melted needle bearing

[user 2993]

A good day of milling came to an end in the middle of the last cut when the chain stopped yet the engine did not.
I've had trouble with this clutch before so I tried it again today, figured maybe it just got too hot.
Cut ok for a little while, then started slipping again and emitting acrid smoke. So, after it cooled off, I pulled the drum and found this:

It got hot, all right. One end of the cage is melted all over the washer at left. There was still grease on the needles and they had not siezed.
What do they make the cage out of? Obviously not metal.

Any input as to things I might have done wrong here?
Saw is Stihl 090, fairly new oregon rim/drum and bearing.

Thanks,
George

 

[Fish]

99 times out of 100, sprocket bearing trouble comes from
foriegn matter, or an incorrect part being used.

You stated that you had trouble out of the clutch before.
What do you mean there?

 

[SilverBlue]

I have seen some modify chain covers by cutting 1/3 off to allow better cooling , that might help.

 

[Onthehillintn]

The bearing really dosn't do anything unless the saw it at idle.
I would think the clutch is slipping and getting the drum so hot that it melted the cage. You may have toasted the crank seal also.
Good luck

Onthehillintn

 

[user 2993]

The trouble I had before was with broken springs and unevenly worn linings on the shoes, which I suppose was a result of the springs going bad.
I scraped off the linings as per a few peoples' advice and surfaced the metal underneath to fit the inside of the clutch drum.
(for those not familiar w/ this animal, the 090 clutch has 6 shoes with 2 springs wrapped around them.)
This has seved quite well until now, and actually, I cut away all of the cover except the bar mount.
One thing I am starting to wonder is this: removing the linings makes a larger gap between the shoes and the drum. This would ( I think ) make the clutch engage/disengage at a higher rpm. Wide milling cuts tend to pull down the engine speed, and maybe my clutch has been slipping, not enough to be noticable, but enough to generate a lot of heat?

 

[user 2993]

Wow, it took me 10 minutes to type that, in which I got another reply. s'pose I oughta pressure/vac test the case?

 

[Onthehillintn]

I don't think I would leak test it, just be aware of it as a possibility. If it does not run as it usually does that would be the first thing to check. Or you could just replace it since you're almost there anyway. ( I'm not familiar with sthil saws maybe you have to remove more than just the clutch to get to the seal). Sounds like you're on the right track with the clutch. The only 2 things I can think of (other than buying a new clutch) would be to try it with 1 spring or tig weld the shoes with bronze and re- machine them back to size. I would do the second because I do that kind of stuff for a living.

I need to be out milling too

Onthehillintn

 

[Fish]

It sounds like it was the use of the Oregon sprocket and bearing
that caused the failure. I have had especially bad luck with GB
sprockets, but can envision the same trouble out of Oregon.
I have also had trouble with the bars, but that is another topic
as well.
However, I have no real experience with milling applications,
so I have nothing of real value to add here.

 

[jokers]

Why hasn`t anyone else considered that if you remove the clutch lining you are changing the diameter of the clutch and ultimately reducing the contact area between the clutch and the drum. Does anyone think that you just might get some slippage between the clutch and drum in a heavy load application like milling that would be exacerbated by lessening the contact area? Naw, it`s just cheap Oregon and GB parts!

Woodbeard is right that clutch lock-up will occur at a higher rpm when the shoes have to "throw" a greater distance, in fact, true lock-up may not even occur depending on the range of the springs. It`s my experience that clutch springs are nasty little b@stards with a very limited range that they will stretch.

Removal of the clutch lining was the wrong approach, fine tuning it so a full mating was achieved should have been done.

Russ

 

[user 2993]

Hi, Jokers. Actually, when I removed the linings, I also ground the shoes to fit the inside diameter of the drum to get full contact.
When you say "lock up", do you just mean full clucth engagement, or some actual seizure of the mechanism, or is that what happens to Fish when he has trouble in bars?

I think you are right about the springs not allowing the full throw of the shoes. Actually it seems like rather lame engineering in the first place. The way those springs are just wrapped around the shoes, I don't see how the tension could be even all the way around due to the way the ends of the springs have to link together.

Anyway, what do y'all think about Onthehill's idea of refacing the shoes with bronze to get a closer fit and correct diameter?
Sounds pretty good to me. BTW, a set of new shoes costs $200
I would be worried that my son's classmates would beat me up for them.

Thanks,
George

 

[cbfarmall]

The springs won't stop the shoes from flying out. I was testing an 045 clutch and left the drum off for some reason or other. Started the saw up, and away the shoes went. Found two shoes within a day and the third a month later, after I'd given up on it.

Removing the lining will stretch them a bit further and may fatigue them faster.

Chris B.

 

[Onthehillintn]

George
Let me know if you got my email.
Its been acting wierd lately.

Onthehillintn