Knife and Baton

J

Jimbo

Joined
Aug 10, 1999
Messages
546
I'd be grateful for some help on a question..

I've been using a 6" Mora ($8.95 CAN)knife for outdoor work for some time. I've used it with a baton for dropping lots of trees, and have split fairly tough wood with it. Yes it's a cheap ugly knife..
Pictures of what appears to be pretty poor construction are here:
Mora
Just go past my ramblings and the pictures should make the construction pretty clear...
The principle of baton work is simple, put full weight on hand holding the handle and beat hard on the tip end of the knife with a piece of hardwood. This chisels the edge through the wood. By cutting out wedges for sidecuts I've dropped many trees over 8" which is longer than the blade length.
I'm trying to figure why the knife is still in one piece, and what forces are inflicted on the knife when using a baton.
Thanks!
 
the local Home Hardware had got a box of fifty or so in. When I special ordered a bunch of other sizes - those came in between $10 for the red plastic handled to $14.
Lee valley has a deal on skinny bladed carving Moras (carbon not laminated) for $8.95 CAN.
LV Mora

The laminated versions go about $14.
Canadian tire often has the Normark (Eriksson black rubber handled Mora) for $10 - but only in stainless. I find those particular ones too soft of steel, but really easy to sharpen. The real thing - Frost's stainless is Sandvik steel for $20.
 
In regards to strength it is dependent on the square of the length along the vector of the applied load. Take a simple
butter knife that is about 1/16" thick and 1/2" wide. If you try to bend it laterally (across its thickness) you will
find it quite easy. It is soft steel, very thin, and doesn't require much of a load to deform. However try to bend it
through its width. It is not 16/2 or 8 times stronger, but 8*8 or 64 times stronger. So while the Mora may be thin
enough so that you can easily bend them up while prying through the thickness (I have done so, it is no great feat of
strength), if you try to deform them through the width it will require a much greater load.

If you want to confirm this for yourself there is a relatively easy way to get a number for the load required. Vice the
blade securely. Now stand on a scale and record your weight. Place your hand on the handle of the blade and cross your
other hand over it. Slowly lean on the handle letting it support more and more of your weight. When it bends record what
the scale reads. The difference between that and what you weigh is the load the knife was supporting. Now this can be
very dangerous, if the knife breaks violently it can send shards flying. As well if you are unprepared for the snap you
can come off balance and fall towards the knife. As well the knife can come out of the vice and similar things can
happen.

Secondly, you can explore the amount of an impact necessary to cause failure. Again vice the knife as secure as
possible, this time by the handle. Now take something of known weight and drop it from a measured height onto the blade.
Keep increasing the weight of the objects used or the height until the knife breaks. If you take the height and multiply
it by the weight you have an energy. For example a 10 lbs maul dropped from 4 feet gives 4*10 or 40 ft.lbs of energy.
To be precise, there will be a skew introduced into the results as past pounding will effect the break point, so the one
shot failure will be higher than what you find, the shift being effected by how many hits performed.

Anyway, the second step is to get a rough determination of the energy of your baton impacts. An easy way to get an
estimate is by using some 3.5" nails and a block of decently hard wood. Drive say 6 nails into the wood by dropping an
object of known weight from a set distance over and over until the nail is about 1/4" from flush. Take the average
number of hits required, multiply this by the weight of the object and the height used and you have the amount of energy
it took to drive in the nail. Now take your baton and drive another 6 nails using the swing you use to do the assisted
chopping. Take the average number of swings and divide it into the energy you just calculated, this is an estimate of
the baton impact energy.

So for example, if you had to drop a 10 lbs maul from two feet, 12 times to drive in the nail this would give a total
energy of 10*2*12 or 240 ft.lbs. If it then required 5 hits with the baton to drive the same nail into the same block or
wood this gives an impact estimate of 240/5 or 48 ft.lbs for the baton impacts. You can then compare this energy to the
energy required to break the knife that you produced before by dropping objects onto it. You will find that the baton
impacts are a *lot* lower and thus the knife is perfectly content to sit back and absorb the baton impacts without harm.

Jim, after you mentioned this on the forums some time back I spent some time working with various knives doing assisted
chopping. I was never satisfied with the performance. Yes I could take some decent sized wood down, but I was suffering
a huge performance loss as compared to a decent large knife or small saw. If the wood isn't larger than the knife, it is
decent as the tip is there to drive on, however if the wood is larger, then the time skyrockets beause I have to work in
little chunks at a time. Loosely, could you provide some estiamates of the time it takes you to take down various sizes
of wood in this way as compared to a small hatchet, large knife or small saw?

-Cliff
 
Thanks Cliff:

It's going to take a while to go over the information.

Timing the knife against the hatchet will have to wait until next weekend but I'll post some times then. I don't have a large knife but I do have the aluminum handled Barteaux.
Interesting - I've never actually compared times to drop similar trees with all three. We'll see.
Were you putting in side notches when using the knife on larger wood?
 
