In designing a shooter, you must design around the ball you will be shooting and what you will be shooting it into. In 2006, I think the Poof balls were much more consistent in their squishy-ness or it was just a lot easier to shoot at a 30inch diameter near vertical goal. Either way, shooters that year did not require as much work due to a more consistent game piece and/or a large goal to shoot at.
This year however, we are playing with a game piece that changes quite a bit throughout the regional and is not consistent in squishy-ness to start with, along with a much more difficult goal to shoot at (18 inches and horizontal). With these factors, creating a shooter that would make every shot without adjustment took a little more time and effort.
From what I have found, the top three options for having a consistent shot are:
1. Catapult (16 is the best that I've seen:
http://www.chiefdelphi.com/forums/sh...d.php?t=103876)
This approach removes ball squishy-ness from the picture. While it's harder to get significant backspin, you can land the ball in the same spot every time if you do it right. The trick is the getting the thing lined up and the right distance away from the hoop.
2. Extended acceleration period (2949 using belts:
http://www.chiefdelphi.com/forums/sh...highlight=2949)
With lower compression and extended acceleration, each ball will exit the shooter at a consistent speed regardless of squish. Backspin is tweakable based on your setup. 2949 had a good setup with their shooter on a turret and their laser targeting system.
3. Shoot it hard with a lot of backspin (341 and I believe many others:
http://www.chiefdelphi.com/forums/sh...d.php?t=103579)
For this setup, you need a decent amount of compression for this years ball and I think it helps a significant amount to be a tall robot. I will definitely be inspecting 341's shooter at champs to see just how they did it. As long as you can hit the backboard in this case, the backspin should put the ball right into the hoop as long as you are lined up correctly.
As to what we (525) did this season, we had to find another way to do it. We didn't wind up having enough height (we are about 3 ft tall) or enough compression on our shooter to easily do what 341 did. We thought about speeding up the last stage of our feeding mechanism to do more of what 2949 did. And obviously a catapult would have been quite a drastic change from what we had to work with. Our shooter used a 6inch Colson with one FP 0801-0673 with just short of 2 inches of compression on the ball and an adjustable hood. We decided we had to adjust our shooter speed/hood angle on a per ball basis in order to have a consistent shot. To do this we added a compression load cell (
http://search.digikey.com/us/en/prod...6948-ND/809394) to measure each balls squish factor. You can find more information about our setup for the load cell here:
http://www.chiefdelphi.com/forums/sh...d.php?t=105394. This setup got us to the point where we hit 9/10 balls in tele-op for one of our finals matches at 10,000 Lakes, hopefully something we can carry on to champs.
I'm sure there are other options for having a consistent shot, bot these are the three designs that have stuck out to me.
I hope this is helpful and I hope I remember all of this for the next game involving shooting a ball.
Kellen Hill