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 Part  I       Part II       

THE STRIKE ZONE / Scott Bailey

 Part III: The basic science of bowling ball physics

Welcome to the third and last article in "The Basic Science of Bowling Ball Physics" series. If you recall, the first section dealt with the importance of ball surface type and texture. Part II was a brief explanation of core design parameters and how they affect your ball reaction potentials. This combination of ball surface and core design will dictate about 85 percent of a bowling ball's reaction potential, and it offers much insight as to the overall characteristic of your bowling ball.

In Part III, we will discuss the process of drill pattern layouts. Topics to be covered are as follows:

Release Types.

Positive Axis Point (PAP).

Mid-Plane or Vertical Axis Line (VAL).

Preferred Spin Axis (PSA).

High RG Layouts.

Low RG Layouts.

Weight Hole Placement.

Common Myths.


Release Types

     The most important factor that will determine your ball reaction is your physical game. How you release the ball, your ball speed, and the amount of leverage you create will dictate how much of a ball's reaction potential is realized.

For instance, a bowler with high speed and little hand rotation will find it very difficult to achieve large hooking action and strong back-end. Likewise, a bowler with slower ball speed and more hand rotation will tend to have much larger hooking action and stronger back-end hook. This will be true no matter what reactive ball or drill pattern he/she uses.

Every bowler who throws a hook releases the ball with a certain degree of axis rotation. If you release the ball with a straight hand, your axis rotation would be zero degrees, while releasing the ball with your fingers on the side produces a 90-degree axis rotation. Most hook bowlers fall between 20 and 70 degrees of axis rotation.

Generally, the more axis rotation you have, the more your ball will skid in the heads, and the harder it will turn on the back-end. However, this does not mean that more axis rotation is always better. This will be determined by the lane condition on which you compete.

The most important factor
that will determine your ball reaction
is your physical game.

     As most of you already know, the harder you throw the ball, the less it hooks. Very few bowlers, though, understand the importance of consistent ball speed. The speed your ball travels down the lane will directly affect its skid length, back-end potential, and pin carry potential.

Many times I have seen bowlers get pumped up after throwing a few strikes in a row. As the adrenaline flows, the ball speed increases until finally they leave a corner pin on a perceived good shot.

In truth, as the ball speed increased, so did the skid length, which caused the ball to enter the pocket at a different angle, thus causing the corner pin. Once again, please concentrate on maintaining consistent ball speed.

The amount of leverage created during your release will tend to affect the strength of the ball roll through the pins. A bowler blessed with good leverage does not necessarily throw a big hook. I've seen many straight players with above-average leverage, with Earl Anthony being the best example. Earl's ball hooked very little, but carried the pins very well. Likewise, many bowlers with large hooks have poor leverage, greatly reducing their ability to carry the corner pins.

Leverage is created through good leg drive and the ball position at the bottom of the swing. PBA Tour star Walter Ray Williams Jr. is a great example of this. Williams drives very hard into his slide step, positioning his hand powerfully behind the ball. His slight outside-to-inside swing plane promotes a flat angle of attack from the inside, which brings the ball very close to his ankle at the bottom of the swing. All of these factors create strong leverage, even though he is considered more of straight player.


Positive Axis Point

     Every bowler's ball is released on a certain ball track. The easiest way to find your ball track is to locate the oil ring on your ball during practice. This ball track can tell you a lot about how you're releasing the ball on a given day.

More common ball tracks include the high roll, low roll, semi-spinner, and full-spinner. Although not very common today, the full-roller track is still around. For all-around purposes, the best ball track to have today is a low-to-medium roll. Before the advent of reactive cover stocks, the high track was the best. However, with today's ultra-aggressive ball designs, very high tracks can and will tend to hook too early, reducing the ball's hitting power.

Also important is the tilt of your track. Track or axis tilt will determine how easily your ball achieves a roll-out state. More axis tilt will reduce the chances of roll-out but will hinder performance on a heavily-oiled lane surface. Less axis tilt will tend to roll-out more, but will roll stronger on heavier oil.

