the seal slips on the outer race - why this design?

[hcoles]

Application - Rear wheel bearing 1989 Porsche 911
Original SKF bearing was a dual row angle contact ball bearing. PN 305988 42mmx80mmx42mm The seal slips on the inner race.

I got a "replacement" FAG 527243CA - the seal slips on the OUTER race. In other words the seal is moving. My question is why do they do this? What application indicates having the seal move with the inner race?

In this application debris can build in the tight area next to the moving seal - therefore I think this is not a good application of the outer slip type seal.

Please comment if you can.
Thanks,
-Henry

 

[MikeHalloran]

... It might be to let centrifugal force energize the seal lip, or to let any accumulated liquid, e.g. water, to bleed out.

If the replacement doesn't last 20 years, you can sue FAG.




Mike Halloran
Pembroke Pines, FL, USA

 

[hcoles]

Mike,
good thinking re. possible functions of seal running on the outside race..
1 - the wheel many times doesn't spin very fast... so likely the rotation would generate fairly low forces
2 - I don't think any water would get in the bearing.. if it did I'd likely have failure before it would drain out

I'm currently contending that this is a mis application for this bearing. I'll try call FAG on Monday and see if I can get an application engineer on the phone.

The main concern is the seal running in debris. I just thought of something... with the seal running on the outside it would have to seal against a pool of water.. whereas if it spun on the inner race it would only have to deal with splash.

Thanks,
-Henry

 

[unclesyd]

Here is little information on the Axial face shield.

http://machinedesign.com/BasicsOfDesignEngineeringItem/718/66016/AxialFaceSeals.aspx

 

[hcoles]

unclesyd,
thanks, seems like the link covered face sheilds in general. I'm thinking that the lip sliding on the outer race is not good for this app. I'll try and remember to post here if I can get to FAG and ask about this...

In any case I think I have to pull the bearing out because a used a bit of grease to slide it in and it probably now has this grease pushed up against the sliding seal.. in a short time I suspect this will pick up all sorts of grit and eat away at the seal.. not to speak of the water that can sit back there.

-Henry

 

[hcoles]

update - I called FAG and talked with app. engineer Antonio Silverio. He pulled the drawing and didn't notice any thing different called out regarding the seal. The seal should be the standard type that slips on the inner ring. We thought to hold the seal and see if I could get it to slip. I also got his email and can send a picture. He did mention that they have seen FAG copies from China, but this is not likely the case, the box and everything else seems to be from FAG. Another thought I had is to glue with rtv the seal to the outer ring... I expect that if I can't get it to spin easily I'll ask for my money back from the one place and buy the SKF from the other place. The SKF costs me $69 and this one was $37. The bearing house price for these is up to $100+

 

[diskullman]

I would seriously doubt that your bearing is a Chinese countefeit. Those part numbers from SKF & FAG indicate that they are specials, face facts, I don't think there is a huge demand for replacement bearings for an 89 Porsche. Usually when the seal slips on the outer race, it is used as a flinger.They work exceptionally well in certain applications.

Russell Giuliano

 

[hcoles]

last night and again this morning I tried pushing the seal to get it moved or locked on the outer ring... couldn't make it happen.. I opened the other bearing box with #2 of this bearing to see if it had the same issue.. it does.

my current conclusion is that the seal is the wrong part for this bearing or somehow the seal has a manufacturing defect..

re. 89 Porsche - if you google around you find that 42x80x42 bearings are used on many vehicles, BMW, MB, Porsche, Crysler/etc. - but yes still I guess not a huge demand. Yes, I agree not a Chinese knockoff.

This is not a flinger app. so I think I'm still solid in questioning that I can't get the seal to slip on the inner ring.

 

[MikeHalloran]

But now you've got two bearings with the same 'defect'.

I'd stop worrying about it unless it gives trouble.





Mike Halloran
Pembroke Pines, FL, USA

 

[hcoles]

I have two bearings with the same defect... I have an RMA number to send them back and get my money back... those FAG bearings are either defective or the wrong application. I'm still working with FAG and the Porsche parts company that sold them to me to help them diagnose if they want me to.. but soon they will go back and I won't be able to do too much.

I already bought a new nice SKF bearing this moring.. the seal runs nicely on the inner ring..

If we find out the root cause on with this... I'll post here.

PS: my mechanic looked at some of his FAG bearings this morning... they had the same issue... the SKF bearings that we've checked do not have the issue.

re. stop worrying about it... I don't want to be driving to the track 200 miles away and have the rear bearings go out.. so while I have the car up in the air, might as well put the proper good part in there..that's my approach.

 

[diskullman]

I would assume the engineer at FAG may have looked at the wrong drawing or revision, as thebearing rings must be machined properly for the type of seal used. FAG makes a fine quality bearing, and I would not give up that easily on this bearing. You may actually have an improved seal design, possibly a non-contact seal that will not drag. What I personally would do, is gently pry one of the seals out and get a better look.

Russell Giuliano

 

[hcoles]

Russell,
yes, I was thinking of doing just that. But still the seal needs to "lock" on the outside ring and slide on the inside ring.. I'll let you know what I find and post another picture.
-Henry

 

[hcoles]

Russell,
I took off a seal and discovered something...
There is another sealing system under it.

The outside ring is lightly sealed with the red seal but looks to be heavily sealed by the black seal underneath.

See pictures...

you should see a angle view of the bearing with top seal off and the black seal part below...

also included a picture of the back side of "front" seal.

 

[hcoles]

I guess only one picture at a time...

 

[unclesyd]

It looks as though the black inner shield is really a lip seal running against the outer shield instead of the shaft.
Your configuration appears to have the out shield acting a landing area for the inner seal and acting as a slinger to keep contaminants out off the lip.

I have been looking for information about a shield that we used that fit on the shaft and ran against the face of the outer bearing race. This arrangement kept all contaminants of the inner shield

It looks like your bearing got a little hot.

 

[hcoles]

unclesyd,
yes, I think it works as you say.
the only remaining question/issue is that where the outer part of the shield runs near the outer ring...I have contamination and the ledge the bearing is pushed against is close to the moving seal..
stay tuned as I get more info.
thanks for the comment

 

[unclesyd]

Could your contamination have come from the lip on the inner seal as the area looks a little black.

Just for information.
Look at the type D seal. It appears that in your case they rotated the lip 90 deg. and had it running against the an added outer shield instead of the inner race. This arrangement is probably due to bearing size.

http://www.dynaroll.com/catalog/pag009.htm

 

[diskullman]

Sorry to say that I'm not getting a good read from your second picture. From what Unclesyd says, it sounds like it is some sort of V seal that contacts the outer shield. Whatever the case, it does not sound like what the FAG engineer described. In any event, this sealing system looks much superior to the standard bearing seal, so I don't think I would worry much about contamination.

http://www.skf.com/portal/skf/home/products?maincatalogue=1&lang=en&newlink=4_3_1

Russell Giuliano

 

[hcoles]

Russell,
I'm probably over thinking this, I've been know to do that.
Take a look at this tread, it has a Visio picture showing that the seal runs very close to the mounting structure and there is a place for debris to build up... this is why I like the conventional seal configuration.

http://forums.pelicanparts.com/showthread.php?t=179300&page=6

 

[diskullman]

Yes, much better read.
I would say that the FAG is a SUPERIOR seal design as it has an outer flinger and an inner contact seal. I would prefer this design to the standard bearing seal. I'd pop that outer seal back on and install it!

Russell Giuliano