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Physics-exploiting axe

Physics-exploiting axe splits wood in record time
Ryan Whitwam
Apr 20 2014

Chopping wood is hard, but it’s something modern society has largely freed us from as a daily activity. That’s nice, but consequently, if you ever do have to chop wood, you’re more than likely going to suck at it. Splitting a log requires a surprising amount of force, but Finnish inventor Heikki Kärnä has invented a new kind of axe that makes it much easier and safer.

Yes, axes have existed since time immemorial, but apparently there’s still room for improvement.

The Vipukirves does what the name implies, assuming you speak Finnish. It’s essentially acting as a lever instead of a wedge (Vipukirves translates as Leveraxe). A regular axe needs to be driven downward with enough force to separate wood along the grain. That’s a lot of force, and if a log is hit off center, the axe blade can deflect at unexpected angles. That’s not good — your squishy flesh is much easier to split than a log.

So what makes a lever different than a wedge in this scenario? The Vipukirves still has a sharpened blade at the end, but it has a projection coming off the side that shifts the center of gravity away from the middle. At the point of impact, the edge is driven into the wood and slows down, but the kinetic energy contained in the 1.9 kilogram axe head continues down and to the side (because of the odd center of gravity). The rotational energy actually pushes the wood apart like a lever. A single strike can open an 8 cm gap in a log, which is more than enough to separate it.

The inventor also claims this tool is much safer because the downward energy that might cause harm is dissipated gradually as rotational energy. So, no abrupt shock, and no deflection. The Vipukirves also naturally comes to rest on its side, which stabilizes the log and keeps the sharp edge pointed away from the operator. It’s really a clever design.

If you want this crazy physics-exploiting axe, it’s going to cost you. The base price is €193.12 in EU countries, including VAT. For US orders, the base price is €155.74 or about $215, plus €47.26 ($65) in shipping.