unusual Spherical bearing wear

[Garz99]

Hello

Can you help at all with this issue - I am having unexpected issues with spherical bearings premature wear/damage and locking up/becoming very stiff after very little use

The application is automotive suspension – bearing is a 15mm ID spherical PTFE lined plain spherical (rose joint)
The bearings run in a suspension joint sealed by o-rings – movement is about 20 degrees of rotation around the axis of the fixing bolt
Suspension was rough and sticking / becoming stiff - when removed this is what we found - bearing is very rough to move / locks up in your hand
We are seeing the following damage only after 250miles light use – see photos - the marks are in line with the edges of the outer race - just inside the race so cannot be seen from the outside until the ball is rotated a little
Nothing else in the joint looked out of place or damaged in any way - No obvious contamination was present on disassemble - joint was free from dirt, water, grit etc

the car has 16 of these joints in total 2 per wishbone - its very light (750kg) and has had only light road use, dry conditions, since fitting the joints.

Other users with the same setup seem to have several years use without maintenance or issue !

note in the picture there appears to be two distinct forms of marking on the bearing ball
1, wear through the polished outer surface of the hardened inner ball - this you can feel as a ridge with your finger nail 2, dark brown/black deposits in the center of the bearing surface ( between the other wear marks) - these are smooth and appear to be deposits on top of the ball.

Is this a known issue you have come across before?
since other users have no issues at all - even after extensive track use - could this be a manufacturing issue
if so what could have gone wrong ?

I would be very grateful if you could shed any light on this

Much appreciated

 

[Skogsgurra]

Yes. It did. But I am used to electric bearing erosion and work a lot with it. The problem was to find the correct counter-measure.

Good that you don't have VFDs or such things. Then your application could perhaps benefit from Teflon/graphite?

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[Garz99]

another update

the replacement bearings i have received are marked GEG15C and branded "LS" on the outer race

i will attach the actual catalog pages

i have an inquiry with the manufacturer to see if their product is always marked

it will be interesting to see if all the originals are marked the same way

 

[Garz99]

here is the more detailed construction description too

 

[Garz99]

the LS factory confirmed today that their spherical bearings are always marked with "lS" stamped on the outer race

the replacements are marked like that - but the originals did not have this marking - so were of some other origin.....

so its becoming clear they are of some other manufacture - unbranded - no name to protect as such - and i suspect just a general quality issue.

the supplier however still claims they are one and the same item / same manufacturer .......very frustrating when people don't just come clean with the truth

 

[Skogsgurra]

Some suppliers are no better than used car salesmen...

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Cierva]

I am a new member and it was this thread that made me join.

Regarding your wishbone application it depends whether its an existing car design, an upgrade kit from a kit supplier, or whether it is a DIY attempt by yourself. For the first two options one would hope that they got bearing selection sorted with the aid of the bearing manufacturer before they went to market.

Points to remember.
1. Never never lubricate bearings having steel/teflon fabric combination. Dirt particles combine with grease to make in effect a grinding compound that accelerates wear of the teflon fabric. Teflon is the most slippery material made by man. Its in your frying pan and will last many years of arduouse service.

2. Do not use steel/teflon bearings in fast reciprocating applications. This is equivalent to pounding the teflon fabric with a hammer on an anvil. Loads on such a bearing should all be in one direction. Consider a push/pull application of 500lbs in each direction. That is not good, but a pushing (or pulling) load varying say 50lbs to 500lbs is OK.

3. Seems to me that wishbone joints are likely to be fast reciprocating loads. Therefore a spherical plain bearing having a steel on steel sliding surface lubricated with MS02 grease is the correct choice. Please note that all MS02 greases are not equal and the SKF grease LGEM2 will extend bearing life coniderably.

 

[Garz99]

Hi Cierva
thanks for joining and posting

the kit is an aftermarket kit supplied by a well known specialist - in fact its a direct copy of one produced by one of the leading and most respected race suspension brands in the UK.
i had originally selected the own brand version because essentially the kit is just a spherical bearing with two aluminium spacers for each joint and as long as the spherical bearing is correct there should be no issue in buying a kit that is dimensional identical - without the brand stamped on it. id not turn out this way however.

both the named brand - and own brand version have apparently sold several hundred sets without any similar reported issues - used both on the road and on track. and the race teams i was in touch with even run them without seals and still get several races and even endurance events out of them before they show any signs of wear. i think the batch i had simply had the wrong specification of bearing in them

so - the above bearings have since all been removed - and a full set of the branded versions been put in - the car is now behaving normally/Good.

interestingly the brand leader advises a good quality NLGI No.2 grease should be used (obviously as long as everything is clean).
as far as i can tell the teflon lined ones are supplied lubricated from the factory - not dry - so as i understand it - this is really just a case of helping ensure it stays lubricated. i have read articles where the service life of teflon line bearings was substantially increased by lubricating them this way. it seems there main reason for existence is to provide a maintenance free option - where access eg in industrial machinery is limited or costly - but that is not to say they wouldn't last longer if lubricated. at least that was the gist of what i read.

all 16 bearings removed were stiff and locking up - all showed showed varying signs of visible wear on the ball.

i am now hoping this is just a case of a poor quality set of bearings and i can now enjoy the promised performance and longevity of the solution from the brand leading supplier.