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

drussell@kettering.edu

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 2

160 Hz160 Hz

600 Hz600 Hz

Bending Modes (common to all bats)

Hoop Mode (unique to hollow bats)1500 Hz1500 Hz

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 3

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

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 4

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

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 5

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

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 6

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

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 7

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

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 8

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

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 9

Hoop Frequency & PerformanceCould hoop frequency be used to detect

illegally altered bats?

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 10

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

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 11

Portable Pendulum TestDirect correlation between contact time & hoop frequencyDirect correlation between contact time & hoop frequency

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 12

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

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 13

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

Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 14

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