The only way to hook a bowling ball is to impart some amount of axis rotation on it at the point of release.
The smaller the axis rotation imparted is the smaller the hook potential is.
The larger the axis rotation is the greater the hook potential is as well.
You cannot make a ball hook without axis rotation.
Of course there are other things that affect hook like axis tilt, ball speed, launch angle (trajectory), and rev rate just to name the most obvious factors, but in this article I want to disregard all of those and speak only of axis rotation and how it and it alone affects ball motion on the lanes.
If you only read one thing:
When a ball in motion has any amount axis rotation the ball will skid one direction (down the lane) while trying to roll in a different direction (towards the left gutter for a right handed bowler).
When the ball has a lot of axis rotation the ball takes longer to transition through the hook phase from skid to roll.
Because it takes longer to make this transition the ball enters it’s roll phase slightly further down the lane than it would have otherwise. The greater axis rotation causes more friction during the hook phase resulting in a final roll that has slower ball speed and a much greater entry angle to the pocket.
In many cases a ball thrown with a very large amount of axis rotation will skid further down lane but will still hook more aggressively in the back ends resulting in high pocket shots or splits.
Think of it this of it this way, a ball thrown with 45-degrees of axis rotation hits the pocket with an entry angle of 4-degrees. That means during the hook phase friction slowed the ball down while it also decreased its axis of rotation by 41 degrees; this is of course assuming the ball rolled out just before hitting the pocket.
In comparison, a ball thrown with 90 degrees of axis rotation that rolls out just as it enters the pocket at a 6-degree angle of entry would have lost 84 degrees of axis rotation during the same hook phase; that’s more than twice that of the previous example and it’s why it takes longer.
Losing that much energy in the hook phase means that the ball will slow much more as it goes through the break point and although the ball will hit the pocket with a greater entry angle it will also be traveling at a slower speed allowing it deflect more if it were to hit low in the pocket.
If it were to hit high in the pocket you would be more likely to drive straight through the pin deck leaving stoned 9-pins or chopped 3-pins.
Alternatively, if the high degree of axis rotation forced the hook phase to occur too far down the lane for the ball to roll out before getting to the pocket then the ball would still be hooking while it hit the pocket. This would result in a continuation of hook through the pocket, a great place to be in if you were hitting light pocket but not an enviable situation if you are hitting high pocket.
Here is a segment of a video that demonstrates the way a ball would transition from skid to roll if you could only change it’s axis rotation keeping all other variables constant.
Note how the 90-degree axis rotation shot in the video hooks later that the 30 and 60-degree shots but it still enters the pins way too high compared to the others.
You may also be able to tell in the video how the ball enters the pins noticeably faster on the 30-degree shot compared to the 90-degree shot.
Depending on how close to the roll phase your ball is when it hits the pocket this aggressive turn can work to your favor or to your disadvantage. Also it will matter greatly if you are hitting high flush or low pocket too!
One of the most enjoyable scenarios in bowling is when the ball is just barely rolling out as it hits flush pocket or if it is finishing the last of it’s aggressive hook while hitting low pocket. It’s hard to not carry strikes when this is the case.
How the Axis Rotation of a Bowling Ball Relates to Other Factors
During the skid-phase (and early mid-lane read) bowling balls don’t usually have noticeable traction; they are largely skidding over the lane conditioner encountering almost no friction at all. This is why all types of bowling balls don’t hook instantly off your hand.
As the rotating ball skids down the lane it usually finds and reads tiny amounts of friction in the heads and mid-lane. Even if you can’t really perceive the hook phase beginning the friction slowly starts turning the ball’s axis of rotation back in line with it’s trajectory. At the same time the friction also begins changing the ball’s actual path on the lane even before it gets to what is widely referred to as the break point.
A hook is when the balls path changes noticeably from one direction to another and although the ball path will change during the skid phase it won’t really noticeably change until sufficient friction is encountered. This typically occurs at the end of an oil pattern as the ball enters the back-end.
A ball skidding with significant axis rotation will actually be less sensitive to minor friction found in heads and mid lanes but will be more sensitive to significant friction found at the break point as the ball speed slows. Typically the ball will lose speed and axis rotation as it skids over small friction zones before actually hooking significantly further down lane.
Bowling with a larger degree of axis tilt, using pearlized coverstock bowling balls, or throwing with higher ball speeds can also play a role in getting your ball to skid longer before reading the friction.
Every time a ball encounters friction on the lane it’s ball path changes slightly and axis rotation is lost. A ball that has fully lost all axis rotation has “rolled out” and no longer has any additional hook potential.
When bowlers talk about a ball’s energy they are usually talking about how much hook potential the ball has left. This is a combination of axis rotation, axis tilt, ball speed, and rev rate but as any of these decrease hook potential decreases as well.
In fact if a bowling lane was infinitely long axis rotation would always adjust back to zero no matter where it started. Axis tilt would eventually adjust back to zero as well.
For some bowlers ball speed of the hand is greater than rev rate while others have a greater rev rate than ball speed off the hand. Given a long enough lane the ball speed will always adjust to match revs and then ball speed would continue to slow until an eventual full stop. This obviously would take a very long time.
Friction is the primary driver for all of these changes in a ball’s roll.
Friction will cause ball speed and rev rate to eventually match each other.
Friction will cause a ball to lose axis rotation as it transitions from skid to roll.
Friction will also cause a ball traveling with axis tilt to eventually travel with no tilt.
When a ball travels down the lane there are three main phases, the skid, hook, and roll phase. No ball can be truly in the roll phase without having lost all axis rotation and tilt. The friction that it takes to eliminate the axis rotation and tilt also slows the ball down eventually causing revs to match the ball speed. This is when everything has rolled out.
If your axis rotation is especially high it will slide further and turn more abruptly than a ball thrown with less axis rotation.
