OK, so we finally have a single wheel ball pitching machine working! For a protoype, we used a simple flat plate to direct the ball above the pitching wheel.
We would like to build a turret for ease of aiming. We also believe that a curved hood will keep the the ball in contact with the wheel longer, resulting in more distance.
Is this a correct assumption? Thanks!
Having contact after accelerating does add to accuracy, but greatly decreases velocity. Think ballistics.
In our experience you want to have a single point of contact of wheel to ball for max distance on a single wheel shooter.
A curved hood will increase contact and you would think impart more distance into the ball but what it does is increase spin and actually reduce distance.
The last thing you want touching the ball is the wheel, any deflection after that will reduce accuracy.
We are not actually considering a curved hood to deflect the ball AFTER leaving the wheel. The curved hood would force contact of the ball to the wheel over a 45 degree arc. The hood would not further deflect the ball after it leaves the wheel.
This is not a new idea. We have seen pictures of this from the 2006 game, as balls were fed into a ball pitching turret from below. We are also thinking that longer contact might allow for lesser crush of the ball. Wouldn’t this be more efficient?
Thanks.
This is only partially correct. The ball needs contact time to spin up to the speed of the shooter wheel, it doesn’t accelerate instantly. On the flip side if the ball is in contact with the wheel for an excessive amount of time it is slowing the wheel down which means if you fire consecutive shots then you need to allow the wheel to spin back up to its previous speed. You have to get it just right.:]
Of course, there is more then one way to shoot a ball…
Regards, Bryan
No, think about it the ball is round and spins on contact with the chute. While it stays in contact with the chute it will gain a little velocity but it what it really gains is a lot more spin.
We learned of this effect from our Luncay shooter. We adapted it for use with this ball and could only shoot about 15 feet and could never get the amount of elevation required to make a basket from more than 10 feet. We remover the shoot and gave the shooter a single point of contact and started shooting 30 feet or about 20 feet over 98"
What are you saying no to, everything I said was true. You will not accelerate a ball to the shooter wheel’s speed with a single point of contact. That is not to say that it won’t work. Just that it won’t be traveling through the air as fast as 1/2 the surface speed of the wheel.
Your experience is interesting. There are many reasons why the ball might not have gone as far. (too much or too little pinch comes most readily to mind) However, as a rule takes about 1/4-1/3 of the wheel curcumference to get the ball up to full speed (1/2 shooter speed) all the way up. So yes it will spin faster, however this is the result of the ball rotating faster as it travels faster. I can draw a diagram quickly if you want but basically with a single shooter the outside of the ball travels the shooter wheel’s surface speed while the middle of the ball (what you care about) travels 1/2 the shooter wheel’s surface speed.
I agree. It would seem to me that added backspin cannot come without added velocity of the ball.
Note that it also takes some energy to crush the ball. Our theory is that a flat plate hood (point contact) requires significant crush to pitch the ball. If the same heavy crush of the ball is used with a curved hood (longer travel), is it possible that this wastes enough energy to result in a shorter pitch?
We are hoping that a longer contact curved hood (with light ball crush) will still result in a long pitch.
Thanks for the discussion, we’ll let you know how it goes on Monday.
Update:
We modified our prototype ball pitcher today by replacing the flat top plate with a curved hood. The hood starts vertical behind the pitching wheel, and extends through a 45 degree arc, so the ball leaves the wheel at a 45 degree angle.
I am happy to report that the ball velocity is at least as fast as with the flat plate the other day. It may even be a bit faster … it was hard to tell because the elevation angle is now a little higher than before, and the ball hits the ceiling under maximum power (a good sign). We are working in a portable classroom with a low ceiling.
Stay tuned!
GO FALCON ROBOTICS / TEAM 3414!
Video or it didn’t happen. 
Here’s ours, which sounds like it’s working about the same as theirs.
We never got around to trimming the top of the shooter, so the students are holding it at an angle. It’s not quite 45 degrees. There is a Lexan flap behind the shooter, that is being held down over the top of the ball before inserting the ball into the shooter.
I feel bad about ours now…
What motor are you using to spin the wheel, we used a single wheel when we had the shooter a few years ago and used a CIM. We are not for sure if we want to use two wheel or one, I like the one wheel because of the amount of space required
for inspiration look at team 1717 and 217s shooters from 2009. Both had adjustable sheet metal hoods powered by window motors (i think) that could adjust their trajectory from about 75 to 150 degrees. while for this competition you would want something lower (maybe 40-80 degrees) the basic design would stay the same.
We are using a 9015 Fisher Price motor, the spec sheet says it’s not as powerful as this year’s motor, but it’s about the same as the AM 0912 motor that came in the kit. We have it connected to a custom gearbox from a previous robot, which uses FP gears to give us 3:5 reduction, then we have another 9:22 reduction from a chain/sprocket set.
We intend to make the departure angle adjustable, possibly similar to what 1717 did with their hood in 2009, although I think they used a small 385 series Banebots motor.
I can address the turret part based on 2006 experience… we built a full pan/tilt turrent… it is awesome to have a turrent… it makes the robot look great, and is fabulous for showing off.
But it is exceptionally difficult for humans to aim. The driver would be turning one way and the “gunner” would have to compensate. We didn’t get our auto-aim working quickly enough or reliably enough… if we had, it would have made a huge difference. Although we occasionally made a beautiful long-distance, over the back shot, we were thumped by machines that could get close and score fast.
This year the hardware is faster and the software better developed… a turret might be a good idea, but don’t count on humans to be fast enough or reliable enough to aim from any kind of distance.
And certainly don’t count on your opponents letting you have time to line up a nice clear outside shot without a well-timed bumper-based greeting.
If you go with a turret, and plan to shoot from outside, computer-based aiming will be critical…
Jason
We’re thinking that computer based aiming will be essential, no matter where we are…and we plan to be over the colored half circle if there are any opposing robots on our side.
“Video, or it did not happen”? Awe come on Mark, smile when you say that so I know that you are joking. 
… and a fellow Falcon no less! Hey, its all fun.
Jason,
Our team is investigating methods of range-finding. We would like to use this input to automaticallly set the speed of the pitching wheel to hit the target basket. I agree that auto-aiming would nice as well, but the range finding will need to come first.
- Jeff
It seems that the amount you compress the ball is a critical parameter. Too little and you get slip, too much and you waste energy. We are looking at about 1.5inch compression of the wheel on the ball. Can you share what you are using and how you calibrated it?
In the video, the ball is being compressed to about 6". We’re working on modifying it so we can do more testing.