Chain "Loping"

[promac850]

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?

As per RandyMac's rules for the forum... rule #4 to be specific, there shall not be any wiggling of thingies on the forum... oke:

As for the chain problem, sounds really weird, never encountered anything like that. Maybe the bar groove is too worn out? That's about all I can think of since just about everything else has basically been covered.

 

[madhatte]

A timing light? Really. Can't you just put on the reading glasses and wiggle the thingies around?

Timing light would show me a dot moving up and down the bar as I revved it up and down, since the chain isn't going to be revolving at the same RPM as the crank. Observing the dot's location relative to the vibration might give me an idea where the vibration is coming from. I don't know whether it'll work, but it'll at least be a reproducible method for diagnosing similar problems if it does prove to be a winner.

This may turn out to be an interesting trouble-shooting adventure.

My thinking exactly. If nothing else, I'll at least learn what doesn't work, and for ten bucks, I can just toss the chain if I never do figure it out.

Maybe the bar groove is too worn out? That's about all I can think of since just about everything else has basically been covered.

3 bars and two saws now, same symptom with all 3 bars on both saws, symptom disappears with different chain in all cases. That rules out everything except the chain itself. I THINK.

 

[madhatte]

OOOHHHH-KAYYY... can't make heads nor tails of the flashy flashes from the timing light. That idea was apparently half-baked. Need to re-think it. Maybe paint every other cutter? Naw, then I might as well just be looking at the chain without paint. Three in a row? That might be more useful than just one.

Note: I'm using old-school white-out as paint because it dries really quickly.

 

[Jacob J.]

How much cutting have you done with this chain?

 

[Busmech]

Sounds like you might have a slightly bent tie strap or cutter, doesn't take much if one is just a tiny bit out of line.

 

[madhatte]

How much cutting have you done with this chain?

About ten minutes, if that. Bought it used, problem caught my interest, you know the rest.

Sounds like you might have a slightly bent tie strap or cutter, doesn't take much if one is just a tiny bit out of line.

I started with that assumption. I still think that's what's going on. What I'm looking for now is a way to measure what's out of line and by how much. This has shifted from a "what's wrong with my chain" project to a "what can I learn about messed-up chains and share with the group" project.

 

[Walt41]

Ok, now I'm in...you know that the chain is moving up and down and obviously not side to side. Maybe brush all the tops of the cutters with white out and clamp the saw down. Now place two straight boards about 1/8" above and below the bar and clamp them in place, I'm thinking 2x4 cutoffs would work, then run the saw till you feel the vibration and hopefully the offending links will touch the board and knock off the white out and reveal themselves.
Maybe.

 

[Terry Syd]

Does it do the same thing if you run the chain backwards?

I know it won't cut that way guys, but we are trying different diagnostic tests to isolate the problem.

 

[madhatte]

I very much like the idea of looking for something sticking up or down. I'm thinking a straight-edge against all dimensions to look for abnormalities?

I haven't tried running it backwards yet. I will, and will report the results. That's a good idea because if it DOESN'T vibrate that way, it almost points to a driver, I think.

 

[splitpost]

did you ever figure it out?

 

[galde]

I would lay the chain out on a clean, flat surface and examine it closely all the way around on both sides of the chain for boogered drive link(s) or rivet(s) not properly spun down. I would hold the chain stretched out and bent both ways into an arc to see if all sections arced smoothly. This is a good way to spot bent or loose links. With the chain on the bar, sight along the chain to look for any top plate or side plate that protrudes beyond its neighbors. With the slack adjusted out of the chain, carefully pull the chain around the bar to feel for any tight spots. If you suspect a tooth binding in the sprocket, for example, make marks on a matched pair of teeth near the dogs -- one on top and and on the bottom. These marks will straddle the suspect tooth. Do you get the vibration only in the cut or also out of the cut? Do you have any teeth with really low-cut depth gauges?

 

[fearofpavement]

Ok, everyone has had their chances and now I am going to throw in my two cents worth to tell ya'll what I think it is. I think the chain is unevenly stretched. I have had this on motorcycles in the past where the chain would get tight and loose as it went around the sprocket. It would make a bit of noise going down the road but usually would eventually even itself up. At the high chain speeds that a saw makes I could see it vibrating significantly. I believe that if you used the chain, it would eventually smooth out but my advice is to just set it aside for stumps or something. It may do more wear or tear on your sprockets and bar than what its worth. (and now you know why it was in the bargain bin)

 

[madhatte]

Yes! Posted elsewhere (sorry), here is the moment of truth:

This is BigBadBob at the last PNW GTG showing me what was wrong with that chain. It had either been spun together from several chains of different origins, or had been jerked hard when something stopped it; either way, different tie straps had been stretched differently and were therefore different lengths. He sniffed out the problem in about a half a second based on his motorcycle experience. Dude is one sharp cookie!

 

[splitpost]

Yes! Posted elsewhere (sorry), here is the moment of truth:

This is BigBadBob at the last PNW GTG showing me what was wrong with that chain. It had either been spun together from several chains of different origins, or had been jerked hard when something stopped it; either way, different tie straps had been stretched differently and were therefore different lengths. He sniffed out the problem in about a half a second based on his motorcycle experience. Dude is one sharp cookie!

thats good to hear,these sort of probs can drive you nuts