Felling wedges used with axes, sledges... ?

[northmanlogging]

I suppose its analogous to a human form of HP to weight ratio with those 'skinny wiry dudes'. They may not have as much pop behind the axe swings as a larger man, but they will make up the difference with repetitions, all day!

I mean, I'm not planning on picking fights with em anytime soon lol

 

[.358 win]

I suppose its analogous to a human form of HP to weight ratio with those 'skinny wiry dudes'. They may not have as much pop behind the axe swings as a larger man, but they will make up the difference with repetitions, all day!

Lotta good info and ideas in this thread.. Impossible to not learn something.. Personally I use an axe to clean bark and scrub before a fall, but usually bang wedges with a hammer.. lighter, more reps.. Only carry them to n from the trailer or truck or tractor, not on my belt.. My dbl bit axe is razor sharp and I have a lot of respect for it. If you look at it too hard it could cut your eyeball.. Which means, put it down when not swinging it like a golf club.... Usually carry the hammer in the loop of overalls.

 

[fields_mj]

I also use a Council Tool boy's axe (2.2#). My theory is that you can get just as much oomph out of it since Energy = Mass x Velocity^2

Only thing I don't like about my boy's axe is that its handle is about the perfect length to hit your ankle if you're not careful. So I'm thinking of either shortening the handle some, and reseating the head, or fitting it with a longer handle, which should give it even more speed.

I use the same axe. I'm 6'2" and it would catch me in the shin. I like the axe, but it's not my favorite splitting tool.

Something to keep in mind. When you're hitting something, KE is not what you want to use. Conservation of momentum is what governs any kind of impact, and that's just mass x velocity.

 

[HansFranz]

When you're hitting something, KE is not what you want to use. Conservation of momentum is what governs any kind of impact, and that's just mass x velocity.

I'm not sure it is. With bullets (I can't think of a better example of "what governs any kind of impact"), the formula is 1/2 m v²

A bullet flying through space and being stopped by a deer is no different from an axe head flying through space and being stopped by a wedge. In both cases, the energy imparted to the struck object is proportional to mv² ... if your theory were true, then a given weight bullet traveling at 1000 f/s would have half the energy of one traveling at 2000 f/s ... but that's not the case. (The bullet traveling at 1000 f/s has only 1/4 the energy of the one traveling at 2000 f/s.)

The difference between KE and Momentum explained here by Gerard:

Now for an intuitive explanation that an object with double velocity has four times as much kinetic energy.
Say A has velocity $v$ and B is an identical object with velocity $2v$.
B has a double quantity of motion (momentum) - that's were your intuition is correct!
Now we apply a constant force $F$ to slow both objects down to standstill. From $F \Delta t = \Delta p$ it follows that the time $\Delta t$ needed for B to slow down is twice as much (we apply the same force to A and B). Therefore the braking distance of B will be a factor of 4 bigger then the braking distance of A (its starting velocity, and therefore also its mean velocity, being twice as much, and its time $\Delta t$ being twice as much, so the distance, $s = \bar{v}\Delta t$, increases 2 x 2 = 4 times).
The work $W$ needed to slow down A and B is calculated as the product of the force and the braking distance $W=Fs$, so this is also four times as much. The kinetic energy is defined as this amount of work, so there we are.

In his analogy, the kerf in the tree is doing the "braking" of the wedge (and the work goes into lifting the tree with the wedge...as well as making some heat and sound)...but I am not a physicist so I'm open to be convinced!

 

[fields_mj]

I'm not sure it is. With bullets (I can't think of a better example of "what governs any kind of impact"), the formula is 1/2 m v²

The difference between KE and Momentum explained here:

Now for an intuitive explanation that an object with double velocity has four times as much kinetic energy.
Say A has velocity $v$ and B is an identical object with velocity $2v$.
B has a double quantity of motion (momentum) - that's were your intuition is correct!
Now we apply a constant force $F$ to slow both objects down to standstill. From $F \Delta t = \Delta p$ it follows that the time $\Delta t$ needed for B to slow down is twice as much (we apply the same force to A and B). Therefore the braking distance of B will be a factor of 4 bigger then the braking distance of A (its starting velocity, and therefore also its mean velocity, being twice as much, and its time $\Delta t$ being twice as much, so the distance, $s = \bar{v}\Delta t$, increases 2 x 2 = 4 times).
The work $W$ needed to slow down A and B is calculated as the product of the force and the braking distance $W=Fs$, so this is also four times as much. The kinetic energy is defined as this amount of work, so there we are.

