someblokecalleddave
Well-Known Member
Keep going let me know what you discover, most people are saying that the 45 degree angle produces the most frequent and obvious drift.
Drift
- Thread starter someblokecalleddave
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Keep going let me know what you discover, most people are saying that the 45 degree angle produces the most frequent and obvious drift.
Perhaps it's not so much the angle of the seam(towards slips) if you would look at the ball from above the wicket, maybe it's the slight slanting of the seam towards the batsman that helps produce the drift. I'm not so sure that when I'm bowling my overspun leg breaks that I am getting a a little slant or tilt as I would think of it. I think that's what may be causing my overspun leg breaks not to drift as my wrist action has evolved over the past year and felt different over the course of time, I'm getting revs on the ball and people near me can hear my fingers as I flick the ball and I hear it fizzing in the air as it leaves my hand. I have been trying different things with my wrist to get it to slant/tilt in with the overspun leg break, but I don't think that I have been releasing it that way. I might have to paint an old ball white on one side to see what sort of tilt/slant and angle of seam I am getting, I'm thinking that I'm getting no tilt at all on the overspun leg breaks, or even tilt on the opposite direction which I have a feeling that Stuart Macgill did with alot of his earlier bowling when he didn't get any drift and almost looked like he was getting drift in the opposite direction to me :S
edit: Also looking at football(or Soccer as it's called here) you can be sure that any time a football that's kicked to make it spin on a horizontal axis makes it curve. In my leg spin bowling I am wanting to get some horizontal axis spin and such is the slant or tilt, but not too much so that it still hits the seam and turns. I remember a while back on the news when a scientist explained that a ball starts curving as it's beginning to slow down, this was when Roberto Carlos scored that amazing free kick.
edit2: Just found this, it's not the video I was talking about but I found it interesting.
These articles are also interesting:
http://blogs.scientificamerican.com...dden-advantage-of-long-distance-soccer-shots/
http://io9.com/5628135/physics-forc...ew-equation-to-explain-impossible-soccer-kick
http://www.bbc.co.uk/news/science-environment-11153466
That might explain why I'm getting a hell of alot of dip and no drift, as the seam is probably vertical in my overspun leg breaks. I wonder what would happen if I could produce a ball that was a top-spinner but had a slant or tilt in. Would it drift?
someblokecalleddave
Well-Known Member
A quick reply as I'm busy, but yeah your observation with regards the tilt of the ball in flight is definitely instrumental. In his book 'The Art and Science of Cricket' Woolmer and his co-writers examine Warnes 'Ball of the century' and one of the key conclusions or theories is that the angle of the ball e.g. tilted is the primary reason for the drift. I seem to remember somewhere (it may be the same article) that if the axis of the seam is spinning exactly at 90 degrees to the direction of flight and the seam is rotating perfectly through a vertical axis this negates the potential for drift, but with the ball tilted. In fact it's more complex than that...
"Most likely, the seam was tilted slightly backwards from the vertical (When seen from above), with the seam on the left side of the ball *slightly ahead. In this position, the axis of rotation (seen from behind the ball) is upwards and to the legside".
*So this indicate the balls not purely 90 degrees which substantiates the arguement that perhaps the 90 degree non tilted ball doesn't drift?
The article although possibly the most recent analysis and backed up with a bibliography that includes a host of expert sources has the caveat that the analysis is speculation!
"Most likely, the seam was tilted slightly backwards from the vertical (When seen from above), with the seam on the left side of the ball *slightly ahead. In this position, the axis of rotation (seen from behind the ball) is upwards and to the legside".
*So this indicate the balls not purely 90 degrees which substantiates the arguement that perhaps the 90 degree non tilted ball doesn't drift?
The article although possibly the most recent analysis and backed up with a bibliography that includes a host of expert sources has the caveat that the analysis is speculation!
macca
Active Member
Hey Dave, this Rod Cross guy from sydney uni has been in the headlines for dodgy physics in his expert witness appearance at a murder trial. They ended up having to quash the conviction and the appeal judges were very critical of the assoc profs work.
Doesnt mean his work on drift and spin is bodgy as well, its just i saw his face and name on a doco and remembered the youtube clip posted here of his spin stuff.
someblokecalleddave
Well-Known Member
Oh blimey, who do trust these days when even the blokes with PHD's are getting it wrong! I'm sure much of what he says is pretty much spot on with regards rotating balls, but it'd be good if he could some on drift relating directly to a cricket ball rather than light weight spheres that readily drift!
Just referencing my old post, I recently found a clip of a Shane Warne dismissal that shows how I imagined myself bowling back then, go 2:16 in & watch exactly how the ball is released, not only does he spin it up but he goes right over the ball & push out the side, creating that dipping path starting withe the arm from the top and then forward, down, back and around forcing it down in circular arm rotation fashion in line with his braced leg. I consider this to be the perfect legspinners delivery. Just look at how Warnes body is at release, you can see a hint of his supporting arm across his right hip. Action is just perfect, im in awe.
someblokecalleddave
Well-Known Member
At the end of last season I'd seen a dramatic improvement in my bowling action after a couple of seasons of relatively poor bowling, I'd managed to improve the speed and the spin and saw a few wickets in the last couple of games I played before the end of the season. The improvements seemed to be down to the increased speed with dip, making it more troublesome for the batsmen. In practice sessions I then noticed on the odd ocassion drift, but couldn't put my finger on what it was that I was doing that increased the chance of seeing the ball drift. I think it's universally accepted that if you can bowl with all the normal attributes of a Leg Break but then also consistently produce drift, your potentially is massively increased.
