The_Effect_Of_Softball_Properties_On_Batted_Ball_Distance (2024)

Introduction

In a previous article [1] we discussed the how the properties of a softballeffect the batted ball speed. It was shown that a softball’s hardness,measured as compression, was the dominant factor with respect to battedball speed. The higher the compression the higher the batted ball speed.

But what about distance? As it turns out correlating distance with ballproperties is a very complex problem. Because a homerun in softball travels300-400 feet through the air the aerodynamic properties of the ball becomevery important. The major aerodynamic properties of softballs that canaffect the ball’s flight include; weight, size, seam height, and ball spin.

The weight of a softball can be important because heavier balls areless effected by drag forces (resistance moving through the air) and thereforewill travel farther than a lighter ball given the same initial speed, angle,grip, etc.

Size of the softball is important because drag forces are directly proportionalto the cross sectional surface area of the ball. Therefore a larger ballwill not travel as far as a smaller ball, with all else being equal.

Seam height can be very important with respect to the aerodynamics ofa softball. Without going into too much detail the seams create turbulenceas the ball moves through the air, and this allows the ball to move throughthe air easier and therefore farther. The dimples on a golfball, for example,have the same affect. However, it is unclear at what point does increasingthe seam height have an adverse effect by effectively increasing the surfacearea of the ball as well as producing turbulence.

Ball spin, i.e. backspin, has a significant effect on batted ball distance.The more backspin a softball has the farther the ball will travel.

Two measured quantities, compression and coefficient of restitution(COR) currently are used to characterize softballs. Softball compressionis 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 bouncingoff of a rigid wall compared to the ball's incoming speed. That is, ifthe incoming ball speed is 60 mph and the rebound ball speed is 30 mphthe COR = 30/60 = 0.50.

Measuring the actual performance of a ball is more difficult. The mostdirect and reproducible method of quantifying performance is measuringBatted Ball Speed (BBS) with a radar gun.

In this study three different hitters, with different abilities, swingingtwo state-of-the-art 30 oz. multi-walled bats with six balls with varyingproperties from 2 manufactures were used to provide both BBSs and battedball distances. These measurements were then used to quantify the effectof ball properties on distance.

Experimental

Ball compression testing was performed according to the proposed ASTMTest Method for "Compression-Displacement of Baseballs and Softballs" [2].All compression testing was performed on an Instron Model 1125 screw-drivenload frame. A crosshead speed of 1"/min was used. The load at 0.25" deflectionwas measured using a fully reversible T/C load cell with a maximum fullscale range of 1000 lbs. Deflection was measured directly from crossheadmovement and checked manually using a dial gauge. The load was measuredat a ball deflection of 0.25" to within +/- 0.002". Testing was performedat 72oF and 45% relative humidity. The balls were conditioned (stored inthe test lab) for at least 24 hours prior to testing.

The CORs listed in this study were the stated CORs on the balls. TheCOR test is an ASTM Test procedure [3] that is intended to standardizea method of measuring the COR of baseballs and softballs. The ASTM CORtest is a repeatable and uniform testing procedure based on ball speedmeasurements before and after impact with either a wood or metal surface.However, the ASTM COR test does not address all safety concerns and statesthe following: “It is the responsibility of the user of this standard toestablish appropriate safety and health practices and determine the applicabilityof regulatory limitations prior to use”. This means that the softball associationsare ultimately responsible for controlling the safety of the balls usedin the sport of softball.

A Jugs professional pitching machine was used to pitch the balls forthe BBS tests. The machine provided consistent pitch speeds (measured viaradar gun) in the 16-22 mph range. These tests were conducted indoors inorder to provide a controlled and consistent testing environment.

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 accurateto within ± 0.5 mph. The gun is used to record the batted-ball speedright after impacting a ball and was placed in the same position for allmeasurements.

The distance measurements were taken using a Bushnell® Laser Rangefinder (model #20-0400?, which is accurate to within 3 feet. Only ballswith “ideal” trajectories, i.e. those producing the longest hits, wererecorded. The average distances for each ball-bat-batter combination werea result of averaging the top 5 distances for each combination.

The bats used were chosen because they are extremely popular Multi-walled2002 models readily available. Both bats were ASA and USSSA certified.The balls used were chosen to encompass a range of compressions, 375 –553 PQI, and CORs, 0.40 – 0.47, and were from 2 different manufactures.

Results

Table 1 summarizes the distance results for all three batters, with6 different balls, using 2 different bats. The average (AVE) for each columnis shown at the bottom of the table. In addition the average for each ballis shown in the last 3 columns of the table for all distances and for eachbat. Note that all the average distances are over 300’.

Before discussing the different balls a few general conclusions canbe drawn from the distance results. Batter 1 hit the ball farther thanbatter 2 who in turn hit the ball slightly farther than batter 3. Also,for each individual batter and for the average of each bat, Bat 2 hit theball farther than Bat 1.

As for the individual balls there does not appear to be any correlationbetween compression or COR with respect to batted ball distance. However,the balls from manufacturer-1 had higher average distances than the ballsfrom manufacturer-2. Plausible reasons for this will be presented later.

Table 2 summarizes the batted ball speeds (BBSs) for all the batter-bat-ballcombinations. Similarly to the distance results player 1 had higher BBSsthan player 2 who had higher BBSs than player 3. However unlike distance,the average BBSs for each individual batter and for the average of eachbat, the BBSs for bat 1 were higher than for bat 2. This was unexpectedbecause this indicates that higher BBS did not correlate with longer distancesfrom bat to bat.

With the exception of the 0.47/375 ball, BBS correlates with compressionfairly closely. That is, the higher the compression the higher the battedball speed. This of course is the expected result, the harder the ballthe more the bat walls can flex and return energy to the ball. However,as shown from the distance numbers no such correlation exists for distanceand compression or COR. Table 3 was developed to help clarify this phenomenon.

