game ball inflation

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Posted by Joe Balint.

Engineer on team #128, Cold Fusion, from Grandview Heights HS and The Ohio State University, American Electric Power.

Posted on 1/10/2000 11:07 PM MST



The rules state that :
'The 'Ball' is a textured rubber playground ball that is
approximately 13-inches in diameter.'
Balls will be inflated to size not pressure. (1.2.2 Basic Gameplay p1)
Our team has noticed that if the diameter is measured across the
seam when inflated, the ball ends up being somewhat eggshaped
and distinctly non-spherical with a long diameter of
about 14.5 inches measured perpendicular to the seam plane.
I would expect this after some use ( similar to the 1998 competition,)
however I would not expect this upon first inflation.
Are other teams experiencing this?
or
Are there some other inflating guidelines besides those I quoted above?
Any information or insight would be appreciated.

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Posted by Jerry Eckert.

Engineer from Looking for a team in Raleigh, NC sponsored by .

Posted on 1/10/2000 11:34 PM MST


In Reply to: game ball inflation posted by Joe Balint on 1/10/2000 11:07 PM MST:



: The rules state that :
: 'The 'Ball' is a textured rubber playground ball that is
: approximately 13-inches in diameter.'
: Balls will be inflated to size not pressure. (1.2.2 Basic Gameplay p1)
: Our team has noticed that if the diameter is measured across the
: seam when inflated, the ball ends up being somewhat eggshaped
: and distinctly non-spherical with a long diameter of
: about 14.5 inches measured perpendicular to the seam plane.
: I would expect this after some use ( similar to the 1998 competition,)
: however I would not expect this upon first inflation.

: Are other teams experiencing this?
: or
: Are there some other inflating guidelines besides those I quoted above?
: Any information or insight would be appreciated.

This sounds like a good situation to me! You now have balls which are closer to what you'll be dealing with in the competition than if they were 'perfectly' round.

Jerry

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Posted by Chris Orimoto.

Student on team #368 from McKinley High School and Nasa Ames.

Posted on 1/11/2000 12:59 AM MST


In Reply to: game ball inflation posted by Joe Balint on 1/10/2000 11:07 PM MST:



Yes it does seem that way. When we first got our ball we almost immediately inflated it, only to find that it was not perfectly 'spherical'. I'm not sure if this was intended, or accidental. On the kick-off show, the balls looked pretty rounded. And also in the manual, there are diagrams showing perfectly round balls. I'm not sure what to say.

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Posted by Greg Mills.

Engineer on team #16, Baxter Bomb Squad, from Mountain Home and Baxter Healthcare.

Posted on 1/11/2000 6:23 AM MST


In Reply to: game ball inflation posted by Joe Balint on 1/10/2000 11:07 PM MST:



:

The voice of experience - save a few uninflated balls for your last few practices. After inflation over an extended time the characteristics of the balls will be different. It will take less pressure to maintain a certain size. At the competitions FIRST will take new balls out of the box and the surface texture and pressure will be different from the old worn out balls at home that you have spent hours rubbing around the carpet.

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Posted by Raul.

Engineer on team #111, Wildstang, from Rolling Meadows & Wheeling HS and Motorola.

Posted on 1/11/2000 6:53 AM MST


In Reply to: game ball inflation posted by Joe Balint on 1/10/2000 11:07 PM MST:



Our ball is also closer to being a big football than a basketball.

I spoke to Eric at FIRST. He said they would typically overinflate them for a while to fix them a little. But BEWARE, he said that this year they will not make as many attempts as in the past to use only the spherical ones in the competion.

Raul

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Posted by Dodd Stacy.

Engineer on team #95, Lebanon Robotics Team, from Lebanon High School and CRREL/CREARE.

Posted on 1/11/2000 8:36 AM MST


In Reply to: game ball inflation posted by Joe Balint on 1/10/2000 11:07 PM MST:



The balls are and will be out of round and variable in 'diameter,' however we want to define that term. The ball handling mechanisms must be tolerant of those variations. We killed ourselves in Ladder Logic by designing our manipulator for a 'perfect' spec ball. Don't repeat our mistake.

The balls will also have very different friction coefficients when you play at a chilly Regional in March and when you play at the Nationals in humid Orlando in April. They will behave very differently and may tend to get hung up inside your ball handler when sticky. Be forewarned.

Finally, I noticed at Kickoff that the balls behave like their CG is off center - not just due to their non-spherical shape, but due (I think) to large local variations in the thickness of the ball material. That stuff is dense! At least this aspect causes the balls to come to rest pretty quickly and not roam all over the field. Good luck everyone with real world balls.

Dodd