HOW AN APPROVED TOURNAMENT BALL
MAKES THE GRADE
The maximum diameter of a ball must not exceed 3 21/32 inches (92.9 mm) and the minimum diameter must not be less than 3 19/32 inches (91.3 mm).
The maximum and minimum diameters of a ball must not differ by more than 1/32 inch (0.8 mm).
The maximum and minimum diameters of balls in a set must not differ by more than 3/64 inch (1.2 mm).
When dropped from a height of 60 inches (1524 mm) from the bottom of the ball onto a steel plate 1 inch (25.4 mm) thick and set rigidly in concrete, a ball must rebound to a height from the bottom of the ball of not less than 37 inches (940 mm).
The rebound height is the average of eighteen measurements: each ball is dropped three times onto each of the two poles and four nodes in the milling pattern.
The rebound heights of a set of balls to be used together must not differ by more than 2 inches (50.8 mm).
All balls must be milled with an identical pattern.
The pattern must consist of two orthogonal sets of grooves and the width of the grooves must be less than the width of the upstands left after grooving.
The weight of balls must be within the range 15 3/4 ounces (446.5 g) to 16 1/4 ounces (460.7 g).
The Equipment Committee is not aware of any definitive assessment of the effects of ageing and use on the rebound characteristics of Championship Approved balls. Ideally, sets of balls should be tested when new and at annual intervals thereafter, but in clubs with several similar sets of balls it is likely to be difficult to keep track of a particular set. To facilitate such performance monitoring, Equipment Committee would welcome the assistance of one-court clubs which are intending to purchase one or two (e.g. 1st and 2nd colours) sets of Championship Approved balls. Finance would be made available to cover costs and to provide some recognition for the effort involved.
With the kind co-operation of John Beech, several sets of four year old Barlow GT balls from the Pendle club have been rebound tested. Most of the balls bounced higher than in the Championship Approval tests and several bounced higher than the upper limit for Approval. A few balls bounced below the Championship range. Since the bounce tests had not been performed on the balls when new, there can be no certainty that the bounce had changed through age or use. However, after rejecting the soft balls, sets of good quality (though not of Championship standard) could easily be constructed by selecting matching balls from the remainder. All the balls had retained satisfactory appearance, but occasional off-vertical bounces were noted which could be traced to relatively minor blemishes on the ball surface.
The above was provided by The Croquet Association