Chain tension on long bars

[komatsuvarna]

Big brown truck came today left me a 36'' bar and chain for the 395. I put it on and adjusted to chain to were there is no sag on the bottom, then just a hair tighter. When I pick up on the chain it will come up to the bottom of the drivers....actually about a quarter inch between the drivers and the bar. Is this about right for a 36'' bar, or do I need to do something different? The tensioner screw felt like it was getting snug.

 

[oscar4883]

Sounds about right to me.

 

[Blakesmaster]

Big brown truck came today left me a 36'' bar and chain for the 395. I put it on and adjusted to chain to were there is no sag on the bottom, then just a hair tighter. When I pick up on the chain it will come up to the bottom of the drivers....actually about a quarter inch between the drivers and the bar. Is this about right for a 36'' bar, or do I need to do something different? The tensioner screw felt like it was getting snug.

I normally run my long bars with the chain a little looser than the shorties. Not sure if this should be done but I figure pulling that much chain, the tighter you make it the more friction you will have and power you will lose. The difference isn't much from normal but it's definitely loser.

 

[buzz sawyer]

Just remember to pick up on the front of the bar before tightening the bar nuts when adjusting the tension.

 

[komatsuvarna]

Just remember to pick up on the front of the bar before tightening the bar nuts when adjusting the tension.

:msp_thumbup: Got that part.

I was kinda concerned that the chain was too loose cause I could pick it up so much. I guess its just cause of the longer span of the bar.

 

[flushcut]

I tend to go a little bit tighter because when you are using it the chain will warm up and expand to the perfect tension IMO.

 

[Evanrude]

I normally run my long bars with the chain a little looser than the shorties. Not sure if this should be done but I figure pulling that much chain, the tighter you make it the more friction you will have and power you will lose. The difference isn't much from normal but it's definitely loser.

:agree2: Thats how I do it.

 

[Gologit]

:msp_thumbup: Got that part.

I was kinda concerned that the chain was too loose cause I could pick it up so much. I guess its just cause of the longer span of the bar.

Like GAS says...no sag, no drag. On a long bar, if you're running a loose chain, the amount of chain that's not firmly in the bar grooves is a lot greater than on a short bar. That much amount of loose chain will derail a lot quicker than a shorter chain. If you pop a 36" chain off you might wind up with some interesting new scars.

Not preaching...just showing what works for me.

 

[Erock]

I tighten it till when i lift up on the chain, the very bottom of the drivers don't show out of the groove. Then after tightening bar nuts i check again and spin the chain. If I can move the chain with one hand and its not super easy and it doesn't bind up its good.

 

[cjnspecial]

Throwing chains on a long bar is a bad thing, especially if you are nealing down flush cutting a stump. I run it a little snug and only run stihl chain on long bars because it is pre-stretched. Haven't thrown a chain since.

 

[zogger]

Tightening in general

I was wondering about this before, just tightening in general. We have all sorts of tools and specs on saws, but I haven't seen anything along the way of an actual factory or pro styled tool designed to grab a link and pull, measure resistance, then match that with factory drag specs (which don't exist yet, AFAIK) Could be anything, just a spring scale, etc. As it is now, it is sorta random as in "snug, but not too snug" etc. I just do a bottom pull, guides just stay inside the groove, then an eeny more tight. I would actually like a more precise measurement than that, also something you could use in the field once it has been warmed up and a few cuts made.

Something like a torque setting, along those lines, chain drag setting following a formula for bar size and gauge and chain type, etc. That would also be useful in checking different bar oils, see which is better in that lubricity aspect.

I know we all get it pretty close, just thought it could be improved scientifically. We measure so many other things, with chainsaws and other mechanical things, why not chain drag and so on? Example, I use a tire gauge, handy, beats guessing, especially when within a few lbs pressure here and there. I have noticed on larger equipment, looking at a set of left and right tires, visually they may look almost identical, but can still be quite different once a gauge is on them. Your fine tuning the carbs, get it by ear close, but to be real precise, the tach comes into play.

