Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 1 Correlation Between Bat Performance and Hoop Frequency

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 1

Correlation Between Bat Performance

and Hoop Frequency

Dan RussellKettering University, Flint, MI

[email protected]


160 Hz160 Hz

600 Hz600 Hz

Bending Modes (common to all bats)

Hoop Mode (unique to hollow bats)1500 Hz1500 Hz


What is the Trampoline Effect?

Ball impacting solid bat

Ball impacting hollow bat

Movie courtesy of Movie courtesy of CE-Composites, CE-Composites,

Ottawa, CAOttawa, CA


mass-spring model of ball & bat (racket, club)

Bat modeled as a linear, damped mass-spring systeminitially at rest and fixed to rigid foundation

Ball modeled as a non-linearnon-linear, damped mass-spring system with initial velocity

Solve the coupled equations of motion numerically

Determine BBCOR = v1out / v1in for a given bat stiffness s2

Set bat stiffness s2

s2 / m2 = 2bat Hoop frequencyHoop frequency of barrel

Simple Model Trampoline Effect

hysteresishysteresis

forc

efo

rce

compressioncompression


Simple Model Trampoline Effect

Very Stiff Bat ball deforms more,

energy lost

Elastic Batbat deforms,

ball deforms less(energy lost)bat < (energy lost)ball

Optimal Bat hoop frequency

tuned for maximum trampoline effect

Soft Bat ball does not rebound

ball parameters softball


Hoop Frequency & Barrel Construction34-inch slow-pitch softball batsbending and hoop frequencies extracted from modal analysis


Hoop Frequency & PerformanceASA era study ASA era study Slow-pitch Softball BatsSlow-pitch Softball Bats ASTM F2219ASTM F2219Cannon fires ball at 110mph towards stationary (pivoted) batBatted-Ball Speed calculated from vout/vin, MOI, impact location

WoodWood


Hoop Frequency & PerformanceCrisco & Greenwald Batting Cage StudyCrisco & Greenwald Batting Cage Study19 players (HS through minor league)pitched balls (66mph) 6 baseball bat models (several of each)BBCOR values extracted by Alan Nathan


Hoop Frequency & Performance

Could hoop frequency be used to detect illegally altered bats?


Portable Pendulum TestConcept:Use a very heavy, very stiff “ball” to impact bat barrel.Measure contact time between “ball” and bat.Contact time determined by

mass of “ball” stiffness of bat


Portable Pendulum Test

Direct correlation between contact time & hoop frequencyDirect correlation between contact time & hoop frequency


Portable Pendulum TestASA era study ASA era study Slow-pitch Softball BatsSlow-pitch Softball Bats ASTM F2219ASTM F2219Cannon fires ball at 110mph towards stationary (pivoted) batBatted-Ball Speed calculated from vout/vin, MOI, impact location


Portable Pendulum Test

Altered bats (barrel compression test)Altered bats (barrel compression test)robot swings bat at 60mph towards stationary ball


Future WorkPortable Pendulum TesterPortable Pendulum Tester

Swing bat against stationary “ball”include mass/MOI properties of bat

Digital readout

Further correlation of data with measured performanceNeed additional bats (with performance data)

Need some funding ($3,000)

Scan along barrel

Documents

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 1 Correlation Between Bat Performance and Hoop Frequency