Game piece inflation

At the Michigan Center Line District event the game pieces were so inflated they were actually squarish. We asked about it and the officials said they had inflated it to the specification of the field reset guide. We designed our robot to pick up 25" (+/- 1") balls as were explained by the GDC. We even underinflated and what we considered to be overinflated some ball in practice. But many of the robots at our event had significant difficulty picking up the balls cleanly. I was surprised that there isn’t a sizing box!

Were they like that everywhere?

They were fine at Palmetto.

They were also exceptionally inflated at GSD

GTRW’s balls were also overinflated as far as many of the teams were concerned. Many robots spent the portion of Friday that wasn’t waiting for the field to work trying to adjust their intakes to deal with the crazy over inflation.

Due to the weather and the temperatures inside the Avanti Dome at the Central IL Regional, at the beginning of the day(40 degrees indoor temp), the game pieces were perfectly inflated but as the indoor temperature rose with robot interaction and increasing outdoor temperatures, the game pieces looked like they were going to burst. We had to drop our 3.5" roller for two 4" wheels spaced about twelve inches apart and we had to change our reduction on that collector to adjust the geometry of our shooter so we could continue to shoot.

The event staff adjusted the game pieces by Friday, however. Teams mentioned the issue to event staff and they did everything they could to improve it! :slight_smile:

I’ll keep an eye on this at N/E Groton & N/E Southington.

They were very much over inflated at Alamo on Thursday, and after many complaints, the balls were slightly deflated during lunch and they were fine throughout the event.

GTRW had a ball sizing ring. It was 25" in diameter and came with the field. I’m assuming other regionals had one as well. Was it being used?

If there was a ring to be used, why wasn’t its size shared with teams weeks ago such that we could test robots accordingly? The inflation level of the balls completely changes how they fly from some shooter designs and changes the intakes too.

Officially, the balls are inflated to the point where they look about right and thats it.

Although I agree there should be a sizing box 100%, this is the first I’m hearing of it being actually used.

+1 GTRW Crew

The problem though, is that many teams at GTRW had to rework their intakes and shooters as the balls at GTRW seemed to be overinflated by the official inflation method provided to teams at kickoff.

There was a sizing box used for Logomotion . Unfortunately it didn’t help because people were still inflating the tubes until they were overflowing from the box and were bigger than most teams expected.

The sizing ring had a hole exactly 25" in diameter. When a few teams at GTRW complained about the ball sizes, they were checked and a few were found to be oversized. Those ones were deflated.

Some teams cam by and used the sizing ring on their practice balls as well.

The ring went in the robot inspectors case.

Does anyone else think that a sizing box is not the way to go here? We have no idea the tolerances that these balls are designed at. If the balls are +/- .5in a sizing box would lead to over and under inflated balls, and then everyone would be complaining about that.

I think there is a bunch of confusion here.
Having all balls the same size in diameter would lead to different levels of inflation.
Having all balls inflated to the same PSI would lead to different sizes, in diameter.

Simply put the tolerances on there balls are not +/-.0000000001 There is no way to have all these balls be the same size and same pressure.

The rules state nothing about ball pressure, but they do state an approximate size. And assuming that all of the covers are approximately the same size the balls should be inflated to around the same size according to the inflation guide. So there is no argument backing pressures since the rules state nothing about it.

We really should not have a problem putting a ball in a box and pumping it up till it touches the sides.

I don’t see why you can’t just pump them up in the morning and check them at lunch each day and be done. Or even just once a day (I’m assuming they may lose some air getting hit and squished all day).

The rules say approximately 2ft diameter. Excuse me for designing for 23"-25".

Has this actually been tried out tho? Its all speculation until you see the actual results.

I don’t think anyone is asking for 10 decimal places of tolerance on the diameter… However a single decimal place or 2 would certainly be welcome.

Honestly I would take one or the other if it helps consistency in an event and event to event. Right now, we don’t have either besides a general ‘look’ and ‘feel’.

-Brando

Remember this video was to address this concern. http://youtu.be/Azc8AKzgEwE

The sportogo makes them as 25" balls, AndyMark sells them as 2’ balls.

They must loose an inch in Indiana air. :slight_smile:

None of the balls at Palmetto looked even close to the example in the video, some where stretching the stiches at the seams.

By saturday about 1/2 the balls on the field had been corrected. but most where still oversized.

The actual result can be seem using chemistry.

Lets say we have a 25’’ Sportlogo ball, and a 24’’ AndyMark ball, I know their the same ball
R1=12.5in
R2=12in
V1=(4/3)pi(r^3)
V1=8181.23in^3
V2=7238.23in^3

Ideal Gas Law, PV=nrT
Assume (nrT) is constant between two balls.
We have have (P1)(V1)=(P2)(V2)
From above (P1)(8181.23)=(P2)(7238)
Notice the two pressures cannot be the same.
Lets say we inflate one ball to P1=7.5PSI, NCAA Basketball recommendation pressure
Now we see that P2= 8.477PSI

What does our result show? Well the Smaller diameter ball is at a greater pressure. Meaning that it is firmer.
If you try to instead control the pressure you’ll see that you get stuck with a different ball diameter.