Daily Archives: March 31, 2010

A Swann in Flight

One of Third Man’s older memories is of lying in bed with his Christmas present of a new and, then, miraculously small transistor radio.  It is very early in the morning and he is listening to a live broadcast of the 1962/63 Australian tour from the Sydney Test.  Fred Titmus is exploiting the breeze across the SCG to make the ball drift away from the right hand bat.  He takes 7 -79.   

Jim Laker, no less, described Titmus as a master of away drift but reserved the accolade of strongest spinner to (the other) David Allen.

It is the Magnus Effect that couldexplain why Titmus got less turn but more drift than Allen and why Graeme Swann is number two in the ICC bowling table.

The Magnus Effect  is what causes the tennis ball struck with top spin to dip steeply.  It is what causes the sliced golf ball to swerve right and Beckham’s free kicks to bend left when struck with the inside of the right foot. 

It and not the breeze is what accounted for the apparent ability of Titmus’ off-spin to drift or fade away from the right hand bat and it explains a lot of what is happening to Graeme Swann’s fiendish deliveries.

There is a trade-off between the amount of turn you can expect and the amount of Magnus Effect.  To maximize turn the bowler would try to send the ball down with the access of rotation aimed at the batsman and the seam rotating either clockwise or anticlockwise.  But this would produce no drift or dip.

By propelling the ball seam towards the batsman with the axis of rotation going across the wicket would produce top spin and dip or back spin and keep the ball in the air longer than expected.

When the right arm off-spinner sends the ball down with the seam rotating towards leg slip there will be varying and unpredictable combinations of drift, dip and turn.

Dip allows the ball to be bowled higher so that it spends as much time as possible above the eyeline of the batsman, a less natural and therefore less accomplished point of view.

There is also a differential reaction to the surface of the wicket depending on how much of the seam strikes the ground.

Angling the seam with the bottom of the ball slightly forwards towards the wicket will then increase the randomness of the grip that the ball takes. Sometimes the ball will land fully on the seam, sometimes fully on leather and all combinations between producing differences in turn and the chance of the ball which lands on leather skidding on along the direction set by the forward momentum and the drift.

This thus maximises variation.

Swann puts something like 1,800 rotations on the ball.  The greater the revs the stronger the resulting motion perpendicular to the relative velocity vector, as well as the greater the change in pace and direction on impact.

Added to this he can vary his pace by as little as a couple of miles per hour.

Doing all this almost at will, he can put together subtle combinations and series of balls like a boxer setting up an opponent for a particular punch.

He aims generally at the right hander’s off stump (the attacking line) so that not only are both edges of the bat in play but also a missed ball is likely to hit the stumps.

The dip, drift and spin variations disturb the batsman’s timing and bring the catch from a mistimed shot into the equation.

Bowling round the wicket to left handers there is a tendency for the seam to tilt more towards the wicket and so an increase in both the extent of the drift and the chances of the ball landing on the leather and skidding through like an old fashioned arm ball.

Finally, Swann is confident and aggressive and communicates the intensity of the moment to batters and fielders.

How wonderful it would be to have the camera images that are possible today for the flight of bowlers such as Laker, Allen, Mortimore, Titmus and even further back to Verity and Rhodes.  (The wrist spinners can speak for themselves.)

AN UPDATE: Over in the Corridor of Uncertainty Jonathan Calder asks sagely, “is off-spin the new leg spin?’   In that revs are back in fashion and that English finger spinners are learning to use the javalin approach, they are indeed catching up with the innovations of the leg spinners and perhaps surpassing them.

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