Monday, November 28, 2011

Leg Spin Bowling - Drift

Drift - Leg Spin Bowling (Work in Progress)

Also see this new post here with details and links relating to Top-spin and Drift and the use of scrambled seam -

Update 26th April 2012 - That's not bad this comes up 5th in the Google search for Spin Bowling Drift. Please note that this is work in progress and doesn't at this point include a conclusion. At the moment it is primarily as series of links to videos and articles all looking at and trying to explain Drift. The reason it's here is that I'm trying to come up with an explanation that I'm comfortable with that the layman and the aspiring spinner can grasp without having a degree in Physics.

Strewth! I've been looking through all those physics papers, looking at Laminar flow and the magnus effect, I looked at Pencil Crickets blog where he's put in a massive effort to shed some light on the matter and just now I've looked at Woolmers book "The Art and Science of Cricket". Now... Bob Woolmer was a man with a lot of connections in cricket and there's a pretty extensive list of people that helped him on that book along with a massive bibliography that cites all sorts of sources. But despite this when it comes to both seam bowling and swing and more so in the case of 'Drift' he concludes with the fact that there isn't enough scientific data to actually pin down either of these phenomena and explain fully why they happen.

Dip and the ball staying in the air with back-spin - that's kids stuff, I can't see why anyone would dispute that and it's easy to put into practice and see it happen, but drift, with the ball drifting in the opposite way to the way that it spins... that's just screwed. What doesn't help either - and I don't know if anyone else sees it in the same way as me, but the illustrations in Woolmers book in the spin section seem to completely miss the relevance of the seam with regards to the direction the ball is spinning? So on that note I declare that I've given up on trying to get my head round this whole issue and join the 'Spin hard' brigade and hope that it drifts!;)

Maybe I'll engage with discussions on empirical observations over at One parting glimmer of hope that I'll maintian some interest in this is that - 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.

Read on if you're interested in what I discovered before giving up on this quest...

One of the points of confusion when describing aspects of spin bowling is the direction that the ball seam is pointed in and the method by which we can visualise this aspect. In order to simplify this on the forum I write and comment on I've suggested recently that we talk about the direction in terms of minutes on a clock. This relates to looking down on to the pitch from above. The pitch therefore would run from 0' to 30' Top to bottom.

This is the phenomenon best exemplified here with the famous ‘Ball of the Century’ bowled by Shane Warne. As Warne bowls the ball its initial trajectory sees the ball head off towards Gatting on a conventional straight line, but then towards the end of its flight it veers (Drifts) towards the Leg-side to then ‘Break’ back on to the stumps. It’s this late veering towards the right as the bowler sees it that is Drift. The batsman on the other hand sees the ball veer off to his left as it dips prior to bouncing.

The more you watch videos and read about spin bowling the more frequently you’ll hear about drift and the sense you’ll get from commentators and protagonists’ is that it’s an attribute that you should have as a part of your bowling. But, there’s a universal problem, all of these people mention it and comment on it, but no-one really seems to pin it down, no-one really says - 'this is what you do in order to make the ball drift' apart from the basic 'Spin it hard'. If you start looking a little deeper and changing your search criteria you get the other side of the coin and that's the Heavy on the Physics approach. Dig a little deeper still, and you then end up with Baseball. The reason for this seems to be that they (The Yanks) seem to take far more interest in the technicalities of their sports, maybe its that whole 'Jocks v Geeks' thing that we seem to get fed as a generalisation about the USA? It could be that, if you're not that clever academically you then seek a route through education studying sports science and playing sport at college? As a consequence, it seems as though there's a lot more information over there on the subject of spinning sphere's - specifically baseballs. But what they seem to do slightly better than us is find a middle ground between the 'Spin it hard' explanations and the 'Magnus effect/Physics' explanations. So hopefully I'm going to be able to come up with a good explanation.

The reason I'm trying to get this across in a different manner is in part due to the fact that I'm whats called a Kinaesthetic Learner and understanding complex stuff like this requires a connection with the actual practice, I can't just read it and fully comprehend it and the process has to include tactile experiences. In addition I find my level of comprehension to be enhanced by connecting the reading with the physical and then explaining it in my terms and this is what this blog entry is - a part of the process of comprehending.

To those of us with an enquiring mind including me, this vagueness "Spin it Hard" isn’t good enough, I want to know how and why, what, when and who? How do you make the ball drift and can I ‘turn the drift on’ and can I ‘turn the drift off again’ at will? Surely, if you can have that degree of control you’re moving towards becoming a master of your craft?

