Why ASTM F2219?

1. Why ASTM F2219? SGMA Annual Meeting Dallas, Texas, October 2, 2003 Lloyd Smith, Washington State University

2. ASTM F1890 • Fire ball at 60 mph • impact the bat at its COP • record the ball pitch speed and bat recoil speed • calculate performance metric (BPF) • compare against association’s limit

3. ASTM F2219 • Fire ball at 110 mph • impact the bat at the COP, 6 in from tip, or multiple locations • record the ball pitch and ball rebound speeds • select a performance measure (BBCOR, BPF, BESR, BBS) • calculate the average performance at each impact location • compare the bat’s highest performance with the association’s limit

4. Motivation For Change • Science • increased understanding of the bat and ball • increased understanding of test methodology • Field Study Results • Montgomery, Alabama (November 2002) • ASA Championship play, A & D level

5. Some science results

6. Impact Location • bat performance depends on the impact location • the highest performance was thought to occur at the bat’s COP • models and experiments show that the sweet spot and COP do not necessarily coincide • (COP depends on the location of the pivot point)

7. Bat Scanning • scanning • measure impact from the pivot point • impact at ½ inch intervals • scanning interval should encompass the maximum performance measure • each location impacted with 6 balls (once each) • bat performance vs. impact location is relatively constant near the sweet spot

8. Normalizing Performance • Fundamental dynamics allow variation in ball weight and COR to be accounted for • Performance is normalized to the properties of a nominal ball selected by the governing association • ???Normalizing relations will be proposed for adoption into ASTM F2219???

9. Normalizing Performance • No current proposal to normalize for ball compression or diameter • Normalizing for variation in ball compression requires further study • The effect of variation in ball diameter in laboratory tests is small • short ball flight distances

10. Experimental Accuracy • ball-out vs. bat-out • ideally, performance from “bat-out” and “ball-out” measurements would be equivalent • momentum is used to find the unmeasured quantity mvir + Iwi = mvor + Iwo

11. Experimental Accuracy • consider a 1% variation on the “out speed” in the test of a 10,000 MOI high performance metal bat at 110 mph • change in bat-out measurement: 1.2% BBS, 2.6% BPF • change in ball-out measurement: 0.2% BBS, 0.5% BPF

12. Experimental Accuracy • ball-out measurements require light curtains (rather than point measurements), rebound angle should be within 5o • bat-out measurements can be affected by bat vibrations that increase for impacts away from the sweet spot

13. Bat oscillations from impact

14. Measuring Bat Speed

15. Boundary Conditions • in the laboratory • the bat is constrained to rotate about a fixed center • the bat is held in a rigid grip • in play • the bat motion is described by an instantaneous center that is constantly moving • during impact the hands of the player impart relatively little force to the bat (i.e. free)

16. Boundary Conditions • the bat-ball contact duration is short (~1ms) • constraint forces are small (negligible) during impact • only the bat motion during impact (not before or after) is needed to represent performance

17. Montgomery Field Study

18. Pitch speed (slow pitch) • Was thought to be 10 mph • from high speed video • measures in-plane speed • average – 23 mph • standard deviation - 2 mph • predicted speed from projectile motion • (in-plane/total) • 50 ft, 12 ft arc  22/28 mph • 50 ft, 6 ft arc  34/36 mph

19. Swing Speed • Was thought to be 60 mph

20. Field Study Observations • the 60 mph ball speed currently used to certify bats is significantly below the relative bat-ball speed observed in play (~110 mph) • swing speed should scale with bat MOI not weight • bats should be tested at their sweet spot (found by scanning) not the COP

21. Laboratory Observations

22. BBS vs. BPF • many results are presented as BBS • there is a strong correlation between BBS and BPF • similar trends should be observed using BPF

23. Does Test Speed Matter? • The trampoline effect increases with impact speed • a ball dropped on a wood and hollow bat would rebound to similar heights • Test speeds representative of play conditions will improve the comparison of the relative performance of bats

24. Does Test Speed Matter? • the performance of a solid bat would be constant

25. 110 ASTM 2219 105 ASTM 1890 100 BBS (mph) 95 90 85 80 Doublewall Techonology High Performing Aluminum High Performing Aluminum High performing Composite bat Very high performing composite bat Very high performing composite bat ASTM 2219 vs. ASTM 1890

26. ASTM F2219 era study

27. Effect of bat MOI

28. Ball Compression (90 mph)

29. 115 Alum. Comp. 110 105 BBS (mph) 100 95 90 40/300 40/375 44/375 47/525 Ball Compression Results from Charlotte field study, 2002 ASTM F2219, 2003

30. Ball Conditioning • Increase RH by 20% • Ball compression decreases 40 lbs

31. Summary • Test speeds should represent play conditions • Impact location should be found experimentally • “Ball-Out” measurements reduce experimental variation • Ball compression can be used to control the ball speed in play