Deflate Gate Examined - Purdue Polytechnic Institute



Deflate Gate ExaminedBy: Steve DriscollPurdue University, Columbus CampusAbstractSeveral students along with staff members of the Mechanical Engineering Technology program at Purdue’s College of Technology, Columbus campus completed multiple tests to investigate the measureable performance characteristics in relation to different inflation pressures of a National Football League regulation football made by Wilson Sporting Goods. Deflate Gate ExaminedIntroductionOn Sunday January 18, 2015 the New England Patriots defeated the Indianapolis Colts in the American Football Conference (AFC) Championship game by a score of 45-7. The game was played on a cool and rainy evening in Foxborough, Massachusetts. Hours after the game a tweet flooded the sports world; (Kravitz) “Breaking: A league source tells me the NFL is investigating the possibility the Patriots deflated footballs Sunday Night. More to Come.” At 9:55pm EST the latest NFL controversy was born, and quickly referred to as ‘Defalte-Gate.’ Over the course of a few short hours Deflate-date exploded as major media outlets reported on leaked information from the NFL. ESPN was the first to report (Mortensen) “the NFL’s initial investigation found 11 of 12 footballs used by the New England Patriot offense were inflated 2 psi below what’s required by the NFL regulations” during the Patriots victory over the Colts. According to the NFL Rule Book (ref-ump) “each team must deliver 12 footballs to the Referee 2 hours and 15 minutes prior to the starting time of the game.” The Referee is the sole judge as to whether the footballs delivered by the respective teams comply with these specifications. The football is under the supervision of the Referee until they are delivered to the ball attendant just prior to the beginning of the contest. (Mortensen) “ESPN Sports Radio 810 in Kansas City reported that the Patriots’ footballs were tested at halftime, and were discovered to be low in air pressure and were inflated to proper specifications.”Many people wondered what advantage would there be to playing with an underinflated football, at the reported 10.5 psi mark? Luckily, at the Purdue College of Technology campus in Columbus we have equipment that can determine what advantages can be gained from playing with a 10.5 psi football versus one at 12.5 psi. The students involved wondered why rely on the varying “experts” on television and discover the plausibility using math, technology, and science!Materials/Team OverviewBeginning on January 27, 2015 a team led by Professor Dr. Joseph Fuehne and his students; Steve Driscoll, Jordan Ezell, Caleb Faulkner, Kevin Raisor, and Jesse Ritchie, with guidance from Metrology Lab manager Matthew Ferrell commenced the process to develop a test plan. The test plan was used to create a structured program for recording measurements to determine the measureable differences between footballs at varying pressures. The footballs used are the exact same footballs that would be used in gameplay. They are marketed by Wilson Sporting Goods as “The Duke”. According to the Wilson website it is the official game ball. Each football was purchased at local sporting goods stores in the greater Indianapolis region at a cost of $100 each. “The Duke” is not the average ball used at barbeques and tailgating parties. A total of three footballs were used. The same pressure gauge and Nike football pump was used for the entire experiment and the accuracy of the gauge was verified by internal processes. Two tests would be performed; a compression test and an environmental exposure test. Compression Test (Load v Pressure)The compression test would determine the possible benefit of a team playing with a football at a lower air pressure than what is allowable. An automated compression testing system manufactured by Instron was chosen to conduct the compression test. The Instron software allowed our team to measure the force required by the hydraulic arm of the machine to compress the ball one quarter of one inch. The 0.25” was used to develop enough data to make a best curve data plot. The data in figure one shows the results of the load required to reach 0.25” and the inflation pressure of the ball before and after the conclusion of the compression test. Included in figure one is the percentage difference in load required to compress the ball 0.25” in relation to the minimum specification from the NFL. The data below is compiled from an average of the 3 samples run through the same pressure range. The test began with the first ball at 8.5 psig and at the completion of each run the same ball was then inflated to the next pressure. At the completion of the 14.5 psig point, the next test sample was used until all samples were exhausted. The pressure of the ball was checked pre-test and post-test to ensure the football pressure remained constant to observe any recordable changes.The results from the compression test revealed some intriguing findings. The change in load from varying pressures was not linear. However, taking the entire range into account there was an average change in load of 6.7%. The change from 8.5 psig to 9.5 psig was greater than the change from 12.5 psig to 13.5 psig. Several members of the testing team found to be noticeable difference in feel of the ball when a large change in pressure took place. The results also confirm with basic principles of a gas under pressure. At higher inflation pressures there will be more energy required to compress the ball then a ball at lower inflation pressure. The appendix has an additional graph with each individual run compiled showing the varying lines of data in relation to pressure. The next step was to determine