falling 101

[czar800]

i may be on to something here. can some others that understand what i said above add or ? with a strong angle back cut you are now pushing the tree with the wedge. with a traditional horizontal back cut you are lifting the tree with the wedge. commonsense tells me that is correct

I am with you on that WLL, I have a feeling that just maybe my other post in the pic. forum got this started.. I pulled this tree with a over 14,000lb farm tractor. Yes it would have been harder to wedge in a desired direction.

I am new a so far i love this sit

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[(WLL)]

i may be on to something here. can some others that understand what i said above add or ? with a strong angle back cut you are now pushing the tree with the wedge. with a traditional horizontal back cut you are lifting the tree with the wedge. commonsense tells me that is correct

I am with you on that WLL, I have a feeling that just maybe my other post in the pic. forum got this started.. I pulled this tree with a over 14,000lb farm tractor. Yes it would have been harder to wedge in a desired direction.

I am new a so far i love this sit

View attachment 61069

View attachment 61068

nice pic's looks like ya cut all the hing off too. good thing the tree wanted to go the same way you hoped she go:greenchainsaw:

 

[czar800]

WLL where at in pa are you from? I live in Ellwood City about 40 miles north of Pittsburgh.

 

[(WLL)]

WLL where at in pa are you from? I live in Ellwood City about 40 miles north of Pittsburgh.

bucks county

 

[smokechase II]

pushing

Pushing a tree with an angled back-cut will be prone to breaking the hinge and ineffective due to its location. That is a very short lever arm and my experience is simply; lifting is effective.

With dead, (lightweight), smaller trees I like to cut as low as possible so I can stop cutting with the correct hinge then just push it over with my body.
My point here is if you're dropping a tree where the angled back-cut would work. Skip it and do the least amount of work.

{On most trees, cutting with a significant angle takes awhile. A cut angled at 45 degrees takes longer not just because of the amount of wood to be cut but at that angle the saw cuts poorly. Great chips at 0 degrees - with the grain, good chips cross cutting at 90 degrees, poor chips at 45.}

Possibly because of how ineffective an angled back-cut is in bigger timber, I've never heard a single experienced sawyer suggest that in the Pacific NW. Every single angled back-cut stump is peed on immediately and openly regarded with disdain.

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Exceptions can exist. Let's say a cutter finds a tree that is already hung up. Of course, he found it this way. It wasn't his fault.
Cut a steep Humboldt and angle the back-cut down to match the angle of the Humboldt. The objective here is to either walk the tree down or have the jump help kick it free.
That sort of angled back-cut, generally without the face - just two angled cuts meeting, has been referred to as a Texas B_____ cut here.
Caution on toes smashed, bars pinched and tops/limbs coming down to kill you.

 

[BC WetCoast]

P

Possibly because of how ineffective an angled back-cut is in bigger timber, I've never heard a single experienced sawyer suggest that in the Pacific NW. Every single angled back-cut stump is peed on immediately and openly regarded with disdain.

**********************

And illegal to use in BC according to Worksafe BC.

 

[(WLL)]

P

Possibly because of how ineffective an angled back-cut is in bigger timber, I've never heard a single experienced sawyer suggest that in the Pacific NW. Every single angled back-cut stump is peed on immediately and openly regarded with disdain.

**********************

And illegal to use in BC according to Worksafe BC.

im 100%
convinced that that an angle back cut is poor practise. iv never put much though in the matter and now have a much better understanding why its poor practise. i treat all trees the same big scale or small and iv never used a angle back and rarely use a wedge. i will be peeing on all stumps i see that have been felled with this poor idea thank you all!!!

 

[moray]

There are times when it may be easier to "push" the tree over with wedges than it is to "lift" it. I can get into the math side of it if necessary, but to simplify it, think of it this way: is it easier to make a standing log fall over by lifting from the bottom or pushing from the side?

