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Correlation Between Bat Performance and Hoop Frequency

Correlation Between Bat Performance and Hoop Frequency. Dan Russell. Kettering University, Flint, MI. drussell@kettering.edu. 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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Correlation Between Bat Performance and Hoop Frequency

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  1. Correlation Between Bat Performance and Hoop Frequency Dan Russell Kettering University, Flint, MI drussell@kettering.edu Dan Russell “Hoop Frequency & Bat Performance” SGMA Baseball & Softball Council Fall Meeting 2004 Page 1

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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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