Styles

[Pinboy]

There are different ways of delivering a bowling ball. The simplest way is maybe in a straight line, but this isn't really effective. Styles that are more effective than the 'straight ball' style are styles which involve letting the ball hook. Styles like these are the 'stroker' style or the 'cranker' style. Another effective style, which doesn't involve hook actually, is the 'spinner' style and is mostly very popular in Asia. The 'stroker', 'cranker' and 'spinner' styles will be discussed below.

[Pinboy]

The 'stroker' style is the classic bowling style. A lot of bowlers will first learn this style before they adopt another style. In this way they will have a good basis for their further bowling career.
A stroker has a graceful approach and tends towards a 'perfect' timing. His 'push away' is exactly at the same time that he is putting his starting foot forward. The bowler's shoulders stay closed, pointing square towards his target. He has a normal backswing with a straight arm, which isn't as high as the backswing of a cranker. The ball arrives in time with the bowlers slide and his shoulders are square towards his target.
This creates a moderate leverage for a good and controllable ball reaction. This also means that the hook and revs of a stroker are lesser than that of a cranker. He doesn't use a lot of muscle at the delivery of the bowling ball, he just let the ball swing and do all the work.
You will mostly find a 'semi-roller' ball track on the bowling ball of a stroker. This track is just beside the thumb and the fingers, being closer to the thumb than to the fingers. Also if the lanes are oiled, you will find some flare on the bowling ball, but not as much as on a bowling ball of a cranker.
A stroker is a better aim than a cranker and is also more consistent. In the long run the stroker will win from a cranker, due to the fact that he can better adjust to changing (becoming dry) lanes. But if there is a huge block lying on the bowling lane, the cranker has more advantage of this than a stroker due to his surplus of hook and revs.

[Pinboy]

The 'cranker' style is a more modern bowling style. This style is used by bowlers which nature it is to open up their shoulders and use power and muscle to deliver the ball.
A cranker will stand deep inside on the approach and he will have a 'late' timing, in which a cranker will use a lot of muscle. The bowler's shoulders are thrown open to accommodate his high backswing. His wrist will be cranked/cupped and his elbow bent to keep his hand behind and under the bowling ball, so that he will be able to lift the bowling ball at the end to create a lot of hook and revs. His slide gets to the foul line before the bowling ball gets there and the cranker will (almost) be standing still at the foul line before delivering the ball (this is also known as 'plant-and-pull'). His shoulders will still be open at this time, due to the high backswing. This results into a strong push towards the finish before delivering the ball.
This creates high leverage for a very good, but less controllable, ball reaction. A cranker throws the bowling ball towards the gutter and into the 'space'. He will play the ball from the heavy oil towards the dry parts of the lane, where it will be screaming back towards the headpin. The ball will have a huge hook and lots of revs, and due to this a cranker is able to play in heavy oil.
The track on the bowling ball of a cranker will also often be beside the thumb and fingers, but will be closer to the fingers than to the thumb. Furthermore you will find a lot of flare on his bowling ball, more than you will see on a stroker's ball.
A cranker is less consistent than a stroker and needs more 'space' on the lane to play his game. But when this 'space' is available to him, a cranker will be very hard to beat, due to his surplus on hook and mostly revs.

[Pinboy]

Another style, which is totally different than the 'stroker' or 'cranker' style, is the 'spinner' style. This style is very popular in Asia, where a lot of bowlers use this style. They use this style to combat really hard conditions. The approach of a spinner doesn't really differ much from that of a stroker. He just lets the bowling ball swing, where the timing is perhaps a little bit 'late'. The most important part in which this style really differ from the others, is the release. This release is called the 'helicopter' or 'UFO' release and a spinner performs this release with relatively light weight bowling balls (10-12 lbs). If he uses heavier bowling balls, the technique can hardly be executed and he becomes even more injury prone than he already is.
A spinner rotates his wrist around the bowling ball during his release, causing the bowling ball to spin down the lane. The axis will be tilted high into the air and there are lots of 'horizontal' revs on the ball. The ball will travel down the lane in a straight line, regardless of the oil pattern.
The ball track on the bowling ball is a typical 'spinner' ball track. The track is very small and far away from both the thumb and the fingers. This results in a small part of the ball contacting the bowling lane and thus little friction (making it easier to play on different conditions).
The high degree of axis tilt and the large amount of revolutions of the bowling ball will create a huge mix of impact on the pins. This will make this style very strike competitive with the other styles. A spinner only needs to hit the headpin, resulting in a 'strange' domino effect on the pins in which the bowling ball will walk down one of the two 'clothes lines' (due to the deflection of the light-weight bowling ball).