In his analogy, the kerf in the tree is doing the "braking" of the wedge (and the work goes into lifting the tree with the wedge...as well as making some heat and sound)...but I am not a physicist!

You're misunderstanding what I'm saying. I'm saying that the law of conservation of momentum is used in applications involving impacts. It doesn't matter whether it's balls on a pool table, cars crashing, an axe hitting a wedge, or a bullet hitting a body. This is mainly because momentum has a direction and that becomes VERY critical in an impact (think direct, head on hit versus a glancing blow). Energy does come into play, but it a totally different way. In the case of a car crashing, or a bullet striking a body, the calculations become very complicated because the impacts are not even close to being "perfectly elastic". Those are the situations where KE comes into play because the objects involved in the collision are deformed significantly. That deformation required energy, often times a lot of it. Pool balls are an ideal example because the collisions are very close to being perfectly elastic. The balls don't flex or deform, and very little heat is generated. The only real loss of energy is from the noise created which really isn't much. Hitting a wedge with an axe or maul is more like the pool ball example than it is a car crash. The big differences (and they ARE significant) is that a wedge does deflect, and there's a lot of friction involved between the wedge and the tree. So it may be closer to the pool ball than the car crash, but there are still a lot of other variables that come into play. Either way, conservation of energy does come into play, but not like you are thinking. Conservation of energy takes into account the velocity of the axe as it rebounds from the wedge, the heat created from the impact, the heat created between the wedge and the tree, the noise, as well as a lot of things I can't even think of any more.

Bullets are also not a good application of KE. Manufactures just hype it up as a marketing ploy. I can build you a 45 cal projectile that weighs less 70 gr and can be pushed over 2,000 fps when loaded into a 45acp case and fired from a 5" barrel. It generates over 800 ft lbs of KE, but it absolutely will NOT kill a mature whitetail deer because it will only penetrate 4" to 6". Conversely, my wimpy compound bow only generates about 75 ft lbs of KE, but I've take 200lb bucks with it with no problem.

I'm not a physicist, but I do have a BS (Bachelors of Science, not the other BS which I think is hilarious in and of itself) in mechanical engineering, and I have the grammatical errors to prove it

 

[EchoRomeoCharlie]

I don't see a point in carrying a tool that is the same weight, yet is less useful.

Axe has many a multitude of applications only 1 of which is pounding wedges. The sledge is literally only a pounding tool.

I see this sentiment a lot though. I can't tell you how many times I've been wedging a tree with an axe and the home owner walks his sledge over to me. Convinced that it will be impossible to wedge the tree over with my 4lb axe. One must use a 10lb sledge lol

 

[HansFranz]

I like the axe, but it's not my favorite splitting tool.

Yeah, I would never use my boy's axe for splitting. I use a maul (or hyd wood splitter) for that.

You're misunderstanding what I'm saying. I'm saying that the law of conservation of momentum is used in applications involving impacts. It doesn't matter whether it's balls on a pool table, cars crashing,

Well, FWIW, the car impact energy calculator I found here also uses mv² in its formula, not mv:

Bullets are also not a good application of KE. Manufactures just hype it up as a marketing ploy.

Not sure what "marketing" is done in a reloading manual since they aren't selling anything...the reloading manuals I've seen are scientific, not hypey. (Being able to accurately calcuate bullet energy also has legal ramifications, for example here in Virginia, where it's illegal to hunt deer with a handgun unless it can deliver at least 350 ft-lbs to the deer.) And in every reloading manual I've ever seen that has tables for calculating the energy of a bullet at a given speed, they use mv² rather than mv.

For example (in RCBS/Speer Reloading Manual #14 from 2007):
in every table that I can find for 1000 f/s, the bullet carries 2.22 ft-lb per grain of bullet weight.
in every table that I can find for 2000 f/s, the bullet carries 8.88 ft-lb per grain (which is 4X - or 2² - the energy per grain at 1000 f/s).
in every table that I can find for 3000 f/s, the bullet carries 19.98 ft-lb per grain (which is 9X - or 3² - the energy per grain at 1000 f/s).
in every table that I can find for 4000 f/s, the bullet carries 35.52 ft-lb per grain (which is 16X - or 4² - the energy per grain at 1000 f/s).