Reading as much as I could on the subject it became evident that all the information that related to drift was either pure physics and to some extent theory written by scientists or at the other end of the spectrum too simplistic "Spin it hard". Woolmer tries to unravel it but then bottles it at the last moment.
With regards to your question, I'd say that if I was able to unravel the facts about drift and was able to convert them into something mid-way between the physics and the spin it hard schools, I'm hopeful that it may be the case that it might be down to a rough set of guidelines...
* Present the seam at (Y) degrees
* Have the rough side of the ball facing (x)
* Improve your chances bowing into a wind direction of (Z)
* Bowl at a speed in excess of (A) mph
* Get right up on your toes
* Follow through
If this was the case and we were able to establish this formulaic approach whereby it was generally accepted that this would increase your chances of producing drift by a large margin, I could bring drift into my plan when bowling. A sequence of small leg breaks 4-5 with more top spin followed by the one that drifts?
Axis of rotation should be pointing to the sky for maximum lateral displacement - this is "swerve" technically, not drift. The more the axis is tilted towards the batsmen, the less it will move but the later that will occur, which is more dangerous in many ways. That's what most people mean by drift.
The rough side/smooth side is irrelevant, as is seam alignment. swerve and drift is pure magnus force.
wind direction - basically the same as the direction you're trying to get the ball to go, with possibly a slight headwind. Could be worked out using ODEs if you had the patience. I would guess at about 100-110 degrees.
speed - again, you can work this out using an ODE, the magnus force is maximised at higher velocities, but if the ball is in the air for less time it will achieve less lateral displacement before pitching. Experience suggests 50-80mph. Put a bowling machine on maximum "swing" and see what speed creates the most displacement. Bowling machines actually use swerve not swing, which is just a 90 degree shift away from drift.
get on toes/follow through are just generic helpful bowling advice, but not specifically about drift.
Those who say "just spin it hard" are probably giving you the best advice available. Big spin = big drift.
I just think of it as swerve as the ball falls down, you don't want exactly the seam exactly upright since the ball path as it's falling down towards the batsman isn't exactly a perpendicular lineto the ground when viewing from side on it still looks rather flat, hence why I think having quite a bit of tilt, meaning having the angle of rotation perpendicular to the average ball path as it drops down should still give you late curve, and more so pronounced(late curve) just as you said with the magnus for when the ball is bowled at higher velocities, just as it did in that Roberto Carlos free kick. I don't mean to bowl flying sauces though as we'd get no deviation off the pitch.
One thing I think that how as most of you guys say that the 45 seam position(towards slips) how it gives you dip as well as drift is good because the ball path is a longer distance as it travels towards the batsmen, whereas a flatter path the ball travels less distance. So I would say maybe just less that 45, perhaps 35-40?
edit: some tilt should also help the ball deviate quicker off the pitch as the seam is almost helping it fall to one side as it bounces, just something I've noticed with cricket balls and bowling topspinner that when tilted slightly but with the seam still pointing straight to the batsman(or ball path) it can act as a leg break, movement off the seam because it's biased to one side
macca
Active Member
I would have to agree what SLA says here.
Grimmett in his chapter "How to make a ball swerve" treats drift as a type of swerve. Swerve he reckoned came from magnus effect, seam size and direction of seam in flight plus atmospheric conditions by which he means air pressure and wind direction.
Grimmett concludes by saying it is impossible to tell someone how to swerve a cricket ball." One bowler might say 'this is how I hold the seam to bowl the ball' ; but if you tried to do exactly the same thing you might find the ball didn't swerve. This is because you let the ball go in a slightly different place, or imparted a certain amount of spin. Both of these things would offset the conditions that are necessary to swerve the ball as you had been shown. A bowler must either do it naturally or be prepared to experiment himself."
someblokecalleddave
Well-Known Member
There's some good basic points made in this really cheesey video here particularly the point about smooth v rough surfaces of the ball. This I can see relates to Top-Spinners and back-spinners, but for me doesn't add anything to my knowledge of Drift. I'm still struggling with drift
someblokecalleddave
Well-Known Member
Looking at this vid this would seem to suggest that the same forces 'Laminar flow' over the ball in swing bowling are the same forces that cause drift - is that right?
'Laminar flow' ? How is that in relation to the lift and drag forces of the magnus effect? The hard thing to get a clear picture in our minds is that the ball doesn't travel in a straight line all of the time when bowling, but you can simplify things but thinking of the 1st 3/4 of the ball path as a straight line parrallel to the ground and then last 1/4 perpendicular to the ground(the ball falling down). So a ball bowled with square seam leg spin as it drops down out of the sky in that last 1/4 is pretty much the same as top spin if you where to look at it from above facing the same way that the short leg position is.