It seems most of the comments here had to do with the relative weakness of the stump when you try to wedge a steeply angled back cut. Can't argue with that. But the math should be identical. In both the flat and angled back cut, the wedge operation does exactly the same thing: it causes the tree to rotate around the hinge as the kerf opens up. The angled wedge should have a slight mathematical advantage in this regard, as it is slightly farther from the hinge than in the flat case, and thus would have a bit more mechanical advantage.

 

[ropensaddle]

I don't normally cut angled but remember doing a slight
angle on a couple of occasions, once to miss a nail I
did not see until face had been cut and another because
I hit something in face witch caused saw to cut crooked
and did not want to climb the hill back to the truck so
cut angled. As a practice no a standard notch is the
one I use.

 

[Cedarkerf]

It seems most of the comments here had to do with the relative weakness of the stump when you try to wedge a steeply angled back cut. Can't argue with that. But the math should be identical. In both the flat and angled back cut, the wedge operation does exactly the same thing: it causes the tree to rotate around the hinge as the kerf opens up. The angled wedge should have a slight mathematical advantage in this regard, as it is slightly farther from the hinge than in the flat case, and thus would have a bit more mechanical advantage.

Not buying that. By lifting the back straight up your moveing the leverage of the top. The angle cut your trying partially to push the tree over at the bottom. Its all about leverage over a long distance. Not pushing on the bottom.

 

[teamtree]

not sure about the math.....

but go out and experiment and you will see a big difference. I bought a few acres sometime ago and spent the winter experimenting with different cutting styles. The idea that the wedge in the angled back cut should offer the same advantage as a flat back cut does not fly with my experience. You get more lift on a flat back cut. On the angled backcut you get more pressure to the outside rather than up. Regardless, I know of no experienced fellers who use a sloping back cut. That should tell you something. I bet if you did about 10 trees (5 & 5) you would see a difference as well. I can't explain the math or the geometry but I know what works.

 

[Unknown Cutter]

the guys that are using the angled backcut are probably not leaving any holdingwood. they cut strait through the hinge.
maybe it does help reduce kickback if your standard practice is questionable to start with

 

[moray]

Not buying that. By lifting the back straight up your moveing the leverage of the top. The angle cut your trying partially to push the tree over at the bottom. Its all about leverage over a long distance. Not pushing on the bottom.

but go out and experiment and you will see a big difference. I bought a few acres sometime ago and spent the winter experimenting with different cutting styles. The idea that the wedge in the angled back cut should offer the same advantage as a flat back cut does not fly with my experience. You get more lift on a flat back cut. On the angled backcut you get more pressure to the outside rather than up. Regardless, I know of no experienced fellers who use a sloping back cut. That should tell you something. I bet if you did about 10 trees (5 & 5) you would see a difference as well. I can't explain the math or the geometry but I know what works.

I'm glad to see this discussion showing some energy!

Let's distinguish between the math and the practice. In practice, wedging an angled cut won't work as well as a flat cut because of the nature of the wood, not because of the math. The thin lip of the cut where the wedge goes in is weak. It can and will bend. In the flat cut, the wood can only crush, not bend. The extra stiffness of the wood means less work is wasted on deforming the wood--the wedge is more efficient. So I agree with all the posters who state the wedge works better in the flat cut.

However, that does not mean the math is different. The trouble with visualizing the whole process using words like "lifting" or "pushing" is that they imply two different processes are at work. But are they? Think of the spoked wheel used to steer a sailboat. I can make the wheel turn clockwise by pusing down on a spoke on the right side, or I can push up on a spoke on the left side. Are those different?

In the same way, it doesn't matter if the wedge is "lifting" or "pushing;" what matters is the wedge, whereever you place it, is causing the tree to rotate around the hinge. The resistance of the hinge to bending is the force that opposes you, and some of the weight of the tree if it is leaning toward the wedge. The very same forces oppose you whether you are wedging a sloping or a flat back cut, and the wedge in both scenarios wins the day in the same way, forcing the hinge to bend by opening up the kerf.