I don't have a spring scale like that, any of you guys ever actually measure resistance on chain pull? Would be interesting to see what that "last little eeny tightened" actually means, for example. One brand of bar might "slide" lots better than another. Stuff like that.

 

[D&B Mack]

Remember, the ambient temperature for the chains will matter too. I.E. if you have your chains outside in 10 deg. weather and get into heavy cutting, they will loosen up more than if it was 90 deg. out. The longer the bar, I tend to make a little tighter. The more chain, the more expansion when heated up, but this too depends on how hard you are cutting.

 

[SawTroll]

I was wondering about this before, just tightening in general. We have all sorts of tools and specs on saws, but I haven't seen anything along the way of an actual factory or pro styled tool designed to grab a link and pull, measure resistance, then match that with factory drag specs (which don't exist yet, AFAIK) Could be anything, just a spring scale, etc. .....

I don't think that is practical at all - there simply are too many variables involved.

 

[galde]

Just a couple of observations to throw out there: Sharp chain in green, cool wood and inadequate oil --- bar heats up more than chain and chain gets tighter. Dull chain, plenty oil -- chain heats more than bar, chain loosens. Also, on a saw with lots of power and torque the tension put on the chain by the drive sprocket will produce elastic stretch in the chain, so a somewhat tight chain will loosen up in the cut when pulled by the drive sprocket. Just look at the chain on a 36" mill when under load. A chain that is tight at rest will have lots of slack when in a long cut. If you start with some slack, you will have a lot more of it in the cut -- the longer the cut, the more additional slack. As stated earlier, a 36" chain thrown at 9,000 RPM is a scary thought.

 

[mdavlee]

I run the chain tight enough that when holding up on the tip of the bar it draws up to the bottom of the bar and just a touch tighter. That seems to work pretty good for the 41" bar.

 

[Bob Wright]

I have had some problems keeping my 50" chain tight. The biggest thing is its a hardnose bar so forget about running it loose because it will come off. So i rest the end of the bar on a little chunk of wood to keep the bar pointed up when tightening the bar adjuster and i make the chain a little tighter than a normal with a hardnose bar. Some day i am going to wack off the bar end and weld on a roller nose if i can find one wide enough. Or i might just take it to my machine shop and build my own...Bob

 

[komatsuvarna]

Thanks for all the replys guys. Sounds like I got it about right, so Ill just keep a close eye on it. I know the chain is going to stretch being as its new.

I can see where a chain thrown from a long bar could turn into a bad picture....thats the reason I started this thread. I learn enough stuff the hard way, and didnt want to learn this the hard way.

Handing out some rep to the ones I can!

 

[mdavlee]

I threw one on the 41" cutting up that big piece that made it to the GTG. I had to file about 25 dl to get it to go back into the bar groove.

 

[komatsuvarna]

I threw one on the 41" cutting up that big piece that made it to the GTG. I had to file about 25 dl to get it to go back into the bar groove.

Yeah that would suck. I was worried about that 3 feet of chain hitting me. I adjusted it like I do the rest of my saws, just didnt expect to be able to pull the chain an inch off the bar....but it quickly snaps back so I feel its alright for now.

Really liking the 395. It pulls a 28'' full comp like nothing. I got a big sweet gum (42 inchs) behind the barn that needs to be taken down. Ill get to try the 36er out on it before long hopefully.

 

[RiverRat2]

Like GAS says...no sag, no drag. On a long bar, if you're running a loose chain, the amount of chain that's not firmly in the bar grooves is a lot greater than on a short bar. That much amount of loose chain will derail a lot quicker than a shorter chain. If you pop a 36" chain off you might wind up with some interesting new scars.

Not preaching...just showing what works for me.

Yeah,,, What Bob said!!!!! :msp_w00t: