Here is a link to another article on this where the inventor entered a comment. Link and copied comment follow:
http://www.mnn.com/family/protection-safety/stories/weve-been-splitting-wood-all-wrong
Hello.
My name is Heikki Kärnä. I am the inventor of the Vipukirves/Leveraxe.
I red the comments and I noticed, that for some people it seems to be very difficult to understand the splitting technique with the Vipukirves/Leveraxe.
There is practically nothing to do with cutting and wedging when splitting with the Vipukirves.
Leverage is the way how to do it.
There is no friction as with the conventional axes and mauls, because on an optimum strike the blade penetrates into the block only about 5 millimetres, less than a quarter of an inch. At the very moment, when the edge of the blade touches the surface of the block, the blade starts to lean to the right. Here comes the leverage that multiplies the splitting force up to 35 times bigger. The edge of the blade grabs to the side of the part of wood. All the kinetic energy turns to the left and pushes the piece away. Initial spitting force can be even 15 tons.
Splitting is now much easier, because you do not have to use so much power. By holding the handle as gently as possible you allow the rotation in your hands. You will not get such chocks to your hands and body as with the conventional axes and mauls.
It is very important to hold the handle so, that you do not resist the rotation.
This way also the safety elements, which are build in to the design of the blade, function as they have planned to do. The blade will stop on the top of the block, or slows down the speed so, that it is fully under the control of the user.
Vipukirves has been on the market over 8 years. There has happened NO ACCIDENT.
It is advisable to split the wood as green as possible, because this way it splits easiest, the insects cannot multiply in it and it dries best.
Vipukirves has spread all around the world. The feed back is excellent.
There is a lot information in my websites, Google etc. Youtube. Search by words Vipukirves and Leveraxe.
I wish you to make yourselves acquainted with this new kind of tool which is in commercial production first time in the history. I would also like you to understand that among the other advantages the safety elements make the splitting really enjoyable because you do not have to be afraid all the time about the blade.
Based to the feed back, so called hard wood is not any more a problem when using the Vipukirves.
Of course it requires some knowledge about the structure of the tree to optimize the splitting.
In the videos you can see myself splitting. I am around 70 years. Now I am 74 and my total experience is splitting firewood consists of 67 years time.
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I think that answers my question about the curved part on the head. It throws the weight to the right twisting the blade in the crack it has just made. I saw it bouncing to the right in the video but thought that was operator carelessness.