Cricket balls: construction, non-linear visco-elastic properties, quality control and implications for the game

Abstract

Compression and stress relaxation tests were applied to five different ball models (Kookaburra Special Test, Gray-Nicolls Super Cavalier, Regent Match red, Regent Match white, and Sanspareils-Greenlands Tournament). Of the five models tested, only the Kookaburra ball was manufactured consistently. All other balls proved to be produced inconsistently with a wide range of stiffness. Additionally, the other four balls revealed two different, yet externally indistinguishable constructions, which resulted in two clusters of different stiffness. The different constructions might be related to the tension of the woolen twine in Regent Match red and the lacquer surface finish and/or cork-rubber mixture in Regent Match white. Gray-Nicolls Super Cavalier was produced with two different core sizes (stiffer ball with smaller core), and Sanspareils-Greenlands Tournament exhibited two different core materials, namely cork or rubber core, with the latter being the softer one. The hard subtypes of Regent Match white, Regent Match red and Sanspareils-Greenlands Tournament turned out to be the hardest balls, the hard sub-type of Gray-Nicolls Super Cavalier and the soft sub-types of Regent Match red and Sanspareils-Greenland Tournament showed intermediate stiffness, and the soft sub-types of Gray-Nicolls Super Cavalier and Regent Match red as well as the Kookaburra Special Test ball proved to be the softest. The viscosity coefficient of all balls increased with the deflection and the stress relaxation followed a power law. The peak impact forces calculated from the power law model correlated well with the experimentally measured peak forces. The two different constructions (sub-types) of Regent Match white, Gray-Nicolls Super Cavalier and Sanspareils-Greenland Tournament behaved like two different balls of significantly different stiffness. The latter fact may have severe implications to the match, as softer balls are more forgiving by causing a smaller impact force, a longer contact with the bat, larger deflections, as well as larger contact areas during impact, and therefore allowing placing the ball preciser. A more stringent quality control and testing standard is required for cricket balls in order to avoid unequal chances for both teams. © 2008 John Wiley and Sons Asia Pte Ltd