(Most modern reloading manuals have 30-50 pages of these tables for bullets of various ballistic coefficients at various speeds, etc.)

So pretty much all of these formulas are using mv² rather than mv. And in every case, where the velocity is increasing lineally, the energy is increasing parabolically. If you graphed it where x=velocity and y=energy, you'd get a parabola.

You're an ME and I only took a year of engineering courses in college, so I'll defer to you...but I still think you're wrong!

 

[fields_mj]

Yeah, I would never use my boy's axe for splitting. I use a maul (or hyd wood splitter) for that.



Well, FWIW, the car impact energy calculator I found here also uses mv² in its formula, not mv:

Not sure what "marketing" is done in a reloading manual since they aren't selling anything...the reloading manuals I've seen are scientific, not hypey. (Being able to accurately calcuate bullet energy also has legal ramifications, for example here in Virginia, where you're not allowed to hunt deer with a handgun unless it can deliver at least 350 ft-lbs to the deer.) And in every reloading manual I've ever seen that has tables for calculating the energy of a bullet at a given speed, they use mv² rather than mv.

For example:
in every table that I can find for 1000 f/s, the bullet carries 2.22 ft-lb per grain of bullet weight.
in every table that I can find for 2000 f/s, the bullet carries 8.88 ft-lb per grain (which is 4X - or 2² - the energy per grain at 1000 f/s).
in every table that I can find for 3000 f/s, the bullet carries 19.98 ft-lb per grain (which is 9X - or 3² - the energy per grain at 1000 f/s).
in every table that I can find for 4000 f/s, the bullet carries 35.52 ft-lb per grain (which is 16X - or 4² - the energy per grain at 1000 f/s).

You're an ME and I only took a year of engineering courses in college, so I'll defer to you...but I still think you're wrong!

 

[HansFranz]

If I'm not mistaken...

1. The only way to know how well an axe will drive a wedge, or how far one billiard ball will drive another billiard ball, or how far one car will push another in a collision, is to know how much (kinetic) energy is being carried by the moving axe or billiard ball or car. Units of energy and units of work -- which is a force applied over a distance -- are directly convertible back and forth without knowing anything else. For example, 1 BTU (unit of energy) = 1055 Joules (unit of work) = 0.000293 kWh (unit of energy) = 1.055056e+10 Ergs (unit of work).

2. The only way to calculate how much work a projectile (such as an axe or a billiard ball or a bullet or a car) can do to the thing it hits (like the wedge) is to calculate how much energy it carries. (Let's just ignore heat/sound/deformation for the moment.)

3. MV only gives you force. MV² gives you energy, which is directly convertible to work, which allows you to calculate how much force over how much distance the projectile is capable of applying...if I'm not mistaken MV is missing the distance component needed to calculate energy (or work). Force alone (without the distance over which the force is applied) tells you nothing about what a moving object can do. For example, you can push on a wedge with your hand, applying 200# of force to it, and you can push on it like that for a month, but if you don't move it (applying a force over a distance), then you have done no work, and delivered zero energy to it. (This is why a shop vac motor speeds up, rather than slows down, if you clog the hose...because it is no longer doing any work because it is not moving any air).

(This is HS-level physics, and it's been a while, but I'm pretty sure I'm right...)

https://www.khanacademy.org/science/physics/work-and-energy/work-and-energy-tutorial/a/what-is-work

 

[fields_mj]

You're not wrong here. We're just talking about different things. If you want to know how hard the car hit somthing, by all means use the calculation that you have. Force = 1/2 mass X velocity squared. If the force is applied over a distance, then the average force is equal to the total force divided by that distance. So if you want to know how hard you hit something, use that calculation. If you are going to hit something and you want to know what happens to that something (how it's speed and direction are changed, ie how far the wedge moves into a kerf), then you use momentum.

