Purdue News
Purdue News
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December 21, 2001
Students get kick from designing 'indestructible' goalpostWEST LAFAYETTE, Ind. – A Purdue University professor gave his students a design project that gave them a real-world goal to aim for – design an indestructible football goalpost.
William K. "Bill" Szaroletta, an assistant professor of mechanical engineering technology, says the assignment was "a month-long open-ended design project." He had his five-person student teams start exploring goalpost technology by doing a patent search and analyzing a goalpost design that fans had toppled in a postgame celebration. The teams then assembled design specifications, selected the best design approach from many conceptual designs and analyzed the computer-designed model using estimated loads and state-of-the-art analysis tools. The students calculated strength of materials, loads, torques, materials and analyzed and put all the information into a computer-designed model. The student teams finished by making PowerPoint presentations on their solutions. "Improved safety was the biggest factor in evaluating designs," Szaroletta said, "because celebrating fans risk serious injury trying to tear down heavy steel goalposts after a big home team victory." During the research-brainstorming, first phase of the project, the students found some interesting background information and also found some imponderables. A Chicago company already markets an "indestructible" goalpost that carries a lifetime warranty. However, students at Kansas State University were able to tear it down. The students also learned that while the diameter of the crossbar is customarily between 3 1/2 and 4 inches, there is no official NCAA specification. The organization only specifies that the crossbar be 10 feet off the ground and the uprights are 18 1/2 feet apart and extend 30 feet above the ground. Szaroletta said the National Football League does not have crossbar or upright specifications either. Nor do high schools. "The NCAA Football Rules Committee attempts to refrain from placing product and equipment specifications upon all of its member institutions unless a specific need or problem is expressed," said Scott Deitch, NCAA national office liaison to the committee. "The manufacturers of football goals are fairly consistent in the diameter of the goals they produce, and the committee has not received any indication from our member schools that a standard diameter should be established." So, in theory, the students could design any diameter crossbar – even up to a 10-foot diameter pipe. Szaroletta said this means "a home team could manipulate the diameter of the crossbar to maximize the proficiency – or lack of same – of its field goal and extra-point kicking game. Larger diameters would certainly increase the probability of a successful kick." The Purdue students used the customary measurements in their designs. Mandy Carlson, a senior mechanical engineering technology student from Detroit, was a member of one of the design teams. "After all the abstract problems we do, I liked having the true variables to work with," she said. "Each team member found his or her role – number crunching, using the CAD software, putting together the PowerPoint presentation complete with animations. "We learned a great deal about communication – both design communication and within our group and with other groups in the class." Carlson's group came up with a braced, welded, steel, two-post gooseneck design. The team's design addressed a major weak point of single-gooseneck goalposts in use today. They are vulnerable to breakage due to combined stresses on the gooseneck itself, particularly if celebrating fans were to concentrate themselves at one of the uprights and rock, up and down and back and forth, without the counterbalance of fans at the opposite upright. The student team's double-gooseneck design makes it less susceptible to a number of people climbing the goalpost and rocking the structure. So, is this goalpost indestructible? It passed all the virtual indestructibility tests the students threw at it. "We discussed a longer, more extensive indestructible goalpost project, including building a full-size, physical model, getting out and instrumenting it to measure the effects of different loads, stresses and torques," Carlson said. Which is exactly what Szaroletta, who holds 12 patents himself, is going to do in the second offering of the class this spring semester. "Every design works on paper," he said. "We will prove out these new designs by building scale models that can be instrumented and thoroughly tested in the School of Technology's Experimental Mechanics Laboratory. "The indestructible goalpost project captured the imagination of the students," he said. "It provides the students with an almost perfect example of a real-world, mechanical design problem. Athletics presents a whole array of equipment design opportunities that students would be equally excited about." Writer: J.M. Lillich, (765) 494-2077, mlillich@purdue.eduSources: William K. Szaroletta, (765) 412-6001, szaroletta@purdue.edu Mandy Carlson, (734) 422-4152, mandy9779@aol.com Scott Deitch, (317) 917-6222, sdeitch@ncaa.orgPHOTO CAPTION:
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