Tuesday, March 16, 2010

Legspin bowling Drift


This is a magical complex aero-dynamic feature of wrist spinning, where the ball is released spinning from the hand on what initially looks like a trajectory heading for your off-stump (RH bat) and then as it approaches it veers to the batsmans left suddenly heading towards the Leg Stump at such a late stage in its flight heading for his blind spot only to then hit the pitch and do what all good Leg Breaks should do – break towards the Off-Stump.

Drift was probably first described back in 1930 in Clarrie Grimmetts wrist spin bible ‘Getting Wickets’. He refers to it as ‘Swerve’………..

Grimmet on Drift

The ball or sphere which is perfectly round, and has no seam, swerves because it is affected by the pressure of the atmosphere. This is dependent on the way that the ball is spinning. Take, for instance, a ball spinning in a horizontal plane from right to left. That is, if you were to put a chalk mark round a sphere, similar to the seam on a cricket ball it would be spinning round at right angles to the line of flight, parallel with the ground. The ball would then be traveling much faster on the right side than on the left, because it is spinning forward. On the left side, the ball is spinning back, and, consequently, not going so fast as on the other side. Hence, the different sides of the ball are differentially affected by the air pressure.

It is therefore, easy to see that the ball must tend to travel or swerve to the side on which there is the most resistance. In this case, the most resistance is on the left because the ball has a spinning motion backwards, and is traveling forward. Consequently, it swerves to the left; and, if the spin is reversed, it will swerve to the right. Similarly, top and backspin operate the same way in their respective directions.

A cricket ball introduces something different again by reason of the fact that it has a seam raised above the main surface of the ball. Through the fact that the seam is in such contrast to the smooth, shiny surface – this varying as the ball becomes worn – it necessarily follows it offers more resistance to the atmosphere than the shiny part. Consequently, it swerves according to the way in which the seam is spinning.

Bowl a ball spinning over towards the slips as for the leg break, the seam being gripped so that it touches the first two fingers and thumb. The seam would be then pointing in the direction of the slips, and, with the atmosphere striking it in this position it would act as a rudder, steering the ball towards the slips – an out-swerve. Now grip the ball with the seam exactly opposite, spin it the same way, and it will swerve towards fine leg – an in-swinger.

It is possible, however, for the seam to spin in such a way that, in the prevailing conditions it does not act as a rudder, and the ball swerves simply because it is traveling faster in one place than in the other, as for instance, the ball spinning on a horizontal plane.

In the case of a ball bowled as for a leg break, a previously described, with the seam spinning like a hoop towards the slips, the top part of the ball is traveling faster than the lower part, and causes the ball to drop quickly. Hence the curving, deceptive flight of a ball from a slow bowler.

In baseball, they use for practice purposes a ball with the seam raised about an eighth of an inch, the idea being to enable learners to get the impression of swerve more easily by means of the contrast between the raised seam and the ball itself. This suggestion could be applied to cricket. Bowlers anxious to solve the mysteries of swerve could have a cricket ball made to order with the seam so raised, and would thus more clearly be able to note the effect of swerve.

Much useful experience can be gained by noting, particularly with the raised seam ball, the effect of the wind. Young bowlers should also watch carefully to see how the swerve varies according to the way they grip the ball.

In swerve bowling, like other branches of the art, it must be the bowler’s object so to regulate his swerve that the ball will hit the wicket. A new ball swerves much more than the old one, and it is vitally important that this advantage should not be wasted.

It is always advisable for a slow bowler to work against the breeze, which causes the ball to dip and swerve, together with other peculiarities of flight impossible to obtain while bowling with the wind.

Philpott on Drift……..

Philpott points us to looking at Tennis and baseball for clues as to the way that a ball spins and we as Wrist Spinners need to be aware of the potential for applying drift to our game.

“For the left handed server (Tennis), it is easier to slice down the left side of the ball, creating ‘Leg-Spin’. The serve now drifts from left to right. It drifts ‘in’. The ball always drifts the opposite way to the eventual ‘Turn’ after bouncing’. Peter Philpott; The Art of Wrist Spin Bowling; 2006; Crowood Press Ltd, Wiltshire.(Page 31).

And that’s it, apart from a diagram that illustrates a ball that is spinning with its seam 90 degrees to the direction of flight. There’s no mention of whether the seam is fully upright or slanted backwards or forwards. The illustration suggests that the ball is delivered with the rotation 90 degrees and perfectly up-right. But then you could argue that Philpotts book is aimed like Grimmetts at young boys and is written in a manner that is accessible to kids in the 1990’s. Whereas Grimmetts is far more complex and assumes that the kids have far less to distract them and therefore will take the time to read it over and over again until it sinks in.

