THE
STRIKE ZONE / Scott Bailey
Part II: The basic science of bowling ball physics
Hello everyone, and welcome to a new season of fun and excitement! I hope
you all had a wonderful summer and were able to sneak in a few games of
practice to prepare for the upcoming season.
Earlier
this summer, I began a three-part series dealing the basics of bowling
ball physics. The first segment dealt with what most industry experts
consider the most important factor in determining positive ball reaction,
the bowling ball's surface. As I stated in the article, no other aspect of
the ball's construction will impact as significantly on its reaction as
its surface structure and texture.
The
second most influential aspect is the makeup of the ball's interior, what
we call the core design. How the core mass is distributed
throughout the interior of the ball will determine the relative dynamic
characteristics of the ball. Factors such as Radius of Gyration,
Differential, Core Torque, and Track Flare are mainly determined by the
internal core structure. Understanding the definitions of these variables
will greatly enhance your ability to purchase the right ball for a given
ball reaction.
Radius
of Gyration is a measure of
the mass distribution inside the ball. Core designs with the mass located
further from the geometric center of the ball have a higher radius of
gyration, or RG. Conversely, core designs with the mass located closer to
the center of the ball have a lower radius of gyration. Because RG is a
product of moment of inertia, this core factor influences the relative
spin rate of the ball. It also gives the bowler an idea of the relative
break point the ball will have.
Balls
with low RG cores will tend to spin faster and hook earlier than balls
with higher RG readings. Bowlers with faster ball speeds and above average
axis rotation will tend to benefit more from low RG core designs,
especially when bowling on more heavily oiled lane conditions. Conversely,
bowlers with slower ball speed or less axis rotation usually see better
reaction out of high RG core designs. High RG designs also work well when
the lane oil begins to dissipate.
Differential
Radius of Gyration is
defined as the measured difference in RG readings between a bowling ball's
high, low, and intermediate RG axes. This concept sounds a lot more
difficult than it is; please let me explain.
As
stated above, RG is the measure of the distribution of mass inside your
ball. Every bowling ball has three major spin axes: the high RG or
"X" axis, the low RG or "Z" axis, and the intermediate
or "Y" axis. The large locator pin that most high performance
balls have marks the "Z" axis. If you were to measure the RG of
your ball, the lowest reading you would record would be on this axis.
Now,
if you were to draw a line from the pin through the label (CG) to a
specified distance, this would place you very close to the "X"
axis. If you were to measure the RG on this point, you would receive the
highest RG number. The difference between the highest and lowest RG
measurement is the Differential Radius of Gyration.
The
DRG greatly influences the amount of track flare potential your bowling
ball will have. Track Flare is the movement of your ball track due to the
core's precession as it travels down the lane. If you notice several thin
but separate oil rings in your ball track, that is track flare. Track
flare maximizes the friction between your ball and the lane surface, so
the more track flare you have, the earlier and stronger your ball will
hook. If you have trouble achieving strong hooking action, you may need a
ball with higher RG differentials. However, if there never seems to be
enough oil on the lane for you, I would suggest trying a lower RG
differential core design.
Internal
Core Torque also deals with
the mass distribution inside the ball, as well as the internal lever arms
created by the core. Basically, it determines a ball's relative ability to
delay "roll out." A ball with high core torque such as the Black
Thunderstorm will have less roll-out tendency than the Danger Zone, which
is a low torque ball. This does not mean that high torque is better than
low torque. To achieve positive ball reaction, you must have the right
amount of core torque for your style of bowling on your lane conditions.
If
you notice that your ball stops hooking on the back end, causing it to hit
the pins with little power, you may need a core design with higher torque.
Likewise, if your ball never seems to achieve a strong roll, lower torque
cores may work better for you.
With
that said, you are probably wondering how this all affects your buying
decisions. Unlike the surface texture, the core design parameters cannot
be altered once the ball is drilled. Therefore, it is very important to
choose the proper design before you purchase the ball. Your physical game
and the lane conditions on which you participate determine which types of
core designs will work best for you.
To
help facilitate your decision, I have included a chart of bowler types,
lane conditions, and possible core design choices that will work best
together. This chart is a very basic guideline, so it is best to consult
your local IBPSIA pro shop technician. He or she will be of invaluable
help in this area.
Lane
Condition
|
|
Straight
Player
|
|
Power
Player
|
Oily
Heads; Dry Back-ends
|
|
Low
RG; Medium DRG
|
|
Low
RG; Medium DRG
|
Medium
Heads; Dry Back-ends
|
|
Medium
RG; Medium DRG
|
|
High
RG; Low DRG
|
Dry
Heads; Dry Back-ends
|
|
High
RG; Medium DRG
|
|
High
RG; Low DRG
|
Oily
Heads; Oily Back-ends
|
|
Low
RG; High DRG
|
|
Low
RG; High DRG
|
Medium
Heads; Oily Back-ends
|
|
Medium
RG; High DRG
|
|
Medium
RG; Medium DRG
|
Dry
Heads; Oily Back-ends
|
|
High
RG; High DRG
|
|
High
RG; High DRG
|
I also will make available a list of bowling balls with their core design
parameters available to anyone who wishes a copy. If you would like a copy
of this list, please contact me at 703/ 560-BOWL or via E-mail at xzone@erols.com.
Next
month, we will take a look at drill pattern layouts, which I believe are
the most misunderstood aspect of bowling ball dynamics. Too often, bowlers
become so engrossed in choosing the proper drill layout that they forget
that surface and core design will make up 85 percent of the ball's
reaction potential. We will discuss this in great detail, so until then,
play well!
Scott Bailey operates The Strike Zone Professional Bowling Store in
Vienna, Virginia.
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