Half a croissant, on a plate, with a sign in front of it saying '50c'
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Pneumatic Cannon Powered Catapult

A heavy cannonball enters the catapult arm and accelerates it.
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This catapult has two main components. The first is a low velocity pneumatic air cannon which accelerates a heavy cannonball. The second component is the catapult, which features a lightweight aluminum tube arm that accepts the cannonball.

The pneumatic air cannon is fixed and angled upward. The aluminum tube of the catapult arm rests against the muzzle of this air cannon. The tube is curved at the end so it smoothly lines up with the cannon barrel.

Upon firing, the heavy cannonball is launched into the catapult arm. The curved section smoothly starts imparting angular acceleration to the arm.

As the cannonball continues moving, it acts like an ice skater's arms being pulled inward. Conservation of angular momentum means rotation must accelerate more and more. Thus, the catapult arm gets accelerated like crazy. By the time the heavy cannonball reaches the hub, most of its original kinetic energy has been transfered to the arm (and projectile).

IJK, Mar 19 2007

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       How is this better than just a cannon alone?
Smurfsahoy, Mar 19 2007
  

       How is this better than just a cannon alone?..Because you can't launch a pie from a cannon. (Well, you could but you would miss out on the pin-point pie suprise attack)
the dog's breakfast, Mar 19 2007
  

       It's better than just a cannon if you want to chuck a pumpkin without wadding (due to contest rules, for example).   

       Also, it's better than just a cannon because catapults are inherently cooler.
IJK, Mar 19 2007
  

       //How is this better than just a cannon alone?//

A cannon alone is useless and probably suffering from depression and feelings of rejection. It will have low personal esteem, will be lacking in motivation and probably doesn't care too much about personal grooming.

+ for use of catapults.
DrBob, Mar 19 2007
  

       Oky...now, what about the basic law of energy that says...no energy is free? The Conservation of angular momentum also means that as the angle decreases, the force will also decrease as momentum increases. Basically, the energy invested (input), less frictional loss, remains exactly the same.
Blisterbob, Mar 20 2007
  

       Of course the energy isn't coming for free. It's coming from the kinetic energy of the cannonball. The cannonball gets tremendously slowed down in the process of accelerating the catapult arm. The catapult arm doesn't add any energy to the system, it merely transfers energy from the cannonball to the payload.
IJK, Mar 20 2007
  

       ILK - check out my pneumatic trebuchet idea directly below this one. I was thinking pumpkins as soon as I started reading this.
bungston, Mar 21 2007
  

       I was inspired by your concept; originally I was just going to annotate your concept with some ideas...but it quickly evolved into an entirely different concept.   

       I realized that in your pneumatic trebuchet the counterweight seemed superfluous, and that the proper position for the pneumatic piston would be on the other side pushing upward or sideways. This sort of arrangement was commonly used for swinging hammer weapons in Battlebots.   

       But then...I dunno...it lacked that certain "je ne sais quoi". I thought maybe it would be cooler if the pneumatic equipment was stealthed inside the trebuchet arm--the arm is a pneumatic barrel which conceals a piston that rams inward to accelerate the arm rotation.   

       That's when I realized that you could leave all heavy barrel and compressed air tank outside the arm in an external cannon. No longer stealthy, of course--the exact opposite extreme!
IJK, Mar 21 2007
  
      
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