This is the second-to last test shot we (Team 1197) took with our shooter prototype to confirm that a single-wheel shooter would give us the repeatability we wanted. Each blue dot on the pegboard is a piece of masking tape representing the spot where a shot landed, and was placed by studying the corresponding shot in slow-motion video. All test shots were taken from the same location, which corresponded to where the robot would be if it had just crossed the outer works along the center of the field (if such a thing were possible).
For this test, we were running a pair of 6" diameter VEXpro traction wheels, powered by 2 mini-CIMs geared up at a 1:2 ratio, and run at 50% power through the FRC control system. We fed the ball into the shooter prototype using a conveyor belt similar to the one on our final robot. In this video and on our robot, there is no closed-loop control of the wheel speed. Our reasoning for not using more sophisticated control of the wheel speed was that if the ball were shot fast enough, its trajectory would be sufficiently straight to neglect any ballistic effects.
For safety reasons, please do not repeat our mistake of running these wheels at such a high speed. The tire-bands for these wheels are not intended for high speed applications. One of these bands failed on our robot at the 2016 Arizona West Regional, fortunately without hurting anyone. For whichever shooter wheel you use, understand the G-Forces it will experience as it spins and be sure that it will operate safely under those conditions. A quick napkin calculation revealed that at full speed, the band that failed on our shooter wheel was experiencing a radial acceleration over 100 times the gravity on the surface of the Sun! (About 3000 Gs at the wheel's circumference for a 6" diameter wheel running at 6000 RPM.)
