# Initial velocity for a shooter wheel

I’m looking at what my team would need to do if we wanted to shoot from various positions on the field. My problem is, i don’t know how fast a typical FRC shooter is. Or how to calculate that. If any of you guys know, it would be much appreciated.

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I’m not completely sure what you mean by “how fast” a shooter is. If you are looking for the velocity of the projectile when it exits the launcher, it depends on how your shooter is made. If the ball is contacted by two plates and a flywheel, the math is kind of tough. It would be like rolling a marble in a channel that contacts it on the side; it accelerates much slower than if it was rolling down a normal ramp. If the ball is pinched between two flywheels and does not rotate (other than due to differences in speed of the two flywheels), you can use a calculator such as JVN’s design calculator and solve for robot driving speed. The power draw will not be accurate, but the output ground speed will be pretty accurate as to projectile speed. If you plan on launching multiple projectiles in a row, make sure to take into account the fact that the flywheels will slow down due to the energy being transferred to the projectile. Attached is my modified version of JVN’s design calculator with NEO, NEO 550, and Falcon specs in case you need it.

JVN-DesignCalc.20200103.xlsx (847.5 KB)

Edit: I will add, if you roll the ball against a flat plate and a flywheel, you can safely divide the output speed by two to get a fairly accurate estimation of the output speed.

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Yes, i meant initial velocity of the projectile, sorry.

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Awesome. Good luck, and feel free to ask if you have any other questions.

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Do an experiment. find a camera (on someone’s phone, most likely) that will take slow mo video. Have someone throw a ball with a trajectory similar to what the robot will. Take video. Analyze it frame by frame.

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