Woolmer on Drift

Woolmer, on the other hand attempts to take a very in depth look at Drift in his book. Page 301 through to 307 he writes several thousands of words illustrated with some good diagrams explaining the Magnus affect. If you want to explanations of the magnus affect youtube is particularly good if you search around links to Baseball as there are video clips of wind tunnel and water experiments showing the affects of turbulence around balls. http://www.youtube.com/watch?v=oph9BP4lKjs

Having tackled the subject of the Magnus effect he then moves on to the ball of the Century from Warne to Mike Gatting http://www.youtube.com/watch?v=LeLn8sEAKfE&NR=1
There’s a couple of interesting points that Woolmer makes that are in opposition to many people’s explanations and theories and the key one contradicts Philpotts diagram of the ball with the perfectly presented up-right seam spinning at 90 degrees to its flight path. Woolmer concludes that a ball presented in this manner will not drift. He then goes on to explain in great detail Warnes Ball of the century which has a great deal of drift, but as he gets into it and starts to explain the theory he then notes “In order for the delivery to drift towards leg, the wake of the ball must be disturbed upwards towards the off-side. How this happens is not yet well described in scientific literature. Thus, some speculation is warranted – and illustrated in Figure 5.23”. Which is the diagram used to explain the ball of the century.

The key revelation within the text is the speculation that in order that the ball does drift in the manner illustrated in the video link, it was probably tilted slightly backwards from vertical (When seen from above). For me personally, its just this line from everything I’ve read that I feel is new and definitely worth looking into. Additionally another resource that is available to everyone on the internet and is exceptionally comprehensive is fellow bigcricket forum contributor ‘Spiderlounge’s blog that looks at the subject - http://pencilcricket.blogspot.com/p/magnus-effect-in-leg-spin-bowling.html
I can follow what he’s saying up to a point but then I get a bit lost but within his explanation I’ve noticed too that he looks at the possibility that big drift occurs when the seam moves off the perfectly upright (Viewed from above) position and slants one way or the other.

I find the difficulty with all of the explanations is the visualising of the written explanation with the reality and sometimes the written explanation and the combination of the illustrations still leaves me confused, Having looked at this now for several days and numerous explanations in books and on videos dealing with the physics of a spinning ball I’ve come to a inconclusive conclusion.

Some of the information relating to spinning balls is easy to grasp and the magnus force when it relates to some types of balls makes sense. But, with regards to wrist spinning and the fact that it in itself is a relatively unexplored and unexplained with very few people prepared to put their hand up and say that they are experts in the field either as protagonists or researchers (the researchers would need to work with the protagonists) it seems that the fact that it is such a dark art amongst all of the cricket specialities that information is scant. The fact that not many people bowl wrist spin apart from Danish Kaneria and 2 others (His words not mine) the scope to explore the physics using players is limited. Then add the fact that we spin the ball around a horizontal axis with the seam 90 degrees to the direction of flight and it all starts to get a bit messy and exceptionally complex. So much so that when you read the few books that there are, that, deal with the subject of Wrist spin in any depth (see bibliography). You then see even the experts in the field with the help of physics and cricket experts come to a similar inconclusive conclusion.

On the Bigcricket Forum as I discussed this with the others we all more or less came to the same conclusion……..

· It is a very complex theory to understand and apply to your actual bowling.
· If you spin the ball hard with your Leg Breaks you will produce drift and if you notice it or someone else notices it keep it in mind and try and work with it.
· Don’t get hung up on it though, because similar to seamers who can swing the ball some days and not other days – it may be the same kind of thing with drift.

Woolmer winds down his section on Wrist Spinning holding Warne up as an amazing bowler with an exceptional degree of technical mastery and that the Ball of the century was probably a ball in a million. He finishes the chapter though quite fittingly as I have at the start of this section on Drift transcribing Grimmetts original work from 1930’s and saying it was Grimmett who literally wrote the book on spin.

Update; Added Aug 2011. Just having a look around the internal workings of my blog and I've stumbled upon the fact that my little blog here is linked to the Guardians website. In which case I think if you're looking at this with regards drift/spin and dip, you might want to have a look at the posts made through Aug 2011. During this phase I reached the point in my own bowling where I'm now able to produce these elusive attributes.

Check out my other blog here - this is all about Leg-spin bowling and nothing else. Double click on the image below.