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BookmarkScienceDaily (Mar. 1, 2001) — When Stanley H. Johnson, professor of mechanical engineering and mechanics at Lehigh University, speaks of "spring-like effect," he isn’t referring to the weather. He’s talking golf.
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The term is at the center of Johnson’s research on golf club heads at the United States Golf Association and of recent disagreements between the USGA and a golf club maker and the European golfing association.
Some new golf clubs have not been accepted by the USGA, but have met with approval from the Royal & Ancient Golf Club of St. Andrews, Scotland. The conflict has yet to be resolved, but in America, USGA decisions apply.
"Spring-like effect," refers to a new phenomenon in which the golf club head has the capability of driving the ball greater distances than would be the case with traditional equipment. The new titanium head incorporates a "diaphragm" face that literally acts as a spring to thrust the ball farther down the fairway. The USGA believes the effect fundamentally changes the game.
Johnson, who holds a doctorate and undergraduate degrees from the University of California, Berkeley, and enjoys "Participating Guest" status at the Lawrence Livermore National Laboratory, has consulted for the USGA for the past 11 years. He first became acquainted with spring-like effect about four years ago. "Before that we didn’t think the materials were available to permit this trampoline effect to happen," Johnson says. But manufacturers began designing clubs that did.
Johnson’s function at USGA headquarters in Far Hills, N.J. is to work with the Test Center staff to design and improve test equipment and instrumentation that determine whether new clubs incorporate the spring like effect. Johnson and Jim Hubbell, senior research engineer at USGA, designed a test "that demonstrates that the phenomenon exists," Johnson says. "We shot golf balls at a titanium disk with a cavity back that shows this kind of club head with membrane configuration indeed enhances ball rebound speed."
The phenomenon lasts about "half a millisecond," and the club head deforms just about fifty thousandths of an inch," Johnson says. But that is enough "to produce a little bit better launch velocity."
With golf representing an annual $6 billion industry in the United States Johnson’s work is important to the future of the game and becomes more so each year. Because manufacturers are developing equipment and balls that push the outer limits of golfing regulations, and because golfers are getting bigger, better and stronger, USGA tests are essential to keep the rules of the game up-to-date. "I look for ways to improve the testing process," Johnson says. "With each passing year the precision with which golf equipment is measured gets tighter and tighter."
Old testing equipment no longer can adequately measure the performance of the equipment. Test tolerances have gone from one percent to a tenth of a percent. "We used to measure in milliseconds. Now it’s done in microseconds," Johnson says.
Golf balls, for example, used to be tested using a mechanical driver called "Iron Byron" because it copied the swing of Byron Nelson, the famous pro. Today balls are "launched" down an all-weather, indoor test range while "ballistic light screens," optical measuring stations designed to study the characteristics of artillery shells, measure the lift and drag characteristics of golf balls at various velocities and spins.
Johnson works closely with Steve Quintavalla, a Ph.D. candidate in mechanical engineering at Lehigh, who is a full time employee at USGA and a lead engineer in the testing of golf balls.
Does the new equipment change the game? The spring like effect certainly does, Johnson says. "It changes the coefficient of restitution of the impact between the ball and club and that should help most people who are reasonably good golfers and add 10 to 20 yards to their drives."
