I just wanted to throw out a theory that has been forming in my mind for some time. Hopefully this is of interest of itself, but also has profound implications for how you grip the ball and go about trying to improve your action to get maximum revs. I hope it won't be too wordy or physics-y for anyone 
Imagine a drill bit in an electric drill, that is secured tightly with the chuck.
When you switch on the drill, the barrel and the drill bit will (if properly secured) rotate at the same rate, the same angular velocity, because they are at rest with one another.
Now imagine pressing a button that causes the chuck to suddenly release. The drill bit will no longer be powered, but will initially be spinning at the same rate as before, i.e. the same rate as the barrel, and no faster.
Exactly the same thing applies to spin bowling - if you are gripping the ball tightly enough to prevent slippage, then as you rotate your arm the ball will also rotate in the air at the same rate.
Thing is, I don't know how fast you can rotate your arm with a cricket ball in your hand, (obviously you can't do a whole revolution: it is still valid to talk in terms of angular velocity for a motion that stops after only going through 180 degrees), but I reckon it's pretty slow - 3-4 revs per second at most.
Yet a hard-spun cricket ball is going much, much faster than that - tens of revs per second. So, something else is causing most of the spin.
I believe that in cricket you are not spinning the ball by rotating your arm the way a drill rotates a drill bit, you are spinning the ball by slicing down one side of the ball the way a tennis player slices down the side of a tennis ball.
Now, spin is created through a rotary force (called a couple or a torque). A torque is generated when a force that doesn't act through the centre of mass is applied to an object (so a pace bowler *does* apply a force through the centre of mass, i.e. "behind" the ball , to generate forward, linear, momentum). Cricket ball spin, I believe, is generated mostly by your fingers slicing down one side of the ball and holding that side back, almost, as it is projected forwards by your arm action.
The overall amount of spin is the product of two things: how strong a torque you are generating, and how long that torque is in operation [a car accelerates much faster than a TGV, but the TGV can reach 180 mph by accelerating slowly for much longer].
So to rip a leggie (or an offie), you need arm speed, but also to keep in partial contact with the ball for as long as possible after you start to release it. So if you grip the ball really tighly and release very suddenly, you are effectively acting like the drill releasing the drill bit in the analogy above: you are constraining the ball to spin no faster than your arm can rotate.
For all the talk of flipping the wrist and so on, I reckon the main reason finger spinners get fewer revs is that (a) the ball is wedged between the fingers rather than gripped, so the ball is more or less abruptly snatched out of the fingers by the sweep of the arm, and (b) the contact is restricted to the side of one of the fingers, whereas a leggie can run the whole of the length of the 3rd finger down the side of the ball as it comes out.
I started out myself bowling donkey drop googlies, and used to be able to get an absolutely ridiculous amount of turn (thing yorker a foot outside off, missing leg by over a foot). What I was often conscious of when bowling well (and still am) was the feeling of my fingers "tickling" down the ball as it came out of the hand.
It's quite an enlightening exercise to just cup the ball in the palm of the hand, without gripping with the fingers, and underarm it a few feet allowing it to roll out of the palm. You can get appreciable movement, which implies that on those days when you're bowling and it doesn't move at all, something's badly wrong with the action....
Any thoughts, gentlemen?
Imagine a drill bit in an electric drill, that is secured tightly with the chuck.
When you switch on the drill, the barrel and the drill bit will (if properly secured) rotate at the same rate, the same angular velocity, because they are at rest with one another.
Now imagine pressing a button that causes the chuck to suddenly release. The drill bit will no longer be powered, but will initially be spinning at the same rate as before, i.e. the same rate as the barrel, and no faster.
Exactly the same thing applies to spin bowling - if you are gripping the ball tightly enough to prevent slippage, then as you rotate your arm the ball will also rotate in the air at the same rate.
Thing is, I don't know how fast you can rotate your arm with a cricket ball in your hand, (obviously you can't do a whole revolution: it is still valid to talk in terms of angular velocity for a motion that stops after only going through 180 degrees), but I reckon it's pretty slow - 3-4 revs per second at most.
Yet a hard-spun cricket ball is going much, much faster than that - tens of revs per second. So, something else is causing most of the spin.
I believe that in cricket you are not spinning the ball by rotating your arm the way a drill rotates a drill bit, you are spinning the ball by slicing down one side of the ball the way a tennis player slices down the side of a tennis ball.
Now, spin is created through a rotary force (called a couple or a torque). A torque is generated when a force that doesn't act through the centre of mass is applied to an object (so a pace bowler *does* apply a force through the centre of mass, i.e. "behind" the ball , to generate forward, linear, momentum). Cricket ball spin, I believe, is generated mostly by your fingers slicing down one side of the ball and holding that side back, almost, as it is projected forwards by your arm action.
The overall amount of spin is the product of two things: how strong a torque you are generating, and how long that torque is in operation [a car accelerates much faster than a TGV, but the TGV can reach 180 mph by accelerating slowly for much longer].
So to rip a leggie (or an offie), you need arm speed, but also to keep in partial contact with the ball for as long as possible after you start to release it. So if you grip the ball really tighly and release very suddenly, you are effectively acting like the drill releasing the drill bit in the analogy above: you are constraining the ball to spin no faster than your arm can rotate.
For all the talk of flipping the wrist and so on, I reckon the main reason finger spinners get fewer revs is that (a) the ball is wedged between the fingers rather than gripped, so the ball is more or less abruptly snatched out of the fingers by the sweep of the arm, and (b) the contact is restricted to the side of one of the fingers, whereas a leggie can run the whole of the length of the 3rd finger down the side of the ball as it comes out.
I started out myself bowling donkey drop googlies, and used to be able to get an absolutely ridiculous amount of turn (thing yorker a foot outside off, missing leg by over a foot). What I was often conscious of when bowling well (and still am) was the feeling of my fingers "tickling" down the ball as it came out of the hand.
It's quite an enlightening exercise to just cup the ball in the palm of the hand, without gripping with the fingers, and underarm it a few feet allowing it to roll out of the palm. You can get appreciable movement, which implies that on those days when you're bowling and it doesn't move at all, something's badly wrong with the action....
Any thoughts, gentlemen?
