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Experiment An experiment was conducted to determine how the two factors of length and material affect a baseball bat’s sweet spot location (the point on the baseball bat absorbs the least energy while the ball absorbs the most energy). The independent variables were the length and the material of the tested baseball bats. The three various baseball bat lengths tested were as follows: 28, 30, and 33. The three various materials tested were wood, aluminum, and composite. The dependent variable that was recorded during trials was the acceleration of the barrel end of the bat. The accelerations of the bat after striking it at different points (five centimeters apart beginning at the handle end of the bat) were then used to decipher the location of the sweet spot of the bat by determining the point of least acceleration (image above). It was hypothesized that the largest length composite bat would produce a sweet spot furthest from the end of the bat while the shortest length wood bat would produce a sweet spot closest from the end of the bat. Results To find the effect of length, the average of the low value of a variable must be subtracted by the average of the high value of length. In this case, the average of the low lengths (11.415 centimeters) must be subtracted from the average of the high lengths (15.215 centimeters). By making this calculation, the effect of lengths in terms of distance from the end of the bat is 3.80 centimeters. As the length increases, the distance from the end of the bat increases. As previously mentioned, the distance from the end of the bat represents the location of the sweet spot on the bat meaning that, in this case, the sweet spot would move 3.8 centimeters on average further from the end of the bat as length increases. To find the effect of material, the average of the low value of a variable must be subtracted by the average of the high value of material. In this case, the average of the low material (12.05 centimeters) must be subtracted from the average of the high material (14.58 centimeters). By making this calculation, the effect of material in terms of distance from the end of the bat is 2.53 centimeters. As the material changes from wood to composite, the distance from the end of the bat increases. In this case, the sweet spot would move 2.53 centimeters on average further from the end of the bat as the material changes from wood to composite. To find the interaction effect between the bat length and bat material, subtract the slope of the line segment of high value of the length by the slope of the line segment of low value of the length. As previously mentioned, the slope of the solid segment is 1.18 and the slope of the dashed segment is 2.62. By subtracting the slope of the dashed segment from the slope of the solid segment, the interaction effect between the length and material based on the distance from the end of the bat is -1.44. In this case, the sweet spot would move 1.44 centimeters on average closer to the end of the bat as the each factor increases. The graph shows that the line segments are nearly parallel to each other. This indicates that there is less of a possibility of an interaction between length and material. This is a dot plot of the variables, interaction effect, and significant effects based on the distance from the end of the bat. The two solid segments locate the range of standards when doubled (negative and positive); these segments determine whether an effect is significant or not. This range is from -26 to 26. The effect of a variable is significant if it is out of the boundaries between double the range of standards. In this case, no effects including the interaction effect are significant, because all of the points are inside of the boundaries. None of the effects have a significant effect on the data. A prediction and parsimonious prediction equation were made to interpolate and extrapolate what the location of the sweet spot of other experiments would be if the values of the factors were increased or decreased for the significant factors. Errors During the experiment, it was noticed that after the baseball bat was hit, the bat would occasionally roll and hit the metal rod that was holding it up, affecting the acceleration that would be recorded. This typically occurred on points closer to the barrel end of the bat. These trials were redone to prevent biased data. However, there is the possibility that a few trials were able to be recorded due to this going unnoticed for those particular trials. This could have been prevented by increasing the distance that the metal rod stands were apart or adding rubber bands to rest on the top of the bat as well to increase the friction on the bat, discouraging excess movement. At points where the metal rod stands were, trials were difficult to conduct because the force hammer was unable to strike the intended point. With the metal rod stand in the way, methods were taken to maneuver around it to allow for the trial to be completed. A possible solution to this would be to suspend the bat on a sling rather than rest on rubber bands. The last error that was noticed was the method of measuring the angle of the string when pulling back the rubber hammer. This was done using a protractor and by the eye of a researcher. This created a possible margin of error of the actual angle that was created, allowing a slightly varied amount of force hitting the bat rather than a constant force as it should be. A possible solution to this would be to have a better, more accurate method of measuring the angle. Application & Future Research There are many other opportunities to expand on this research. The brand of bat is a factor that could be additionally observed due to the fierce competition amongst baseball bat producers. In terms of wooden bats, multiple types of wood (bamboo, maple, etc.) could be tested since different bat types have various densities and such which would potentially produce different results than the wooden bat that was conducted upon during this experiment. The length and width of the barrel of the bat is a factor that was not taken into account that may have changed the results and therefore should be looked upon in the future.
