I need help with a challenging physics/engineering momentum launcher!?

Question

I need to construct a device to launch a launching sphere ( a wooden ball about the size of a grapefruit or a small canteloupe) across a field. It has to go REALLYY FAR!!! here are some rules:
-must be completely mechanical: no chemicals or combustion
-must have wheels attached to the bottom
-must be free to roll once it has been fired
-cannot exceed 4ft in any dimension (h,l,w,)
-must remain upright during and after launch

Answer 1

I.ll add late but few initial tips.
1) Throw the sphere so that when it leaves it is aimed to rise and move at exactly 45 degrees to the ground to cover the maximum distance
Now adding some ideas how to throw it but u need to try them to see which ones work.
Think of bicycle remove front wheel. reduce the height of sitting so that you and it are seated in height of less than 4 feets. You may modify so that wheel rotates on you side but it should have large diameter 3 1/2 feet. Now make the wheel rotate as fast as you can after tying the projectile by 1/2 feet chord. When it is at the top speed. cut the thread by bringing sharp knife in its way so that it projects at 45 degrees, if you find the ideas interesting write back to me and I may devote more time to help you work out other things.
Another one. Take a very very tough spring say 4 feets big. Mount it at 45 degrees to the ground and fasten it on two side with screw arranged exactly as car jacks are arranged. Just that rotational motion is used to lift the car u use the rotational motion to compress the spring and then when it is compressed you release it. release it simultaneously from both sides, You need to fix an easy release mechanism Just study rat traps to get the idea of how to hold tense spring and then release.
Mind you circular motion can be carried over a long time to store enormous energy which can be released as described,

This one should definitely give you an edge if implementation is possible. Here you have a sealed small but very strong sturdy chamber like gas cylinder fitted with valve. you got it we will push air in it by a mechanical air pump. if the pump can be made to work on circular motion that you can paddle great just sit and pump preassure in the cylinder . Keep a preassure meter mounted to be in safe limits and then it is just a matter of time that you put as much preassure as you desire. Mount a small mettallic ball at the exit and release the lever to shoot the ball in air. Since there is no limit to the preassure build up You could even calculate the distance to which it will fly and make sure before hand that you are winner.
Hope these are sufficient but feel free to ask for hurdles and better communicate the results also.
2) The higher the momentum means better result so it should be powered by a heavvvvy object and should itself be light.
3)Ensure maximum transfer of momentum. How? I may return later to add.

Answer 2

Create enormous air pressure behind it and then suddenly release the air or make it swing really fast by means of some rigid arm and the sphere in a cup shaped container and suddenly open the cup by means of some mechanism in the rigid arm and launch the ball.

Answer 3

Maybe a trebuchet (a fancy catapult) or a seriously torqued out ballistae (A super heavy crossbow).

I'm also assuming you can do anything electric with it.

Answer 4

I particularly have been your secure practices blanket like yule wrapping paper labels, graffiti. heat, needy, grasping. like the 1970z hippy affliction society bubbles burst extensive like cotton candy unrolled sticky, groovy.

Answer 5

How about a cannon?