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

 

[romke]

deposits must come from something that was in the bearing - was there any form of lubricant used? and if so, was that the same type of lubricant that was used in the other applications where no problems occurred?

if some form of lubricant was used the lubricant needs to adhere well to both of the mating surfaces - if one of them has a PTFE coating sticking of the lubricant to the surface may be negatively influenced which might result in difficulty to form some form of lubrication film and hence can cause wear.

 

[Garz99]

hi
thanks for your reply
they are teflon /kevlar lined spherical bearings so i was advised not to use any lubricant

we used a v small amount of grease on the o-rings to ease assembly but were careful to keep it off the bearing itself

 

[Tmoose]

How does the teflon liner look in the housing of the ball on the left with scoring/galling?

Who is the manufacturer? What do they say?

What are the dimensions of the housing the spherical bearing gets pressed into? interference, wall thickness, bore roundness after welding up the control arm/link , etc.

 

[goodguy1405]

I would call this a manufacturing defect. If the tolerances were not correct for the fitment this would appear. If the edges were not rounded out it would also appear. We had this same problem and then we switched vendors and no more problem. Good luck P.s. I would lubricate them.

 

[Garz99]

hi
thanks very much for your replies - will try to answer your questions as thoroughly as i can

@ Tmoose- the bearing is of unknown brand - no markings on the race at all - a sample has been returned to the point of sale - they will not say who the manufacturer is - but have forwarded it to them for analysis
so far all i know is it has been scanned dimensionally and is apparently ok from that point of view - no distortion

dimensions are (all via digital vernier so not super accurate)
OD 29.96mm
ID 14.98
race width 9.96mm
Ball diameter across flats 15.90mm
ball diameter 24.96mm

they were a light interference fit into the wishbone eyes - light insertion force only - wishbones were made to tight tols - all the same - estimated 100lbs of lateral force - applied to the outer race only - ball revolved smooth and easily after insertion - only binding up after use

good suggestion on looking at the liner - have rotated the ball and can take a photo with some strong light so we can see what its like in there - will post that up now below

 

[goodguy1405]

Well in this photo it is apparent you need a new vendor. lol Definately a breakdown there. Somehow either trash got into the system or poor material or loading. My guess. Good luck

 

[Garz99]

@goodguy -
when you say "Definately a breakdown there. Somehow either trash got into the system or poor material or loading. My guess"

just to clarify - do you mean trash got into the manufacturing process - or something since
similarly - do you mean loading during the manufacturing process ( i think the race is cold forged around the ball so that will be a critical step)

thanks again

here is another shot of the race inner lining

 

[Compositepro]

Where are the o-rings and what do they look like?Is it possible you extruded some rubber into the spherical bearing? That would explain what you describe.

 

[Garz99]

hi

@ Compositepro

the o-rings are in perfect condition - they sit on the aluminium spacers about 5mm away from the bearing surface at the closest point - so v unlikely they have been deformed into the bearing - but thanks for your suggestion - all observations and ideas are welcome

since i note you are of a chemical background - one remote possibility i have been considering is that some constituent of the grease used on the o-rings could have somehow caused this teflon layer breakdown

now i need to make clear that - we were very careful with using any grease at all - after taking advice that this was not needed or even beneficial for these teflon lined spherical joint

none was used on the bearing itself - a small amount of spray grease was applied to a finger tip and a tiny amount of that wiped on the inside of the bore before inserting the aluminium spacers and o-rings - just to help the o rings seal and help resist any potential corrosion from occurring on the inside of the mild steel wishbone eyes.

does it seem possible / likely that this grease could have caused the breakdown of the bearing ?

will attach a photo of the bearing in its aluminium spacers - together with o-rings

 

[Tmoose]

Do you have a spare new bearing to see what a new liner looks and feels like?
The liner pictures // look // gruesome but are they as rough and irregular as they appear.
Sometimes surface finishes are not well communicated with pictures.

"will attach a photo of the bearing in its aluminium spacers - together with o-rings"

The sealing components look too small to me to seal the ball/race interface.
Are the o-rings covered with dirt?
If that is all true, then I think the spherical bearing was eating dirt.

 

[Garz99]

i don't have a spare unfortunately

the picture is pretty close up so with the naked eye the surface doesn't look quite so dramatic

the main thing i took from them is that you can see the teflon surface is breaking up and the coating is coming off exposing the substrate underneath - which i take it is not meant to contact the ball

the edge of the race is also v sharp - potentially damaging the ball - esp if combined with above

the puzzling question is why or how has this occurred

ref sealing of the o-rings - the oring fits inside the wishbone eye - the outer lip of the spacer stays outside - hence is larger diameter - the o-rings themselves are a snug/tight fit to the bore of the wishbone eye - they seem to do a good job of sealing - no obvious dirt inside the joint - of course there will be dust etc on the outside of everything bolted to the car as the outside of the joint is exposed to the elements so will collect dust etc

i will attach a photos of one of the joints installed in case it helps

the o-rings themselves seem to have some grease residue on them - bit slimy - dark - but smooth = not full of grit
i am satisfied that grit did not get past them into the joint

we also know that racers run these joints exposed - no orings for many races without binding up - so it points to something else going on here i think

