Exponent's Fundamentally Flawed Research By Mike Greenway July 19, 2015 A fundamental flaw in Exponent's experiments invalidates their conclusion that the Patriot's deflated footballs. Many of Exponent's experiments are based on the heat gain and hence the pressure increase of a football on a stand (Figure 1). The Patriots footballs were not on a stand they were in a bag in the officials locker room waiting to be tested. 72 F air surrounds the football on a stand. The footballs in the bag (Fig 2) are surrounded by other footballs at 48 F and the air in the bag that is at 48 F. The bag prevents 72 F air reaching the footballs and therefore the heat gain and hence the pressure increase of the footballs in the bag is much slower than the football on the stand. Exponent determined that the low pressure of the footballs in the bag was caused by deflation when in fact it was due to less heat gain. Figure 1. Acknowledgements: The photograph of a football on a stand is taken from the Exponent appendix in the Wells report dated May 6, 2015.
. Figure 2. Photograph of 11 footballs in a ball bag showing how they may have looked in the officials locker room prior to testing. Patriots Game Balls taken to the officials locker room for testing The Wells report states that it was raining at half time when the ball boys collected the Patriot's game balls from the field and placed them in a bag. The bag now contains 11 cold wet footballs and cold air from the field. The balls were taken in the bags and placed against the back wall in the officials locker room for testing (Figure 2). Testing started after 2 to 4 minutes and took a further 4 to 5 minutes. The balls were tested in the locker room using the Logo and Non Logo gauges. The Logo gauge reads 0.4 psi higher than the Non Logo gauge.
Exponent's Flawed Transient Experiments The crux of Exponents argument for deciding that the Patriots probably deflated footballs results from their transient experiments where they use a football on a stand to determine the heat gain and hence pressure increase of the footballs in the locker room. The following description is taken from Exponents Appendix to the Wells report. Comparing Transient Data with Converted Game Day Averages The entire aim of the transient experiments is to identify how the pressure inside the football varies with time and thus expose the underlying governing physics behind the pressure vs. time relationship of warming footballs. The transient curves outlined in the following section reflect the best prediction and simulation of the actual pressure path experienced by the footballs on Game Day. This is accomplished via control over the environmental factors that directly affect this pressure path, namely the pre-game temperature, the field temperature, the halftime locker room temperature/relative humidity, and the condition (wet vs. dry) of the footballs. With this method we can determine the range of pressures at specific times that are theoretically possible to have been reached on Game Day within the constraints that are known about the various environmental factors. 38 Specifically, with such transient curves we can determine the range of potential pressures that could have been observed based on natural causes during the Locker Room Period. 39 A direct comparison can then be made between the transient curves generated in the laboratory and the recorded halftime data from Game Day. In terms of the scientific method, it allows us to compare predicted results with actual field results. Whereas it is unknown exactly when in the Locker Room Period each measurement was made (or, therefore the time impact on the corresponding average of the measurements), it is known that the measurements must have occurred within the 13.5 minute window of the Locker Room Period. If the experimental transient pressure measurements are equal to the Game Day averages at some time within the Locker Room Period window, then the Game Day results can be explained by the transient physics. If, however, there is no point during the Locker Room Period in
which the transient measurements equal the Game Day average(s), i.e., the predicted results never match the field results during the 13.5 minute Locker Room Period, then the measurements taken during halftime of the AFC Championship Game cannot be explained by environmental and timing factors alone. 38 Theoretically in this sense is meant to convey that while these results were experimentally produced in the present investigation, they can be viewed as what theory would predict. 39 The phrase Locker Room Period will be used to mean the period of time that the balls were inside the Officials Locker Room during halftime, which we understand was approximately 13.5 minutes. Exponent is completely wrong. Experiments conducted using a football on a stand do not predict the actual pressure increase experienced by the footballs on game day. All of Exponents conclusions based on their experiments using a football on a stand are invalid. In all honesty, even Exponent cannot make the assertion that a football on a stand replicates the heat exchange characteristics of cold footballs surrounded by cold air that are contained in an impermeable ball bag. The transient curve and Game day average. Exponent's explanation of how they came to the conclusion that the Patriots deflated footballs follows and is taken from Exponents Appendix to the Wells report. Graphically speaking, if the Game Day results can be explained by the governing physics, then the transient curve will intersect the horizontal line representing the relevant Game Day average at some point between 0 and 13.5 minutes. If the Game Day results are not explained by the physics, the transient curve will NOT intersect the Game Day average within the allotted time window. These scenarios are schematically depicted in Figure 23 in which Game Day Average A is a scenario in which the average does intersect the transient curve and is explained by the governing physics, and in which Game Day Average B is a scenario in which the
Pressure (psig) average does not intersect the transient curve and is thus not explained by the governing physics. 13 12.8 12.6 12.4 12.2 12 11.8 11.6 11.4 11.2 11 10.8 10.6 0 2 4 6 8 10 12 14 16 Figure 3 Time (min) Exponent states that " Graphically speaking, if the Game Day results can be explained by the governing physics, then the transient curve will intersect the horizontal line representing the relevant Game Day average at some point between 0 and 13.5 minutes. (The football on a stand does not in any way represent the governing physics. The eleven Patriots footballs were in a bag.) Exponent also stated "That there is a strong time dependence of the pressure inside the footballs upon return to the simulated locker room is of significant impact in the present investigation". Unfortunately Exponents football on a stand experiments caused them to overestimate the expected pressure increase of the footballs in the locker room which led them to conclude that the low pressure of the Patriots footballs was caused by deflation when in actual fact the footballs in the bag experiment shows that the low pressure was due to less heat gain and hence less pressure increase.
