Game piece inflation

[Bochek]

Originally Posted by Jim Wilks

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?

After reading this I tried to inflate ours to 25". It would not get any bigger then 24" no matter how much air i put in. (almost to the point of bursting). Are the balls supplied by the field different than the ones supplied in the KOP? I sure hope not.

[Pretzel]

Originally Posted by Racer26

Changing air temp from 20C to 21C would add 0.028" to the diameter of a ball. (If T1 = 15C and T2 = 22C, the ball changes 0.200" in diameter)

Did I do that right? It doesn't seem right to me. I think changing temperature will also change P.

You did it correctly assuming that pressure remains constant. If pressure remains the same then your volume will increase as temperature increase and vice versa. Unfortunately this doesn't translate perfectly to the real world since the balls would most likely increase in both pressure and volume. If you had the measurement of one of those two factors (before and after of volume or pressure) you could find the other one fairly easily.

Our team has also noticed a large variability due to temperature of the ball. When prototyping our shooter and performing initial testing with it mounted on our robot we tested outside. We noticed a significant difference after moving our testing into an abandoned Sears building (free rent since it's soon to be demolished) and the temperature was a good 40* warmer.

[Racer26]

Originally Posted by Pretzel

You did it correctly assuming that pressure remains constant. If pressure remains the same then your volume will increase as temperature increase and vice versa. Unfortunately this doesn't translate perfectly to the real world since the balls would most likely increase in both pressure and volume. If you had the measurement of one of those two factors (before and after of volume or pressure) you could find the other one fairly easily.

Our team has also noticed a large variability due to temperature of the ball. When prototyping our shooter and performing initial testing with it mounted on our robot we tested outside. We noticed a significant difference after moving our testing into an abandoned Sears building (free rent since it's soon to be demolished) and the temperature was a good 40* warmer.

That's what I'd thought, was that it would change in pressure and volume together (and thus the volume would change). I looked around hoping some kind of formula exists to model that relationship, but was unable to find one. I suppose it would depend partially on the pressure vessel, as a compliant vessel like our balls would be able to expand more in volume than a steel tank.

[brandon.cottrell]

I can assure you, inflated balls happened from time to time. But every instance where we noticed it we just asked for a different ball and we were very gracious to receive one.

[Annatreptic]

They were extremely inflated at teh Glacier Peak PNW regional as well. So inflated in fact, that it started to continuously stall our motor and wouldn't allow us to gather the balls at all. We want to put some slop in our pneumatic mounts to our arm to try to fix this problem, any other teams done things to help this problem?

[MarcD79]

This thread can go on and on, but the one thing to remember is that according to the Filed manual, the balls should be inflated to the point where the zipper is not touching itself, nor stretched into a football shape. They are to be inflated where the zipper is slight pulled apart where the inflating plug can be inserted. The zipper should be able to be pulled closed with some slight resistance. I did not receive any complaints at the Groton District event. I checked all balls often & they were consistent. We did have 2 balls checked at the beginning of the Eliminations & found to be slightly over-inflated by a volunteer who was just trying to keep up & was pumping them up rapidly. After that they seemed to be consistent. They will be scrutinized at the Southington District Event to be properly inflated.

[tickspe15]

Originally Posted by Annatreptic

They were extremely inflated at teh Glacier Peak PNW regional as well. So inflated in fact, that it started to continuously stall our motor and wouldn't allow us to gather the balls at all. We want to put some slop in our pneumatic mounts to our arm to try to fix this problem, any other teams done things to help this problem?

we noticed that the balls were more inflated than we expected at auburn mountain view during week 1 and upon further testing found problems similar to the ones you describe. We then altered our intake by moving the roller up about an inch to decrease ball compression and avoided problems at glacier peak. Though the balls may be over inflated they have been consistent at PNW event

[Ether]

Has anybody out there actually measured the difference in pressure between a properly inflated ball and a slightly over-inflated (and under-inflated) one?

Is it a large enough difference that it could be reliably measured with a relatively inexpensive gauge at the events?

[MrForbes]

Originally Posted by Annatreptic

They were extremely inflated at teh Glacier Peak PNW regional as well. So inflated in fact, that it started to continuously stall our motor and wouldn't allow us to gather the balls at all. We want to put some slop in our pneumatic mounts to our arm to try to fix this problem, any other teams done things to help this problem?

Last week, 4183 lengthened their pickup arms an inch to allow the more-inflated balls to fit without stalling the motor.

Measuring the pressure would require a special fitting or gauge, although it wouldn't be too hard to make something to do it. 1/4" pneumatic tubing fits into the inflation hole in the ball.

The extent of wrinkling at the seams of the ball gives an indication of how full it is...until the wrinkles go away entirely, then who knows?

The balls aren't exactly round, either...they're sort of cube shaped.

I think this is a game where you need to take a lot of effort to make sure your robot will work with the game pieces, whatever they end up being like at the competitions. If you didn't, you're going to have problems. The low goal is a good option if you can't shoot into the high goal reliably.