DIY

February 10, 2012

You Built What?!: A Compact Mechanical Crossbow With the Precision of a Laser

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Last October, after hurting his knee playing hockey, Patrick Priebe was holed up in his apartment near Cologne, Germany, with nothing to do. He was sitting at his computer, staring at his keyboard, when the “Y” key caught his eye. Priebe didn’t see a letter. To him, it looked like a crossbow. Immediately he knew what his next project would be.

For years, the German lab technician had built laser weapons, including a working Iron Man–style palm-fired blue-diode laser. After all those futuristic gadgets, he wanted to make a completely mechanical contraption. Priebe doesn’t draw up designs for his projects; he just starts tinkering. In his home shop, he cut some bars from an aluminum sheet and fastened together a Y-shaped frame that fit perfectly over the back of his hand.

Next he gathered more aluminum, copper, and brass sheeting. He ordered steel wire usually used in model planes, carbon-fiber tubing for the arrow shafts, and a few cylinders of low-friction Teflon plastic. He cut out two pieces of flexible spring-steel to act as the bow and stretched the steel wire between them for the string. Using a lathe, he shaped pieces of brass for the arrowheads, glued them to the carbon-fiber tubes, cut a groove down the center of one of the Teflon bars, and placed it in the center of the crossbow.

To fire, he pulls back the wire, hooks it around a brass block, and places an arrow in the groove. When he flicks the thumb trigger, the brass block drops, the wire pops forward, and the arrow flies.

Priebe can use the crossbow to pierce soda cans, smash lightbulbs, and tag apples. And although his creation isn’t the smallest crossbow in the DIY world, none match its mix of power and accuracy, quick reload and ability to fire one-handed. Still, he has no plans to use it, not even for home security. For that, he says, “I have a pretty sturdy hockey stick that would do the trick.”

Go on to the next page for three more DIY projectile launchers.

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