Regulating the Performance of Baseball Bats

04/19/23 Regulating the Performace of Baseball Bats

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Regulating the Performance of Baseball Bats Alan M. Nathan

Department of PhysicsUniversity of [email protected]

• Defining, measuring, and regulating bat performance

• Do the regulations work?

• Recommendations


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Summary of my key points

The current understanding of the science of bat performance is markedly improvedWe know how to define, measure, and regulate

NCAA performance standards work

Organizations should consider adopting the NCAA model of having an outside panel of experts to advise on bat performance issues


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My credentials….

Physics professor at U. of Illinois for 30 yr Long career as experimental nuclear physicist

—continues today More recent interest in physics of baseball

webusers.npl.uiuc.edu/~a-nathan/pob Author of several papers regarding bat

performance including “Characterizing the performance of baseball and

softball bats” “blueprint” for how to define, measure, regulate

Consultant to ASA, NCAA, …


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Batted ball speed (BBS) in the field is the only sensible definition of performance

Three parameters determine batted ball speed (BBS) in the field

My only formula:BBS = (BESR-0.5)vpitch+(BESR+0.5)vbat

• vpitch: pitch speed

• vbat: bat speed

• BESR: Ball Exit Speed Ratio


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BESR a joint property of ball and bat Can be measured in lab, then used to

calculate BBS in field with assumptions about vpitch and vbat

All bats with same BESR that are swung identically will perform the same

But not all bats are swung identically more on this later

BBS = (BESR-0.5)vpitch+(BESR+0.5)vbat


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BESR depends on two additional properties of the ball and bat

Ball-Bat COR (BBCOR) The “bounciness” of the ball-bat collision Larger BBCOR means larger BESR, higher BBS Typically larger for aluminum than wood (trampoline effect) Bat Performance Factor (BPF)

Ratio of BBCOR of bat to that of wood

Moment of Inertia (MOI) of bat Measures weight and its distance from the knob Typically larger for wood than aluminum

Affects both BESR and swing speed Larger MOI: larger BESR, smaller swing speed Smaller MOI: smaller BESR, larger swing speed


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Moment of Inertia (MOI) is sometimes referred to as “swing weight”—it depends both on actual weight and on how far weight is from the knob

A B

• A and B have same weight and length• MOI of A larger than MOI of B• B is easier to swing about knob than A


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Summary of Important Concepts BBS

field batted ball speed: the ultimate metric of performance

BESR measure of performance for a given swing speed

MOI affects both BESR and swing speed

BBCOR or BPF affects BESR

• All of these except BBS can be measured in the lab• BBS can be inferred from lab measurements, with additional assumptions about vpitch and vbat


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Techniques to regulate bat performance

The direct technique Regulate BBS directly (ASA, fast-pitch NCAA)

Indirect techniques Regulate BESR and MOI (NCAA, high school) Regulate BPF (LL, USSSA)


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Regulating BBS directly…

Measure BESR in the lab Choose “typical” vpitch

ASA: 25 mph for slow-pitch

Choose vbat based on MOI ASA: ~85 mph, more or less depending on MOI

Use equation to calculate BBS Reject bat if maximum BBS exceeded

ASA: 98 mph (one size fits all)

BBS = (BESR-0.5)vpitch+(BESR+0.5)vbat


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0.94

0.96

0.98

1

1.02

1.04

1.06

6000 7000 8000 9000 10000 11000

Bat Speed at 6" Point vs. MOI

MOI (oz-in2)

y = m1*(9000/m0)^m2

ErrorValue

0.00194070.99461m1

0.012320.23385m2

NA15.206Chisq

NA0.97945R

dashed: n=0.25solid: n=0.23

ASA field study shows how bat speed depends on MOI for slow-pitch softball


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40

42

44

46

48

50

8.5 9 9.5 10 10.5 11 11.5

I6"

(103 oz-in2)

knob

(rad/s)

y = m1*(9/m0)^m2

ErrorValue

0.392146.218m1

0.0574220.28747m2

NA3.8574Chisq

NA0.93138R

Crisco/Greenwald Batting Cage Study

wood

aluminum

Batting cage study show how bat speed dependson MOI for college/semipro baseball players


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Regulating BBS Indirectly:The NCAA Method Specify maximum BESR

relative to wood

Specify minimum MOI to limit bat speed smaller than wood

Together, these determine a maximum BBS BOTH are essential to the technique


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same BBS

More details on the NCAA protocol:

MOI

BESR

Same BESR, lower MOI Higher BBS

Same MOI, lower BESR Lower BBS

Higher BESR, higher MOI same BBS

higher BBSlower BBS


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MOI limit

BESR limit

0.65

0.67

0.69

0.71

0.73

0.75

9000 9500 10000 10500 11000 11500 12000

BESR

MOI (oz-in2)

typical woodmax vf

102 mph

97 mph

All bats below horizontal line and to right of vertical line are allowed

Example: 34” Bats


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Summary:

The NCAA certification protocol limits field performance of nonwood bats

Under “standard” conditions--- Wood = 97 mph Nonwood < 102 mph Difference < 5 mph, or about 5%


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The NCAA bat compliance program has resulted in return of offensive statistics to earlier levels

NCAA home runs/game

0.350.450.550.650.750.850.951.051.15

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

year

HR

aluminum -5 rule BESR MOI


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Regulating BBS Indirectly:The BBCOR or BPF technique

BBS depends on two properties of the bat BBCOR or BPF MOI

For a given BPF, the effect of MOI partially cancels Larger MOI means larger BESR but smaller vbat

Smaller MOI means smaller BESR but larger vbat

Therefore, ignore MOI altogether and regulate BPFLittle League: BPF<1.15NOTE: this DOES NOT mean BBS is 15% larger than wood


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1.3

1.32

1.34

1.36

1.38

1.4

96

97

98

99

100

101

6500 7000 7500 8000 8500 9000 9500 10000

BPF

BBS

BPF

BBS (mph)

MOI (oz-in2)

Computer simulation

For slow-pitch softball bats, BPF does nottrack with BBS

I do not recommend using a BPF standard for slow-pitch softball


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Become educated in bat performance issues Talk with the experts Take advantage of lessons learned by the NCAA

Consider forming an NCAA-like panel to advise you on these issues Test broad selection of bats to see range of BESR,

MOI, BPF,… Do a field study to determine swing speeds, BBS, etc. From these studies, develop bat policing program

Recommendations:


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Summary of techniques for use Direct regulation of BBS Joint regulation of BESR and MOI Regulation of BPF

What is best for your organization? Suggestion: form an advisory panel similar to NCAA

Summary and plan for the future:


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Summary of my key points

The current understanding of the science of bat performance is markedly improvedWe know how to define, measure, and regulate

NCAA performance standards work

Organizations should consider adopting the NCAA model of having an outside panel of experts to advise on bat performance issues

Documents

Regulating the Performance of Baseball Bats