Having more or less axis tilt is not good or bad. The type of track works better is determined by the lane environment on which you bowl.

One factor that all of these tracks have in common is they produce what is called your Positive Axis Point or PAP. Your PAP is the line that runs through the center of your ball and is perpendicular to your ball track. Like the north and south poles on a globe, your ball spins around this line. Your PAP becomes very important when trying to create drill pattern layouts for different types of ball reaction potentials.

Also important is the mid-plane or vertical axis line (VAL). This line runs through your PAP, perpendicular to the grip mid-line. This will be discussed later in greater detail.


Preferred Spin Axis

     Every contemporary bowling ball has what is known as a Preferred Spin Axis or PSA. Where this PSA is located is determined by the shape, size, and density placement of the ball's core. These factors also will dictate how powerful the PSA is, and how much effect it will have on the ball reaction.

A bowling ball's PSA is the axis through which the ball would like to spin. In layman's terms, a sphere that is rotating around an unstable axis will seek a more stable axis of rotation. The axis the ball seeks is its preferred spin axis. Most often, this is the X axis or high RG axis, which was discussed in last month's article on core design. Bowling balls with traditional three-piece cores or generic two-piece cores exhibit a rather weak PSA. Balls with more dynamic core shapes and densities will tend to have much stronger PSAs. A ball with a strong PSA is not always better than one with a weaker PSA. Which works better for a given bowler is determined by the lane surface and oil patterns.

The position of the PSA in relation to your mid-plane and PAP will determine the shape of the hooking action. There are three basic hook shapes: arc, flip, and hook/stop. Most bowlers like to see their ball react in one of these fashions. Knowing which one you'd like to see will help in the drilling layout process.

I know from experience that most of you will say the flip reaction is what you like to see. However, most of the best bowlers in the world today reach optimum scoring with the hook/stop reaction, la Walter Ray Williams Jr., Tim Criss, Mike Aulby, and Norm Duke.

A good pro shop technician, utilizing knowledge about a specific bowler's physical game, lane conditions, and a ball's axis migration to its PSA, can very accurately predict a bowling ball's reaction potential. The two best examples of this that I know of are Del Warren of AMF and Brian Pursel of Ebonite International. Both of these gentlemen have a gift for laying out the perfect ball for a bowler on a given lane condition. Doing this at their level requires a great deal of knowledge, vast research, and tons of experience.

I would like to think that I am a competent pro shop technician, but I am constantly amazed at their level of skill and knowledge. I owe them both a great deal in helping me learn what I have so far.


Drilling Layouts

     Once your pro shop technician has an understanding of the ball reaction you seek, your Positive Axis Point, and any other pertinent information, he/she can begin to help you choose the right ball. Consumers must understand that a drilling layout can only change the ball reaction within the parameters of that ball.

For instance, a Columbia Boss has an RG value of about 2.47 on its low RG axis with a differential RG of .039. This means that the highest RG value around any axis in the Boss is 2.509, which is still very low.

Therefore, no matter how this ball is drilled, it will not display High RG reaction characteristics. It will never roll, for instance, like a Black Thunderstorm or Ebonite Sea Wolf, regardless of the drill pattern. The Boss is meant to roll early and strong, and there is nothing your pro shop technician can do to change that!

At best, drilling patterns will fine-tune a particular ball reaction, making it slightly more conducive to the lane surface. Drill patterns will not change the inherent characteristics of the ball. Please remember that before purchasing your next ball.

Once you have chosen the right ball, now is the time to consider the different types of layouts. For our purposes, drilling layouts will be classified into three basic categories: high RG layouts, low RG layouts, and leverages. These categories are outlined below.


High RG Layouts

      As a general rule, high RG layouts will tend to have more length through the pines, and a moderate-to-mild back-end reaction. These patterns work well for bowlers with slower speeds, or lane conditions with dry heads and pines.

