59 inch bar chian tensioning.

[Walnut33]

I know some of us have the 59 inch bars on our big saws. How do you tension a chain this big? mine often slides out side the bar as its about to enter the sprocket. Also my sprocket is able to move in and out on its shaft. is this normal? Thanks.

 

[BobL]

I know some of us have the 59 inch bars on our big saws. How do you tension a chain this big?

I tension it the same way as any saw but just a touch more because I know it will stretch more when it is warmed up. The difference in tension between a 60" and 30" chain is that the 60" fair snaps back into place when pulled back to where a full drive link is showing, whereas the 30" more glides back into place.

I have often thought about designing a tensioning tester and played around with small weights hanging off cutters but nothing really seemed to work consistently.

mine often slides out side the bar as its about to enter the sprocket.

I don't quite understand this, do you mean while running or while tensioning?

Also my sprocket is able to move in and out on its shaft. is this normal? Thanks.

Yes this is normal.

 

[Walnut33]

while running at full speed. the chain stays in the sprocket but comes off the bar about 10 inches before the sprocket. The chain also seems to jump on the top of the bar a bit.

 

[BobL]

while running at full speed. the chain stays in the sprocket but comes off the bar about 10 inches before the sprocket. The chain also seems to jump on the top of the bar a bit.

I assume you mean on the top of the bar? if so, small amounts of chain lift is normal, its just more evident on long chains. The sprocket pulls the chain tight underneath and onto the sprocket, simultaneously it pushes the chain ahead of the links in front creating a slack section of chain. Compounding this effect, various chain vibrations and speeds, the width of the cut and the cutting action itself will combine to produce a range of "waves" with different wavelengths right around the bar that can bounce the chain up off the bar. I sometimes see a smaller wave of chain lifting off the bar about 6" before the nose sprocket. This bouncing action can pound chips off and dips into the bar rails so if the waves get too high just tighten the chain a touch more.

Cheers
Bob

 

[Walnut33]

No it just sometimes comes off on the bottom right before it enters the sprocket. i will be playing with it today on a big chinese elm log. just for practice and to get used to the saw.

 

[BobL]

No it just sometimes comes off on the bottom right before it enters the sprocket. i will be playing with it today on a big chinese elm log. just for practice and to get used to the saw.

That can still be a result of a "resonant wave" effect resulting from the chain cutting action. Few people realize that the chain does not sit flat on the bar rails while cutting. Sequential sets of 2, 3 or more cutters porpoise up off the rails biting into varying amounts of wood. These waves are pulsed throughout the chain and are often seen where you describe. One problem they create is if inboard wheels are used that are too close to the chain the wheels can be mangled by the cutters. Another problem is that with the saw laying down in the milling position, if the propagating wave is large and the throttle is blipped, the wave can propagate back onto the sprocket and your chain can come off is it is too loose.

 

[Walnut33]

Ok thanks! Now I got a few more questions. 1. It also seems to catch and stop the saw chain in a cut. (I hope this doesnt happen during milling) I was guessing it wasn't oiling enough as to the cutting problem so i trurned the oiler all the way up. Not too much difference. Not sure whats going on here. (It has a standard shihl chain on it now, not any sort of skip which i hear you need on bigger bars.) 2. When I cut for a few minutes with the saw at full throttle it will often die right after I let off. Could this mean that I need to turn up the idle speed? (maybe due to pushing this big of a bar?)

 

[BobL]

Ok thanks! Now I got a few more questions. 1. It also seems to catch and stop the saw chain in a cut. (I hope this doesnt happen during milling) I was guessing it wasn't oiling enough as to the cutting problem so i trurned the oiler all the way up. Not too much difference. Not sure whats going on here. (It has a standard shihl chain on it now, not any sort of skip which i hear you need on bigger bars.) 2. When I cut for a few minutes with the saw at full throttle it will often die right after I let off. Could this mean that I need to turn up the idle speed? (maybe due to pushing this big of a bar?)

What is it?

 

[Walnut33]

Just the 880. The saw itself in action.

 

[BobL]

So rewriting this

1. The 880 also seems to catch and stop the saw chain in a cut. (I hope this doesnt happen during milling) I was guessing the 880 wasn't oiling enough as to the cutting problem so i trurned the oiler all the way up. Not too much difference. Not sure whats going on here.

What part catches the saw chain? If it's the chain catcher or sprocket cover then the chain is too loose.

With a saw like the 880, unless you are using a 24" or smaller bar (then one might well ask why?) then I would leave the oiler always on max.