My apologies on the reloading info. Again we were talking about different things. I thought you were talking about factory ammo. It drives me nuts when I see manufacturers advertising their ammunition based on its KE. You're states hunting regs are a great example of that. There's no way of actually knowing how much KE is imparted to the deer by a projectile unless the actual impact velocity is known, and the bullet remains inside the animal. Per your state's regs, you could legally use the 45 acp load that I mentioned above even though it won't penetrate deep enough to kill the deer quickly. At the end of the day, the advertised KE of factory ammo is what goes on the box, so that's what the state tries to use to establish a reasonable limit.

As far as reloading data, KE is absolutely an important piece of information. As you said, regardless of the shape of the projectile, or what powder is used, for a given bullet weight a specific amount of KE is required to achieve a specific velocity. As you compare one powder/projectile combination with another, the KE gives an accurate assessment of how efficiently a specific amount of a specific powder is transferring its potential energy to the bullet while maintaining safe chamber pressures. None of this has anything to do with how effective the projectile is on an animal, and that's what I was talking about because a lot of people incorrectly think the KE is an effective way to determine "how lethal" their ammunition is. Of course none of this has anything to do with hitting a wedge with an axe vs a maul or sledge.

 

[Bob Wilkie]

Kinetic energy is the total energy that a moving object has. When it stops that energy can be turned to sound, heat, and some of it can be used to move a wedge. Momentum is the property of an object to continue on its present course, which is precisely what you need to move a wedge, given that you hit it straight. Momentum though is not squared, it is just mass times velocity.

 

[Bob Wilkie]

In a physics class we did an experiment where we built a mechanical chronograph and fired a .22 round into a piece of firewood suspended by two wires. The wood barely moved and we measured how much. We did the calculations of the movement of the wood and the work required to move it that far, and compared it to the kinetic energy of the bullet. They weren't even close. The point of the exercise was to illustrate all the other places that energy could go...
High velocity friction in wood is gonna create heat, sound, vibration, tearing of fibers. In a deer it creates hydrostatic shock which equals tissue damage, sometimes widespread, but not necessarily penetration. Momentum is better for that.

 

[Captain Bruce]

I'm not sure it is. With bullets (I can't think of a better example of "what governs any kind of impact"), the formula is 1/2 m v²

A bullet flying through space and being stopped by a deer is no different from an axe head flying through space and being stopped by a wedge. In both cases, the energy imparted to the struck object is proportional to mv² ... if your theory were true, then a given weight bullet traveling at 1000 f/s would have half the energy of one traveling at 2000 f/s ... but that's not the case. (The bullet traveling at 1000 f/s has only 1/4 the energy of the one traveling at 2000 f/s.)

The difference between KE and Momentum explained here by Gerard:

Now for an intuitive explanation that an object with double velocity has four times as much kinetic energy.
Say A has velocity $v$ and B is an identical object with velocity $2v$.
B has a double quantity of motion (momentum) - that's were your intuition is correct!
Now we apply a constant force $F$ to slow both objects down to standstill. From $F \Delta t = \Delta p$ it follows that the time $\Delta t$ needed for B to slow down is twice as much (we apply the same force to A and B). Therefore the braking distance of B will be a factor of 4 bigger then the braking distance of A (its starting velocity, and therefore also its mean velocity, being twice as much, and its time $\Delta t$ being twice as much, so the distance, $s = \bar{v}\Delta t$, increases 2 x 2 = 4 times).
The work $W$ needed to slow down A and B is calculated as the product of the force and the braking distance $W=Fs$, so this is also four times as much. The kinetic energy is defined as this amount of work, so there we are.

In his analogy, the kerf in the tree is doing the "braking" of the wedge (and the work goes into lifting the tree with the wedge...as well as making some heat and sound)...but I am not a physicist so I'm open to be convinced!

Another solemn example of the fun one can have, on this site. Now, being a woodsman, and a scientist? is normal. Pure nonsense, and pure fun..

I intend to check back with my method of a 5-Wedge Fall, with a 4 lb. Drill Hammer. I've fallen countless 24" - 30" standing trunks. The sound of the crack is lost with a running saw.

Right now, I off to the other think-tank thread. Theres a guy with a mill that turns 20" x 30 - 40' Black Walnut logs, into Archemides Screws..........

A Cityit bought a Farm with a 10 acre Walnut Grove, planted when Dale Earnhardt won the Daytona 500. His screws point up....

