DeflateGate Experiments

This video chronicles experiments and/or demonstrations regarding football inflation.
It demonstrates a drop of 0.3 PSI after setting the PSI to 12.65, as the football reaches equilibrium.
It demonstrates a drop of roughly 0.45 PSI due to football activity, independent of temperature.
(An epilog has been added below that confirms the 0.45 PSI drop.)
It demonstrates a greater than 10°F drop in football temperature due to evaporative cooling. (Corresponds to 0.5 PSI.)

The sequence of measurements and activities is:

Test football pressure measured at 8.45 PSI.
Control football pressure measured at 12.45 PSI.
Ambient air temperature measured at 71°F.
Test football temperature measured at 74.8°F.
Control football temperature measured at 74.4°F.

Wait 10 minutes.
Test football pressure measured at 8.45 PSI.
Control football pressure measured at 12.40 PSI.

Deflate test football to 6.00 PSI.
Test football pressure measured at 6.05 PSI.

Wait 10 minutes.
Test football pressure measured at 6.00 PSI.
Control football pressure measured at 12.35 PSI. (-0.10 since beginning)

Mash test football.
Test football pressure measured at 6.15 PSI.

Inflate test football to 14.55 PSI.
Deflate test football to 12.65 PSI.

Wait 10 minutes.
Test football pressure measured at 12.50 PSI.

Wait 10 minutes.
Test football pressure measured at 12.45 PSI.
Control football pressure measured at 12.35 PSI.

Wait 10 minutes.
Test football pressure measured at 12.35 PSI. (Equilibrium established after 30 minutes and 0.3 PSI drop.)
Control football pressure measured at 12.35 PSI.

Wait 10 minutes.
Test football pressure measured at 12.35 PSI.
Control football pressure measured at 12.35 PSI.

Exercise football for 16 minutes, 40 seconds, applying an approximate weight or 210lb.
Test football pressure measured at 12.90, 12.85 and 12.80 PSI in sequence.

Wait 10 minutes.
Test football pressure measured at 12.20 and 12.25 PSI. (Test ball pressure is below before-exercise pressure.)
Control football pressure measured at 12.45 PSI. (Control pressure is increasing.)

Wait 20 minutes.
Test football pressure measured at 12.15 PSI. (Test ball reaches equilibrium.)
Control football pressure measured at 12.50, 12.55, 12.55 PSI in sequence. (Control pressure is continuing to increase.)
Ambient air temperature is 72.2-72.6°F.
Test football temperature measured at 75.8°F.
Control football temperature measured at 75.0°F.

Wait 10 minutes.
Test football pressure measured at 12.15 PSI.
Control football pressure measured at 12.60. (Control pressure is continuing to increase.)

From the before exercising the ball to this last measure, the control football increased pressure by 0.25 PSI. The reason for this can only be inferred to reflect temperature or background air pressure.

From the before exercising the ball to this last measure, the test football decreased pressure by 0.20 PSI. But for the exercising, it should have increased with the control football by 0.25 PSI. The inferred pressure deficit due to the exercise is roughly 0.45 PSI. The Exponent analysis concluded that activity does not change the pressure independent of temperature.

Epilog:
On Monday morning, 2 days later, I measured the pressure in control and test footballs. The balls had been stored in their "as new" packaging and a shipping box. They were almost certainly in thermal equilibrium. The control football was measured at 12.30 PSI. The test football was measured at 11.80 and 11.85 PSI, in sequence. The measurement confirms the 0.45 PSI delta between the two footballs, subsequent to the activity and re-gaining thermal equilibrium. The change in football pressure as a result of activity is thus confirmed.

Evaporative cooling is demonstrated.
A wet football at 75°F is cooled to 63.4°F by evaporative cooling. The ambient air temperature is 73.6-74.0°F.