High RG layouts are characterized by placing the large locator pin farther away from your PAP or closer to your ball track. As I said, this will increase skid length. The back-end hook shape will be controlled by the PSA placement.

If you have slow ball speed, a lesser degree of axis rotation, or if you bowl on lightly-oiled lanes, you probably will like high RG drilling layouts.


Low RG Layouts

     Low RG drill patterns will tend to roll earlier and produce mild-to-moderate back-end reactions. Bowlers with faster ball speeds, strong axis rotation, or those bowling on heavy-head and pine oil with dry back-ends, will benefit most from low RG layouts. Because these patterns roll earlier and are fairly stable, they are easier to control on local "house" oil conditions.

Once again, you can change the hook shape by placing the PSA in different locations relative to your PAP and mid-plane.


Leverage Layouts

     Most bowlers who come to me with a specific layout request most often ask for a leverage pattern. I assume this is due to the myth that leverage layouts will skid longer and flip harder on the back-end. This is definitely not true! Leverage patterns do have the most potential for overall hooking action, but they will not go longer than the high RG patterns listed above.

In fact, by leveraging a strong core design, you run a good risk of making the ball hook too early due to increased friction from larger amounts of track flare. If the ball hooks too early, you will definitely lose back-end reaction, not gain it. Leverage patterns are strictly for heavy-head and pine oil with carry-down.

Straighter players can use leverage patterns on drier conditions, but I still don't recommend it. The simple fact is, with the super high friction cover stocks on bowling balls today, if you are unable to hook the ball, then chances are there is some problem in your physical game. If this is the case, you are better off spending your money on lessons than buying a new high-performance bowling ball.

     That being the case, there are situations where leverage patterns work very well. If you are trying to create more area and "open up" an oily lane, a leverage pattern certainly will help you. Also, if you bowl in tournaments out of this area, you probably should carry one or two balls with some type of leverage pattern, just in case you hit a heavy-oil lane condition. As with the other layouts above, the hook shape is controlled with the PSA.


Weight Hole Placement

     Some of the patterns listed in this article will require balance holes to meet ABC/WIBC specifications for positive side and finger weight. While it is true that drilling a balance hole changes the static balance of the ball, this is not the reason for the ball reaction change. Placing a balance hole in the ball changes the RG values around your PAP.

For example, placing a balance hole in the ball will probably lower the RG value around the spin axis or PAP. Therefore, placing a balance hole in the ball will make it spin slightly faster and roll slightly earlier than the same ball without a balance hole. Small holes drilled deep will lower the RG values less than larger holes drilled shallow.

The balance hole also changes the position of the PSA. This fact allows us to slightly increase or decrease track flare potential in the ball, depending on the balance hole position in relation to your PAP.

It is important to remember that balance hole positions are very minor in their influence on your ball reaction. They are simply a process by which your pro shop technician can fine-tune your bowling ball.


Common Myths

     There are so many misconceptions about bowling and bowling balls that I cannot begin to cover them all in this article. I have, however, picked out a few that I believe to be important enough to discuss here:


Pin-out balls are better than "pin-in" balls.

For several years now, many bowlers were incorrectly told that balls with locator pins farther away from the CG are better. This is simply not true. The bowler's physical game and the lane conditions ultimately determine which pin location is better. Pin-in balls will tend to spin faster and be more controllable on the back-end. Pin-out balls will spin slower and react more violently on the back-end. Which is better for your game depends on the environment in which you participate.


Certain high-performance balls carry better than others.

There are many factors that determine your carry percentage. The most important of which is pocket entry angle. The simple fact is good pin carry is as much about proper alignment to the break point as it is about the bowling ball.

Think about this: Every ball on the market today has produced a 300 game or 800 series for someone. If your ball is not carrying the pins for you, chances are you're using it at the wrong time and in the wrong environment.


Reactive balls hit too hard.