Experiment Using Dry Footballs in a Bag An experiment was carried out that replicates the conditions that the Patriot's footballs were subjected to in the officials locker room using a dry football. Half time conditions were simulated by placing 11 footballs in a ball bag which was then placed in a fridge at 48 F for two hours to ensure the air in the bag and the footballs were at 48 F. This simulated the conditions when the 11 footballs were carried off the field to the officials locker room for testing. The bag of footballs was removed from the fridge and placed in a 72 F room. The initial pressure of an NFL game football in the bag was measured and then the pressure was measured every minute for twenty minutes and then every ten minutes for a total of 60 minutes. The balls remained in the bag while the temperatures were measured. A graph of the results (Figure 4) follows where the transient curve, and hence pressure increase of one of the 11 dry footballs in the ball bag can be compared to Exponents transient curve of a dry football on a stand. The transient curve of the dry football on a stand was generated by Exponent during their experiments and is taken from Exponents Appendix to the Wells report.
Pressure (psig) Locker Room Period 12.6 12.4 12.2 Balls brought to "Locker Room" Exponent's Transient Curve Dry Football on Stand 12 11.8 11.6 11.4 Greenway,s Transient Curve Dry Footballs in Bag Patriot's Game Day Average Pressure (Logo Gauge) 11.2 11 238 240 242 244 246 248 250 252 254 256 Figure 4 Time (min) The transient curves confirm that the pressure increase of footballs in a ball bag is much slower than the pressure increase of a football on a stand. The transient curve generated by Exponent using a football on a stand does not in any way replicate the governing physics that the balls were subjected to in the locker room despite Exponents assertions to the contrary. The temperature rise and hence pressure increase of the balls in the bag is going to vary depending on the position of a ball relative to the other balls. The test ball was positioned near the top of the bag and is probably in the middle of the range. Balls at the bottom of the bag are going to experience less heat gain and hence less pressure increase. The variability in pressure due to the position of a ball in the bag probably accounts for the variability in the pressures of the Patriots game day footballs that Exponent suggested was due to uneven deflation.