 

[slabMan]

Kinetic energy is the total energy that a moving object has. When it stops that energy can be turned to sound, heat, and some of it can be used to move a wedge. Momentum is the property of an object to continue on its present course, which is precisely what you need to move a wedge, given that you hit it straight. Momentum though is not squared, it is just mass times velocity.

Thank you for that clarification! lol I thought 'momentum' [m x v = momentum] was in there somewhere!

 

[HansFranz]

In a physics class we did an experiment where we built a mechanical chronograph and fired a .22 round into a piece of firewood suspended by two wires. The wood barely moved and we measured how much. We did the calculations of the movement of the wood and the work required to move it that far, and compared it to the kinetic energy of the bullet. They weren't even close. The point of the exercise was to illustrate all the other places that energy could go...
High velocity friction in wood is gonna create heat, sound, vibration, tearing of fibers. In a deer it creates hydrostatic shock which equals tissue damage, sometimes widespread, but not necessarily penetration. Momentum is better for that.

Cool...I wish I had your physics teacher! If we tried that experiment in NJ, somebody woulda gotten locked up!

When I asked my physics teacher about this (I asked, if my .270 Win carries 2850 ft-lbs of energy, then if you had a car that weighed 2850# and parked it on a perfectly smooth frozen lake, and shot it with the gun barrel perfectly level, then the bullet should push it a foot...right?) she said that a large portion of the energy would be converted directly into heat -- or indirectly into heat via sound -- rather than moving the car, and some of it would be carried away in the bullet fragments that vectored outward from the impact site, and some of it would be expended punching holes through the steel, etc...

TBH, I'm still mystified by the difference between MV and MV² (now you know why I dropped out of engr school LOL) ... maybe if I manipulate the units algebraically, some units will cancel out somewhere and it will become clear.

Let's see... M is mass is mass...V is distance/time...so does V² equal distance²/time² or distance²/time or distance/time²? This is starting to frustrate the crap outta me...where's Mad Professor?

ETA: Got talking about this with a friend who's a millwright, machinist and former engr student like me, and he got me thinking about it right, I think. As he said, for some tasks, like driving a big heavy pin out of a hole, you're better off with a BFH going slower than a small hammer going fast, and I've noticed that, too. For example, if you're peening something over like a rivet, a small/fast hammer is good for upsetting/expanding the rivet, but if you're driving a big pin out of a hole, a bigger/slower hammer is better because it doesn't mushroom the head of the pin so much. This seems to be related to the hammer speed, where if you're trying to accelerate the struck object too much, it tends to splay out the force sideways more, causing mushrooming/upsetting of the metal. So by that logic, I guess a big heavy axe is gonna be better for driving wedges than using a small axe and swinging for the fences... I may not always be wrong but when I am, I go down kicking and screaming.

Sorry for the thread derail, OP!

 

[.358 win]

Cool...I wish I had your physics teacher! If we tried that experiment in NJ, somebody woulda gotten locked up!

When I asked my physics teacher about this (I asked, if my .270 Win carries 2850 ft-lbs of energy, then if you had a car that weighed 2850# and parked it on a perfectly smooth frozen lake, and shot it with the gun barrel perfectly level, then the bullet should push it a foot...right?) she said that a large portion of the energy would be converted directly into heat -- or indirectly into heat via sound -- rather than moving the car, and some of it would be carried away in the bullet fragments that vectored outward from the impact site, and some of it would be expended punching holes through the steel, etc...

TBH, I'm still mystified by the difference between MV and MV² (now you know why I dropped out of engr school LOL) ... maybe if I manipulate the units algebraically, some units will cancel out somewhere and it will become clear.

Let's see... M is mass is mass...V is distance/time...so does V² equal distance²/time² or distance²/time or distance/time²? This is starting to frustrate the crap outta me...where's Mad Professor?

ETA: Got talking about this with a friend who's a millwright, machinist and former engr student like me, and he got me thinking about it right, I think. As he said, for some tasks, like driving a big heavy pin out of a hole, you're better off with a BFH going slower than a small hammer going fast, and I've noticed that, too. For example, if you're peening something over like a rivet, a small/fast hammer is good for upsetting/expanding the rivet, but if you're driving a big pin out of a hole, a bigger/slower hammer is better because it doesn't mushroom the head of the pin so much. This seems to be related to the hammer speed, where if you're trying to accelerate the struck object too much, it tends to splay out the force sideways more, causing mushrooming/upsetting of the metal. So by that logic, I guess a big heavy axe is gonna be better for driving wedges than using a small axe and swinging for the fences... I may not always be wrong but when I am, I go down kicking and screaming.

