The popularity of wood and pellet stoves has increased in the last few years, even as the debate goes on about whether burning wood for heat is green or not. Nevertheless, for those who already heat with wood and are familiar with the hard labour involved in chopping wood, there are a number of improved axe-like tools out there that do make the job easier.
This unique axe has an extra edge over the conventional axe: using the power of leverage to make woodchopping easier, this specially designed "Vipukirves" axe by Finnish inventor Heikki Kärnä simultaneously acts as both a lever and as a wedge when chopping wood.
Vipukirves translates to "lever axe," and when swinging down, the axe cuts wood and also pushes it apart, thanks to the off-center shaft and its unique form that shifts the axe's center of gravity. The result is that less force is needed to chop, making the activity less dangerous. More details on the physics:
Upon hitting the top of the log and penetrating it slightly, the leading edge of the axe head begins to slow down. Where the axe blade widens sharply it stops the axe’s penetration. However, the mass of the axe head still has kinetic energy and the off line center of gravity forces it to rotate eccentrically down towards the wood. This rotational movement causes the leading edge, or sharp edge of the blade to turn in a lever action, forcing a split with all the force of the kinetic energy of the axe multiplied by the leverage of the axehead. The widening blade edge also has a benefit in that it helps to prevent the axe from penetrating into the wood and getting stuck there as is often the case with traditional axes.
It's pretty amazing to see it at work in the video above; a whole section of tree is transformed into perfectly sized firewood in less than a minute. It weighs only 4 pounds and is priced at USD $281 -- pricey but certainly cheaper than heating with fossil fuels all winter long. More over at Vipukirves.