In Table 3 the ratio of distance to BBS was calculated and 3 was subtractedfrom this ratio for each batter-bat-ball condition to help evaluate theresults obtained for different batters, bats, and balls, Dist./BBS –3 (D/Bratio).

Interestingly batter 3 had the highest D/B ratio followed by batter1, both of which were significantly greater than those for batter 2. Themost probable reason for the difference was the grips the batters used.Both player 1 and 3 use the Reverse Rotation grip while batter 2 used theoverlap grip. The Reverse Rotation grip appears to be performing as itsname implies and producing greater backspin than the overlap grip, whichin turn increased the D/B ratio.

For each individual batter and for the average of each bat, Bat 2 hada higher D/B ratio than Bat 1. This indicates that there is some fundamentaldifference between the bats. Again the most probable difference is theability to produce backspin. This implies that bat 2 had less ball slippagethan bat 1 and because there was less ball slippage with bat 2 greaterbackspin was produced, which increased the D/B ratio.

As for the individual balls the balls from manufacturer-2 had much higherD/B ratios than the balls from manufacture-1. Therefore it appears thatthe aerodynamics are different based on the manufacturer.

The balls from the different manufacturers can also be compared strictlyon a distance basis. The average distance for the two balls from ball manufacturer-1was 334.9 ft, while for the four balls from manufacturer-2 the averagedistance was 318.0 ft. The balls from manufacturer-1 out distanced thosefrom manufacturer-2 by 5.3%. While for BBS the averages were 91.0 and 89.4mph for manufacturer-1 and manufacturer-2 respectively. Giving an increaseof only 1.8%. This illustrates that the difference in distances obtainedfrom the different manufacturers was most likely due to some differencein the aerodynamic properties of the balls.

Table 4 lists some of the pertinent softball properties that could effectthe ball’s aerodynamics. Note that seam heights are not shown in Table4 because no significant difference was noted in seam heights for theseballs.

The resistance due to drag forces is proportional to the cross sectionalsurface area of the ball. The higher the cross sectional area the moredrag forces effect the ball and with all else being equal the ball withhigher cross sectional area will not fly as far a ball with lower crosssectional area. Both the balls from manufacturer-2 have higher cross sectionalareas than the balls from manufacturer-1. If all else were equal this wouldimply that the balls from manufacture-1 should have farther distances thanthose of manufacture-2. However, this was not the case and all else isnot equal.

The effect drag forces have on a softball are proportional to the weightof the ball. The heavier the ball the less affect drag forces have on theflight of the ball. This can be easily demonstrated by throwing both aplastic practice golfball and an actual golfball. Because the plastic golfballis so light compared to the actual golfball it will not fly nearly as faras the actual golfball. The weights for the balls from manufacturer-2 aregreater than those for manufacturer-1, probably due to the larger sizeof the balls from manufacture-2. This would indicate that with all elsebeing equal the balls from manufacturer-2 should fly farther than the ballsfrom manufacturer-1, as was seen. However, both the cross sectional areaand weight need to be lumped together in order to accurately determinetheir affect. Since both the effect of area and weight are proportionalto the effect of the drag forces these properties can be combined in toa single property, Area/Weight ratio.

For the Area/Weight ratios shown in Table 4, the lower the ratio thefarther the ball should travel. However as shown the Area/Weight ratiosare fairly close and do not correlate with the D/B ratios. This is especiallytrue for the 0.44/511 softball that has an Area/Weight ratio very nearthe overall average and a D/B ration much greater than all Manufacturer-1’ssoftballs. Therefore it appears that the difference in distances betweenthe balls is not due to size/weight differences.

Ruling out size, weight, and seam height leaves backspin as the mostlikely cause for the increased D/B ratios of manufacturer-2’s balls. Whatcould allow certain balls to produce more backspin than other balls? Twopossibilities are slippage between the bat and the ball or slippage betweenthe cover and the polycore of the ball. Visual inspection of the ballsfrom manufacturer-1 indicated there was some wrinkling of the covers. Thismay indicate that there was some slippage between the cover and the polycoreof the ball for manufacturer-1’s balls during hitting with would accountfor the lower D/B ratios. No such wrinkling was evident with manufacturer-2’sballs. However, this is far from definitive evidence and it may very wellbe that the covers of manufacturer-1’s balls slipped more on the bats thanmanufacturer-2’s balls.

These results prove that balls and bats can be produced and chosen thatminimize the danger to pitchers by having safe BBSs, while maintaininggood distances for the homerun hitters.

Conclusions

• Batted ball distances did not correlate with either softball compressionor COR.
• Batted ball speeds did correlate fairly well with softball compression.The harder the ball the higher the batted ball speed.
• Backspin is a very important aerodynamic factor affecting the flightof softballs. The more backspin the farther the softball travels.
• The type or bounding of the cover affects the backspin produced.The less a cover slips on the bat or the polycore the more backspin produced.
• The surface of the bat is important for providing backspin to thesoftball. Again the less the ball slips on the surface of the bat the morebackspin produced.
• The Reverse Rotation grip is superior for providing backspin thanthe overlap grip.
• Balls and bats can be produced that minimize the danger to pitcherswhile maintaining good distances for the homerun hitters.

References

1. “The Effect of Softball Compression and Coefficient of Restitutionon Batted Ball Speed,” Michael V. Ciocco and Mark McDowell, Senior SoftballMagazine, July, 2002.
2. Standard Test Method for Compression-Displacement of baseballs andSoftballs, ASTM Designation F 1888-98.
3. Standard Test Method for Measuring the Coefficient of Restitution(COR) of Baseballs and Softballs, ASTM Designation F 1887-98