Rational Blog: Thoughts on Golf and the World

Have you ever wondered what #Swingweight is, how it came about, and if it is still relevant?A typical Swingweight Scale

Matching of golf clubs has been considered the Holy Grail of golf since the beginning of golf club manufacturing about 500 years ago. A properly matched set of clubs will provide superior consistency with regard to ball flight, direction, and distance. Golf enthusiasts have explored a few non-scientific methods over the last hundred years, most notably the Swingweight method, still used by the vast majority of golfers today. The golf industry seems to have given up on the search for a scientific method of matching golf clubs. 

Robert Adams developed the first known system for matching golf clubs within a set in the 1920s (US Patent No. 1,953,916, 1934). He measured Swingweight, the upward force at the grip end of the club when balanced on a point 14 inches down the shaft on a “Lorythmic” scale using an arbitrary system of letters A to G and numbers 0 to 9, with A0 being the “lightest”, and G9 the “heaviest”. Other scales were developed, but none proved popular. 

If a set of clubs having the exact same grips and identical shafts trimmed incrementally are matched by Swingweight using only the clubhead for making adjustments, then the MOI of each club will be reasonably matched. This was the original intent of the Swingweight process. When the Swingweight method was introduced, it had some credibility as all the shafts in the set of clubs at the time were made out of wood. However, today, with the more modern shafts, that have purposeful variation along their length, and the tendency to mix and match a variety of shafts within a single set, the less likely it is that a Swingweight matched set is relevant as a method of matching golf clubs.

Another glaring flaw in the Swingweight system is that it does not take the properties of the golfer into consideration. It is an easy way for club manufacturers of matching golf clubs as they can produce standard clubs that will, supposedly, fit any golfer. There is, of course, no such thing as an off-the-shelf set of clubs that are fitted or matched to every golfer. 

When Robert Adams was matching his set of golf clubs by waggling the golf clubs in a horizontal plane, he was 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 of golf clubs 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. He found that all his balanced clubs would have similar upward force at the end of the grip when balanced over a fulcrum 14 inches from the grip end. As an instrument for measuring the MOIG is now available from Rational Golf LLC of Florida, it would be irrational to continue to use the approximate method of Swingweight. Matching by MOIG would be a step in the right direction for matching golf clubs; however, there are further complications to overcome. The mass of the clubs and the properties of the golfer´s body also plays a role.

The Swingweight Scale is meant as a tool for adjusting the clubhead weight of golf clubs for all the clubs in the set to have the same feeling, heft or MOIG. However, most club fitters misuse the scale today. Most club makers today believe that the Swingweight of a club will be reduced by adding weight to the grip end of the club. This is due to a flaw in the Swingweight instrument. As weight is added to the grip end, the device will show a lower Swingweight. However, the feeling of heft when waggling the club has not changed. By adding 50 grams of weight to the butt end of a typical 7-iron of Swingweight D2, the new Swingweight becomes C1. However, the heft or moment of inertia around the center of the grip has not changed. Thereby the intended property of the club as described by the Swingweight system has not changed. However, the measured Swingweight has changed considerably. 

It seems that the industry, in general, pays less attention to Swingweight these days. The Swingweight of every club sold is specified, but it is not unusual to see a set consisting of clubs of various Swingweights. In general, every new development in golf club technology brings the golf club further away from the original clubs used for developing the Swingweight method.

The Swingweight method is an attempt to make all the clubs feel the same. There is, however, no reason to believe that a set of clubs that all feel the same would be superior. The ball really could not care less for what the golfer feels. To make all the clubs in a set feel the same, all the clubs would have to have identical MOIG, Mass, and center of gravity. If we are only considering how a club feels when swung, we may ignore the center of gravity as its role is insignificant. A better approach is to make a set of clubs in such a way that the golfer can apply the same consistent swing for all the clubs in the set.

If you still believe Swingweight is a good way of matching golf clubs, consider this:

1.    The fact that Swingweight is not measured in a mathematical number system should be a dead giveaway that it is not a physical property. It is measured in a combination of a letter and a number. For example, C3 and D2. How much is C3 + D2? Or C3 divided by D2? Definitely not a physical property. Robert Adams, the inventor of the Swingweight scale, states in the patent document that “swing weight in itself is a rather indefinite quality”.

2.    The Swingweight measuring scale does not have a zero. All physical properties have zero value in the absence of the property. For example, if you have 0 Kg of chocolate, you have no chocolate. Zero Kelvin means that there is no temperature, etc.

3.    Physical properties can be related to any object. For example, temperature and mass can be determined for any known object or substance. It would, however, be difficult and meaningless to attempt to determine the Swingweight of a car, bus, or a pencil. Swingweight is not a physical property.

4.    The Swingweight is related to the center of gravity of the golf club. However, the center of gravity of a golf club does not enter the equations describing the motion of a golf club being swung. It is only relevant when the golf club is static. Newton’s second law of circular motion states: Torque = Moment of Inertia x Angular Acceleration.

5.    The Swingweight is measured around a balance point 14“ down the shaft. 14” is not a physical constant such as, for example, π (3.1416...). The selection of the balance point is random. If for example a balance point of 12” or 16” had been chosen instead, golf clubs would have been different, still completely wrong, but different. At one point in time, the golf community found that 12” worked better than 14” and the Swingweight scale was changed accordingly. Later it was changed back to 14”. Quoting, Robert Adams, the inventor of Swingweight “I have found in actual practice that satisfactory results are realized if the fixed point be located a distance of fourteen inches from the grip end”. He further explains “the preferred distance is approximately fourteen inches for golf clubs, although the distance may be varied somewhat from this preferred value.”

6.    During one period the golf community would match the irons to one Swingweight and the Woods to a different Swingweight.

7.    It does not make sense that the Swingweight is increased if one installs a lighter grip. Similarly, by adding weight to the grip end of a club the Swingweight becomes “lighter”. Adding a pound to the grip, and your Swingweight would become “superlight”.

8.    Club fitters will normally advocate a high Swingweight to large, strong persons and a lower Swingweight to smaller and weaker persons. One way of increasing Swingweight is to install a lighter grip, thereby lowering the overall weight of the club.
It does not make sense that a smaller, weaker person should swing a heavier club than a large, strong person. Still, the clubs of skinny young girls are fitted with heavy grips. Then they are told to come back when they are stronger, and the club fitter will change to lighter grips.

9.    There is no logical explanation for why a set of clubs that happens to have the same upward force at the grip end, when balanced on a fulcrum 14 inches from the grip end, should perform better than any other set of clubs.

10. It is commonly believed in the golf community that Swingweight was designed purely for golf clubs. According to the Swingweight patent (US patent no. 1,953,916) which is available for anyone to look up online, the Swingweight concept was designed for sports equipment in general. The patent document mentions sports like tennis and baseball.

It is absurd that today’s “high-tech” club heads, shafts and grips are assembled and matched by an obsolete method, creating a set of mismatched clubs. It is causing golfers to learn a different swing for every club. As each club needs to be steered differently, at a subconscious level, consistency and dispersion will suffer.