Sorry for the thread derail, OP!

I recently listened to some jawboning about horsepower and torque.. Made me think of this thread,, I did not participate in it.. But some of it was eerily similar.

 

[Captain Bruce]

If it doesn't fit, get a bigger hammer///////

 

[Chevboy0167]

 

[056kid]

I'm trying to figure out why a professional logger would opt to carry a single bit axe to drive felling wedges, rather than lets say a 3 1/2 or 4 pound sledge?
If for instance, tree limbs, loose bark, or punky wood around the back cut needs to be removed, it would be faster and probably safer to buzz through the stuff quickly with the saw, instead of beating on it with an axe.
Sure the axe might help you free up a pinched saw... maybe, with a fair amount of time and effort. Other than that, I see no reason to carry an axe instead of a sledge.
Weight would be close to the same. The flat side of the single bit axe would be rougher on the plastic felling wedges than a sledge.

On those same lines, whether you have an axe, or a sledge to drive wedges, you'd want a long handle, like 36" to have more striking force and to be back farther away from the impact. Only problem I see with the 36" handle would be the awkward bulkiness of the long handle, knobbing you in the back of the head/helmet, when its worn in the belt holder.
What do you folks think.

LOL!!
Okay, how do you not notice that the butt of an axe is identical in size to the typically sized wedge? Basically everything but the little 6" jobs is a perfect fit to a typical axe. I like council.
A 5lb ax when hit flush with the wedge, transfers energy very efficiently & does very little damage to the wedge. I have a 7lb axe as well that will really drive a 12" K&H. A good example of the efficiency is what happens to wedges when you can't hit them square. They mushroom.
The axe carries 10 times better than a hammer due to its flat shape & weight distribution. An old leather belt does the job.
The axe doubles as a plumb bob.
The axe also doubles as a lean indicator when hung in a kerf.
The axe can chop a saw chain in two in an emergency. Same for wire rope.
The axe CUTS! I once chopped my saw out of a good 20" of poplar. 3 minutes with a flat file can get enough of an edge to get work done.
I've chopped my saw out way more times than I can remember...
The axe stands up way better to dirty bark than a sharp chain. The axe is a great tool for busting face cuts out
The axe doubles as a hanger for your gear as well.

There's just no comparison. Maybe if you're driving giant metal wedges because you went back in time 100 years, the hammer would be better,but then you're going to want much more than 4lbs.

The 36" handle would work for a chopping axe, but something shorter is almost always more usable in the modern logging woods.
I always just held the ax by the beard with an extended arm & cut the handle so it ends right in my armpit. So basically arm's length.
I wouldn't even bother going out in the morning if I couldn't have an axe, that's for sure.
If you had to spend 6 hrs a day behind the handle, you'd see very quickly why the axe is mandatory.
I mean, why not carry a blade when you're surrounded by wood?

 

[056kid]

I don't use wedges a lot, but what I've noticed is this. It's not so much about how hard you hit them. The tree weighs thousands of pounds. If I can move it with a wedge and an 8 lb maul, then I can probably move it almost as quickly with the same wedge and a boys ax. Since the ax is easier to swing, I focus more on using good form so that I can place my hits more accurately doing less damage to my wedges.

And then theirs carrying around a 6lb or 8lb sledge on my belt. Having spent 6 years doing residential construction and primairly using a 28 oz framing hammer, hanging 8 lbs off of a belt seems insane. Depending on how the tools is oriented (up vs down), the longer handle is either going to stick up over my shoulder or constantly be catching me in the back of the shin. Neither are good, so I prefer using a boys ax.

A boys ax and 3 wedges was all I needed to put this on the ground. Not a good pic, but the bar is 42"

I take it you've not ever hit a wedge that bounced your axe right back at you?
Thats when more weight makes a tremendous difference. It's a very noticeable feeling when you hit one square & that energy transfers.