PDA

View Full Version : Special grease for ceramic bearings?



A.K. Boomer
03-08-2018, 02:47 PM
Not totally ceramic they are a hybrid, silicon nitride balls on a steel race,
I know they make special grease for full ceramic bearings but it contains sub-micron particulates of ceramic, maybe not good for the hybrid set up? any suggestions?

QSIMDO
03-08-2018, 04:43 PM
Muddy water?
;o)

MattiJ
03-08-2018, 04:54 PM
RPM? load? water ingestion?

A.K. Boomer
03-08-2018, 04:58 PM
No water - extremely low RPM's and high loads. and thanks MattiJ been reading allot of your post and your spot on with allot of stuff.

Willy
03-08-2018, 05:18 PM
Ball or roller type?
Operating temps anticipated?

MattiJ
03-08-2018, 05:26 PM
Bicycle bearings? In that case you probably want something quite light to reduce drag...

I suspect that ordinary quality lithium grease like Mobilith SHC 100 would work just fine.

A.K. Boomer
03-08-2018, 05:37 PM
Their ball Willy - it's not anything conventional - it's full loading of the cranks sprocket on an independent bearing from the cranks bottom bracket --- the saving grace is i have tons of surface area it's almost 4" diameter and im going with 5/32" ceramic balls and there will be about 32 of them as every other one will be a 5/32 delrin ball as a makeshift cage (to keep from ball to ball contact of the hardened ones)

Matt I was wondering is moly cv type grease would be the ticket ? if just good quality lithium is fine i will run it - was thinking of the unit pressures CV joints go through and part of the reason they use moly there...

Willy
03-08-2018, 06:00 PM
From what knowledge I have on hand here is that in electric motor applications SKF recommends a large number of EP2-3 grease types, including common lithium soap base greases, depending on load and temperature conditions. Hybrid bearings are often specified for these types of use due to the non-conductive nature of this type of bearing.

More info here here on hybrid bearing lube and use.

https://www.gmnbt.com/ceramic-hybrid-bearings.htm


The use of a syringe is recommended to inject the grease right between the balls into the ball/raceway area. Nearly all standard greases are compatible to our rust preventive, so in most cases it is not necessary to wash the bearings prior to greasing. The only exceptions are special greases, based on silicone or fluorocarbon oils or PTFE-thickeners. They require a clean oil free surface to obtain good adhesion of the grease.


Oil lubrication

In general, there are no particular running-in specifications for oil lubed bearings, nevertheless it proved advantageous when


lubricant is available prior to start up. Consider length of feed pipes to avoid insufficient lubrication,
when performing a short running-in procedure to allow the bearings to settle in their seats.

Grease lubrication
Grease lubrication calls for running-in of the bearings. Even when a reduced grease pack is applied to the bearing, a certain amount of surplus grease causes additional friction. A complete grease film must cover all contact surfaces.
GMN recommends the following procedure for the majority of applications:


Starting sequence at 10 per cent of operating speed followed by a stop to allow the bearings to cool off to ambient temperature.
Distribution sequence at 50 per cent of operating speed where actual operating temperature slightly exceeds final operating temperature. When the temperature has reached a maximum, the unit is stopped to cool off again to ambient temperature. Test sequence, first operate at nominal speed. If target operating temperature is exceeded, the distribution sequence should be repeated.
Length and number of sequences depend on specific properties of the application. Grease reservoirs, limited space, operating speed and environmental media have a strong effect on the distribution of the grease.



Or just go down to the bike shop and get something like this, only 7 bucks and no second guessing about overexerting yourself due to a tad more friction than you can tolerate.:)

http://www.bikeman.com/LU9400.html




http://www.bikeman.com/store/graphics/00000001/Alt-imageB/LU/LU9400B.jpg

AK, moly grease's main claim to fame is it's ability to lubricate under marginally dry/sliding conditions like CV joints pins and bushings etc. Not so much a rolling element application.

A.K. Boomer
03-08-2018, 07:14 PM
Thanks for the tips on the moly Willy if there's no real benefit id be fine not using just for the fact that you can't really tell when it's dirty - it starts out dirty looking so nothing really changes lol

but most of the CV's i work on don't really have any sliding surfaces just spline drive and then balls fitting into sockets

only other benefit with the stuff i use is it's kinda caught between an oil and a grease - stays real flowie and never cakes and dries out but i will have this thing torn down every so often so not a factor,
im just going to go with a high quality lube and call it good just wanted to make sure I was not making a serious error and sounds like that's safe to do...

I looked up before posting and kinda weird to find out that some grease for full ceramic bearings actually has ceramics in it - would think about the one thing you would want to keep away from them (besides diamonds lol) ???

Willy
03-08-2018, 07:34 PM
but most of the CV's i work on don't really have any sliding surfaces just spline drive and then balls fitting into sockets

You just pointed out the two most prominent sliding surfaces in the cv joint.:)

From the literature I have here and what's available online, cleanliness is key to their longevity but I'm sure you're very well informed in that regard.

A.K. Boomer
03-08-2018, 07:38 PM
You just pointed out the two most prominent sliding surfaces in the cv joint.:)



Willy - perhaps a joint with no load, but once under load the balls act like total ball bearings - the inner drive hub an inner race, the outer receptor an outer race... is this not how your seeing them? or am i seeing them wrong?

Willy
03-08-2018, 07:48 PM
I realize of course there are a number of style and types of automotive cv joints but this is what I was thinking of.
Lots of slippin and'a slidin goin on in there.

http://cyoum84abk-flywheel.netdna-ssl.com/wp-content/uploads/2016/11/rzeppa-cv-joint.jpg






Not nearly so much here.





http://cyoum84abk-flywheel.netdna-ssl.com/wp-content/uploads/2016/11/Plunge-cv-joint.jpg

A.K. Boomer
03-08-2018, 08:16 PM
The rzeppa are the ones i was referring too - im guessing the cage does go through some scuffing action esp. where it meets the balls but i think the balls are not scuffing on the inner and outer races.

the others are very common also but mostly see them as a combo with the rzeppa's - rzeppa's on the outer joint and the tripods on the inner to allow for suspension travel.

JRouche
03-08-2018, 08:22 PM
I like the white lith grease for its lightness (slipperiness) and the apparent shelf or service life. JR

ikdor
03-09-2018, 04:58 PM
Grease with extreme pressure additives is usually used on bearings which run slow and are heavily loaded as in that situation the rolling elements and raceways weld together (micropitting). On a bike slow is certainly the case, but once you go to such a large bearing the loading could be moderate, it depends a bit on the bearing design.
When you switch to hybrid bearings they can't weld anymore so they perform fantastic under these conditions and there are no downsides to them except price. We tested them in ridiculous conditions using just refrigerant as a lubricant for a compressor client when I was with SKF R&D.
So I'd think any grease will suit your needs.
Overfilling will not be an issue at your speeds either, except for slighly increased drag but you're not going to melt you "cage" at that speed.

We had a cycling enthousiast colleague in the German office who designed a bottom bracket and managed to get it into production with a hybrid CRB on the sprocket side and a hybrid DGBB on the other side. Quite an elegant solution but I'm not sure whether it's still in production.\
This might be the one:
http://pardo.net/bike/pic/fail-001/i42.photobucket.com/albums/e347/bogeyman666/isisskf.jpg

Magicniner
03-09-2018, 06:59 PM
Would a WS2 dry lube be suitable?