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Rational Blog: Thoughts on Golf and the World

Swingweight Table From the table, the calculated force corresponds to a Swingweight of D7.8. Measuring the club in a Digital Swingweight Scale gives the same Swingweight of D7.8. The club used for this example is a TaylorMade 5 hybrid. The fact that a letter scale and a measuring tape can replace the Swingweight Scale, which has been utilized for almost a century, will come as a big surprise to the majority of golf club fitters. This ought to raise some concerns even for the die-hard Swingweight supporters. As the center of gravity does not enter any equations describing circular motion, the Swingweight of a body cannot be related to how a body acts under circular motion. Newton’s second law of circular motion states: Torque = Moment of Inertia x Angular Acceleration. There is, therefore, no relationship between Swingweight and how a golf club behaves when acted upon by a golfer. Ever since the Swingweight principle was developed in the 1920s, it has been the accepted method for matching clubs within a set, so they all feel alike when swung. In short, it is a measurement of the weight distribution of the club. And with the introduction of lighter shafts, grips, and club heads, the possibility of a wider range of Swingweights, and thus more inconsistency from club to club is greater. When Robert Adams was matching his set of golf clubs by waggling the golf clubs in a horizontal plane, he was in fact attempting to measure the moment of inertia of the club around the center of the grip. The moment of inertia around the center of the grip is henceforth referred to as MOIG. One can imagine how difficult it would be to adjust all 13 clubs until they all felt like having the same MOIG. There were no instruments available for measuring the moment of inertia at the time. Robert Adams made an instrument that would provide an indication of whether all the clubs in a set of golf clubs would have similar MOIG. The clubs used to develop the swingweight method all had similar wooden shafts. That is no longer the case. The Swingweight system is therefore even less useful today than it was 90 years ago.

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