This research is primarily geared towards professional baseball players and bat producers. However, studying within this field is not limited to only that. For example, with an understanding about frequencies and resonances, one can apply that knowledge to forensic investigation (insert citation to the forensic science application). Frequencies and resonances can additionally applied to construction to prevent collapses and disasters within buildings and bridges. For example, the Tacoma Narrows Bridge collapse was caused by these same concepts.
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ProcedureThis is a diagonal view of the set-up. The suspended rubber hammer can be seen to the left of the baseball bat. The mini-LabQuest is attached to the laptop and accelerometer (end of the bat's barrel; not seen). The rubber bands along with the circular rod clamps holding them up can also be seen. The boxes seen are being utilized as weights and spacing to keep the set-up stable. This is a side view of the set-up which is the view from the perspective of the researcher who swings the hammer. The hammer is pulled back 15° (based upon a protractor that is attached to the same metal rod as the hammer is attached to; not seen) and let go to hit the bat. During this time, LoggerPro on the laptop records the acceleration recorded by the accelerometer. The data value is recorded in a table to be used in a 2-factor DOE. Development When we initially began with pre-trials, we did not know how we were going to apply a force to the bat. Our first idea was to drop a baseball onto the bat at a constant height. We found that this was extremely inconsistent. Mr. McMillan assisted us by providing us with a dropper that ensured that the ball was dropping at a constant height and in a similar fashion each trial. However, this was still inconsistent. Mr McMillan then proposed that we could have a hammer swing at a constant angle. After some "engineering", we were able to put together a hammer swing system to hit the bat. After testing with it, it was much more consistent than the ball dropping. We were happy to have a working procedure. We learned how our data should look on LoggerPro as well where as we were confused before on what to look at in particular.
We also made a few minor improvements that we previously did not consider. One would be putting circular clams onto the metal rods underneath the rubber bands in order to prevent them from sliding down. We also learned how the accelerometer worked and how it was supposed to be placed upon the bat. Our last addition was to add weights and spacers to the bottom of the metal rod stands to improve the overall stability to the set-up. Topic:When it comes to baseball, many look for as large of an advantage as they can obtain. Research in this field is greatly appreciated and applied to the top players in the sport. We specifically will be looking at the baseball bat and its sweet spot. We will be comparing different materials and lengths to determine the best option for a batter. We decided on this topic due to the ever increasing popularity in baseball. The more research and knowledge that can be provided to players, the better performances shown to audiences and recruiters. Sources Found:The knowledge already out there is greatly beneficial to our understanding of our topic. For example, Dr. Daniel A. Russell, a major researcher in this field, has provided information through his portfolio of baseball research. Much of the concepts mentioned by him in his papers will move this experiment along in the right direction, including the method of conducting the experiment. Our best method of finding our sources was through the Michigan Electronic Library (MEL). This allowed us to sort the articles by whether or not it has been peer reviewed which improves the overall validity of the research. Plans for the Future:We plan on creating a similar experiment that Dr. Daniel A. Russell conducted that including placing a baseball bat on top of two raised stretched rubber bands (placed on metal rods). The bat will then get hit by an impact hammer that measures the force applied while an accelerometer measures the acceleration. The ratio between these two values will be found and used in a modal analysis. We plan on contacting Dr. Daniel A. Russell in the future for further guidance in our endeavors.
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