Ball Damage

[cbolin]

Hi,
After test firing for an hour (about 150 test shots) we stripped off about 10 - 15% of the surface of the ball. The ball is still useable but sure is ugly. Any idea if there are limits to ball damage by a bot? Shooting a ball one time causes no noticeable damage...but 150 it becomes obvious to everyone.

Regards,
ChuckB

[generalbrando]

Generally in the past: Unless your robot rips a couple of new balls to pieces, the Ref usually won't even question it. They expect wear and tear. So if you mess up an old ball, no worries.

They'll replace balls as necessary to make sure they are reasonably consistent, but you have to take some variance into account in your design.

[Unglued]

i noticed that the part where the 2 colours meet seperates very easily, and once there's a rip it only gets worse.

however this dosn't take out any chunks of the balls, the foam stays intact.

by limit i guess you mean when a ball would be taken out of the game?
i think as long as the ball keeps it's original shape it'll be kept in play.. since balls can be scored on either net i doubt some colour wear would get them replaced.

unless they are worn down creamy coloured balls of foam?

anyways i apart from them being ugly i don't think you should worry.

[Taylor]

Ball wear is a definite concern, especially for shooter bots. Any non-sphericalness (yeah, I just called up Noah Webster and had that put in the dictionary) will distort the ball's path. I've seen quite a few pics and movies around with people using belt sanders etc. to move balls - while I realize these are only mockups, similar methods will be used. So be advised - don't design a robot that is based on perfectly round balls.

[Kilrath]

Originally Posted by boiler

Ball wear is a definite concern, especially for shooter bots. Any non-sphericalness (yeah, I just called up Noah Webster and had that put in the dictionary) will distort the ball's path. I've seen quite a few pics and movies around with people using belt sanders etc. to move balls - while I realize these are only mockups, similar methods will be used. So be advised - don't design a robot that is based on perfectly round balls.

The balls are not perfectally spherical at the start. They are close but not perfect. We like a couple other teams have found the ball not to be perfect but it doesn't seem to affect how they shoot. So unless you are very anal about the shooter shooting perfectally spherical balls you should be fine.

[dtengineering]

Earlier I posted that our shooter was seriously ripping up the balls and was seeking to hear if other teams had developed shooters that did not.

We have since gone back to the drawing board and have replaced the wonderfully grippy 8"x2" (actually closer to 9" dia.) Skyway pneumatic wheel with two 8" skyway kitbot wheels and rebuilt the turret to account for the reduction in diameter.

Our ball velocity is down a bit... but that's not a bad thing seeing as how we were well over 12 m/s before. Tonight we hit the 3 point goal from 20' out about 8 times out of ten (the variation was due to how the ball was fed in, I believe... we'll call it human error) with no noticable ball damage.

A note to teams that are ripping up the ball... the rethink and redesign advice is probably good advice. Ball shooters that do essentially zero damage can be built. Ours is a single wheel design (the two skyway wheels are on the same shaft) and it sounds like there are many other zero-damage designs out there.

Thanks to the other teams that have posted their successful zero-damage ball shooting results... it was sounding for a while like EVERYONE was ripping the ball to shreds like we were.

Jason

[Veselin Kolev]

My team is also using a two wheel design, but the wheels are about 5" apart center to center, and are angled inward. Before we angled them inward, the sharp rubber corners would cut into the ball as it was being shot. Now with angled wheels, we have tandential contact, so it works beautifully. Plus having the wheels out like that reduces the height of the shooter, and gives you a mechanical advantage because you're pushing the ball from closer to its center. With six inch wheels direct driven off the CIM, we're getting exactly 11.6 m/s, and about 32 feet at 45 degrees. And zero damage to the balls.

[Greg Needel]

Originally Posted by Unglued

i think as long as the ball keeps it's original shape it'll be kept in play..

In 2001 the black balls which were inflatable became eggs. First just left them on the field as long at they were inflated. I suspect that balls will remain on the field as long as they can roll.

also just out of curiosity what kind of thrower are you using when you are messing up the balls, might it have something to do with the material the ball touches?

[Billfred]

For reference, I put a question in at FIRST Q&A to see if they've set a criteria to determine when a ball is Too Pooped To Play. We shall see what we're going to have to deal with.

[Nitroxextreme]

Also teams need to consider how much the ball will be broken in...

a new ball when compacted will shoot further than a used ball that isn't as tough and squishes easier

[teh_masterer]

we played with the ball (in dodgeball fashion) around the shop and saw how much the ball was damaged after a few hours. Besides a few gashes and holes in the ball we seemed to make the ball alot less rounder than it was. Good thing we ordered an extra 24 we will have plenty more to use. When does first think the ball has expired?

[Jeff Rodriguez]

Originally Posted by Official FIRST Q&A by GDC

An official point of a ball not being useful has not yet been determined.

FIRST will attempt to get the maximum use of all playing objects, while still ensuring the objects are useful to teams.

Teams should not expect that all scoring objects will remain in an "as new" condition for the entire event.

http://forums.usfirst.org/showthread.php?p=473

[Leo 1529]

What if a ball has split in half during a match. Like if it splits in half from being run over or just over use or shot too many times. How would FIRST score the two halves of the ball?

[Andrew Blair]

Well, if they were destroyed during firing, they probably wouldn't roll down to the camera for scoring. If they were run over, they probably wouldn't ever make it into a scoring area. Regardless, we will see a half of a ball score eventually.

[Leo 1529]

Originally Posted by Andrew Blair

Well, if they were destroyed during firing, they probably wouldn't roll down to the camera for scoring. If they were run over, they probably wouldn't ever make it into a scoring area. Regardless, we will see a half of a ball score eventually.

I hope im there to get it on video so i can put it in this years robotics movie.

What about balls that get gashes or holes that might be still be playable. would anyone think that the balls should be allowed to still be used with some chunks taken out or gashes in them?