POPPED - Cargo Inflation PSI and Failures


#1

Hey everyone,

We finally got the courage tonight to inflate our Cargo more, but we are still a little afraid to inflate to a full 13" diameter.

I’d like to get documented cases of ball inflation sizes, inflation PSI, and ball popping scenarios and any details you have.

Official q&a did not yield a PSI from FIRST, and the variance in the manual is quite a lot.

So, how big are your balls? We are currently at a risk averse 12.5" diamater and plan to design for 13" +/- .5"


#2

We got ours pretty close to 13" but I’m afraid to go near it


#3

We got a number of balls in today. Tomorrow we will be making one of our balls as big as legal (13.5") and will probably be terrified of working with it. We will also set a 12.5" and 13" ball.

We numbered all our balls and I will report here which of our balls end up popping.


#4

Thanks Andrew, I believe Spectrum is also doing something similar and even made a few sizing rings for their diameters.


#5

We inflated ours to 13, and it’s holding up fine. Agree it’ll be a good idea to test within the +/-.5"


#6

We inflated ours to about 13" diameter, and measured the pressure at about 2 psi.

Played with it with last year’s robot for a little while, then a student noticed it had got a sticker in it (what we call a goathead here in Southern Arizona). the air leaked out.

still working on patching it.

The iffy replacements should show up tomorrow. I ordered some from Gopher. We’ll see how close they are. Since we don’t plan on shooting them, etc, they will probably work ok for robot development.


#7

A RI3D team that I know had a cargo pop after it rolled slowly into a spinning compliant wheel. It rolled slowly enough that it didn’t bounce off. It looks like the edge of the wheel burned right through the cargo.


#8

They did; I actually went up to have them laser me a couple of rings. It’ll be a nice help!


#9

That’s what happened to 1678. I then soldered the hole closed using urethane belt as filler rubber. It’s a good thing it isn’t a thermoset rubber.


#10

Our ball is inflated to slightly over 13" and hasn’t popped, but I have a feeling that it will before the end of build season. I’ll report back if it actually does pop.


#11

So, my main worry now is competition - is there any indication of how much FIRST is going to inflate the cargo pieces for competitions? Are we going to be facing a field littered with the deflated carcasses of cargo pieces that were over-inflated, or because teams inflated them to a lesser PSI during build season? I did not see anything in the rules that specified a PSI rating for the cargo, but I want the students to design something as close to game-day specs as possible. Am I wrong and did I just miss it somewhere in the rule-book?


#12

We’ve taken our cargo to 13" but we did it in steps. Saturday we blew it up. Tuesday we blew it up a bit more and Thursday we blew it up to the 13." It’s a bit tight but we have used it in the prototyping process and it’s holding up well.


#13

, we never even got to inflate ours, it came with a 1.5 in hole in it. We ordered more from AndyMark as soon as they were available. When they arrive, hopefully we can start working with them. Y’all aren’t making me optimistic


#14

If you haven’t done this already, you should apply to get a replacement cargo via the “Order Replacement Parts” option in the new “TIMS”. The deadline is today at noon, so hurry! Instructions here:


#15

Yes, we did that immediately


#16

Wew inflated ours to 13.5" initially accident and had no problems. We did it with my little tire inflating compressor because I didn’t trust us filling it slowly with shop air.

If I remember correctly it was 9-10 psi.

We just got 6 more yesterday from AM and I will have the students make a sizing fixture and record the different PSI’s for each to try and find some consistency.


#17

Measuring the air pressure is tricky…I would not trust the gauge that is on a compressor, to give any kind of accurate reading at this low of pressure.


#18

Same here, intake rollers kept spinning and melted a hole in 2-3 seconds


#19

I wonder if cold temperatures makes the plastic more brittle? You might want to make sure your Cargo is at room temperature before inflating.

In 2003’s “Stack Attack” the playing element was a hard plastic tote. We heard reports of teams unloading the totes on a cold winter day, bumping & shattering the plastic.

FIRST defines a diameter, not a pressure. Use whatever pressure it takes to get the 13". But I fully expect the Cargo in competition will range from 12" to 14" diameter.


#20

If you break a ball during a competition, does that mean you damaged a field element considering how common it is right now and people have barely used it?