Yes, I did make side cuts to thin the profile, however in retrospective I didn't put maximum effort into the process once it became obvious as to the time and effort disadvantge it was suffering compared to a blade that could chop well on its own. It could be a problem with the technique though. I'll be interested to see what you post up. After I get some more chopping done with the Wetterling and a few other blades I'll try the assisted work again and see how it compares to how you fared.

-Cliff
 
Here's how I did on a small dry log with the Mora and baton, machete, Gransfors and junker axe. Not too many pics as the camera wasn't charged.
So - a few minutes with a hatchet, lots more with a machete - and close to an hour with a baton. For sure I'll be trying again with a better baton! This is pretty tough compared to cutting green wood!http://oldjimbo.com/survival/baton.html
I think things will show a dramatic improvement with a proper baton - it was really time consuming to widen the notch with what I had. The good news is that no Moras were hurt in the test.
 
First off Jim, thanks for doing the work. I had intended to do some experimenting the weekend, but finished up some other work I had on hold for some time, cutting with the Wetterling and chopping with the Bruks against a couple of other blades (bowie, khukuri). Anyway, a few comments :

In regards to the machete, the edge looks really thick, have you tried running it with a more acute bevel? For felling or bucking wood I would run the edge a lot more acute. If you wanted to use it for limbing though, you can't do that as the small contact area on the limbs will dent up the edge, depends on the wood type or course. The handle looks brutal, I remember you mentioning it was metal before, but that picture makes a much bigger impact.

In regards to the cuts, the angles look high (except for the left cut with the cheap axe), were you getting glancing at lower angles?

In regards to widening a cut, I spent quite some time last year looking at chopping techniques with blades that could not make a full cut because of inadequate penetration, I found that opening up multiple notches is *far* better than widening a single notch after v'ing out. This of course is well known, I was simply interested in the magnitude of the performance differece.

Anyway, just based on the expected stroke count for a perfect cut, a double notch is only about 33% slower than a single notch, in practice it is a little less because you tend to get better penetration on the cut as the splits are more dramatic because the distance between the cuts is lower. Widening a notch however can make the time increase in multiples, staggers as you mention will just cause it to skyrocket.

The method is fairly straightforward. Open a notch however wide as the penetration allows for you to single cut it open and just continue to cut until it is v'ed out. Now open another notch the exact same size right next to it. Now just knock the piece out of the middle and continue on. As you note in the bottom, if you stagger when widening the stroke has little to no effect, when multiple notching the effect is not nearly as drastic. As well, even if your aim is perfect, multiple cutting when the chips are not being cleared will produce a huge loss in penetration due to wedging, and of course the blade binds heavily as compared to when it is knocking the chips out.

The pictures are very informative thanks, I was going to put up some pictures showing the difference for various techniques (knot clearance for example) and such but was not sure if there was any interest.


-Cliff
 
Hi Cliff:

For sure the machete bevel is too steep. Another of the jobs I'd been putting off.. It showed up with glancing and that was the main reason for the narrow notching.
That machete should have kept up with the hatchet.
Basically yesterday was a sudden opportunity since the rain stopped for a while so I grabbed stuff and went for it. Lots more work yet before any real information is forthcoming!
The double notch is a good idea on just about anything but old well aged alder like that one. You can drop an alder and split it with a light axe when green. Once it dries well though, the splits run all over the place - it can be tough to split properly even with a good maul or heavy axe. I'm not sure why this should be so, and questions on the survival forums haven't gotten me any answers.
 
The first thing I thought of was that it could be friction against the axe as the living wood is obviously filled with a natural lubricant. To test this I simply did a few partial splits on small wood and then pulled them apart with my hands thus friction was not a factor. The dry wood was easily still much harder.

There are a few factors I can think on. First off all the sap in a living tree contains a lot of water, however when it dries, much like sugar water it becomes a glue. This effect is easy to see for yourself by mixing up a thick sugar solution and pasting sheets of cardboard together and watching what happens when it dries out.

Secondly when wood dries, because the process is uneven the grains I think deform and strengthen the material as a whole increasing the resistance to a split. I think this could be one of the more dominant reasons because baked lumber is not difficult to split. Note as well the strength of the individual grains also increases as they dry out and they becomes far more rigid and thus resist being compressed.

I am not sure what exactly on a micro-scale is responsible for the increase in strength, it could be the lack of a lubricating fluid (the "blood" of the tree if you will), and thus the cells become rigid when dried out because they can't move past each other. As well once dead they probably can't easily deform themselves for similar reasons on an even smaller scale.

I assume Hoodoo would know more about this in any case as it is a bio question, I would suggest dropping him an email.

-Cliff
 
I thought that I'd replied to Cliff's post - oops!

Those are great ideas. I'll see if between us, Hoodoo and I can get to the bottom of this little puzzle!
Thanks, Cliff!
 
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