Ball Pitcher Hood Design
 

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!

Re: Ball Pitcher Hood Design
 

Having contact after accelerating does add to accuracy, but greatly decreases velocity. Think ballistics.

Re: Ball Pitcher Hood Design
 

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.

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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.

Re: Ball Pitcher Hood Design
 

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

Re: Ball Pitcher Hood Design
 

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"

Re: Ball Pitcher Hood Design
 

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.

Re: Ball Pitcher Hood Design
 

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.

Re: Ball Pitcher Hood Design
 

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!

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Video or it didn't happen. :D

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Here's ours, which sounds like it's working about the same as theirs.

http://www.youtube.com/watch?v=jeLe2WWemWA

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.

http://www.youtube.com/watch?v=jeLe2WWemWA

Re: Ball Pitcher Hood Design
 

I feel bad about ours now...

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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

Re: Ball Pitcher Hood Design
 

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.

Re: Ball Pitcher Hood Design
 

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.

Re: Ball Pitcher Hood Design
 

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

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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.

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"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

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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?

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In the video, the ball is being compressed to about 6". We're working on modifying it so we can do more testing.

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Jim,
could you have gotten away with less compression? Have you tried 1" and 2"?

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We did get a chance to play with it, and it really does like the 2" compression. Also we noticed that having the ball escape while it is still compressed, results in quite a bit of variation in height. But using a flat plate that lets the ball uncompress gradually, allows very precise height control. So make sure your shooter has some "follow through" with the hood extending gradually away from the wheel.

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Squirrel, your plywood box looks very much like ours. We are using 2 wheels together but, about the same effect. Now how to get the balls off the floor, and cross the bump and get them up 2 the shooter and control feeding and aim and calculate shoot speed and and and.

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Jim, it looks like you have 2 wheels sandwiched together with a gap in between them. Is your 6" compression from the shroud to the edge of the separated wheels?

We got incredibly precise shots from the top of the key with a single pneumatic wheel and much less compression (< 1").

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We have a single wheel. I expect there are quite a few different ways to tackle this problem....

Re: Ball Pitcher Hood Design
 

What was the range?

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We haven't tested the full range yet because it was an electric drill running it and we were testing things like energy absorption of the backboard, consistency of shot, best angle to approach the basket from the key, etc. Our results are similar to Jim's video, but I suspect that the reason for our convergence to similar results from different setups is the fact that we use a heavier/bulkier wheel with grippier tread versus his lighter/slippier -- both are tradeoffs between the designs and there doesn't appear to be a 'better' one so long as the implementation makes up for any potential shortcomings. It's pretty interesting.

As-is I suspect our shooter gets the ball far enough to cover half the field before it hits the ground again, which is good enough for a ball-delivery bot should the situation arise. Once we get a starting point for a more realistic motor/gearbox we'll adjust speed with some extra room for maximum "oomph" (and also some breathing room for drained batteries). It won't do full-field shots, but we're not trying to do those in the first place. At best we'll try to hit the mid or high goal from ~24 feet away.

Re: Ball Pitcher Hood Design
 

Jim-

How are you guys doing on consistency? Looks like I saw 2 balls in the video being cycled through. Do you have more? Have you tried more? How about highly damaged balls versus new balls?

Nice work so far!

-Brando

Re: Ball Pitcher Hood Design
 

With no feedback on the motor, we have to let the motor get back to speed for about two seconds before making the second shot, or it will be short.

The balls have lots of faint lines marked on them, and the labels are getting faded, but they don't appear to have any damage from the shooter.

Re: Ball Pitcher Hood Design
 

Jim,
We tried your suggestion with an extended top piece. It was a little more consistent shot after shot. We did not see a difference between a 1 1/2 and 2 in compression, for our design.
The AM wheel from 2008 is definitely much better than the grippy ones this year. We shredded 3 balls in 5 minutes with them. The smooth older ones definitely grip better with less slippage and doesn't damage the ball other than small scuffs.

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Have you thought about using 2 FP's to power the thrower? That would get you double the power, thus allowing double the torque for a set speed. That should reduce the time between shots. I know you were concerned about needing another FP somewhere else, but per the game design rules (R48) you're allowed 2 FP's and 2 AndyMark motors, which are relatively the same in output. Hopefully this should mitigate any hesitation for using both allowed FP's.

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We have thought about it, but having speed control will still be an issue...battery voltage fluctuates during a match, etc. It looks like a single FP motor is powerful enough.

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Jim,

Are you running your present set-up at full voltage? Or did you do your testing at, say, 9 volts, to leave some headroom for a speed controller in case you needed it?

