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Chip Sutherland
03-31-2007, 5:49 PM
I'm usually spinning wood but I got a request from the church ladies that run our annual pumpkin patch to build something a little medieval. Starts with 2x4s and gorilla glue. We had a plan but it was for a trebuchet 1/3 the size. The overall design was kept but it really came down to custom cutting and fitting. The arm was totally made up. I took 3 twisted pieces of african mahogany and ripped them in strips. Took the best of the best, flipped everyother one to reorient the grain then laminated them back together. Strong but not strong enough so we laminated some white oak on the sides. Then I took some peruvian alder and laminated the tail end to add weight and....more strenght. Low quality, odd-ball wood I would never have found a use for became a throwing arm. As you can see we used stnd weights for the counterweight. I don't have any pictures of the trigger mechanism but we got it off the web. The axel looks wimpy but it's a steel rod in a steel sleeve. I doesn't flex even under load. We dialed it in to throw 2-3lb pumpkins consistently about 150-180 feet. Longest throw was ~215ft. Total lbs was 175 dead wt. The trough took a hit when the weight's got dropped but that was expected sooner or later. We generated a bunch of money from dads/sons...Crowds loved the countdowns. 3,2,1, 'fire in the hole'....swoosh....splat. Imagine what we could do with 4x4s and 6x4s and 350 lbs. Enjoy.

Christopher K. Hartley
03-31-2007, 6:17 PM
Hey Chip, break out the pole lathe and it will fit right in. Looks like fun!:)

Jon Shively
03-31-2007, 6:50 PM
Ever watch the TV show "Little People, Big World"? They have one at their pumpkin patch, last show of the season showed the one son and hired hand getting hurt I am guessing the sling used to hold and throw the pumpkin somehow entangled them after the throw as they were drug under the arm. Both survived, but beat up. Be careful as with all tools, looks like a ton of fun. If I were building, think I would go for a pumpkin gun instead of a potatoe gun!!

Chip Sutherland
03-31-2007, 10:01 PM
The most dangerous thing is setting the arm back down and locking the trigger. We used 3 people. We stood 15 feet to the side and pulled the release. One thing about trebuchets, when they misfire, they misfire backwards or straight up. The key is to make sure all bystanders are watching and they stood back 20 feet to the side.

Cliff Rohrabacher
04-01-2007, 8:23 AM
Are there calculations you use for the moment arm the weight and scale?