Ball's Circumference

[May_Walter]

Hi everyone,

Does anybody know what is the exact circumference of the soccer balls used in the competition (HS300, DTI Sports)?

[Nathan Streeter]

The regulation in the rules says the balls must have a circumference between 27 and 28 inches, when properly inflated... This makes the diameter a fraction below 9 inches. Hope this is the information you're looking for!

[tim-tim]

We found during the build season that the balls can vary depending on air pressure and how they have been used and abused.

At the competitions (Chesapeake and Buckeye) it did not seem that the balls were inflated to 9psi because they were not nearly as hard as the ones we used at the shop. It never made sense to me why a ball rated for 6-8 psi was inflated to 9psi...safety issue?

But to answer your question better - we saw 27.2" - 27.9" range

[sircedric4]

Originally Posted by May_Walter

Hi everyone,

Does anybody know what is the exact circumference of the soccer balls used in the competition (HS300, DTI Sports)?

I don't know why you want that data, but if you are expecting the balls to perform the same throughout the matches be warned that they probably won't. We have a ball looper that we designed for the balls based on the speed of the ball coming down our ramp in the shop and an average from the kickoff video, and the only time we got a chance to deploy our looper at the Bayou the ball came down the return ramp twice as fast.

It's funny, but after evaluating the speeds of the balls coming down the ramps from video of the tournament, that was the fastest ball ever at our tournament. Naturally it was just a hair too fast and missed our net. Our lesson learned, and the reason we have an additional bolt on net for Atlanta to remedy it, is that you can't count on repeatability. If there's even the slightest chance that something will malfunction or not perform correctly, it will undoubtably do it at the worst possible time. Murphy's Law, like the laws of physics, still remains undefiable. We're prepared for even the statistical outliers now and I suggest you be as well.

[thefro526]

Has anyone measured any of the balls at competition to see what the actual variance is? They didn't seem to vary too much to me, but then again I can't really eyeball differences in circumference that well.

For design purposes though, I averaged out the Soccer balls to have a 8.75" diameter, which is about a 27.5" Circumference. This worked well for me, as competition soccer balls should vary less than 3/16" +/- from this 8.75" Dimension.

[tim-tim]

Originally Posted by thefro526

Has anyone measured any of the balls at competition to see what the actual variance is? They didn't seem to vary too much to me, but then again I can't really eyeball differences in circumference that well.

For design purposes though, I averaged out the Soccer balls to have a 8.75" diameter, which is about a 27.5" Circumference. This worked well for me, as competition soccer balls should vary less than 3/16" +/- from this 8.75" Dimension.

No I didn't measure them, but I can tell you that as the competition went on the balls got "weaker." At the beginning of the day (Match #2) the balls were well inflated (not 9psi by any means probably at 8psi), but by Match #20 they had deflated a considerable amount. From our testing at the shop proved that ball pressure would be such a big factor in its trajectory we had to constantly readjust the kicking strength over the competition. They must have re-inflated them each morning because we saw a jump in performance after not touching it from the previous match the day before.

I think part of the pressure issues comes from rough robot play. However, most of it is probably coming from the seams stretching and an over inflated ball.

[James Tonthat]

I worked Field Crew at Dallas, we inflated the balls to a specific pressure and tested the other ones to be approximately the same (doing a bounce and "thumb push" test). There was no "standard" given pressure that was told to us, we used the indicated pressure on the ball and a gauge. But mostly we were looking for was consistency in the balls.

Balls were inflated so that when dropped from shoulder level, would bounce back to approximately waist level.

We tried keeping ball pressures the same as the day went on, would check between matches. Your results may vary, it's up to the your field crew to keep balls consistently and properly inflated.

Edit: Sorry if I'm not to informative, I'm about to leave for class. I'll elaborate later.