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The Tennis Ball Trebuchet

This trebuchet was built in August of 1999, based on the plans found on Ripcord's Page, well before the formation of our team. The plans there call for a frame made from 3/4"x3/4" lumber, but that seemed a bit too flimsy. So, the general proportions of the frame were retained, but angles were simplified and lengths slightly modified. Furthermore, the frame was made from stock 1"x2" lumber, actually 3/4"x1 1/2" in size. This seemed significantly stronger and more likely to hold up over time.  The arm was also made from 1"x2" lumber, tripled up around the axle. Instead of slightly angling the frames inward as Ripcord suggests in his plans, this trebuchet was designed with simple upright frames, in order to further simplify the construction.

The construction took little over a day with a handsaw and a cordless drill. The main axle is a length of 3/8" cold-rolled steel, and spans a roughly 9" gap. Unless the counterweight exceeds roughly 20 pounds, this axle holds up just fine. The counterweight is made up of numerous hand barbell weights, allowing for fairly simple adjustment of the counterweight weight, and the barbells are held in a simple wooden bucket.

This trebuchet launches tennis balls most of the time, as that is what it was designed for. Living in the city, and knowing that the trebuchet would likely be firing down a sidewalk most of the time demanded that the projectile be fairly non-destructive. Tennis balls fit this bill quite well. However, when at an actual field, this trebuchet has also fired baseballs, lacrosse balls, and golf balls. The tennis balls tend to max out around 120 feet or so, although there was a 140 foot shot once (slight tailwind seemed to have helped that one, though). Baseballs seem to be roughly the same in overall performance, generally landing around 110-120 feet downrange. Lacrosse balls, being roughly the same in weight and density as a baseball, tend to do pretty much the same. Golf ball launches have only been attempted twice, as the old hanger arms cracked after the second attempt, and spares were forgotten that day. It hasn't fired at an open field since. Still, the golf ball went roughly 225-250 feet, a respectable range for a 3 foot tall trebuchet, with poor tuning as well.

Overall statistics on this trebuchet:

Height 3 foot to the axle
Arm 50" long overall -- 40" long arm, 10" short arm
Axle 3/8" cold-rolled steel, ~9" span
Counterweight 15-20 pounds, comprised of hand barbell weights
Projectiles/Normal Range tennis balls -- 120 feet
baseballs/lacrosse balls -- 120 feet
golf balls -- 250+ feet

We now have Ripcord's Tennis Ball Trebuchet Plans available here for download.

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Use "common sense" when operating trebuchets and catapults. Even little ones can be dangerous. Do not place anything you are not willing to lose in the plane of the arm rotation (this includes yourself, body parts, car windshields, cameras, etc). These catapults and trebuchets are capable of throwing just as far backwards as forwards, and the use of a backstop of some sort is recommended, though the use of one does not make the region behind it safe.

Also, just because the throw got away safely downrange does not mean the end of the danger. The arm is likely still swinging wildly along with the counterweight, and there is a sling whipping around. One thing many people fail to take into account is this sling; some people put a metal ring on the slip end of the sling and this ring can HURT when whipping around!

Have fun hurling, but please KEEP IT SAFE!!!