So, with these unanswered questions and the whole vagueness issue, I set about looking at what is out there by way of explanation and trying make sense of it and ascertain if it is possible or even desirable to produce drift on demand and what is it you need to do to produce it.

The 'Spin it Hard' section.

Here's a few starting with Terry Jenner - the interesting details in this account are the fact that he focuses primarily on aspects associated with body actions and position - shoulder rotation and side on alignment. He mentions that Top-Spin wont produce drift, as that creates dip and he says that seam alignment needs to be side ways. In this video here (Cloverdale series) he simplifies it, stripping it down to 'If you spin the ball hard it can drift in to the RH batsmans leg stump and spin away sharply towards leg stump'. (1:44 seconds into the vid).

This site here compiled by Julian Fountain is another useful one. It's interesting in that at the start of this website he too questions the lack of understanding associated with Drift and the Magnus Affect, which is the scientific explanation. I find his simple scientific explanation still difficult to grasp in relation to drift. I can see how it works with Top-Spin with the seam aligned between 30 and 60 minutes, but once I try and get my head around the seam aligned at somewhere between 45' and 55' I can comprehend this would still produce the dip that we need, but why it veers off course away towards the Leg-side (drift) I'm still unclear and his explanation doesn't clarify it for me. There's a video on the site here, but I've got to say I think this is too much, yeah maybe the students that compiled the video can make some sense of it and explain it, but to the layman all that maths is way over the heads of most people and serves no useful purpose to the majority of us. One of the more interesting aspects of the video is the sequence at 2:35 where the kid kicks the ball and it's shown in slow motion. There's virtually no spin on the ball at all and yet the ball appears to initially veer slightly to our left as we view it and then finally very late in its flight sharply to its right! I'll return to this point a little later. But for me that's a very basic contradiction "Spin the ball hard and it'll drift". Er, this ball barely spins and yet it drifts at the end of its flight?

This video looks at Warnes ability to spin the ball and to get it to drift it doesn't get that technical, but there's some good footage of his release in slow motion and Jenner talks about his drift in rudimentary terms.

Going back to the application of basic spin e.g. Top Spin or Back - Spin this science video has an excellent demo on the affects of back-spin and the magnus affect and how it makes the spinning object stay in the air, but still for me has no bearing on diagonal spin and how this makes an object move laterally through the air. *Edit - I've just sussed a visual explanation that satifies me and could be up-loaded as a very basic video explanation!

The saving grace is that at the end he reverts back to the standard advice -

Spin bowlers use the magnus effect, perhaps sometimes unknowingly, to create drift & turn. They do it by imparting revolutions onto the ball; the more revolutions the bowler can make the ball do in flight, will directly affect how much drift (and consequently turn once the revolving ball hits the pitch) is achieved. So it basically boils down to making the ball rotate in the air. The more efficiently the ball rotates, the better. Also, the ball will behave differently depending how the seam is presented; i.e. if the ball is spun across seam, as opposed to down seam, it will cause a difference in the air pressure waves.

I've also written this which will need to be incorporated and edited , but in the short term might be worth a look at.

To put it simply as Menno Gazendum says "The technical term for this is called the “Magnus Effect” but all you need to know is that the harder you spin the ball and the more flight you give the ball the more it will drift".

Bibliography/Links 3:18' The Knuckle Ball (Baseball) slow mo footage of Knuckle ball (Wakefield). - Blitzball (reduced drag caused by textured surface a la' Golf Balls. - Curve Ball using Blitzball instructions using Top-Spin - this is interesting in that there's an explanation as to how to increase 'Drift' in a curve ball through the alignment of the seams on a baseball. The ball can be pitched with a 4 seam alignment or a 2 seam alignment, the 4 seam alignment then starts to take on the attributes of a golf ball or a blitz ball in that it has a rougher surface presented to the air causing reduced drag. This is the bloke at The University of Sydney.

This here is one of the seminal pieces on the subject and is definitely worth a look -

Swap golf ball dimples for rough texture on a cricket ball with this one
This is another good article written by my on-line mate 'Pencil Cricket' who has studied Physics - this is more accessibe to the Layman than most. The interesting thing that I've picked up from Pencils article is that he's pretty much convinced that the ball that is spinning at 90 degrees to the direction of flight is the type that is going to produce the most dramatic amount of drift. Yet I recall in Woolmers 'Art and Science of Cricket' he says it's not that simple and that the ball needs to be tilted backwards or forward through the spinning axis. More on this later.

