Quote:
Originally Posted by YashBrowns
Our team is new to shooting high goal this year so we just wanted to know what to use for motors and wheels for an working shooter.
So far we have been using a 775 pro motor with a 5:1 gear ratio.
We used the kit of parts andymark wheels for the fly wheels
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There have been a lot of good suggestions so far, especially on the control side of things. But as a note on the actual shooter design, it's hard to say whether 5:1 is a good speed for your wheels without knowing what size wheels you're using. There are probably four main variables in designing a shooter in FRC*: wheel surface speed, contact distance, compression profile, and wheel/hood material (durometer, coefficient of friction). Of course, wheel surface speed and contact distance are both functions of wheel diameter. So if you use larger wheels, you can have a higher reduction from the motor, but for small wheels, you'll want them spinning faster.
In an ideal world, you would have plenty of traction and distance to get the balls up to speed and have no slip between the balls and your wheel(s)/hood. Then the exit velocity of the balls could be calculated quite simply by equating the surface speed of the wheel(s) and balls.**
This, put simply, is not going to happen in real life. The balls will slip on the wheels, but how much they do so depends on how well the wheels can grip the balls. The more distance you can keep the balls in contact with the wheels (this means larger diameter wheels or a larger angle in contact), the closer you can get to this ideal. Softer wheels are also sometimes advantageous for this, at the expense of faster wear.
Additionally, how much you compress the ball/wheels how that compression is distributed over the path of the ball has a major, if somewhat complicated, impact on your shots. In general, more compression can allow for more energy transfer, but only up to a certain point. After that point, you're just excessively deforming the balls and bogging down the shooter.
And finally, a general rule of thumb that I've come to follow is that softer balls should take harder wheels and vice versa. This year, the prototypes I've seen online and with my old team are suggesting that hard wheels will probably be fine—These balls can compress a bit. But all these are just guidelines, and your mileage may vary with any of them.
*Actually, I'll add a fifth, but it's not as much about geometry and it's important this year, so I'll keep it separate: motor power. Shooters this year should have a pretty high throughput, so be prepared to use your newfound closed-loop control knowledge that you got from the fine folks here to keep your shooter at its proper speed as you're shooting. With that in mind, consider whether one motor will have enough power to keep the wheels spinning at their proper speed as balls go through. If not, you can add another motor to increase your available power and help your speed rebound between shots.
**If you use a single-wheel shooter with a hood, the exit speed of the ball would be half the surface speed of the wheel, and for a double-wheel shooter like a pitching machine, the ball speed would equal the average of the two wheel surface speeds.