Physics: Calculating the impact of different size axes/mauls used for splitting.

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What type of splitting axe (maul) do you use?

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tradergordo

tradergordo

Minister of Fire
May 31, 2006
820
Phoenixville, PA
gordosoft.com
EDIT: In the time since the original post, based on real world experience I have concluded that the heavier mauls (6-8lbs.) are generally more effective for splitting for most people (the effectiveness curve of speed vs. weight probably peaks around 8lbs for the average male wood splitter - only a physically weaker person will benefit from a lighter weight maul/axe - you physically cannot get the velocity of a lighter maul up enough to compensate for the lower mass). Originally I had only tested 4# and 12#, the 4# worked better, but since then I have tested others...

OK - I know this will sound geeky, but I've been having a little debate with friends on the best tool for manually splitting wood. Its real hard to test this in the real world - every log is different even if cut from the same tree, same length, and every person is obviously different too. I know there is no one shoe fits all answer, but I was hoping maybe science could help solve the question of what shape/size/weight/length maul/splitting axe works best?

My neighbor for example uses a 12lb "log blaster" maul which I do not like (tires me out REAL fast, feels like it weighs a lot more than 12 lbs, is short, and doesn't seem to split that well).

Anyway, I admit to being new to splitting wood, I never owned a wood stove or fireplace at any point in my life until just recently. I've been cutting/bucking/splitting wood for about a month now (a couple cords). I am definitely getting better and stronger each day. Anyway, I studied some tips found here: Woodheat.org: How to split wood

I’m also interested in physics/science (computer scientist by trade). Many people I run into, including my neighbor, seem to think bigger is better when it comes to mauls. I have tried 3 very different mauls, and so far the one that works best for me is the $25 red fiberglass handled splitting axe they sell at Walmart! The handle is super light weight but extremely strong (lifetime warrantee), the head is a weird shape - sharp but quickly flares WAY out (much moreso than a traditional maul) and weighs just 4 lbs.

The thing is - and this is alluded to in that "how to split" article above - the formula for kinetic energy is 1/2 mass times velocity squared. A difference in velocity can be much more significant than a difference in mass because this factor is squared. I'm not sure how these variables, "in the real world" balance themselves out - for example obviously you are going to naturally swing an 8 lb. maul slower than a 6 lb one, but will the difference tend to balance so that total kinetic energy is roughly the same?

I googled, but could not find any sample data for the speed at which a maul head is traveling when it hits the wood. It would be neat to measure one’s speed with different weight mauls and actually try to calculate kinetic energy (I know they sell radar tools for measuring golf swings for example). Even though I couldn't find data for axes/mauls, I found data for baseball bats – apparently they can be swung at 70 miles per hour. Even though it’s a totally different motion, I think this number is probably comparable to an overhead axe swing with a light weight axe (?). I suspect actually that an axe can be swung even faster than a baseball bat but I’m not sure (reasons = arms seem better designed to move quickly up and down than horizontally, gravity may help the downward stroke as well).

So anyway, with only this flawed data I did some calculations:
4lbs = 1.8kg
70mph = 31.2928m/s

KE = .5 * 1.8kg * 31.2928m/s^2= 881.3 Joules

If you can only swing a 6 lb. maul 50 mph (I have no idea, just a guess)
6lbs = 2.72kg
50mph = 22.352 m/s
KE = .5 * 2.72kg * (22.352 m/s)^2=679.5 Joules

Clearly you are getting MUCH better KE with the lighter axe in this example. What would be the break even point? i.e. how fast would you have to swing a 6 lb. maul to equal the KE of a 4 lb. maul swung at 70mph?

.5*2.72kg*X^2=881.3
X^2=881.3/(.5*2.72kg)
X=25.456 m/s = 56.94 MPH

If you could swing the 6 lb. maul about 57 mph you should have the same theoretical impact as a 70 mph 4lb maul.

So who’s going to buy the radar gun? :)
 
just roll up your sleaves and swing. You lost me way back there, i think at the point of 4lbs=1.8kg LMAO. I use a 8 lb maul, i dont worry about efficiency, i like the exercise.
 
That link is a good summary of the process, even though I disagree with their main point. In my experience, weight trumps velocity every time.

I base this observation on the fact that I can split bigger rounds much easier with an 8 lb maul compared to a 6 pounder.

