From Team 449 Wiki
A shooter is any mechanism designed to launch game pieces into a goal. Since 2006, a majority of games have had game pieces that could be scored into goals or other targets, so shooters are frequently employed on robots.
The point of a shooter is to move game pieces (usually balls) from the robot to a target some distance away. They do this by launching them from the robot at speed on a trajectory that will land them on target. Shooters can be classed according to their mechanism and their accuracy.
There are three mechanisms used in shooters: wheels, punchers, and catapults.
A catapult shooter uses a rotating arm to accelerate the game piece. Generally, they fire a single projectile on predictable trajectory. The arm can be spring-powered, pneumatic, or motorized.
This type of catapult has a spring-loaded arm which is locked back and then released. The springs provide the energy needed to accelerate the arm.
A pneumatic catapult uses pneumatic cylinders to accelerate the arm. It functions similarly to a spring catapult, but is safer, as pneumatic cylinders don't need to be mechanically locked back while pressurized before firing.
Motorized catapults use a motor to rotate the arm. This makes it easier to have an adjustable trajectory, but this variety is less powerful than the others.
A "puncher" delivers a linear impulse to the game piece to shoot it. Our team has never built one, but they can use the same acceleration mechanisms as catapults.
Wheeled shooters use spinning wheels to shoot the game piece. They can be classed as either intake or flywheel shooters.
Intake shooters use the same set of wheels to both pick up and eject the game piece, almost always a compressible ball. Our team used this mechanism on Ballbasaur and ROUS, although Ballbasaur's was primarily an intake for its catapult shooter.
Flywheel shooters use a fairly heavy wheel spinning at a very high speed, often close to 6000 rpm, to shoot light game pieces. This is the only type of shooter that we have used to shoot objects other than balls, as on Panda, we shot Frisbees with a flywheel shooter. Flywheel shooters can be either single or double.
Single flywheel shooters have a wheel or set of wheels (the flywheel) one one side of the game piece and a curved surface on the other. The wheels and curves slightly compress the game piece, which allows the flywheel to apply an impulse and cause it to accelerate. The game piece only needs to touch the flywheel for a short distance, since after that, it is at its maximum speed. Any section of curve after that only serves to guide the game piece into a release trajectory.
A double flywheel shooter has two counter-rotating flywheels. The game piece is pushed into the gap between the flywheels, and it gets shot out.
Shooters can also be classed by accuracy. Target shooters deliver game pieces one at a time, but land almost all on target. Vomit shooters may deliver more than one game piece at a time, or deliver them rapidly. They are not as accurate, since the game pieces interfere with each other's trajectories, but can compensate for this with volume of game pieces scored.