| |
 Does A White Cricket Ball Swing More Than A Red One? It is widely believed that the white cricket ball possesses swing properties that are very different compared to those of a conventional red ball. So is there any truth to this, and can it be supported by scientific facts? What are the manufacturing differences between the white and red balls and can that account for the observed differences? And what about reported differences between balls made by different manufacturers? In particular, what are the differences, if any, between the red Dukes ball used in Test Matches in England, the red Kookaburra ball used in Australia and the red SG Test ball used in India? All these questions are addressed in this article together with a discussion of what properties of the ball the bowlers should really concentrate on in order to maximize the swing performance. This is a topic on the minds of all players and coaches and one of the questions that I am asked frequently. This whole debate started in 1999 during the build up to the World Cup when Dukes introduced the white ball that was going to be used in the tournament. Many players claimed that this white ball possessed swing properties that were different compared to those of a conventional red one. In particular, it was claimed that a new white ball swung noticeably more than a red one. At first there was some debate over the accuracy of this claim and it was attributed to perhaps just a visual perception. However, in some testing performed by the BBC in New Zealand using a bowling machine it was demonstrated that the white ball swung measurably more than the red one at around 70 mph. So what caused this difference in the swing properties?
Well, it turns out that the Dukes white ball manufacturing process is not quite the same as that for the conventional red ball. With the conventional red ball, the leather is dyed red, greased and polished with a shellac topcoat. This final polish disappears very quickly during play and it is the grease in the leather that produces the shine when polished by the bowler. The finish applied to the white ball is slightly different. The leather is sprayed with a polyurethane white paint-like fluid and then heat-treated so that it bonds to the leather like a hard skin. As a final treatment, one coat of clear polyurethane-based topcoat is applied to further protect the white surface so that it does not get dirty easily. This extra coating ends up affecting the ball aerodynamics by making the surface smoother. On inspecting the Dukes white ball it is quite apparent that the surfaces over the quarter seams are much smoother compared to those on a Dukes red ball, where the ridges created by the internal stitching can be clearly seen and felt. As a consequence, a new Dukes white ball behaves like a two-piece ball and it will swing more, especially at the higher bowling speeds. A smooth surface on the side of the ball facing the batsman helps in achieving conventional swing. The smoother surface also means that reverse swing is harder to obtain with a new white ball, even at very high bowling speeds. With the additional outer coating, one may also expect reverse swing to occur later in the innings. The Dukes red ball was used in the memorable 2005 Ashes series and a lot of England’s success was attributed to their bowlers’ ability to produce reverse swing. Well, it turns out that it was a combination of reverse and contrast swing, but the point is that for both swing types, a rough surface on one side is the key. And, starting off with a relatively rough quarter-seam helps in achieving this condition sooner. So what about the Kookaburra red and white balls? Well, Kookaburra maintains vehemently that their red and white balls are manufactured using exactly the same process, except, of course, for the color. On inspecting the red and white Kookaburra balls, I must admit that the geometric specifications look identical and I would therefore not expect any difference in their aerodynamic performance. I am not sure if all the players and coaches are convinced of this and I have also heard that they feel it is easier to polish a red Kookaburra ball than a white one. I would venture that this may perhaps be more due to visual appearance and perception than the quality of the achieved smoothness. The other interesting point about the Kookaburra balls is that both their white and red balls also exhibit a relatively smooth quarter-seam region. Although, a thin line can be seen along the quarter seam, it does not feel as rough as the ridges on a traditional red ball. Therefore, the red and white Kookaburra balls will also behave more like two-piece balls and they will swing more than a conventional red ball, especially when new and at the higher bowling speeds. Of course, once the surface becomes roughened, reverse and contrast swing will readily come into play as was recently witnessed in the Champions Trophy in India which utilized the white Kookaburra ball. The red Kookaburra ball is currently being used in the Ashes series in Australia and it will be interesting to see how long it takes before the bowlers start blaming the red ball for their woes! It turns out that the red SG Test ball used in India is very similar to the Dukes red ball. The ridges along the quarter seam are very apparent and this will make it easier to produce reverse swing with this ball. Again, the increased roughness along the quarter seam means that reverse swing can be obtained at lower bowling speeds and the amount of reverse swing at the higher bowling speeds is increased. What about the role of the six rows of stitching that make up the primary seam? They are certainly not identical on balls made by different manufacturers. In fact, they often vary between different brands made by the same manufacturer. For the balls discussed here, the primary seams on the red Dukes and SG Test balls are certainly higher and more prominent than the tightly wound seams on the Dukes white ball and both (red and white) Kookaburra balls. So what effect does this have on the swing properties? Well, our wind tunnel testing showed that the primary seams on almost all new balls are high enough and rough enough to cause the flow asymmetry which is necessary to produce swing. However, starting off with a relatively high seam means that the chances of it remaining prominent in the latter part of the innings are improved. This is relevant because a prominent primary seam is critical for both conventional and reverse swing. The condition of the primary seam has less effect on contrast swing. In fact, the primary seam can be completely bashed in and the ball (with one side smooth and the other rough) can still be contrast swung. In addition to the ball aerodynamics, the condition of the seam will also affect movement off the pitch. A prominent, wedge-shaped seam will generally result in more deviation than a low, flat seam. So rather than getting excited about the color of the cricket ball, the bowlers would be better advised to spend time examining the condition of the primary seam and the surface roughness, especially in the quarter-seam regions. I have also noted that the embossments that are stamped on the balls sometimes provide an additional roughness, which is not always the same on both sides of the ball. This is a feature that I would cherish as a bowler since it helps in producing reverse and contrast swing from the get go. If there is enough roughness added to one side through the embossment stamping process, then perhaps the temptation to tamper with the ball’s surface will be reduced. I hope the ball manufacturers and the cricketing authorities are paying attention! Rabindra Mehta Sports Aerodynamics Consultant and NASA Scientist based in California. (rabi44@aol.com) |
This
Site is Maintained By SIM's Graphics. Contact Us at admin@newyorkcricket.com
|