if the weather could have played a role in lowering the pressure of the ball.Environmental Exposure TestOne theory that was introduced was if a game being played outdoors in January at Gillette Stadium in Foxborough, MA played a role in the inflation pressure dropping below the legal limit. The footballs are given to the Referee who is located in a conditioned air environment, and then the footballs are played in the elements. The game time temperature in neighboring Norwood, Massachusetts was 52.0° and with a steady rain (Weather). According to the Ideal Gas Law if the temperature of a container is increased, the pressure increases; furthermore if the temperature of a container decreases the pressure decreases. We used this law as our previous measurements indicated there was a minimal change in the footballs dimensions as the diameter of the ball only changed a max of 0.002”. Thus we felt the Ideal Gas Law was the most relevant to our study. The equation for the Ideal Gas Law is simply the initial absolute pressure (P1) divided by initial temperature in Kelvin (T1) equals final absolute pressure (P2) divided by final temperature in Kelvin (T2), or graphically demonstrated in figure 2. In our initial experiment we used 2 footballs, one at 13.5 psi and the second at 12.5 psi and allowed them to reach equillibrium in the temperature controlled environment in the lab. The lab environment is a stable 68°F. The footballs were placed inside of a refridgerator that had a measured temperature of 33.8°F for 60 minutes. At the conclusion of the time the pressure of the footballs were measured again. We did not believe 60 minutes was enough time to reach equillibrium however we wanted to see if there was a correleation between the equation above and what actual results showed. The data compiled showed the measured end pressure and the calculated pressure derived from the Ideal Gas Law was a good estimation of the change. There was a difference of 4.06% on average from the calculated to measured values. The environmental exposure test will continue as there is a need for multiple repeats to ensure thorough data quality. However, with this initial data we can calculate the expected result of this test if we use a 13.5 psi and 12.5 psi sample and place them into a chiller at 52°F to represent the same conditions on game day. According the Gay Lussac Law and using an error of 4.06% the results are expected to be in the range shown in figure 4.Further testing is needed to explore the football’s behavior when lowering the temperature a smaller amount as best to simulate the conditions at gametime. Test ObservationsThere are a few noteable observations during the test that should be noted for further discussion or testing. The football pump needle made a very poor seal when inflating the football. A noticeable amount of air was felt coming around the side of the needle when inflating the football. The amount of air leaving the football when removing the pump needle from the ball also released a small amount of air each time. The team estimated that with each removal of the valve 0.1 psi was released as we closely observed the behavior of the interaction between the needle and the football. Thus, it could be plausible that if a ball is inspected several times in succession without being inflated could be subjected to a significant loss in pressure and should be noted for further testing.ReviewIs it possible the New England Patriots gained a performance advantage with a football that was measured below minimum allowable air pressue? As our data shows there is a 10 % increase in compressibility of a football at 10.5 psig in comparison to 12.5 psig., thus it is plausible the Patriots gained a performance advantage from a ball control standpoint. Tom Brady would therefore be able to throw one of his wicked hard fastballs a bit easier in the rainy conditions due to the increased compressibility of the football. Is it possible the weather had an effect on the pressure of the football and contributed to the 11 of 12 footballs measuring below allowable specification? The data collected along with the calculations derived from the Ideal Gas Law in addition to the error we measured in relation to our test it appears the weather could account for as much as 64% of the total pressure loss. In addition to the environmental loss, if a football is checked using similar equipment as what we have, which was standard issue there would need to be a very quick measurement as pressure is lost the entire time the needle is pressed through the air bladder valve. If the balls that were inspected were not allowed to reach equillibrium in the air conditioned space then a loss of 64% would be instrumental.ConclusionThe testing team was able to prove that there is measureable difference between force and its relationship to inflation pressure of an NFL football. The team was also able to prove using calculations and measureable data points to determine the weather would contribute to a significant loss of inflation pressure of an NFL football using the current process being used by the league.ReferencesKravitz, B. (2015, January 19). Breaking: A league source tells me the NFL is investigating the possibility the Patriots deflated footballs Sunday night. More to come. Retrieved January 30, 2015, from , C. (2015, January 21). 11 of 12 Pats footballs?underinflated. Retrieved January 30, 2015, from ?. (2014, January 1). Retrieved January 30, 2015, from History for Norwood, MA. (n.d.). Retrieved January 30, 2015, from Rule 2: The Ball() Appendix AppendixAppendixBall 1 Compression DataAppendixBall 2 Compression DataAppendixBall 3 Compression Data ................
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