I doubt that mere (un steroided) mortals can swing a baseball bat at anywhere near 70 mph. I also doubt that Barry Bonds could swing a maul anywhere near as fast as he can swing a baseball bat.

The most important aspect of successful wood splitting, IME, is accuracy. Attitude has a lot to do with it as well.

So, in summary, I would say that you should use the heaviest maul that you can swing comfortably and accurately. For most people, that's probably a 6- or 8-pound maul.

Interesting analysis all the same, gordo. Too bad you can't split wood with math.
 
My analysis has shown that my 490 pound hydraulic splitter provides the most energy.

YMMV.
 
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BrotherBart said:
My analysis has shown that my 490 pound hydraulic splitter provides the most energy.

YMMV.
Click to expand...

Yeah but its slower :)

I swing an 8lb and would like to try a 10lb maul.
I know the 8 blows the 6 away but the 10 may wear me out quicker
 
Hi All,

I love these summer time threads....

I use a 6lb. I have an 8lb, but it I have never felt quite comfortable with it. I think it is the handle, which is straight and made of fiberglass. My 6lb has an oak handle, which is curved and somehow gives my swing more punch.

Maybe its because I am a girl.

The best combo is my husband with wedges and a sledge hammer and me with the 6lb. I start things off. If it doesn't split first shot, he finishes it off with the hammer/wedge combo. We go through wood fairly quickly.

My back, however is rooting for me to buy an electric splitter.

Have a good one,

Donna
 
Donna said:
Hi All,


My back, however is rooting for me to buy an electric splitter.


Donna
Click to expand...

Its funny you should say that, because a related discussion I had recently was the plus/minus of using a gas/electric splitter vs. a maul. My one friend who has been splitting wood pretty much all his life, says his Dad rents a gas powered splitter sometimes and they go head to head - my friend with his maul is faster (as was mentioned by someone else here). But one thing he said that struck me as interesting was that his bad back prefers the maul over the automated splitter. WIth the auto-splitter, you have to pick the logs up, with a maul, you don't. Both of us have bad backs, and both of us agree that manually splitting wood actually doesn't bother our backs at all!

So I would be curious as to other's comments on manual wood spliting and your back. Perhaps your technique could be adjusted slightly so that you don't hurt your back. Either way, picking up logs isn't going to be back friendly...

p.s. The main advantage of manually splitting wood for me is that I could really use the exercise. Besides I think its fun!
 
A couple people I have discussed the physics of splitting with have assumed the achievable maul head speeds are relatively low. I suspect (but could be wrong) that those who believe this are underestimating reasonable maul velocity (at least with a lighter maul!). I did some more searching and found this interesting study on the swing speed of amateur slow-pitch softball players:

http://www.npl.uiuc.edu/~a-nathan/pob/SwingSpeed.pdf

"The average swing speed (at 6 inches from the end of the bat) of the A and D
level players was found to be 89 and 81 mph, respectively. These speeds are
higher than have been observed in baseball."
 
tradergordo said:
Its funny you should say that, because a related discussion I had recently was the plus/minus of using a gas/electric splitter vs. a maul. My one friend who has been splitting wood pretty much all his life, says his Dad rents a gas powered splitter sometimes and they go head to head - my friend with his maul is faster (as was mentioned by someone else here). But one thing he said that struck me as interesting was that his bad back prefers the maul over the automated splitter. WIth the auto-splitter, you have to pick the logs up, with a maul, you don't.
Click to expand...

I used to split all of my wood with a maul and would like to see somebody hand splitting beside my 60 year old self all the way through one of my two hour sessions on the hydraulic splitter. I can't understand why anybody wants to wreck their back using the splitter horizontally. I set the sucker up vertically next to the the stack of rounds and just roll them to it, stand them up and split'em up. No lifting of the rounds required.

I maxed out my macho years ago. Now I just want that stuff on the woodpile. NOW!
 
tradergordo said:
If you could swing the 6 lb. maul about 57 mph you should have the same theoretical impact as a 70 mph 4lb maul.

So who’s going to buy the radar gun? :)
Click to expand...

I think you are on the right track. Sure, dead weight is good, but it's all in the snap - and, as our good brothers said, in the exact aim.

You can aim a lighter mall better....and I think most can swing it faster.

