**Introduction**
**The performance of different softballs is a much discussed and debated
subject in men’s slowpitch softball. Power hitters want to know which ball
will maximize distance. While league directors, tournament directors, and
associations try to balance performance with safety. Two measured quantities,
compression and coefficient of restitution (COR) currently are used to
characterize softballs. Softball compression is a measure of the force
(lbs) required to compress the ball 0.25 inches. Softball compression is
commonly reported as PQI (lbs/0.25 inch compression). The COR is defined
as the ratio of the rebound speed of the ball bouncing off of a rigid wall
compared to the ball's incoming speed. That is, if the incoming ball speed
is 60 mph and the rebound ball speed is 30 mph the COR = 30/60 = 0.50.**

**Measuring the actual performance of a ball is more difficult. The
most direct and reproducible method of quantifying performance is measuring
Batted Ball Speed (BBS) with a radar gun.**

**In a recent article, “On The Ball”, in Softball Magazine[1] the effects
of softball compression and coefficient of restitution (COR) on batted
ball speed were presented. There are two important points about this article
need to be discussed. First, the article states that the BBSs and distances
were calculated. Secondly the article states that the calculations for
BBS and distance were based on an “A” player with a 70 mph bat speed.**
**With respect to the first point, the mechanics of batting and bat
– ball collision cannot be perfectly modeled via calculations because of
inconsistent data on angle of deflection, inconsistent ball compression
values, ball cover slippage properties, and varying MOI values for each
bat model. Therefore, actual measured values would provide more accurate
results. As for the second point, measured bat speeds for “A” level players
are typically in the 85 – 100 mph range based on our testing over the past
6 years. This further complicates the use of “calculations” in any attempt
to quantify effects of PQI and COR on BBS.**

**In order to remove the generalizations introduced by using “calculations”,
and allow for realistic swing speeds, a study was undertaken in order to
provide real world data. This real world data was then used in determining
the effect of PQI and COR on BBS. In no way is this study meant to be an
attack on the “On The Ball” article. Instead it is hoped that by employing
measured BBSs a better understanding of actual effects of PQI and COR on
performance can be determined. And this in turn would allow players, directors,
and associations to make a better-informed decision when deciding which
ball to use.**

**In this study, a typical “A” level player, swinging two state-of-the-art
30 oz. Multi-walled bats with balls of various PQI and COR values, was
used to provide actual BBSs. These BBSs were then used to quantify the
effect of PQI and COR on ball performance.**

**The CORs listed in this study were the stated CORs on the balls.
The COR test is an ASTM Test procedure that is intended to standardize
a method of measuring the COR of baseballs and softballs. The ASTM COR
test is a repeatable and uniform testing procedure based on ball speed
measurements before and after impact with either a wood or metal surface.
However, the ASTM COR test does not address all safety concerns and states
the following: “It is the responsibility of the user of this standard to
establish appropriate safety and health practices and determine the applicability
of regulatory limitations prior to use”. This means that the softball associations
are ultimately responsible for controlling the safety of the balls used
in the sport of softball.**

**Swing speed was measured using an ATEC Sports Speed Trainer 2000
bat speed meter that measures the average swing speed at the end of a bat.
Note that depending on the swing mechanics of a player and the location
of the sweet spot on the bat the speed of the sweet spot will be 85 to
90% of the end-of-bat speed.**

**A Jugs professional pitching machine was used to pitch the balls.
The machine provided consistent pitch speeds (measured via radar gun) in
the 16-22 mph range.**

**The radar gun used was a Jugs Professional Cordless MPH RADAR GUN
(model # R1000). This device is used to measure batted-ball speed and is
accurate to within ± 0.5 mph. The gun is used to record the batted-ball
speed right after impacting a ball and was placed in the same position
for all measurements.**

**The batter hit each ball at least 9 times in order to provide 5 “good”
measurements. Good measurements were defined as line drives that had a
low trajectory and did not hit the top of the net.**

**The bats used were chosen because they are extremely popular Multi-walled
2002 models readily available. Both bats were ASA certified. The balls
used were chosen to encompass a range of compressions (411 – 553 PQI) and
CORs (0.40 – 0.47).**

Ball - COR/PQI |
||||||

Bat |
Swing
Speed |
0.47/533 |
0.47/474 |
0.44/511 |
0.40/533 |
0.40/411 |

1 |
88 |
95.6 |
91.8 |
92.8 |
98.8 |
94.0 |

2 |
87 |
93.0 |
90.4 |
92.4 |
96.0 |
92.2 |

**It should be noted that softball compressions vary from about 200
to 600 PQI, a 400 PQI difference, for different balls. The corresponding
change in BBS, for a 400 PQI difference, could be as much as 17 mph, correlating
to a distance change of about 55 feet. This is most definitely a significant
effect.**

**In order to accurately determine the effect of COR the results first
need to be normalized to the same PQI. Adjusting the batted ball speeds
using the results from the effect of PQI on BBS can do this. Table 2 summarizes
the adjusted BBSs, adjusted to have a standard PQI of 500. Performing statistical
analysis on this data yields the effect on COR on BBS. For an increase
of 0.07 in COR (0.40 to 0.47 COR) the BBS decreases 3.57 mph (±
0.28 mph). This result was opposite of what was expected. Again from
a previous study[2] this correlates to an approximate decrease in distance
of 11-12 feet.**

Ball - COR/PQI(500) |
||||||

Bat |
Swing
Speed |
0.47/533 |
0.47/474 |
0.44/511 |
0.40/533 |
0.40/411 |

1 |
88 |
94.2 |
92.9 |
92.3 |
96.6 |
97.8 |

2 |
87 |
91.6 |
91.5 |
91.9 |
93.8 |
96.0 |

**There are a couple of possible explanations for this surprising result.
It may be that the actual COR of the ball at real impact speeds (100+ mph,
80+ mph bat plus a 20+ mph pitched ball) may be very different from the
ball’s stated COR. The COR test uses an impact speed of 60 mph, much lower
than the actual impact velocities of 100+ mph and it has been shown that
COR is a strong function of impact speed[3]. Also while the cover of the
softball has no real effect on its compression value, cover slippage has
a significant effect on batted-ball performance. The better the cover is
bonded to the ball, the less cover slippage, the better it will perform.**

**Another possible explanation for the relationship of decreasing BBS
with increasing COR may be that the compression measurements are conducted
at somewhat lower forces than are actually present in a bat-ball collision.
The force required to change the motion of a 6.5 oz. ball pitched at about
20 mph to a 90 mph hit ball in the 1/1000 of a second of bat-ball contact
is over 2000 lbs. And since the compression measurements resulted in compressions
of between 400 and 600 PQI it follows that the balls may perform differently
at the higher actual forces.**

**It is clear that the biggest safety factor involved in the game of
softball today is the ball. High-Compression balls have no place
in the game of softball at any level. The BPF 1.20 and ASA 2000 testing
methods have capped the performance of bats and while both tests have their
flaws, they at least keep the performance of bats at a reasonable level.**

*** Softball COR was found to have a slight negative effect on
batted ball speed. Increasing the COR from 0.40 to 0.47 actually resulted
in a decrease in batted ball speed of over 3 mph and correlated to a decrease
in distance of about 11 feet.**