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Correlation Between Bat Performance and Hoop Frequency. Dan Russell. Kettering University, Flint, MI. [email protected] Bending Modes ( common to all bats ). 160 Hz. 600 Hz. Hoop Mode ( unique to hollow bats ). 1500 Hz. What is the Trampoline Effect?. Ball impacting solid bat.

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Presentation Transcript
slide1

Correlation Between

Bat Performance

and Hoop Frequency

Dan Russell

Kettering University, Flint, MI

[email protected]

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

slide2

Bending Modes(common to all bats)

160 Hz

600 Hz

Hoop Mode(unique to hollow bats)

1500 Hz

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

slide3

What is the Trampoline Effect?

Ball impacting solid bat

Ball impacting hollow bat

Movie courtesy of

CE-Composites,

Ottawa, CA

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

slide4

hysteresis

force

compression

Simple Model  Trampoline Effect

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

Ball modeled as a non-linear, damped mass-spring

system with initial velocity

Bat modeled as a linear, damped mass-spring system

initially at rest and fixed to rigid foundation

Set bat stiffness s2

s2 / m2 = w2bat Hoop frequency of barrel

Solve the coupled equations of motion numerically

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

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

slide5

Optimal Bat

hoop frequency

tuned for maximum

trampoline effect

Elastic Bat

bat deforms,

ball deforms less

(energy lost)bat < (energy lost)ball

Very Stiff Bat

ball deforms more,

energy lost

Soft Bat

ball does not rebound

Simple Model  Trampoline Effect

ball parameters  softball

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

slide6

Hoop Frequency & Barrel Construction

34-inch slow-pitch softball bats

bending and hoop frequencies extracted from modal analysis

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

slide7

Hoop Frequency & Performance

ASA era study Slow-pitch Softball BatsASTM F2219

Cannon fires ball at 110mph towards stationary (pivoted) bat

Batted-Ball Speed calculated from vout/vin, MOI, impact location

Wood

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

slide8

Hoop Frequency & Performance

Crisco & Greenwald Batting Cage Study

19 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 8

slide9

Hoop Frequency & Performance

Could hoop frequency be used to detect

illegally altered bats?

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

slide10

Portable Pendulum Test

Concept:

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 10

slide11

Portable Pendulum Test

Direct correlation between contact time & hoop frequency

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

slide12

Portable Pendulum Test

ASA era study Slow-pitch Softball BatsASTM F2219

Cannon fires ball at 110mph towards stationary (pivoted) bat

Batted-Ball Speed calculated from vout/vin, MOI, impact location

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

slide13

Portable Pendulum 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 13

slide14

Future Work

Portable Pendulum Tester

Digital readout

Swing bat against stationary “ball”

include mass/MOI properties of bat

Scan along barrel

Further correlation of data with measured performance

Need additional bats (with performance data)

Need some funding ($3,000)

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

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