I could liken it to tennis. I have massive arms and forearms, but my ball speed is not that great. I see 13 year old girls with stick arms hitting the ball twice as fast (and, as the man says, speed IS power) as I do. Why? Because they know how to snap.

The perfect examples of this are everywhere in the summer - sure, those "ring the bell" exhibits at the fair. But these add one more variable - getting the head to hit flat on the target.

Swings must vary greatly. For instance, many would lift a mall and then let it drop. I keep pressure on the maul the entire time, so there might be a torque factor involved other than just the speed....like towing capacity. In other words, not just the speed of entry, but how fast it is slowed - all happening in microseconds.

We need more than a radar gun. We need high speed video cameras. We need some kind of constant target -not wood, but preferably a manufactured material. We need "The Science Guys" or "Myth Busters".

I once had a smart warehouse employee who figured out the amount of energy developed by a 16 inch naval gun shell (right at the tip) after flying 20 miles. It was quite a lot, as you can imagine, and could penetrate 6+ feet of concrete let along any wood you might put in the way.
 
tradergordo said:
Well I jokingly call my friend the hulk, so he may not be a good example. I know I couldn't keep up for 2 hours against your hydraulic. I also didn't know they had "easy on the back" vertical versions - that sounds good. What is the max diameter it can handle? Model/price?
Click to expand...

It is an old 15 or 20 year old Duerr but most of the splitters I see in stores and adds can work horizontally or vertically.
 
Gotta agree with Eric on this one. Weight is more important than speed.

My 8lb maul is the ticket, compared to lighter tools. Not ready for the splitter just yet.
 
I use a 8lb maul and 4lb ax on small stuff. I can swing faster and recover with the ax. It seames to work good for me.
 
I think this could be debated all day long, but in the end... this is really something that comes down to what works for you. Splitting with a maul is something you have to be comfortable with. The only reason I don't do too much of it anymore is time. For the most part, splitting by hand is faster than your traditional splitter. If you are going to spend the whole day splitting wood, and want to be able to walk the next day, then you would probably have some type of wood splitter.

When splitting by hand, I use a 8# maul, and what I've found is that, once you've brought it over your head, and it is on the downswing, bring both hands together on the handle, and focus more on where you are hitting, rather than keeping pressure on it all of the way down. I think it's more about accuracy on your strike that will pop it apart.

So I guess what I'm saying is that regardless of the physics involved, there really is no "best" size or weight to be the best splitting tool - you have to try different ones and find what works for you, and the final test is usually how you feel the next day :)
 
Harley said:
I
So I guess what I'm saying is that regardless of the physics involved, there really is no "best" size or weight to be the best splitting tool - you have to try different ones and find what works for you, and the final test is usually how you feel the next day :)
Click to expand...


All this talk and no one has mentioned the importance of the surface that the round sits on!

1. If not stable, a lot of the energy of the swing will be dissapated by vibration. Bare ground is not good - a giant stump will do the job.

2. Height is good - if the maul contacts at much less than a 90 degree angle (to ground), then splitting seems harder and also danger of hitting your leg or foot increases.
 
Harley said:
I think this could be debated all day long, but in the end... this is really something that comes down to what works for you.
Click to expand...

I think there may be a lot of subtle technique involved, much like a baseball swing. I suspect rotational energy and torque are very important and tweakable factors to a great swing just like they are in baseball. I don't know though if anyone has studied the swing of a maul with high speed cameras or described in great detail the subtle techniques that make all the difference as they have with baseball.


From: Choosing the right bat (maul?)
"Swing mechanics is not the only factor important to bat speed. The bat has a lot to do with it too. Here's why...
The energy generated by the bat is equal to one-half the product of bat mass times velocity squared.
E= M/2 * V^2
In other words, speed is more important than weight - which would seem to encourage hitters to use the lightest bat that can be swung the fastest.
However, the transfer of bat energy to the ball, which determines how 'hard' the ball is actually hit and how far it will travel - depends on the simple momentum of the bat.
T = M * V
So what you should consider using is the heaviest bat you can swing without losing bat speed. Use the Swing Speed Radar to plot swing speed vs bat weight on a graph and you'll find the point where speed starts to decrease more rapidly as weight is increased. Balance that with bat control and you've found your ideal personal bat weight. Now you can really work with the SSR on improving your swing mechanics."