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Has anyone tried a Colson as a shooter wheel? We thought their greater mass near the edges would make it a decent "natural" flywheel.

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We tried a 4" Colson in our lab. Gripped the ball well. Speeds started to get a bit crazy though in terms of RPM to get the shot we wanted with a 4". I imagine they'll work just fine for a shooter, among other things. ;)

-Brando

Re: Ball Pitcher Hood Design
 

We have it on a speed controller, and we can get sufficient distance running the motor below full speed. I dont know how much it is below full speed yet.

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Neat. We're using 6" colsons extensively on our robot this year, but haven't gotten them all plugged up and ready for hex yet, so it's good to have a positive review.

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Has anyone tried to use the BaneBots wheels on their shooter? I have a feeling that their softness may result in marks.

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We used BaneBots wheels in 2009. Never had any issues with them marking the orbit balls. Now obviously these balls are different, however I wouldn't expect the wheels to leave marks on the balls. Taking chunks out or pulling skin off? That's another matter that you would have to determine through testing.

Re: Ball Pitcher Hood Design
 

I'm new at this, but have a couple mentors who built a decent shooter for Lunacy. We made a prototype 4" ABS pipe shooter wheel, lined with 3M grey tub grip tape from Ace. It is very gentle on the balls, yet very grippy.

Our prototype has 1" compression against two curved 1/2" EMT conduit rails spaced 4" apart for the top of the shooter ball path. This gives the ball a trough to roll in, which makes for very accurate azimuth control of ball path.

I'm thinking of using a 2012 orange-ring Fisher Price motor with ~4:1 reduction, but we'll see what's possible to make in a short time. McMaster Carr sells 32 pitch nylon and metal gears that should mate with the FP motor pinion, if my math is correct.

We also plan to try the Jaguar speed control feature. It should provide hours of amusement to get that working well.

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http://www.youtube.com/watch?v=DvnbttY_4Ks
Video, heres your proof.

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The other day I had together a 4 wheel/2 motor Banebot (550s) with 4:1 ratios. We were using the wheels that came in the new KOP and we could easily launch it starting at a height of 0 and hitting the wall 30' away at 5' up.
But in front of the shooter it looked like someone tried to make orange snow from the foam basketball.
We plan on trying the grey rubber wheels or the plastic lunacy wheels.

Re: Ball Pitcher Hood Design
 

We too had issues with the shooter "spraying orange snow" with high speed but realized that it was a function of a too low friction cooeficient between the wheel and the ball. The wheel we used was the AM Performance with the grippy tread. We realized that the "tips" of the grippy part of the tread was acting like a chain saw blade and having its way with the ball. Rather than slow down the wheel or change the tread, we increased the cooeficient by squishing the ball into a smaller confine. BINGO. 27 foot shots and NO SNOW! All other variables remained the same.

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The 2012 kit wheels basically destroy the balls. We had one prototype with those wheels and now the ball that tested it is known as the "bad ball". It barely bounces any more.

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my team intends to use a material called wacky wood which is basically a plywood with a layer of rubber in the center this makes it extremely flexible the only problem is that it is hard to find but if you live in New England than we found ours at Boulter Plywood in Somerville, Mass. they also have a website to

Re: Ball Pitcher Hood Design
 

This is our first experience making a shooter and we were struggling with our prototype until I came across this thread. Thanks to the advice given here we finally got a good proto running today. Made over 60% of our 3-point shots from the free throw line. Over 90% doing 2-point layups.

We ended up using two 8-inch AM FIRST wheels mounted side-by-side on a 1/2" shaft. The proto is powered by a CIM with a 1:1 chain drive. We plan to use two RS-550s with a CIM-U-LATOR gearbox on the robot. Not sure how much we'll gear it down yet. Today's proto used a flat plywood hood fixed at 60 degrees. Compressing the ball by 2-2.5" seems to work best. Range dropped when we backed off to 1.5". We're going to try a 70 degree hood next as the 60 degree trajectory looked a little flat. We could make a rotating hood, but today's testing showed that we can probably make shots consistently from up close to the top of the key with a fixed angle just by changing the wheel speed.

A big mahalo to all who contributed to this thread! We'd still be struggling without your coopertition! On to the next challenge!

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As far as I can tell, if you have a lot of backspin so the ball bounces down off the backboard into the basket, you WANT a flat trajectory...then you don't need to worry about how far away from the goal you are. One less thing to sense and control.

At least that's how we're planning to play the game.

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Good observation. You're right a lot of our 3-point free throws were off the backboard. We'll still test at 70 and compare.