Chain "Loping"

[madhatte]

Got a loop of chain which won't run right no matter the bar. For those of you who are curious, it's a 32" loop of Oregon round chisel, 72-something. I don't know Oregon numbers too well.

Here's the symptom. You know that sound when you load the washing machine off-balance and it vibrates the whole house? You go downstairs, move one pair of socks to the other side of the washer, and everything balances out again? Yeah, well, that's what it feels like running this chain.

At first I thought it was an uneven grind (caliper says no), then I thought it might be a banged-up driver, but I couldn't find any telltale shiny spots or see any distortions. It's also not any links failing to articulate, and it's not the bar or the saw, because I got the same vibration on 3 different bars on 2 different saws. I suspected a clutch for a moment until I tried the other saw, which put that theory to rest pretty quickly.

Ideas?

 

[oldsaw]

Do you have any links binding up? I've had this happen before. Work the chain in your hands when it's off the saw to see if any links are tight.

 

[madhatte]

Checked that. That's what I meant by "failing to articulate". All links seem to be rotating freely, none seem to be binding.

 

[kev1n]

I've had a chain do that to me and it was because the connecting link was installed upside down. I filed it down and works fine now.
Kevin

 

[madhatte]

That I didn't check for. Thanks for tip!

 

[Dan_IN_MN]

Did you check to see if you had 2 socks on the same foot? :hmm3grin2orange:

Sorry the only input I have at this time.

 

[slowp]

Can you take it back to whence it came from? Trade it for a good one?

 

[madhatte]

Can you take it back to whence it came from? Trade it for a good one?

Bargain Bin at Madsen's? Ehh, maybe. I'd rather just fix it, if I can figure out how.

(freshly-ground 32" chain with 80% left for $10? Yes, please)

 

[slowp]

Ohhh. I may be heading that way today or tomorrow. I need to turn my dollar hat into a ten dollar hat. Also I shall look for bargain wedges. I like their bargain bin wedges.

 

[Jacob J.]

Since it's an Oregon chain, it may have a .404" preset and tie strap tying the chain together instead of a 3/8". There were some older .404" presets that would fit the holes on the drive links of modern 3/8" chain. Also- make sure all the drivers say 72 on them. This indicates a .050" gauge chain. Somebody may have installed an extra driver to get that chain to 105 links and mistakenly used a 73 driver (.058" gauge.)

 

[madhatte]

Excellent input as always. I'll investigate this evening when I get home and report accordingly.

 

[watsonr]

That's what I was going to say, make sure its not got any .404 links in it.

 

[splitpost]

opcorn:opcorn:

 

[madhatte]

The plot thickens: all cutters and all drivers are stamped identically (25/75 -- it's a .063 ga chain now that I look at it, and I should have remembered that was what the bars were as well -- all of my >32" bars are .063)), and I can detect no difference in any tie straps. Further, everything shows even and identical wear. No tie straps are upside-down. No tie straps are of a different make. Unless there's a lead slug hidden under the top plate of one cutter or something, I can't see any difference that would account for this chain rotating eccentrically.

 

[watsonr]

Did you check the sprocket? I know you said two different saws.

 

[madhatte]

Did you check the sprocket? I know you said two different saws.

Yep, both of 'em. Same Oregon 7-pin, both more than serviceable, both showing normal wear.

I wish I had a camera -- I smashed my last one and haven't replaced it yet. They usually last me about six months; this one lasted almost a year. Maybe this weekend I'll get one.

 

[Terry Syd]

Have you determined which part of the chain is causing the problem? Maybe you could paint the side of a link with white paint and see how close it is to the point of the problem. Once you have that as a reference point, you could guesstimate about where the spot is and then paint a link on the other side.

It may get you in the ballpark as to where the problem is located.

 

[madhatte]

Well, I've considered how to do that. To refer to the original post, I have almost always been able to see as the washer winds down where the heavy side is, and to find the right offset weight within a couple of tries. In the case of this chain, however, the vibration begins about 3/4 of the way to WOT, or somewhere between 10-11KRPM, and by the time it winds down enough that I can see individual drivers, it's long since smoothed out.

I suppose I could fake it with white paint and a timing light? That might actually work: separate 12V battery to power the light, trigger probe on coil wire, white paint on a random driver, wind it up, see how far before or after the flash the white mark shows up against an arbitrary point -- say, the center of the nose sprocket -- and compare that against where the shake occurs. That should give an offset in degrees between the flash and the mark, and between the mark and the shake.

Geeze. Lotta work for a stupid chain, but it's got me curious, and now I have an idea. OK, lemme think this out some more.

 

[slowp]

I saw a chain on the bargain table, but it looked too well used.

The Madsen's were trying to figure out how to fix a flippy cap gone bad. It sounded serious. I think there are other flippy cap haters out there.

Now, back to your chain. A timing light? Really. Can't you just put on the reading glasses and wiggle the thingies around?

 

[Terry Syd]

You're not the only one who's curious. This may turn out to be an interesting trouble-shooting adventure.