[RRLedford]

Those here to gain insights as to how to make the best shooter should be aware of some factors influencing your choice for type of shooter and how you design/build it..
Most teams will use either a swing arm (catapult), a ram punching the ball, or spinning pinch wheels (or belts) to launch their balls.

1) Since at 2.75 LBS, the balls are fairly light, this means that a catapult arm style launcher does not require the arm to have very much structural mass, making it easier to accelerate the COMBINED mass of both catapult arm and the ball to a higher velocity with less force applied.

2) With the 60" height and 20" protrusion beyond the 112" circumference frame limits, the length of a swing arm design is rather constrained.

3) A set of spinning wheels (or belts) launcher is fairly compact, but needs to grip ball without damaging it from high slippage/friction/heat/melting.

4) Both ram and swing arm can be powered pneumatically or via winch stretched surgical tubing (or bungee cords).

5) All methods of launching need energy stored and ready to be delivered by a triggering method.

6) Best game performance requires launcher that fires at a wide range of speeds and angles.

7) High goal accurate shooting favors launcher designs that reach higher ball velocities, but it also favors launcher designs where their accuracy does not require a consistent level of ball inflation pressure, which the ram and pinch wheels designs do require for accuracy.

8) Missing high goal shots in auto is to be seriously avoided, since no assist points can accrue until all missed shot auto balls are retrieved and scored, which could easily take the whole rest of the match if defenders are good.

9) Catapult swing arms launchers are potentially highest accuracy and more consistent for handling ball pressure variation, of the three types, but they are less capable for reaching higher ball velocities.

10) Variable shooting speed & angle combined with shot triggering and trigger resetting is not a trivial design task.

11) Winch designs that retract an energy storing element (metal spring, air spring, bungee, latex rubber tubing, etc.) to store a variable level of launch energy are tricky to design, especially the triggering and trigger resetting mechanisms. However, they do favor better precision control of amount of energy delivered per shot.

12) Slow turning winch designs where the launch trigger system releases drum to free spin as ball launches have issues. Care must be taken to avoid too much slack of an unwinding cord/cable, which must be prevented from snagging, and cord/cable must also then be fully rewound before next shot is ready for launch. In addition, much of the stored energy can be wasted on accelerating the free spinning winch drum instead of delivering launch energy to the ball. Consider nylon winch drums.

13) Ram designs require that the ram velocity be absorbed by the robot frame after launched ball separates from the ram. A well optimized ball-to-ram mass ratio and a well tuned peak velocity ram acceleration allows ram rebound off the ball to help limit the ram speed at the limit of travel stopping point.

14) Swing arms also have end of stroke arm travel concerns, but if air cylinder power is used, pneumatic pressure can be used for an end of travel cushion.

15) Ram launchers only impart energy to ball while ram maintains contact with the ball. Inadequate ram speed and travel can give too little ball penetration/compression by the ram end. compressed ball acts like a spring and extends time/distance that ram stays in contact with ball.

I am sure others can add more thoughts to this list.

-Dick Ledford