Does anyone know what PSI the cargo (orange ball) should be at?
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There does not appear to be a specification, and I suspect any potential variance is an intended challenge.
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Iām not seeing anything either anywhere else. I donāt recall them ever specifying a pressure for game pieces (I could be wrong) - I think they usually just specify a diameter (for balls) or thickness (for tubes).
2014 (aerial assist) had entire āBall Inflation Guideā (unfortunately I canāt find a working link) and an accompanying video, but I think thatās the most prescriptive theyāve been on inflation. 2008 (overdrive) has a similar guide that had a lot of indicators that your ball was inflated properly (overall size, weight, zipper covering tightness), but no specific PSI.
The 2011 manual stated:
The GAME PIECES are inflated to nominal size, not a specific pressure.
So youāre right- FIRST generally avoids specifying inflation pressure. Thereās going to be variation between balls and events, and there are some variables outside of FIRSTās control like ambient air pressure, so getting that prescriptive is problematic.
Given the information on tolerance in team update one, here is the maximum size (left), minimum size (middle) and average size (right) of the cargo. This variation seems incredible as the minimum size of the ball is just 85.74% of the area of the maximum size ball.
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I appreciate the surface area measurement, what about psi in each at those sizes, just so we can get a range?
Per first question:
https://frc-qa.firstinspires.org/qa/1
No psi specified.
I think I saw 1.5 PSI on the label of a different size playground ball at a storeā¦so that might be what theyāre designed to be inflated to. But we didnāt do the pressure gauge thing on our official game piece, or even get the diameter right, yet. I expect it will be quite a bit higher than that. It take some pressure to get these things that big.
Looks like about 2 psi at 13 inches at 4200 ft elevation.
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These are playballs of unknown uniformity and material spec. Size is the only requirement. 13 +/- 0.5 inches. Iām guessing most will be around 12.6 since they will be less prone to popping during competition.
Get a piece of string, wrap it around the ball. It should be about 41" give/take 1.5 inches. If itās less than 39 1/4", you need more PSI. If itās more than 42 1/2", you need less. And, check them periodically ā the rubber stretches and they lose air.
And, realistically, you should try with different sizes in that range. You donāt want your robot to work great with smaller balls, but not at all with larger balls.
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We made a āpi tapeā as well, where we used a long piece of tape (or string) and marked out 12.5āā, 13āā, and 13.5āā times pi. Simply wrap the tape around the ball to get itās diameter, and then adjust the ball accordingly.
Our ball seemed wayyyyy bigger than we thought it would be. We had it inflated to ~10āā, but after checking the measurements, we inflated it up to 13āā. The whole time I thought it was going to explode, it just seemed so large.
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Run a tape measure around it. Youāre looking for 13*pi, or 40.84 inches.
I believe the ball is thin enough that if they gave you pressure, it would vary with the barometer.
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Although slightly off topic, I can now speak to the irregularity in these pieces, we had a brand new one come out of the package, inflated it, and it was a complete egg shape. I have a feeling this will be a concern during game play and I am not sure if this will be monitored either from the sound of the rule
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Iām also pretty sure there will be popped balls on the field. Can you score with one?
Yes if the cargo is popped it can still count as a score.
What happened if the balls pop during a match? We just popped ours and now Iām worried that thereās a penalty for it.
If a robot pops a ball it may get referred to the LRI for a check to determine if it was a one time random occurrence, or some flaw or sharp object in a ball mechanism that can be mitigated.
If a robot pops a lot of balls, then that could be elevated to field damage.
The blue box of G15 specifically says that āā¦ popping ā¦ GAME PIECES are violations of this rule.ā Iād suggest reading that rule carefully.