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This page has moved to http://webpages.mcgill.ca/students/jfletc6/web/trebuchets/trebuchets.html. <-- Check out the trebuchet video page for a clip of the trebuchet in action.
Our first encounter
My father and I first saw a trebuchet on our local public television station on a program called NOVA. We were very impressed with the show and we were inspired to build one of these machines.
In the beginning
We started off by first assembling a small test treb. It was about 2.5 feet tall and made out of a MECCANO building set. It was a success and could throw a marble about 30-35 feet. It was throwing too far to use in the house and fearing that we would lose the marbles in the grass if we took it outside, we had an excuse to build a bigger one. Unfortunately, this treb no longer exists as its parts were dismantled for other projects.
We go one size bigger
The next one we built(unofficially called Newton) is made out of wood scraps and is about six feet tall with the beam up. It has a three piece beam with a swinging basket and uses cement patio stones for the counter-weight. It throws golf balls 120 to 135 feet depending on the golf ball thrown. Well you might think us satisfied at that, but no, we had to go bigger.
The monster is born
So we built our largest trebuchet (unofficially called Thor) so date, measuring in at 30 feet tall. The frame is made of wood from our woodlot, the axles are solid steel, and the counterweight is made up of 2300 lbs of reinforced concrete blocks. Its size was only limited by the materials available to us at the time to make the trowing arm (as it is the largest piece). Next, we gathered a number of bowling balls and started throwing them. At first, we were using a piece of rubber belting for a sling, and we were getting a 14 pound bowling ball to fly about 190 feet. We were unhappy with this, as from simulations and calculations we figured it would go a lot further. We wanted more, but could not figure out how to achieve it. We got lucky as one day as we were taking pictures of the treb firing, we noticed that during the release, the ball would slide out the side of the sling before the sling unhooked. That meant that the ball was not getting all of the energy available to it. So we took off the sling. We drilled a hole though the bowling ball and attached it with a rope. Now instead of a sling we have a bowling ball on a string. The string flies along with it the bowling ball after it is launched. Attaching the ball in this manner has increased our range to just over 600 ft with the same counterweight and ball.
The large trebuchet meets its makers.
Modifications to Thor over time
We have made a number of modifications and repairs to the treb over its life. It is the culmination of all of our trebuchet knowledge rolled into one. We have added extra weight onto the basket, initially believing that we needed weight for the ball to go farther (it turned out to be the sling problem as mentioned above but having the extra weight doesn't hurt). We have also replaced parts in the priming and release mechanisms which have broke over time due to wear and improper design. We have also added extra bracing to the sides to add stability and extra supports to help out in bearing the weight of the main axle.
Future plans
We had had plans on extending the sides of the treb higher so we could have had a longer throwing arm and thus more leverage and thus farther distance. However, instead of rebuilding the wooden trebuchet, which will eventually be unusable due to the deterioration of the wood structure, our current plans are to construct a larger steel one. Though, as with building any very large object there are more complications then we originally thought, so it may take a while before it actually comes to fruition. Stay tuned for updates on our progress.
A view down the firing range.
Last updated on: December 7, 2008
