Bucking Question

cory

Tree House enthusiast
Joined
Aug 23, 2008
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A small, simple question, one I feel like I should know the answer to, but I really don't: you are bucking a log (into firewood or long lengths, doesn't matter), you cut say 3/4 or 4/5 of the way thru and then roll the log to finish the cut. When you stick the bar into the kerf to finish the cut, why does it cut so much better and easier and sometimes a bit faster when you do it with a pushing chain (top of the bar) than with a pulling chain (bottom of the bar)? In either case, the bar is inserted equal depths into the kerf.
 
No friggin clue! I almost always use a pushing chain when I can. Not sure why, but it is what it is.
 
You guys kinda spoiled it for me...
I was gonna mess with the lurkers and newbs by saying the rakers are just a tad different on top of the bar than the bottom...











:D
 
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  • #10
Less wood being cut would be my guess.

I dunno, if the bar is in the same depth for pulling or pushing, same amount of wood should be being cut, no?

Is it faster, or does it feel faster?

It definetly feels easier, may be faster, maybe not. It feels like the saw is being sucked into a sweet spot in the cut.
 
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  • #11
I think I figured it out: whenever the chain is spinning in a kerf there is some degree of contact between it and the sides of the kerf. This contact tends to drive the tip, and so the top of the bar, upward. The tip is acting like a wheel or a gear and causing the bar to walk upward to some degree, and upward is where the uncut wood is located. So, when using a pushing chain, the tip in the kerf is naturally driving the bar into the uncut wood. With a pulling chain, the bar is not driven into the uncut wood, a little force from gravity and/or the sawyer is needed to feed the bar into the wood.

Some empirical proof can be felt by cutting a small diameter log where the bar tip is not in a kerf, it is free in the air. The saw seems to cut with the same ease/speed with either a pulling or pushing chain; the tip has no kerf to react with.
 
Good analysis by Cory.....It also seems to me that pushing chain tends to track the tip along the existing kerf better whereas a pulling chain is happy to deviate and start a new semi-bypass of the existing kerf....thus actually cutting more wood than the pushing chain and requiring more work.
 
Good analysis by Cory.....It also seems to me that pushing chain tends to track the tip along the existing kerf better whereas a pulling chain is happy to deviate and start a new semi-bypass of the existing kerf....thus actually cutting more wood than the pushing chain and requiring more work.

I'm with your take on it, Justin.
 
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  • #14
It also seems to me that pushing chain tends to track the tip along the existing kerf better whereas a pulling chain is happy to deviate and start a new semi-bypass of the existing kerf....thus actually cutting more wood than the pushing chain and requiring more work.

Agreed, but why is this? Is it because of what I described above or is it something else. You can clearly feel it happening, I'm just wondering why it happens.

Gerry B, you are a cutting guru, do you have an opinion here??
 
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  • #16
Well I will ask this: do you know the answer? Is it in FGTW? What page:)?
 
Not specifically, Cory. I present the method of back chaining as an alternative means to cut with the chainsaw, but it's really situation dependent and ones preference how we use the method, and really, I can't say one way is better than the other.
 
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  • #20
Not specifically, Cory. I present the method of back chaining as an alternative means to cut with the chainsaw, but it's really situation dependent and ones preference how we use the method, and really, I can't say one way is better than the other.

But would you agree that back chaining to finish a cut, as presented in the original post, is easier/better than with a pulling chain cuz the saw is naturally sucked into the cut?
 
When pre commercial tree thinning where we back bar, angle slash most of the trees. It is a fact that the top of the bar cuts a bit faster than the bottom. I think????? It is because even with the bearings in the tip some torque is still lost when the chain goes around the tip. Bow bars, where they are cutting before the full curve of the end of the bar. Are known to be dangerous torque monsters. But they cut at the end of the bar . But again I can't prove it But if your pre commercial tree thinning you get many thousands of opportunities to experiment.
 
I have to agree with the previous responses. I think it's the angle, and the chain passing through less wood. Also agree with what you said Cory about the sprocket helping you in the kerf.

8)
 
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  • #24
When pre commercial tree thinning where we back bar, angle slash most of the trees. It is a fact that the top of the bar cuts a bit faster than the bottom.
I've never done the commercial tree thinning. I wonder if the back barring works better there because it is more ergonomic instead of because the top of bar cuts faster? When back barring at that angle you are letting the saw support most of its own weight vs when cutting with a pulling chain you are supporting most of the saws weight so it feels more comfortable and easier.

The tip of the bar eating up some torque is interesting, but, if it is making the bottom of the chain spin a little slower, isn't the top of the chain spinning simultaneously at the same slower speed?
 
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  • #25
I think it's the angle, and the chain passing through less wood. Also agree with what you said Cory about the sprocket helping you in the kerf.

I am seriously curious about this question lol. Maybe it is a combination of reasons - Some of it could be the(1) ergonomics of back chaining, with the saw supporting a lot of its own weight. And then(2) the sprocket helps you in the kerf, as Grendel says above. And how bout the reason that (3)the pulling chain can tend to start another kerf whereas the pushing chain doesn't do that cuz the tip is giving little micro kickbacks when it is inadvertently guided to the side of the kerf; it is repelling itself from the sides of the kerf so it is staying centered in the kerf.
 
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