 

[TexasTreemonkey]

Its kinda off topic but how do you get the tree to jump away from the stump?

 

[juststumps]

It seems most of the comments here had to do with the relative weakness of the stump when you try to wedge a steeply angled back cut. Can't argue with that. But the math should be identical. In both the flat and angled back cut, the wedge operation does exactly the same thing: it causes the tree to rotate around the hinge as the kerf opens up. The angled wedge should have a slight mathematical advantage in this regard, as it is slightly farther from the hinge than in the flat case, and thus would have a bit more mechanical advantage.

the math isn't identical.......

lets say you have a 12 inch deep back cut,, you pound a 1 inch wedge in there... you have a 1 to 12 ratio

lets go with the 45 % back cut... to get to the same place at 45 % where the hinge is ,, is 17 inches !!!!!! now your down to a 1 to 17 ratio

on a flat cut your driving a force into the stump straight down,, and lifting the far end of the tree over your hinge....

on the angeled cut,, the driving force is pushing against the thin wood at the start of your cut... (some one posted this could break out ) and pushing into your hinge... instead of lifting it over....

on something with that small of a back cut,, it might not really matter,,,, but on bigger stuff,, it might...

 

[(WLL)]

Its kinda off topic but how do you get the tree to jump away from the stump?

well he%# thats easy, just use a jump cut. i have never made a tree jump off its stump without the help of blk powder

 

[techdave]

Look AT Physics of angled backcut+fibre considerations

Hi guys, after reading all of this, and thinking about it (disclaimer-no beers were consumed in the analysis of this technique, so my creativity may be impaired), here are my observations. I AINT CALLING YOU DUMB if you use this method, just pointing out some reasons that just cuz it works for you dont make it right either. If it works for you and you are experienced with sloped backcuts, so be it.


Sloping baccuts probably should NOT be used for at least three reasons that dont require mechanical analysis:

The greater tendency of wood to split as it is wedged closer to parallel to the grain. Cant wedge firewood apart at right angles to grain, can at parallel to grain, at 45 degrees likelihood of splitting is MUCH more than at right angles like in anormal backcut. Besides the oft mentioned worry about splitting the stump side of the backcut off the tree, might have to worry about the fibres at the hinge since he backcut does meet the hingewood, by definition. Propagation of a split at the hinge could cause a barberchair.

The complications that a sloped backcut causes if nipping corners or a similar correction to the initial hinge is needed. Much harder to meet cuts evenly without going into the hinge wood you want to leave intact.

The fact that wood is easier to compress under load if struck or loaded parallel to the grain than if it is loaded at right angle to the grain. Hammer onto the side of a 2x4 and then repeat at end, see which compresses easier. We want movement of the wedge, and the work expended to do so to actually move the tree, not to go for deforming it in the area of the cuts.


AND there are a few reasons to scorn sloped backcuts that are revealed when a diagram is drawn to analyze the physics involved.

First off, lets get out of the way the only advantage a sloped cut has:
In THEORY the force generated by trhe wedge is acting over a longer lever arm than for a right angled AKA regular backcut. True enough, draw it out and you will see. But skilled fallers who need to use a short backcut and still get a wedge in will bore the backcut to accomodate the wedge. or cut the backcut first and then the facecuts. OR If a longer backcut is needed the face is not cut as far in towards the center of the tree. (Why a longer backcut?? Longer backcut means less movement of top of tree for each inch of opening of the backcut, but also means less effort to drive the wedge each inch, and less stress on the fibers where the wedge is working.)

So much for Fiber, what about forces?

The typical analysis of these forces and moments is based on the assumptions of classical physics. A frictionless pivot, or one whose friction is equal for all orientations of force and moment applied to it. A pivot whose integrity wil not be compromised for the range of forces and momentrs acting on it. And forces applied steadily and held constantly.


