3D Printed Trebuchet

This week’s blog is by Nick Stone, Z Corp. Project Leader, Mechanical Engineering, Research and Development.

When I was 15, I saw a PBS program on trebuchet’s and decided to build one in my backyard. Honestly, it was disappointing. My trebuchet threw a tennis ball about 10 feet and sliced a trench into our lawn.

I always wanted to give it another try, so I decided to 3D print a fully-functional trebuchet. I printed all of the parts on a ZPrinter 650. The axels ride in plastic bushing that are used in the ZPrinter 650 feeder assembly. The wheels do turn and are supposed to give you a little extra push. I found a video from the History Channel which provided some good advice on relative lengths, as well as a good way to hang the sling. The length of the string controls the release point as does the weight of the projectile. The heavier the projectile, the earlier the release, and thus the higher the angle. I’m not sure if this is typical of all trebuchets or unique to my sling.

Fully-functional trebuchet 3D printed on a ZPrinter 650

I’ve been threatening one of my fellow engineers, Guy, with my trebuchet since I started designing it. He finally had enough of my taunts and began ZPrinting his own trebuchet. His is about 20” tall and seems strong enough to launch a baseball a good distance. And so the arms race begins…

I decided that, because I had proven trebuchet technology, and since Guy was still perfecting his trebuchet, I’d be best served by improving my projectiles. I had been launching Delrin balls and drywall anchors, but decided to really strike fear into my enemies/co-workers. We have a low melt temp metal on hand, so I ZPrinted some molds and waxed them. I used a heat gun and hot plate to melt the metal and pour it into my molds.

ZPrinted mold for trebuchet’s metal projectile

A flying spiked metal ball is pretty scary (and dangerous, so here’s my disclaimer: Neither I nor Z Corp recommend you try this; if you do, you do it at your own risk and we cannot be held liable for any adverse results!). If Guy starts mobilizing his trebuchet, I might be forced to hold a demonstration near his cube. Until then, I think it’s enough that he knows I have the capability and am crazy enough to try it.

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