2. When I cut for a few minutes with the saw at full throttle it will often die right after I let off. Could this mean that I need to turn up the idle speed? (maybe due to pushing this big of a bar?)

It sounds like you might need to tune the L screw as well.

 

[Walnut33]

The chain just seems to get stuck in the cut of the wood often, and bog the saw. The chain is new. Should i be running a skip chain on this 59 inch bar?

 

[BobL]

The chain just seems to get stuck in the cut of the wood often, and bog the saw. The chain is new. Should i be running a skip chain on this 59 inch bar?

OK - rather than guessing, let me ask some questions;
Are you holding the throttle wide open?
How wide a cut are you making?
When was the saw last tuned correctly?
How hard are you hoiking on the saw - does is bog down just under it's own weight?

 

[056kid]

This is rather scary, you are running a 60 inch bar and it sounds like you dont know a saw fro a hole in the ground!!

Be careful!!

 

[BobL]

This is rather scary, you are running a 60 inch bar and it sounds like you dont know a saw fro a hole in the ground!!

Be careful!!

I agree he needs to be very careful, but better he asks here, than the guy next door with the wild thing he uses once a year or he tries to work it all out for himself.

 

[Walnut33]

The saw in Brand new. got it last week.(maybe wasnt tuned right at the factory?) The saw is being run at full trottle. The cuts are about 36 inches in diameter. Im not pushing the saw much at all, so yes under its weight. I have cut and milled tons of lumber for the last 3 years with other saws, and I bought this Big 880 to step up the game and I dont get why the chain stops and it seems to bog so bad. Even sometimes when I start a cut the chain just stops dead in its tracks in the wood.

 

[BobL]

The saw in Brand new. got it last week.(maybe wasnt tuned right at the factory?) The saw is being run at full trottle. The cuts are about 36 inches in diameter. Im not pushing the saw much at all, so yes under its weight. I have cut and milled tons of lumber for the last 3 years with other saws, and I bought this Big 880 to step up the game and I dont get why the chain stops and it seems to bog so bad. Even sometimes when I start a cut the chain just stops dead in its tracks in the wood.

OK then it definitely sounds like it needs a tune. Ideally it needs to be tuned to the cut (make small [1/16] turns to the H screw and time cuts) which is something they don't do in the factory

FWIW, when I first got my 880 it was slower and a lot more gutless than my 066. But perhaps more than any other saw a new 880 needs to be run in, and definitely not at full throttle or with a 60" bar on it.

I put a 30" bar on mine and bucked up 20 - 30" logs over a range of throttle settings from 3/4 to WOT for ~5 tanks of mix. Then I tuned it. Then I did some "light milling" with a 42" bar for ~10 tanks of mix at varying RPMs (7000 to WOT), then tuned it again, and then I put on the 60" bar. Some say this is not necessary but whether they are run on like this or not they still take time to develop their full power.

I'd say it took ~25 tanks of mix through before it came close to meeting my expectations.

 

[Walnut33]

Ok thats what i wanted to hear. Tommorrow I will put the 36 inch bar on and tune it and then I will post an update. Thanks alot Bob, you have helped me out quite a bit since I have joined this site. Thank you.

 

[huskyhank]

I'd put a 7 tooth sprocket on it if it's an 8 now. Then run it on the mill being very careful to feed it into the cut gently and easy. Keep gentle steady pressure so the saw keeps rpm with just a bit of load. As you run it it will break in and get stronger. You will get better at feeding it and your milling will go better. If you can't tune it be sure to have you saw shop tune it for you. Tell them you are using it on a mill and to make a little rich.

 

[BobL]

I'd put a 7 tooth sprocket on it if it's an 8 now. Then run it on the mill being very careful to feed it into the cut gently and easy. Keep gentle steady pressure so the saw keeps rpm with just a bit of load. As you run it it will break in and get stronger. You will get better at feeding it and your milling will go better. If you can't tune it be sure to have you saw shop tune it for you. Tell them you are using it on a mill and to make a little rich.

Yeah, that's also what I did, start with 7 and then move to 8 (and soon to 9 and maybe 10?)

 

[Walnut33]

Yeah I tuned it to the instructions in the manual and had to turn the LA screw like 2 and a half times to get the chain to move. It ended up way too rich and it would flood and die so I backed it off alot. Before it sounded like it was barely staying alive. Tomorrow i will stop by the shop and get it tuned a bit rich. Thanks.