I need to make a catapult that will shoot a tennis ball about 150 feet, any ideas?

Answer 1

None of the answers so far is a catapult. There are two kinds, both based on a swing-arm lever. A pivot point is located near one end and a heavy weight is attached to the shorter length of the lever. A basket is attached to the other end (for one type) or a rope and sling. You pull the long end down toward the ground, lifting the weight up on the short end. Insert tennis ball in basket, then let go of the long end. The weight spins the long end up until the weight hits the ground. This gives momentum to the tennis ball, which then flies out of the basket.

Or, put the tennis ball into the sling and as the long end rotates up it will pull the sling with it and cause the rope and sling to describe a long arc. This was the serious form of catapult, called a trebuchet, used very successfully in warfare. See http://www.trebuchet.com for ideas, plans, kits, etc. Really, this is the only catapult you will ever need!

I have omitted some details that you must consider. Obviously the pivot point must be some distance above the ground. You decide how high, based on sound engineering principles, or just experiment. Heavy weights, large ratios of long arm to short arm length, and long levers all produce more momentum in the object launched. Have fun, but make sure your “field of fire” is clear of spectators.

Answer 2

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Answer 3

The other answers were not catapults.

What you need to do is get 24 feet of surgical tubing. Cut it in half so you have (2) 12 foot lengths. Get an old pair of pants or shorts and cut them off about 6-8" below the crotch. Cut a hole threw each leg and stick the tubing through it. Tie each end of one 12' length of tubing together to make loop. Do NOT tie the tubing to the OTHER tubing length.

Now you have the mechanical moving parts of your catapult. Next you need some sort of framework to loop each length of tubing around. We used 2 other dormitory residents to stand about 6 feet away from each other and each of them held one tubing loop. Then all you do is put the projectile (tennis ball, water balloon, or whatever) into the crotch of the pants, grasp the pants and projectile through the pants, pull back as far as you can and then let go. pulling down slightly will raise the trajectory as needed. Do a few practice runs and you will become surprisingly accurate.

If you are not allowed to us other humans or require a mechanical trigger. I would consider using a bench press weight bench or anything you have handy that could serve as two tie-off points. Tie the tubing on each "fork". Pull back the shorts/projectile and tie it to something. Once ready to launch, cut the tie.

Answer 4

150ft is a looooooooong ways for a tennis ball using a catapult. The answers above cover it off. If you are looking for an actual catapult, I fear that you are going to have a big rig. If you just need to shoot it that far: potato gun, baby.

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Answer 5

PVC pipe barrel, a globe valve, and something to act as a big tank that can hold some volume, like an old propane tank (or two or three or four...).

The longer you make your barrel, the longer you will accelerate the ball. You can build some astonishing muzzle velocity with only shop air, if you have a big enough tank and a big enough outlet valve. Be sure to limit your tank pressure to the pressure rating for your barrel PVC pipe (use schedule 80 or a pressure holding pipe, not sewer pipe).

Soak the tennis ball in lighter fluid and ignite just before shooting for added fun...

Answer 6

Without a doubt......"Potato Gun"