Exponent states " Graphically speaking, if the Game Day results can be explained by the governing physics, then the transient curve will intersect the horizontal line representing the relevant Game Day average at some point between 0 and 13.5 minutes". In other words using Exponents own reasoning, if the average pressure taken at half time of the Patriots game day footballs intersects the Greenway Transient Curve (which it does) then the footballs were not deflated. It has been confirmed several times using two pressure gauges that the pressure of a dry football inflated to 12.5 psi at 72 F will decrease to 11.15 psi when the temperature is decreased to 48 F. This is lower than the calculated pressure and is not entirely unexpected when all of the variables such as the flexibility of the leather, stitches, laces and the bladder are taken into account. Equipment The pressure of the football was measured with a Dwyer model DPGA-05 digital pressure gauge permanently connected to an official NFL game ball with a flexible tube. The temperature of the fridge was controlled with a Johnson Controls A419 ABG-3C electronic temperature control. Air was circulated in the fridge with an 8 watt pancake fan to eliminate any temperature gradient. The fridge temperature was monitored with two thermocouples connected to digital readouts. The image shows the pressure of an Official NFL Game Ball being measured while the footballs are in a ball bag Figure 5
Pressure (psig) Experiment with Wet Footballs in a Bag The experiment described previously was repeated with wet footballs in a bag. The Patriots footballs collected from the field at half time were wet so this is a better representation of the actual heat gain and hence pressure increase of the Patriots footballs in the locker room. Locker Room Period 12.4 12.2 12 Balls brought to "Locker Room" Exponent Transient Curve Wet Football on Stand 11.8 11.6 11.4 Greenway Transient Curve Wet Footballs in a Bag 11.2 11 10.8 238 240 242 244 246 248 250 252 254 256 Figure 6 Patriots Game Day Average pressure Non Logo Gauge Time (min) The Patriots game day average pressure for the 11 footballs using the Non Logo gauge was 11.1 psi. This average passes through the Greenway Transient Curve of the wet footballs in a bag hence using Exponents own reasoning the footballs were not deflated. The transient curve and hence pressure increase of the wet footballs in a bag is far slower than the pressure increase for the football on a stand. The Patriots footballs in the bag are at a lower pressure because they did not warm up as fast as the football on the stand. The low pressure is not due to deflation.
Gauges A major part of Exponents reason for determining that the Patriots deflated footballs hinges on which gauge was used for the pregame measurements. Two pressure gauges were used by the NFL. The Patriots results show that on average the Logo gauge measures 0.39 psi higher than the Non Logo gauge. Figure 7 Figure 8
Figure 9 Figure 10 Acknowledgements: the previous Images of the gauges (Figures 7-10) are taken from the Exponent appendix in the Wells report dated May 6, 2015. Figure 9 shows the severely bent needle on the Non Logo gauge. Exponent does not show a side view which would enable the degree of bend in the needle to be seen. Figure 10 shows the slightly bent needle on the Logo gauge. The needles on both gauges are probably the same length therefore the degree of apparent shortening of the needle on the Non Logo gauge can be used to establish the severity of the bend in the needle.
Figure 11 Figure 12 The images (Figures 11 and 12) were taken for this report to show the severity of the bend in the Non Logo gauge needle. It is emphasized that this is not the needle in the Non Logo gauge. It is a needle that was bent to establish the degree of bend based on the foreshortening of the needle in the Exponent image.
It is important to establish which gauge was used for the pregame measurements. Mr. Anderson's best recollection is that he used the Logo gauge to check the footballs pre-game. Pressures with the Logo gauge read 0.4 psi higher than the non-logo gauge. Exponent presented an argument that they said proved Mr. Andersons best recollection was not true. They said the referees must have used the low reading Non Logo gauge. This allowed them to use the pressure measurements from the low reading Non Logo gauge for the half time measurements and hence a greater pressure drop compared to the Logo gauge. The combination of the red logo (Figure 8) which would be clearly visible during pregame testing of 24 footballs and the relatively straight needle on the Logo gauge which would make it easier to use are features that are difficult to forget. The Non Logo gauge with the severely bent needle(figures 11 and 12) was probably inconvenient to use. Figure 13
The image (Figure 13) of the needle inserted into a valve on a football shows that the needle has to be inserted all the way up to the bend for the tip of the needle to clear the inside of the valve in order for the pressure to be measured. If the referee used this gauge then the defect in the needle is probably difficult to forget. If this case goes to court an interesting line of questioning would be to ask Mr. Anderson if he remembers seeing the red logo gauge during testing and if he does not then does he remember the inconvenience of using the severely bent needle in the Non Logo gauge. Hopefully this line of questioning will refresh Mr. Anderson's memory and finally identify which gauge was used for the pregame pressure measurements. Conclusions Exponents experiments with a football on a stand do not represent the governing physics that the footballs were exposed to in the locker room. Exponents error in asserting that a football on a stand can be used to replicate the heat gain and hence pressure increase of the footballs in the locker room invalidates their investigation. The pressure increase of footballs in a bag represent the governing physics in the locker room. The temperature increase and hence pressure increase of footballs in a ball bag is much slower than the temperature and hence pressure increase of a football on a stand. Comparison of the transient curves of the football in the ball bag with the football on a stand confirms this conclusion. The most important conclusion is that using Exponents own reasoning, the average pressure of the Patriots game day footballs taken at half time with both the Logo and Non Logo gauges intersect the wet and dry transient curves of the footballs in a bag. This confirms the Patriot's footballs were not deflated.