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moot1337 · 10-26-2005, 02:59 PM

Are you a tinkerer, or do you need actual plans to follow? Trebuchets are a bit more finicky than catapults because of the sling, but if you're up for some trial and error, and lots of tinkering/testing, they're not hard to make.

Pretty much, you design a base that will be tall enough for the weight not to hit the bottom when it swings underneath the pivot, and wide enough to give room for the sling... probably a good 4x the width of the object you intend to load into it.

Then, you make an arm with a pivot hole in it, the pivot being about 3/4 to 2/3 down the arm from the sling-end. Attach to the short end a weight (it can be a bucket filled with something, or a solid object like lifting-weights) and put an adjustable hook on the sling-end. By adjustable, I mean something that you can bend or adjust the angle of, that will let the loop of the sling fly off at some point in the air.

Remember that torque=force * lever arm: if you want to launch something heavy, you're going to need something a good deal heavier if you want to give it some good velocity. The length of the sling will also influence the way it shoots. A short sling is going to whip around and release very quickly, wasting some of the energy remaining in the weight. Too long of a sling is not going to be past that critical point around the arc when the weight doesn't add to the energy of the projectile. Fortunately, all that is easily adjustable.

On the base, in the middle, make a running board for your sling's pouch and the projectile. It needs to be snag free, and ideally it will gently center the projectile/pouch in the middle of the board, so it doesn't come out until it needs to. This should run from as far back as the sling goes in the armed postion and then some, back to about as far as the arm extends out of the back of the trebuchet when it's horizontal.

If you get this thing built, the length of the sling, and the angle of that adjustable release hook are what control the release point of the sling. Too late, and your projectile will slam into the ground... too early, and it'll go backwards or straight up in the air

10-26-2005, 02:59 PM	#4 (permalink)
moot1337 Insane Location: Learning to Fly...	Are you a tinkerer, or do you need actual plans to follow? Trebuchets are a bit more finicky than catapults because of the sling, but if you're up for some trial and error, and lots of tinkering/testing, they're not hard to make. Pretty much, you design a base that will be tall enough for the weight not to hit the bottom when it swings underneath the pivot, and wide enough to give room for the sling... probably a good 4x the width of the object you intend to load into it. Then, you make an arm with a pivot hole in it, the pivot being about 3/4 to 2/3 down the arm from the sling-end. Attach to the short end a weight (it can be a bucket filled with something, or a solid object like lifting-weights) and put an adjustable hook on the sling-end. By adjustable, I mean something that you can bend or adjust the angle of, that will let the loop of the sling fly off at some point in the air. Remember that torque=force * lever arm: if you want to launch something heavy, you're going to need something a good deal heavier if you want to give it some good velocity. The length of the sling will also influence the way it shoots. A short sling is going to whip around and release very quickly, wasting some of the energy remaining in the weight. Too long of a sling is not going to be past that critical point around the arc when the weight doesn't add to the energy of the projectile. Fortunately, all that is easily adjustable. On the base, in the middle, make a running board for your sling's pouch and the projectile. It needs to be snag free, and ideally it will gently center the projectile/pouch in the middle of the board, so it doesn't come out until it needs to. This should run from as far back as the sling goes in the armed postion and then some, back to about as far as the arm extends out of the back of the trebuchet when it's horizontal. If you get this thing built, the length of the sling, and the angle of that adjustable release hook are what control the release point of the sling. Too late, and your projectile will slam into the ground... too early, and it'll go backwards or straight up in the air __________________ And that, my liege, is how we know the Earth to be banana-shaped. This new learning amazes me, Sir Bedevere. Explain again how sheeps' bladders may be employed to prevent earthquakes. Oh, certainly, sir.