clutch-drum spline wear ...

[Molecule]

rim sprocket wobble and uneven bar wear ... I put a new rim sprocket on which is the right size, but the it seems to wobble on the splines of the clutch drum. The inside of the clutch drum has normal polish, but no groove IMHO. The reason I ask, is that the groove in the prior bar was worn unevenly - apparently the bar was never turned and the somehow the wear inside the groove favored one side over the other, leaving one rail almost twice as wide as the other.

I was wondering whether the rim sprocket might be turning sideways during rotation of the clutch drum (as the chain tightens during a pull, the rim sprocket "sets" to one side or the other), and this "set" of the rotating sprocket disk then adds a twist to the drivers of the moving chain, which then put a kind of sidewise "standing wave" within the chain, which then wears against one side of the groove ... (it's a used eBay saw, so I can't tell if it was the inside or outside rail which too the most wear.)

does that sound like what might have been happening?

is there a general rule about replacing clutch drums like there is for replacing sprockets with chains -- e.g. 2 chains per sprocket., then 2 sprockets per bar, then a new clutch drum for each new bar ?? Loosely speaking, for a prorperly maintained saw, does a clutch drum generally last as long as a bar?

 

[Bills Oak]

drum spline wear

Molecule, try a new sprocket on the drum, if it wobbles at all replace both the drum & sprocket. I normally get about 3 sprockets per drum average on my Husquvarnas, McCullochs only about two. I get about 3 sharpenings per chain replacement & I go through about 4 sprockets per chain I have found that using a "graphite grease" on the splines seems to help cut down on sprocket to spline wear...Hope this helps--Bill Irvine,,BILLS OAK

 

[JimL]

wholey crap, i bet ive got 50 sprockets on the drum on my 066. Its worn alot where the clutch rides and also where the sprocket rides. Im going to run it till its toast to see just how long i can get out of one. Guy i work with replaces his every 5th sprocket. I keep them cause I can't see hardly and wear on them.

 

[Lawn Masters]

I havent had to replace the drum on any saw with a rim sprocket setup as of yet, but that'll change sooner or later I'm sure.

 

[Molecule]

I'm sure this rim_v_spur must have been hashed out again and again, but IMHO the clutch drums with spur sprockets used to last longer (cost less) than these rim drums with floppy sprockets. I'd get ... maybe roughly 5-6 chains per fixed spur sprocket (admittedly I file a lot) ... although the last chains did stretch out quicker. But still, I wonder if this "new" floppy rim system is any better or cheaper. (It's new to me.) Although, if you got one of those aftermarket drums where the spurs poked thru, it played h3ll on the clutch and chain.