kickback

[Roger Sisler]

Hello, I have a question about chainsaw kickback.Will a short bar kick back more easily and more uncontrollably than a longer bar? It seems to me that a longer bar will take more time to actually kick and has a longer length to travel to reach vertical.Also I think the operator will have more leverage against this with a long bar.Just wondering?Just don't know? Roger

 

[fishhuntcutwood]

Either is dangerous. If you think about it, the longer bar would have a longer lever arm, and while it would have to travel further, it would require less energy to initiate the kickback, relative to the fulcrum, which is your left hand on the handlebar. With either bar, you're going to lose. Few are the men that can notice and overpower a solid kickback. Little jumps here and there are manageable, but best avoided, but a solid intense kickback on any saw is gonna hurt, short or long bar. A longer bar may weigh more and require more engery to move all the way back to your face, but it'll also be more akward and cumbersome to combat. Each comprimise between short and long, equals itself out to being just as dangerous as the other. I never think about how long the bar is, I just think about kickback. Period.

Jeff

 

[West Texas]

Roger, when you hit an unexpected hard object it can 'kickback' -- I had it happen today when cutting across a 'crotch cut' or 'vee' joint in hard dead oak; which surprised me; but as Jeff said it was a 'small' and controllable kickback. If you hit a nail or spike buried in a tree trunk or limb, it can cause serious kickback without warning. And if you let the nose of the bar touch another limb or log while sawing, it can kickback. And my advice is never cut with the nose tip of the bar, as you may notice the 'cheapie' saws even have nose guards on the bar to prevent you from using it. Cut close to the 'dogs' on your saw and you will usually be in good shape on a big cut. Middle of the bar when limbing is usually OK for a beginner too.

There is absolutley no substitute for common sense; and, its getting rarer and rarer.

Good luck with your saws.

 

[tonka]

I've always heard that a long bar can exert more force in a kickback because of its increased leverage. Don't know if that is correct. Thank God I've never experienced a full blown kickback.

 

[asb151]

Also be aware that some chains have more tendency to kickback than others. A recent post here showed left hand and leg as the #1 injury locations. Just be conscious of kickback as you cut. Always keep an eye on where the bar tip is and what is around it. Invest in some protective clothing, gloves and a good pair of boots. Wear ear and eye protection while you’re at it.

 

[ross_scott]

Roger there are some very good points posted by the other guys stick to these tips they are giving and you should have a enjoyable day of work. Also remember keep the saw to the right of your body and to keep your left arm on the wrap around handle straight as a straight arm is always stronger than a bent arm and preferably have a safety mitt attached to the wrap around handle and turn your body if you are going to turn the saw to cut at a different direction so it is always to your right, Kickback can hapen at anytime so keep your mind on the task and observe everything around the area you are cutting small twigs etc will cause a kickback if you are not careful if you have any limbs touching the end of the bar while the chain is stationary prior to starting a cut then cut that branch away so it will not be a hazard and a potential cause for kickback

 

[Sizzle-Chest]

does anyone have a kickback story? i guy i worked with at the FS got hurt really bad one winter when he was bucking some windfall and caught the bar right in his knee (not clear how). He came to work the next summer with a huge scar on his kneecap. He werent wearing chaps neither.

 

[Oregon Engineer]

Hello, I have a question about chainsaw kickback.Will a short bar kick back more easily and more uncontrollably than a longer bar?

Testing on a kickback machine shows a saw with a shorter bar has less inertia to rotation so it rotates faster than a saw with a longer bar. The kickback on a saw with a shorter bar will be more dangerous than with a longer bar.

Check out the following thread for movies on kickback
http://www.arboristsite.com/showthread.php?t=26226

 

[Lakeside53]

I've always heard that a long bar can exert more force in a kickback because of its increased leverage. Don't know if that is correct. Thank God I've never experienced a full blown kickback.

It's correct, and why Stihl always "recommends" short bars on their big saws, not that most take any notice. Although it takes more to start the action, the longer bar has more inertia due to its mass, and is harder to stop once moving. A big Saw has PLENTY OF hp to get a big bar moving... As for a long bar on a small saw (underpowered for the bar length/weight), not sure, but if the saw has insufficient power to kick the bar greatly, then the bar would have an dampening effect on the kick.

 

[Sizzle-Chest]

It's correct, and why Stihl always "recommends" short bars on their big saws, not that most take any notice. Although it takes more to start the action, the longer bar has more inertia due to its mass, and is harder to stop once moving. A big Saw has PLENTY OF hp to get a big bar moving... As for a long bar on a small saw (underpowered for the bar length/weight), not sure, but if the saw has insufficient power to kick the bar greatly, then the bar would have an dampening effect on the kick.

correct me if im wrong, but suggesting a small bar on a big hp saw has the chain spinning with more force than if it were on a longer bar, which creates more inertia. in my expereince, holding a big saw with small bar in the air and pulling the trigger makes the saw want to go up more than same scenario with bigger bar. not only does the saw have to work harder to create the same amount of turning power, but the bar changes the balance so the tip wants to stay down more. like i said, i might be wrong, but i feel that the more horsepower and the smaller the bar, the more likely the kickback.