A comprehensive description of the effects of air passing over a spinning ball. Primarily this relates to seam bowling and getting the bowl to swing, but as far as I can make out this may also apply to the spin bowling and be the explanation for why drift occurs In addition take note of the bowlers comments and about the nature of the inconsistency e.g. this is not something that you can produce at will, some days it happens other days it doesn't.

Note to self - Illustrate the Magnus effect turned on its side like the Benuad Flipper with the ball spinning forwards with Top-Spin, video from above and rotate the ball from the Benaud Flipper through to the 52' angled Leg Break. Note observations regarding the RPM of Baseballs in comparison to cricket balls spinning.

Drift thoughts - posted on 26th April 2012 *I've looked at the following material and discovered some contradications, so it's back to the drawing board. Currently I'm looking at this - but to be honest this is all looking to be a bit beyond me.

The section below is nonsense it seems and I'm looking into more research...

So, looking at more vids and reading more I’ve come up with this. One of the universally agreed and tested theories that applies to a sphere and specifically a cricket ball in flight is the laminar flow theory (Link). The majority of the information relates directly to seam bowling and the phenomenon of ‘Swing’. Looking at the link provided which has research conducted at Leeds University, the agreed theory is that the air that passes over the ball in flight and creates ‘Laminar Flow’. As the video shows, the turbulence in the wake of the balls flight has characteristics which then affect the balls direction making it veer either left or right depending on nature of the surface of the ball. A perfectly round smooth ball we would imagine would have straight flight through the air because the turbulence behind the ball would be equal either side, above and below, but a cricket ball becomes worn and the players look to exploit the laminar effect by making one side of the ball rougher than the other. The air passing over the smoother surface initially and then releasing over the rough side in its wake exploits the laminar effect to make the ball ‘Swing’.

It then struck me that these experiments conducted in a wind machine which primarily look at swing bowling omit the inclusion of the ball spinning, so the laminar effect works without spin being a factor. The conclusion I’ve now drawn is that if a ball was mechanically shot out of a machine with no spin, the surface of the ball combined with laminar effect physics would mean that the ball would swing or not swing. Scuff the  rear surface of the ball (Wake side) or present the seam diagonally to the direction of flight and you’ll optimising the laminar effect as the wind passes over the ball and the ball would probably ‘Swing’ left or right. The main point to take from this going forwards is that the ball isn’t spinning.

Seam bowlers it seems, angle the ball slightly in order to have the smooth side of the ball on the leading (Into the wind) side of the ball to facilitate the laminar effect, the slight angle also then brings into the equation the seam, the wind passing over the seam disrupts the air-flow exacerbating the laminar effect. Now think of the perfectly presented spinning seam as bowled by a Wrist Spinner… The ball is projected down the wicket with the seam presented spinning perfectly round its own axis maintaining a regular plane/axis. This would then mean that the air moving over the ball would optimise the laminar effect beautifully meaning that the ball would in effect ‘Swing’ in exactly the same way as a seam bowlers ball would. Interestingly Clarrie Grimmet in his book ‘Taking Wickets’ doesn’t use the term ‘Drift’ using instead "Swerve" which then leads me to question where did the term drift come from and how long has it been around and why the differentiation if the forces on the ball are the same?

Speed is a factor needless to say, but I’ve observed younger and older seam bowlers produce balls that swing very effectively off of relatively slow bowling 40mph + so it’s not essential that the ball travels at great speed in order to be effected by the laminar effect.  So it follows then if you’re a spin bowler and you’re able to bowl the ball with the seam spinning around an angled axis and not wobbling the nature of its flight through the air would mean that the ball would ‘Swing’ because of the physics of laminar flow. The spinning of the ball would then mean the ball turns off the wicket in the ways that we all understand. To me it seems that the key to getting the ball to drift is as follows…

(1). Have the smoother side of the ball facing the direction of flight.
(2). Spin it hard trying to release the ball spinning so that it doesn’t wobble in the air, the more perfect the spinning of the seam around its axis the more the you’ll optimise the laminar effect over the ball.

Maybe it’s the case that the combination of the ball spinning and ‘Swinging’ has become known as drifting in order that when someone talks about the ball ‘Drifting’ we can then assume that it was a spin bowler and not a seam bowler?


Another observation I’ve made which I’ll mention and may complicate things slightly, is that, all of the illustrations appear to depict that these Physics theories applied to the ball from above and below and not from side to side, or possibly more complex – diagonally. The obvious answer seems to be because another import physics theory is that of gravitational pull which is downwards and applied in a vertical plane up and down and not side to side? But, again is illustrates that the whole are can be looked at in a more complex way yet again!

To be continued..............

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