Side vs. Top Shooter

[MrForbes]

We are working on a single wheel shooter to give the ball backspin, so it will bounce downward and go in the basket when it hits the backboard. We'll aim for the backboard. We also are hoping for a relatively flat trajectory, since in our experience it's not too hard to aim side-side, but it is pretty difficult to accurately judge distance, so we're trying to minimize the effects of how far the robot is from the goal.

We haven't got there yet....this is all still theory! but it's based on watching 2006 robots play Aim High

[DjMaddius]

With our teams prototypes we have found that if you power both the top and bottom and supply 30% power less to the top then the ball gets the perfect backspin. Though these change with different designs and such. This will power enough for distance and backspin though so its what we are going for.

[farmersvilleRob]

Well... I think it has more to do with the context of the shooting. Firstly, spinning wheels to shoot a ball are always unpredictable based on:

1. Spinning wheels, as that on a pitching machine, rely on deformation of a ball in order to get the desired friction to shoot the ball. (even baseball pitching machines deform the ball!) And this deformation is different from ball to ball, let alone balls that are quishy in general!

2. Spinning wheels need to speed up to the desired RPM before a ball can even be placed into it, and the balls then put into it slow it down enough to where you again have to wait to put the next ball in

3. The efficiency of a wheel powered shooter is probably very low considering the power is distributed by friction (which also means more compression of the ball would be needed to make the ball go further thus affecting points 1 and 2)

4. Every single ball shooter that operates by wheels has either been right up to the goal hugging the side of the fender, where every robot will try to shoot from as well if they go with a shooter and even there the balls in youtube videos has scuffs on it which means its only a matter of time until something gives.

5. When shooting a fastball from a pitching machine, there's a reason why the wheels are different speeds for the slope of the ball. When shooting a crazy basketball that weighs more than twice as much, the slope will be incredibly hard to tune to the wheels speed and compression of the ball and even THEN the distance will play a HUGE role in the speed of the wheels as well which means the wheels would have to be tuned while moving which requires a lot of time, just like a pitching machine warming up

Now for a horizontal v. vertical shooter:

Horizontal shooters basically are side spin magnets meaning if you even have the motors a little off the somehow magically set speeds, there will be a curve left and right. That curve isn't and will never be enough to get around objects like a boomarang either since the curve on a ball is actually made by a low pressure system on one side.

You also cannot shoot a ball with a slope since the horizontal motors means there is no y component. Then shooting at a basket becomes dodgeball, and the ball's compression would make a nice bounce right back, and never make it from more than 5 feet away because the speed would need to be too high to make it the right distance in a straight shot.

Vertical are basically the same, however, they, being vertical, means they have little affect on left and right movement. That's good, but then like in the first 5 points on wheel shooters, there is so much unpredictability, that it's better to go a more direct mechanism to ball shooter such as a catapult. However, the effect of a tension/spring method weakens with every shot which means its impossible to tune as well without the fear of fatigue affecting shot.

We went with a rotational shooter. Direct, and doesn't have fatigue.