trebuchet

It’s an ethereal sound, Doppler-like and downright spooky. “It scared us the first time we heard it coming at us,” says Kurt Modert, from whose Minnesota backyard the sound emanates. “Who would have thought a bowling ball could make such a sound?”

Modert, with his friends Roger A. Bacon, Ryan Krueger, and David Proehl, built an enormous trebuchet on Modert’s exurban St. Paul property. Enormous even by medieval standards, their catapult is large enough to throw heavy objects 700 feet into a grassy field, now well-pitted and cratered from hundreds of high-impact landings.

The builders are skilled scroungers, picking up most of the building materials at a fraction of the retail price. They made the trebuchet frame mostly from scavenged lumber. The swinging counter-weight, the key to any good siege engine, is a 265-gallon oil tank they got for free off Craigslist and filled with sand.

Still, their investment is at about $3,000 and growing, much of that going for expensive hardware and fasteners. But the cost is minor compared to the joy they get when they hurl stuff.

Projectiles to date have included a variety of non-working items: television sets, microwave ovens, bicycles, a wheelchair, a ladder, and several gas grills.

According to the four builders, the best “tossables” are bowling balls. A full rack of multicolored bowling balls sits in a nearby shed. Their favorite ball is nicknamed The Howler.

The Howler is a green 13½-pounder, once used in a bowling alley pro shop to help bowlers find the best place to drill finger holes in customized balls. So it’s got a lot of holes. When launched, the spinning ball careers through air, the aerodynamics of the holes producing a loud, human-like wail that pretty much freaks out everyone who hears it.

Modert’s nearest neighbor is several hundred feet away. That’s probably a good thing.

Trebuchet Group: makezine.com/go/fbtrebuchet