Thursday, April 26, 2012

Drift Legspin bowling

Drift - Wrist Spin Bowling; The Leg Break

So, after many months of coming back to this and asking questions of people and looking at the research involved I've come to a conclusion.

There are several on-line academic articles on the subject, but because they are academic articles they usually require higher levels of maths and physics knowledge in order access the information and then turn it into something that the layman can get to grips with. Of these articles one of the most respected and often cited is the one produced by Vaughan Roberts which you'll find here if you can make sense of it and present it in practical terms e.g. slant the ball so, angle the seam towards y, bowl into the wind, bowl around 45mph and get it a massive rip and then say why, without having to resort to using Reynolds numbers and the likes please do so and get back to me on!

For the moment, although I'll still look around for the answers and explanations presented in a way that I can comprehend I've given up on this task and here's why. It does seem when you look around that there are articles on the dynamics of spinning balls, but for the most part the research is looking at footballs, golf balls, baseballs and cricket balls - but only in relation to 'Swing' and seam bowling and 'Dip' in relation to Spin bowling. Drift it seems is so complex that there is a limited amount of info and as with the Vaughan Roberts article this is complex and inaccessible.

There are a number of phenomena described in Physics that work on the ball whilst it's in flight and these can be tested using air flow and smoke in wind tunnels and water flow and dyes in tanks. These explain and demonstrate visually the effects of the spinning ball in simple terms and are readily understood when explaining dip with Top Spin and the way the ball travels further without dipping early with Back-Spinners like the Vertical seamed Flipper and the Orthodox Back-Spinner as described by Peter Philpott in his book 'The Art of Wrist Spin Bowling'. Furthermore these theories which are described as being The Magnus Effect can be turned on their side and demonstrate 'Swerve' creating a spinning effect which looks like Drift at first look, but is (According to Vaughn Roberts) totally different to Drift. 'Swerve' is demonstrated exceptionally clearly in this video here in a series of experiments conducted by  professor Rod Cross at Sydney Uni. Unfortunately for us as Wrist Spinners Rod Cross's background is in Baseball, so his key area of interest is in this sport and as a result he doesn't seem to be aware of Warnes Ball of the century and drift. I'm trying to get in touch with him, to try and get him to do a Youtube explanation, because I reckon if he was to do so, he may be able to produce the kind of explanation we could all access and comprehend?

The nail in the coffin though came about when totally frustrated with getting no-where I returned to Bob Woolmers Art and Science of Cricket which is a massive tome of a book published in 2008. I re-read the sections on the aero-dynamics of cricket balls and again struggled to understand the descriptions. Again, I'm not sure whether it's just me or not, but the graphics they use I find very difficult to visualise in practical terms, which is a common source of frustration and confusion when trying to understand what is being proposed in many of the explanations. This very point is raised by a fellow blogger and forum commentator 'Pencil Cricket' who himself with some educational background in physics has had a stab himself at offering an explanation here. Pencil cricket too has raised issues around Woolmers explanations both graphically and within the written content, pointing out that whilst Woolmer was an excellent coach he was never a physicist or a Wrist Spinner and looking through his bibliography and credits at the back of the book Vaughan Roberts isn't recorded as a source. But in conclusion at the end of both the 'Swing' and the 'Drift' Sections, Woolmer writes...

In the end, the mystery remains (Swing)

in the final analysis, all these theories and hypotheses are exactly that: to our knowledge, no-one has yet shown conclusively (using a swinging delivery produced by a swing bowler in a real match) that these factors discussed above provide exclusive explanations for why the ball does or doesn't swing. The explanations given here are based on solid principles in physics, but because it is not yet possible to measure all these variables on a swinging delivery out of doors, the real contribution to the generation of swing of each of the listed theoretical factors remains largely unproven.

The Magnus Effect and the ball of the century

What happened from an aero-dynamic point of view? Generally, a ball moving away from us in a horizontal plane, and spinning left to right (Anti-clockwise) moves to the left (Equivalent to the off-side in cricket) and not to the right side (Leg Side). This can be seen when a right-sided kicker in football takes a penalty and strikes theball on its rights side. The ball always curves to the left. But in this case, Shane Warne spin the ball from right to left - yet it deviated to the right (Leg Side). Had it deviated to the left (As expected), Gatting would have been in line to play an appropriate shot.
       In order for the delivery to drift towards leg, the wake of the ball must have been disturbed upwards towards the off-side. How this happens is not yet well described in the scientific literature. Thus, some speculation is warranted.

Bob Woolmer, Bob Woolmer's Art and Science of Cricket, 2008, New Holland Publishers, London

I think one of the things that works against us is that, as a breed within the game Wrist Spinners are rare. So it follows that perhaps it'll take a Wrist Spinner in the future to study Physics to PHD level to conduct the research? The chances of that happening do seem to be on par with finding a colony of Dodo's alive and thriving on Canvey Island! Spin bowling having nearly died in the 1970's & 80's has re-emerged primarily because of Warne and is making a good comeback especially in the T/20 arena. So maybe it will happen, or maybe one of the organisations looking to develop spin will finance such research - hopefully over-seen by someone who actually bowls it and produces drift readily.

In the short term I'll continue to post links to sites that look at the physics involved or illustrate the effects of spin in bowling.

Maybe I'll engage with discussions on empirical observations, Woolmer in his analysis of Warnes BoC proposes that the ball was spin at almost 90 degrees to the direction of flight and that the axis of the spin was either tilted upwards or downwards which if was the case, kind of ties in with some of the data I found on the effects of laminar flow, but still goes nowhere near explaining drifts direction being opposite to the spin direction.

If you're looking for instructions as to how to get more drift, the guidance does seem to be fairly vague. Spin it hard is the main advice and that comes from all of the protaganists. A lot of people say that the seam alignment should be at 90 degrees, but some people including me and Woolmer reckon this works against getting drift. The seam slightly off-set from 90 degrees would help to facilitate some of the physics - laminar flow. The axis shouldn't be horizontal to the flight path either and should be experimented with angled upwards or downwards slightly - again this crops up in the analysis of Warnes Ball of the centrury in Woolmers book. Increadibly there's no readily available footage of anyone bowling employing drift using High Definition - high speed cameras so that any of this can be substantiated.

This is a stub which is part of a bigger/earleir (out of date) piece on drift - see here

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