A bowling ball can never hit too hard-it can only hit at the wrong angle. During the days of plastic and rubber balls, a solid pocket shot was about the 17-1/2 board. Today, because reactive balls have more friction and less deflection, the solid pocket shot is closer to the 16 board. Therefore, the pocket has moved slightly to the right. The high-carry percentage shot back then was "high pocket"; today it's the light-pocket shot.

The next time you rip the 5-pin into the 7-pin or send a "messenger" headpin across the lane to take out the 10-pin, ask yourself, Do I really want my ball to hit weaker?


There you have it, folks, a three-part crash course in the basics of ball dynamics. I have to tell you, however, that this series just scratches the surface. Every ball manufacturer has any number of brilliant engineers and chemists devoted to optimizing the performance of your bowling ball. New discoveries are made each day, so things will only get better.

Of course, all the technology in the world will not turn a bad bowler into a good one. It is incumbent upon you to prepare yourself properly to take advantage of this equipment revolution. Seek out a qualified instructor, practice hard, and devote yourself to improving your game. Then find a pro shop technician that you can trust-one who can give you a solid hand fit and who understands the complexities of today's bowling environment. Only then will you achieve optimum performance.



Arc Reaction
- An arc ball reaction is a smooth and continuous hooking action.

Axis Rotation - Axis rotation is the amount of side turn you put on the ball. It is measured in degrees, starting at zero, which is a straight ball.

Axis Tilt - Axis tilt is the amount of vertical tilt associated with your axis point.

Balance Hole - A fourth hole added to your ball to make it legal under ABC regulations. A balance hole can also be used to fine-tune a particular ball.

Center Line - The line that runs between your finger holes and through the center of your thumb hole.

CG - The center of gravity of your bowling ball. The point on your ball that designates the exact static center of the ball. It is usually marked with a small punch mark near the label of the ball.

DRG - The differential radius of gyration, which is found by measuring the difference between the low and high RG axes in the ball. DRG is a product of the mass distribution inside your ball and dictates the amount of track flare potential in your ball.

Dynamic Balance - The balance of your bowling ball while in motion (Mass x Distance2).

Flip Reaction - A ball reaction style with a very sharp hooking action on the back-end.

Hook/Stop Reaction - A very effective hook style when used on the right lane conditions. The bowling ball makes one distinct move towards the pocket then rolls in a strong end-over-end manner.

House Lane Condition - A type of lane condition used in many bowling centers for their leagues. It usually connotes heavy oil in the middle of the lane, with dry outside boards and back-ends. A very high-scoring oil condition for the average bowler.

Mid-Plane - A line running vertically through your PAP that is perpendicular to the grip mid-line. The mid-plane and the vertical axis line are the same th

Mid-Line - A line running horizontally through the center of your grip, perpendicular to the center line.

PAP (Positive Axis Point) - The axis line that your ball spins around, based on your release. Everyone's PAP is slightly different. The PAP is very important when using exotic drill patterns.

PSA (Preferred Spin Axis) - The axis line that your ball prefers to spin around, based on the interior dynamics of the core. This spin axis is usually the high RG axis.

RG (Radius of Gyration) - RG is a product of the mass distribution inside the ball. It will determine the effective spin rate of the ball. Low RG balls have their mass located closer to the center of the ball. High RG cores have their mass located farther from the center of the ball.

Static Balance - The balance of a bowling ball while at rest (Mass x Distance = Force).

Track Flare - The movement of the ball track caused by an unstable axis of rotation. This is evidenced by the multiple oil rings on your ball after the delivery.

X-Axis - The highest RG spin axis on a ball. Usually the "Preferred Spin Axis."

Y-Axis - The intermediate spin axis on a ball. Located 6" from the X and Z axis.

Z-Axis - The lowest RG spin axis on a ball. It is usually marked by a large locator pin.

Scott Bailey operates The Strike Zone Professional Bowling Store in Vienna . He can be reached via E-mail at




 Part  I       Part II       Part III