I think if you just replaced "bat" with "maul" it would directly apply.
 
I have a horizontal splitter with the use of a cage milk carton and 3' 3/4 plywood. I can roll the rounds in place toss the splits in the backhoe bucket. 16 ton Electric splitter 20" round capacity by 20" long. It will split larger rounds but not down the middle.
I do not spend all day splitting. A little here a little there. Flip the switch and I'm splitting no exhaust to breath in no noise. The neighbors never know I'm splitting. I own two malls and still split quite a bit with them . In a short peroid of time straight grain wood the mauls are quicker. I use the 6 or 8 lb which ever one i grab first. After a couple of hits if it does not split time to turn on the splitter, once on no sense using the maul. I got the electric splitter last Fall. 12 cords later with 8 more to go, it still amazes what it will handle.

My splitter also can be equiped with a gas engine, (up to 5.5 hp honda),, a swap time of about 10 minutes. I know it is tied to a 20 amp electrical outlet. IT is 200 away. First 100' 10 gage extention cord next 100' a 12 gage cord works fine. Witnessed by many, including Hot Flame, a fellow forum member
 
Gordo - don't want to get into the details of the physics, but what your muscles provide is constant average power. Basically if you double the weight it will take you four times as long to complete a stroke if you put out work at the same rate. I'm sure someone has done specific analysis on maul swinging, but one site kind of related is this one which a physicist put together to analyze tennis racket swing - www.racquetresearch.com. The muscles used in maul swinging are different, but the same sort of physics - that of swinging a weight at the end of a handle eventually transferring the energy to another object. Some differences, but you might get a good idea on how to do the physics for this kind of thing. Yes and I have seen the splitter elk has - and I think it beats a maul any day. By a long shot.
 
I have nothing against splitters, but in something like splitting wood (just like burning wood), it's not all about efficiency and ease of use. As alluded to in most descriptions of hand splitting, it can be a lot of fun and it can be satisfying. Can you say "endorphins?"

There's a sense of satisfaction to be gained from processing a pile of rounds by hand (for those who are really into it) that can't be quantified.
 
Eric Johnson said:
I have nothing against splitters, but in something like splitting wood (just like burning wood), it's not all about efficiency and ease of use. As alluded to in most descriptions of hand splitting, it can be a lot of fun and it can be satisfying. Can you say "endorphins?"

There's a sense of satisfaction to be gained from processing a pile of rounds by hand (for those who are really into it) that can't be quantified.
Click to expand...


That's pretty much where I am right now. I need the exercise, and I do find it fun. There is a lot of satisfaction in manually splitting wood that I really wasn't expecting. Maybe after a few years and many cords, I'll have a different view :)

At any rate - just curious Elk - what is the model splitter you bought? Anyone used the cheapies from Harbor Freight? I don't intend to buy one, but will gather info for that possibility somewhere down the road. Not sure about rolling the rounds up a ramp but its better than picking them up.
 
I suggest you search the Gear Room where electric splitter have been discussed I have detailed my experiences with a few
 
I like my 20+ lb monster maul. Go Figure. I think there is more physics involved than a couple simple equations. Ie. When you swing a bat gravity doesn't aid.

All I have to do at times is lift my maul 3ft above a log and let it drop. No swing involved sometimes.
 
UPDATE - so I finally went out and bought a heavier maul for no real reason other than to compare it to what I have been using. I bought a 6 lb. maul from harbor freight ($20, has bright yellow light fiberglass handle and pretty standard looking blunt maul head and seems like a decent tool with the exception of some foam/rubber band just under the head which fell off after 30 seconds of use but didn't seem to have a purpose).

Anyway - I can definitely confirm what others have already noted - its easier to split with the 6# maul compared to the 4#, and I can swing it pretty fast. I'd still love to see actual speed data, but that's probably never going to happen. I suspect that swing speed would decrease enough with an 8# maul that it would not split as effectively (for me) as the 6# one.
 
I use an 8 lb head with fiberglass handle and solid block underneath...

Maybe this is so obvious everyone does it???? I try to wait a week or so before splitting the rounds, especially the tough stuff. Most times a crack will develop in the center of the round..This is my splitting guide for the round and I use that as a target.
 
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