 

[Sizzle-Chest]

It's correct, and why Stihl always "recommends" short bars on their big saws, not that most take any notice. Although it takes more to start the action, the longer bar has more inertia due to its mass, and is harder to stop once moving. A big Saw has PLENTY OF hp to get a big bar moving... As for a long bar on a small saw (underpowered for the bar length/weight), not sure, but if the saw has insufficient power to kick the bar greatly, then the bar would have an dampening effect on the kick.

correct me if im wrong, but suggesting a small bar on a big hp saw has the chain spinning with more force than if it were on a longer bar, which creates more inertia. in my expereince, holding a big saw with small bar in the air and pulling the trigger makes the saw want to go up more than same scenario with bigger bar. not only does the saw have to work harder to create the same amount of turning power, but the bar changes the balance so the tip wants to stay down more. like i said, i might be wrong, but i feel that the more horsepower and the smaller the bar, the more likely the kickback.

 

[Lakeside53]

We may not be talking about the same thing - likely 'cos of the the two beers just consumed, but I'm talking about inertia AFTER the kick has happened (no matter what causes it). The inertia I refer to is not from the chain spinning, but the "bar in motion". The bar has inertia by virtue of its movement, is basically rotating around your hand grasp, and mass with velocity is what it's all about. Low chain speed kickbacks tend to be far more common and on large saws, and far more brutal than those at high rpm. Dig that .404 chain at "slower" speed just above the tip on a big saw and :blob5: Big bar or not.


I'm guessing that the larger mass of the long bar balances the motor mass more easily allowing for an easier rotation. Conversely, the smaller bar length has less effect on the motor mass, so the motor tends to dampen it.



Hmmmm... I'm not making much sense even to myself. Maybe someone else would like to argue my point with math.

 

[fishhuntcutwood]

This thread is going to go round and round.

Lakeside, I understand what you're saying. This is kinda what I meant when I said that the compromises equal themselves out.....

I was going to try to explain what I'm now talking about, and it would just make things worse...how about we all just agree to try to avoid kickback!

And I haven't even had a beer yet.

Jeff

 

[PWB]

Welll..............

Kickback is dangerous whether the bar is short or long. The other question is, which is more dangerous? Think about a homeowner bucking with a little saw and a 16" bar. Holds the saw directly in front of him about waist high. Where does the saw tip go when it kicks? straight to his face. now look at the same scene with a big saw and a 36 or 42" bar. #1 the guy running it is likely going to have a little more experience, and not have it in quite as bad a position. #2 if it does kick (AND he holds on to the saw) the tip will be way over his head, not right in his face. If the brake works as it's supposed to.........

Still dangerous, but which is more likely to cause serious injury?

I've been told that for a while at least, WSIB (safety guys up here) wouldn't let fallers (BC) use a saw without a brake with less than a 28" bar for this reason. Don't know if it's true though. Went looking in our "green book"(regs) a couple of weeks ago, it says no brake, no use. Anybody know the right answer?

 

[Billy_Bob]

I read somewhere that it is better to use a long bar sawing logs on the ground while you are standing straight up with the bar pointing in a downward direction. As opposed to using a short bar sawing the same logs on the ground, having to bend down, with the bar straight out from you.

The theory on this was that with the bar pointing in a downward direction, the bar would have to travel quite a distance before it comes up and smacks you in the face/shoulders, etc. And with a bar pointing straight out from you, there is less distance for the bar to travel before it smacks you.

Additionally, if cutting above shoulder height with the bar pointing in an upward direction, this would be extremely dangerous as there is a very sort distance for the bar to pop up and smack you.

I don't know if this is true or not?

 

[Oregon Engineer]

PWB,
In a kick back situation a shorter bar is more dangerous on a saw because it will rotate faster than if the bar is longer. The computed kickback angle on saws with short and long bars always shows the shorter bar to give a larger computed kickback angle.

The speed of the chain on the tip of a bar is the same whether it is short or long (assuming the saw has the cc's to pull it). When the chain at the tip of the bar digs into the wood it starts the bar rotating.
1) a longer bar will require more energy to be delivered to the wood before it starts to rotate because the mass of the system is greater. This removes more energy from the kickback so the bar rotates slower.
2) the longer bar tip is farther from the center of rotation so the rotation is slower than on a shorter bar. Picture driving down the road at 60 mph. Which rotates slower; an 8" trailer tire or a 15" trailer tire??? Slower rotation in a kickback buys you more time to react or more time for the chain brake to stop the chain before it hits you.

Before a kickback occurs: a shorter bar can keep the average consumer from hitting objects on the back side of the log being cut. Many people involved in a kickback were not watching what was on the "hidden" side of the cut and wound up contacting another log with the tip of the bar.


If you are not trained as a professional then the best bet is to get an ANSI BLUE LABELED SAFETY chain and use it. Each chain manufacturer puts out a fitup guide that will show how you can make your saw/bar/chain combination a BLUE LABEL SAFETY system.

 

[Roger Sisler]

Well thanks.This is all good stuff. I am sure that someone else besides me learned something from this. Cant have a thread on this to often .Gotta keep it fresh in everybody's mind. :Eye: :Eye:

 

[Billy_Bob]

Any chainsaw manufacturer ever try a chainsaw with two chains, each chain rotating in an opposite direction?

I would think that this would counteract any kickback forces...

 

[2manysawz]

so the moral to the story is.........kickback is very dangerous and needs to be avoided at all cost,never mind all the ********,short bar vs long bar?kickback is a bad day,plain and simple,avoid,avoid,avoid!!!

 

[Timber MacFallen]

so the moral to the story is.........kickback is very dangerous and needs to be avoided at all cost,never mind all the ********,short bar vs long bar?kickback is a bad day,plain and simple,avoid,avoid,avoid!!!

Well that, and the fact that even a 15+ year old post and discussion can still trigger a response from someone on the Internet.