You also have to remember that pointing the seam at slips, is that part of the surface of the ball is spinning as a top spinner and the other part of the ball as a leg spinner. In my mind is see that, the part of the ball that is acting as a top spinner with create dip for all of the path of the ball and the one creating the drift(top spin looking from above) is happenning as the ball drops out of the sky.
Found this nice University of Sydney science paper that also has some nice pictures about fluid physics. I haven't read through it yet but it's intruiged me.
http://www.physics.usyd.edu.au/~cross/TRAJECTORIES/Fluidflow Photos.pdf
edit: looks like it's the same bloke from the University of Sydney, Rod Cross. so you've probably seen it before.
I like the picture of the difference between laminar flow and turbulent flow in relation to the way it seperates from the sphere at different parts.
Also this snippet seems to suggest that in the magnus force one side is of the laminar flow type, but the page is missing which shows the diagram. (edit: this happens in reverse magnus force........I think :S)
http://books.google.com.au/books?id=vROcxJj4igQC&pg=PA723&lpg=PA723&dq=magnus effect laminar flow&source=bl&ots=XdmE3eCI1m&sig=xuOBsk91BZKtiA4_PjNEG-36Ut8&hl=en&sa=X&ei=7tWYT4zyFaOpiAeF3dXsBQ&ved=0CG4Q6AEwCA#v=onepage&q=magnus effect laminar flow&f=false
http://www.physics.usyd.edu.au/~cross/TRAJECTORIES/Fluidflow Photos.pdf
edit: looks like it's the same bloke from the University of Sydney, Rod Cross. so you've probably seen it before.
I like the picture of the difference between laminar flow and turbulent flow in relation to the way it seperates from the sphere at different parts.
Also this snippet seems to suggest that in the magnus force one side is of the laminar flow type, but the page is missing which shows the diagram. (edit: this happens in reverse magnus force........I think :S)
http://books.google.com.au/books?id=vROcxJj4igQC&pg=PA723&lpg=PA723&dq=magnus effect laminar flow&source=bl&ots=XdmE3eCI1m&sig=xuOBsk91BZKtiA4_PjNEG-36Ut8&hl=en&sa=X&ei=7tWYT4zyFaOpiAeF3dXsBQ&ved=0CG4Q6AEwCA#v=onepage&q=magnus effect laminar flow&f=false
someblokecalleddave
Well-Known Member
Laying in bed last night thinking this through (As you do) I've got a question and a theory that might clarify some of this, later though as I'm off to work now...
Perhaps this is helpful:
http://www.amazon.com/Slazenger-Cri...U4XG/ref=sr_1_7?ie=UTF8&qid=1335440875&sr=8-7
(I've often found that really old balls afford very little grip and make it frustrating to concentrate on other aspects of bowling.)
Theoretically, an overspun legbreak due to its component of sidespin should also drift. I've often observed that my legbreaks drift when the seam angles towards RHBs gully. Also found that scrambled seam produces no drift ( might be relevant)
someblokecalleddave
Well-Known Member
Ooh yes, that chimes with my current research, I'll be posting up my thesis in the next few hours or tomorrow night, but I reckon as far as I'm concerned I may have come up with an explanation that I'm happy with that even the not so bright such as me can get their head round!
This is interesting - swap dimples for rough texture on a worn cricket ball
someblokecalleddave
Well-Known Member
W'Hey the old dude at Sydney Uni has got his act together and put this together - laminar flow AKA Swing, but I suspect also Drift! Grimmett calls drift and swing "Swerve" who coined the term Drift? http://www.youtube.com/watch?src_vi...id=annotation_859181&feature=iv&v=t-3jnOIJg4k
Thoughts on Drift
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. 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 balls 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?
Caveat
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!
This is a stub which is part of a bigger piece on drift - see here http://mpafirsteleven.blogspot.co.uk/2011/11/leg-spin-bowling-drift.html
Damn! I thought I'd got this sussed, but looking at it some of the wind tunnel experiments again, it makes no sense at all! But then I've looked the name of the physicist who conducted the experiment and I can't find anyone of that name associated with Sheffield Uni where the experiment was done.
Thoughts on Drift
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. 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 balls 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?
Caveat
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!
This is a stub which is part of a bigger piece on drift - see here http://mpafirsteleven.blogspot.co.uk/2011/11/leg-spin-bowling-drift.html
Damn! I thought I'd got this sussed, but looking at it some of the wind tunnel experiments again, it makes no sense at all! But then I've looked the name of the physicist who conducted the experiment and I can't find anyone of that name associated with Sheffield Uni where the experiment was done.
someblokecalleddave
Well-Known Member
Cricket
Drift and Swing the same? Simply a ball that change its path in the air due to the laminar flow?
Drift and Swing the same? Simply a ball that change its path in the air due to the laminar flow?