Team 2851 Shooter Prototype

Here is Crevolution’s latest prototype making half court shots in the top net:

http://www.youtube.com/watch?v=dJGS8LPw1yg&context=C32d36d3ADOEgsToPDskLqJfQ1lfBz8rrN7E979ICk

We used 1 direct driven CIM motor, 8" wheels, and it is positioned 60" above the ground. Our plan is to use 2 Fisher Price motors on our robot.

And yeah, it’s duct taped to a ladder.

Only 2 out of 3? What do you think caused that shot to be off?

Inaccurate feeding is probably our biggest problem. Once we get a consistent feeding mechanism, we believe accuracy will greatly improve. And also the distance the ball travels through the air obviously creates variation.

Is that a single-wheeled shooter?

Yes. We like that design because of the backspin.

how much did u guys pinch the ball

I believe that our compression was about 2".

Have you guys thought about two wheels to help with accuracy? We found that with 2 8’’ wheels spread apart a bit gave us better accuracy.

Take a look

Yeah, sorry, we actually did use that system. What I meant by one wheel is that it wasn’t a pitching machine type approach, the ball was only being moved by one axle.

That makes more sense!

This might be because the ball had a different density. We built our prototype and it wasn’t shooting all the balls at the same spot. We figured out that this was because many balls have different densities

Yeah, we actually just figured that out as well. When testing a brand new against a 2 week old ball, there was a great difference in the trajectory and the distance traveled. I think such long range shots in the competition are going to be pretty rare simply because the balls are so unpredictable. You might find a “sweet spot” in practice, but once you get a different ball that spot might change.

So for us more rookie type teams, what did you find necessary to help compensate for the aging balls? Faster shooter speed, more compression
on the ball (more than 2 inches)?

Why do 2 wheels make it more more accurate? Also, would a wide roller serve the same purpose as 2 large wheels, or do you need 2 separate pts of contact?

2 wheels give a bit of a groove for the ball to “settle” into, resulting in the ball leaving from the same place every time (and thus having exactly the same spin every time). It’s not really an accuracy aid, but a precision aid. A single wheel may have the tendency to let the ball slip sideways to one direction or the other, causing less-predictable spin.

A single wide roller could act like one wheel or two, depending on exact construction–with a shallow groove in the middle, or a groove/depression on the compression bar/hood, it’ll act like 2; if neither has that, there’s no telling. It might act like 1 or 2 wheels.

Less compression actually seemed to make the shooter more consistent, but we’re still working on solutions to the problem. We’re even prototyping catapults now (something we hadn’t even considered before) because they should be more consistent.