 

[Garz99]

Report back from the place i purchased the bearings and the bearings have now gone back to manufacturer for analysis
who have inspected and pressed the ball out to inspect further - the factory say the marks on the ball were pick-up and they were easily polished off with some scotchbright

this is rubbish.......

the marks around the ball circumference are wear through the bright polished surface showing the crystalline material underneath

doesn't look like i am going to get a straight answer from them

may need an independent expert

 

[Garz99]

still no proper answer from the manufacturer - but have a bit more information

bearing is GEG-15ES type - per below

manufacturer is LS -
china's largest spherical bearing exporter - seems they have had a successful trading relationship with people like caterpillar

Design characteristics : Outer ring of carbon chromium steel，fractured，hardened and phosphated，sliding surface treated with MoS2. Inner ring of carbon chromium steel，hardened and phosphated，sliding surface treated with MoS2. All bearings have an annular groove and lubrication n holes in each ring except those of the E design. Bearings of the 2RS design are fitted with seals at both sides.

Sliding contact surfaces: Steel/Steel

Permissible operating temperature range:

GEG…E －50℃～＋150℃

GEG…ES －50℃～＋150℃

轴 承
型 号
Bearing
number
外 形 尺 寸
Dimensions mm
额定载荷
Load ratings kN
重 量
Weight
≈kg
d
D
B
C
dk
rs
min
r1s
min
α˚
≈
动载荷
Dynamic
静载荷
Static

GEG15ES
GEG15ES-2RS
15
30
16
10
25
0.3
0.3
16
21
106
0.048

 

[MikeHalloran]

The specs you quote don't mention a teflon lining.
Therefore you should and must grease the hell out of the bearings.

The specs do mention MoS2, which is suitable for indefinite storage and then a few dozen cycles, after which it starts to act like an abrasive.
The black deposits you report are likely MoS2.
The wear track you report is likely due to the MoS2.
The binding you report is likely due to wear products generated by the MoS2.




Mike Halloran
Pembroke Pines, FL, USA

 

[Garz99]

Thanks for your Post Mike

i now have a replacement full set of bearings and am in the process of replacing all 16 on the car

i note the replacement set came with a noticeable layer of grease on the ball - semi transparent - yellowish
don't recall seeing this on the originals - but then wasn't scrutinizing them at that stage as these are supposed to be a well known low maintenance, trouble free option.

they( both the originals and the replacement set) are supposed to be PTFE lined versions - i think LS do make PTFE versions - but i guess the first set could be MSO2 versions supplied without grease...

is there any quick test you know of i can do that would determine if they are indeed PTFE or MSO2 / if MS02 is present ?

thanks again

 

[MikeHalloran]

The only no-lube PTFE lined bearings of which I am aware have a very noticeable woven fabric liner on the interior surface of the shell, easily visible by skewing the unmounted ball.

If it looks like the ball and shell are both metal or metal-ish, you need grease.



Mike Halloran
Pembroke Pines, FL, USA

 

[Garz99]

thanks Mike

that's interesting - there is something weave/grid like on the inner surface
i took a photo - see my post above dated - 13 Nov 14 19:00 - its obviously degraded - but looked like there was something there

 

[Skogsgurra]

The "Spherical Bearing" in the heading made me disregard this thread for several weeks. And now, when I finally look at it, it is not at all about spherical bearings in my sense. I call this a spherical joint - or ball joint. And I have had a few problems with such joints.

First, a general remark. The vendor was not willing to reveal the manufacturer. That alone is something that would make me suspicious. He then says it is a Chinese brand that has done well delivering to Cat. Is that a hearsay or is it true?

I have had problems with this kind of joints in a few places. The type was FLURO GIRSW 30 RR and they are Teflon lined with graphite in the Teflon. Our problem was electric current flowing through the lining (high-frequency residues from a VFD) and since graphite is a far better conductor than Teflon, it took out the (almost "nano" particle) graphite on both surfaces after only a few months.

Handling that problem was another problem. Simple by-passing with a copper braid didn't work as well as we had hoped for and the forces involved made it difficult to insulate the linkage.

But, I don't think that you have that kind of problem. Or are there variable speed electric motors involved? Doesn't have to be VFD controlled. DC motors with PWM controllers are actually worse.

Gunnar Englund

http://www.gke.org

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

 

[Garz99]

thanks for the contribution Skogs - but thankfully no - the vehicle is internal combustion engine powered
no major electrical current spikes / noise anywhere near the joints that i know of

interesting case you mention thou - bet that took a bit of figuring out