pic: FRC 225 -- 2014 Robot

[Ben Martin]

Originally Posted by Conor Ryan

Can you go more in depth about this mechanism, I'm having a tough time conceptualizing how it works.

I'll do my best--

The catapult arm pivots about an axle ~18" off the floor. Two large-diameter cylinders are positioned such that the end of the catapult arm moves very quickly while still applying the required force. The extension-side of the cylinder vents to atmosphere, making the cylinder extension very quick. Gravity/a slight surgical tubing assist returns the cylinder to its dropped position.

Because the cylinder extension still wasn't fast enough, we added a gate latch actuated by 2 additional cylinders to block the throw of the catapult arm. This allows us to "pre-charge" the cylinders a bit, creating an air spring to increase the speed of the throw. By varying the amount of time we allow it to pre-charge, it adjusts the force of said "air spring" and varies the shot (oddly enough, our most common shot uses a delay of 225 ms).

The catapult foot is made of sheet metal and plastic cutting board material with the tips covered in rubber roughtop. The throw has a lot of backspin, and this helps to reduce it slightly and increases the height of the throw.

Underneath the catapult foot, we have a photo eye detecting whether or not a ball is directly above it. If the ball is too high, we run the collector roller in reverse until the sensor sees the ball--it's a pretty simple way for us to detect if the ball is sitting too high for throwing.

Thank you for all the great compliments, everyone! We really appreciate it.