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What Have We Learned from a Decade of Bat Research?

Alan M. Nathan University of Illinois, a-nathan@illinois.edu. What Have We Learned from a Decade of Bat Research?. NCAA Trends in Home Runs. Q1: Why does aluminum outperform wood? Q2: What changed in 2011?. 2. 2. “You can observe a lot by watching” ---Yogi.

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What Have We Learned from a Decade of Bat Research?

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  1. Alan M. Nathan University of Illinois, a-nathan@illinois.edu What Have We Learned from a Decade of Bat Research?

  2. NCAA Trends in Home Runs Q1: Why does aluminum outperform wood? Q2: What changed in 2011? 2 2

  3. “You can observe a lot by watching” ---Yogi Collision is very inefficient Bat speed matters a lot Bat slows down 3

  4. Quantifying “bat performance” Batted Ball Speed (BBS) under game conditions BBS depends on • Pitch Speed • a little • Bat Speed • a lot • “collision efficiency” • joint property of ball and bat

  5. What determines collision efficiency? • Coefficient of Restitution • Bat weight

  6. 1. Coefficient of Restitution (COR) “Bounciness” of ball ~1/2 for baseball Bounces to ¼ of initial height bat matters also 6

  7. Contribution of Bat to COR:Vibrations and the Sweet Spot! “sweet spot” outside 7

  8. Vibrations, BBCOR, and the “Sweet Spot” + vibrations minimized COR maximized BBS maximized best “feel” e vf Evib demo 8

  9. Vibrations, BBCOR, and the “Sweet Spot” + e vf Evib 9

  10. Why are aluminum bats better?The trampoline effect Net Result: BBCOR larger  Better performance demo 10

  11. 2. Weight of bat • Not the actual weight (“swing weight” or “MOI”) • Larger when weight concentrated in barrel • Larger for wood than aluminum • Higher swing weight means more weight in barrel • Higher collision efficiency • Higher BBS • Higher swing weight means lower bat speed • Lower BBS • Two offsetting factors roughly cancel out • Leaving BBCOR as primary property determining BBS

  12. An aside: Corking the Bat • Corking the bat… • increases bat speed • decreases collision efficiency • Which one “wins”?

  13. Bat struck at barrel Handle starts to move only after noticeable delay When reflected wave reaches barrel, collision is over Therefore, nothing on handle end matters knob, handle, grip, … Batter could just as well drop bat just before impact! Aside: A curious feature

  14. And here’s the proof:Todd Frazier’s No-Hands HR

  15. The New NCAA Standard • BBCOR is “surrogate” for BBS • Since swing weight mostly doesn’t matter • Where to “draw the line” • 0.500…just barely above wood

  16. Measuring BBCOR in Lab

  17. NCAA Trends in Home Runs science works! ~10% reduction in max BBCOR  factor of ~2 reduction in HR 17 17

  18. Dealing with composite bats BBCOR improves with use “Accelerated Break-In” or ABI Effect of ball on bat performance The bottom line: We know much more than we did 10 yrs ago about how to characterize, measure, regulate performance of bats Other Issues

  19. webusers.npl.illinois.edu/~a-nathan/pob Thanks for your attention

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