The video we posted of our pneumatic catapult prototype was viewed almost 800 times. I had the pleasure of having someone come up to me at our regional this weekend and tell me that their catapult was based on the video we posted. Such a compliment!
After posting the prototype video, the design evolved drastically. By switching from one to two cylinders we found that we decreased our air consumption. We use high flow servovalves and pulse to get variable trajectory shots, though we've found that pulsing consumes a lot of air.
We experimented to find the lowest system pressure which produced a consistent trajectory shot. We added a pressure sensor to our HP supply to monitor pressure. We use a spike to power our camera light ring and a LED strip on the other side of the robot. When the pressure drops too low for a good shot, the lights turn off. That way, as long as the lights are on, the driver and operator know, without taking eyes off the robot, that the pressure is good.
It works great. We used it to get what we think was the highest un-penalized match score at our regional.
Video here. Notice that we started just a little low on our precharge pressure. The indicator lights go off during the second auto shot, and it falls a tad short. After that, you can see the lights going off during the match as we operate the pneumatics and consume air, and then back on as the compressor catches back up.