The pivot in this case is the hingewood, a non-linear and inelastic band of uncut fibres in the middle of the tree, not fricionless. But the fact the hinge doesnt behave like the ideal probably does not make a sloping backcut anyworse than the regular right-angled one.

The question of pivot integrity is a different kettle of fish. In an angled backcut a big portion of the force generated by the wedge is trying to push the tree forwards, a shear force on the hingewood that does not exist AT ALL in regular backcut. Probably wont matter for many to most situations, but in some thin hinge situations could be catastrophic extra load causing abrupt hinge failure before tree commits!!!!


Forces applied are not steady, nor held constant, and there is some friction-generated force on both sides of the backcut as the wedge is driven. These are abrupt shock loads, for an instant much bigger than the amount of force that actually does useful work moving the tree through measureable distances . These probably do not cause more probs in the sloped, unless the tree/cut is such that its near barberchairing Using SHIMS would usually greatly reduce this frictional problem in most types of timber.


Looks like long story short , most of the resons for not using a sloped have to do with the nature of wood fibres and grain and the stump and bole. But in at least one way the charaacteristics of the forces and moments involved in a sloping backcut may be less effective or more dangerous than in a regular horizontla one.

Thanks, Dave.

 

[smokechase II]

Texas Tree Monkey

One trick that can be used to get a tree to jump off the stump is to use a conventional undercut that is wide. 50 degrees or so.

On the flat place a flat rock or whatever is handy that takes up 1/3rd to 1/2 of this gap in the widest part of the face. Then don't leave too much hinge, but leave some. Don't be cutting all the way through as it goes.

You want that hinge to provide some resistance when the top of the face connects to the rock insert, but weak enough that it will pop. You want the face a bit wide to make sure that you get momentum working to make it pop. But if you go with a really wide face, I.e. open face 70-90 degrees, the Pop and jump is too late.

This jump effect helps firefighters constructing helispots or fire lines move tree butts away from those projects. Breakage isn't an issue.

If one limits themselves to Humboldt or true Open Face technique, you'll never get to do this distance jumping.

I need to mention that this jump technique is somewhat limited to trees with height and/or weight that make their descent powerful. Also dead or brittle wood doesn't provide the pop needed.

***************************

A Block Notch with adequate snipe may accomplish the same jump.

 

[moray]

the math isn't identical.......

you have a 1 to 12 ratio ...

lets go with the 45 % back cut... to get to the same place at 45 % where the hinge is ,, is 17 inches !!!!!! now your down to a 1 to 17 ratio

on a flat cut your driving a force into the stump straight down,, and lifting the far end of the tree over your hinge....

and pushing into your hinge... instead of lifting it over....

I think we are saying the same thing...almost. The "bit more mechanical advantage" that I alluded to you have shown precisely for the 45 degree case. When I say the math is the same, I mean the formula is the same, and nowhere does the formula include any reference to the orientation of the wedge or whether the back cut is flat or otherwise. I am trying to dispel any notion that wedging a flat cut has some sort of mathematical advantage over a sloped cut. When you figure the math, you and I both conclude there is more mechanical advantage in using the sloped cut, not the other way around. If you do a more complete anaysis that includes the properties of the wood (such as elasticity of end-grain vs face-grain, and the friction of each type of grain against the wedge, and the ultimate strength of the wood in both orientations), then things can get complicated. But the wedge doesn't know and doesn't care if it is "lifting" the tree or "pushing" it over.

 

[teamtree]

I am not sure who is saying what but for those of you who think the math works out the same on a sloping back cut as a flat back cut when the wedge is inserted you are wrong. If you think of the tree as a bunch of pencils in a circle the example makes sense as you are applying a mostly up lifting pressure in a flat back cut. In a sloping cut you are applying pressure side to side and little to up lift. So the math, would come out more direct up lift with a 90 degree back cut than say a 45 degree. Simple math.

At any rate, you are a fool if you think the sloping back cut is an appropriate procedure.