The United States golf association enforces strict standards governing the characteristics of golf balls.
An official ball must not weigh more than 1.620 ounces; it must have a diameter of at least 1.680 inches; it must be spherically symmetrical; the velocity of the ball must not exceed 250 feet per second when launched by a USGA-approved mechanical striker; the ball must not travel farther than 280 yards when struck by a standard testing apparatus at the USGA proving grounds.
When golf ball manufacturers want to introduce a new product, they set up a pilot run to produce a limited number of new balls. The balls are tested at the manufacturer’s in-house research and development labs.
The tests determine what production changes must be made for the balls to meet USGA specifications. After passing in-house testing, sample balls are sent to the USGA headquarters in Far Hills, New Jersey, for official USGA testing.
If the balls make the grade, the manufacturer calibrates the factory machinery to duplicate the approved ball and proceeds with a full production run, making the balls that will finally be stamped, packaged, and sold.
Select balls from this run are tested for deviation; if any flaws are detected, the machines are readjusted until the production-run balls meet USGA requirements.
The USGA testing facilities include three indoor laboratories. In the first lab, balls are tested for spherical symmetry and for behavior when struck. The USGA impact standard holds that a ball should remain in contact with the driver clubface for 0.000450 seconds.
To test this, an air gun fires balls at a metal plate and a computer records the amount of time the ball spends in contact with the plate and the velocity at which it rebounds. Conformity to the symmetry standard, which maintains that a ball must fly the same height, the same distance, and remain in flight for the same length of time regardless of how it is placed on the tee, is tested with the help of Iron Byron, a robotic golfer.
Iron Byron has the ultimate golf body: one club connected directly to a mechanical shoulder, with no knees, hips, back, head, or other mobile parts to interfere with his perfect swing. He always hits the standard ball 280 yards, with a 6 percent margin of error. Since Iron Byron is perfectly consistent, any deviation in the flight of the driven ball must stem from the ball.
The aerodynamics lab consists of a wind tunnel, slightly longer than six feet, where balls are tested for flight properties such as backspin and wind resistance. The flight trajectory of a golf ball is the product of its dimples, which create an air flow pattern that reduces wind resistance, and of the backspin that is the normal result of hitting a ball with a club.
To measure “lift force,” the air flow pattern created by a dimpled, back-spinning ball, testers mount a golf ball in a vise-like device in the wind tunnel and buffet it with high-speed air streams that simulate the wind currents experienced by a golf ball in flight. By recording the effect of wind on the mounted ball, technicians are able to measure lift force and predict how it would perform under ordinary conditions.
The third lab, where size testing is done, is kept at a constant temperature of 23 degrees Celsius to prevent the balls from shrinking or swelling because of temperature changes. The size test consists of dropping balls through a ring gauge equal in diameter to the legal ball minimum-1.680 inches. A test victory is declared if fewer than twenty-five out of one hundred randomly dropped balls pass through the ring. This lab is also where balls are measured for initial velocity, or the speed of the ball off the clubface.
To test for initial velocity, balls are launched into the air by a mechanical striker that has been adjusted to send the balls flying at a speed of 250 feet per second, the legal limit. The flight of the ball is measured photoelectrically, and any ball that exceeds 250 feet per second, plus or minus 2 percent, is deemed too springy.
After passing the indoor lab tests, the new batch of balls is taken out to the test range to be checked for conformity to the overall distance standard. Iron Byron strokes bucket after bucket of balls 280 yards straight down the fairway. If too many of the test balls resist Byron, either by soaring too far or falling short, the batch is discarded as faulty.
Golf ball manufacturers produce thousands of test balls, none of which are ever labeled or sold, before making a single ball for retail. The balls carried by sporting goods stores have not themselves been tested, but represent instead exact duplications of successful test balls.