve the problems in the future.

I have also pulled the bearing today and it seems to be functioning as it should again, so maybe the silicone has been eliminated and the friction action is able to work again. I haven't tried it with any motor torque though, so it might still slip with more torque. I have two new ones on the way regardless.

[liveforphysics]

If it's slipping on the shaft, generally the shaft will be scared in that area and never be flat enough to grip effectively again in that area unless you surface the shaft.

[kevo]

Even when these have worked for me, they are annoyingly loud during regen downhills.

[Hillhater]

Even when these have worked for me, they are annoyingly loud during regen downhills.

How do you manage to regen through a one way clutch ???

[StudEbiker]

Well, as it turns out it wasn't the 1-way clutch at all but the planetary. The grooves holding the splines on the shaft the 1-way clutch rides on stripped out. Luckily I had a spare lying around. I also put some lithium grease on the #25 chain and it rides much quieter now. Hopefully now that I'm not trying to pull such a tall gear now this planetary will last awhile longer.

It did help me to realize that with a mid-drive, there are certain items that I should definitely have backups of on hand. Namely, a planetary, some #25 chain, and the whole roller clutch assembly.

I have ordered some new roller clutches, but it sounds like if the clutch goes, I'll need to replace the shaft as well, so probably best to just have a backup pack of the whole thing.

As I was doing this, I was hoping that I could carry a couple of back up parts with me (planetary, 19t cog w/roller clutch) and the two tools it takes to replace them (allen wrench and phillips screwdriver) and if this happened again in the future to be able to make the repair roadside. Unfortunately I don't think that would be terribly easy. I might still throw it on the bike just in case, but for the most part I think I would rather just pedal home and make the repair here.

[kevo]

Hillhater wrote:How do you manage to regen through a one way clutch ???

Flip it. Allow freewheel when desired, regen when desired. Same small roller clutch pointed out by
Grinhill in his build thread http://endless-sphere.com/forums/viewtopic.php?t=9172.
Was great at low speeds, just wasn't rated for fast downhills.