Why ASTM F2219?
SGMA Annual Meeting
Dallas, Texas, October 2, 2003
Lloyd Smith, Washington State University
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
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
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
• Some science results
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)
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
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???
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
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
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
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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
Bat oscillations from impact
1.6
1.4
Bat rotation (radians)
1.2
1
0.8
ASTM 1890
0.6
0.4
24
28
0.2
0
0.00
32
0.01
0.02
Time (s)
0.03
0.04
Measuring Bat Speed
110
105
BBS (mph)
100
95
90
Ball out
Bat out
85
1890 (30-60)
1890 (5-90)
80
22
24
26
28
30
32
Impact location (distance from knob, in)
34
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)
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
• Montgomery Field Study
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
50 ft, 12 ft arc 
50 ft, 6 ft arc 
(in-plane/total)
22/28 mph
34/36 mph
Swing Speed
100
Average Swing Speed at 6 in Point (mph)
• Was
thought to
be 60 mph
95
90
89
85
81
80
75
A level
D level
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
• Laboratory Observations
BBS vs. BPF
1.6
1.5
1.4
BPF
• many results are
presented as BBS
• there is a strong
correlation
between BBS and
BPF
• similar trends
should be
observed using
BPF
1.3
1.2
1.1
1
85
90
95
100
BBS (mph)
105
110
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
Does Test Speed Matter?
110
110 mph
• the performance
of a solid bat
would be constant
BBS (mph)
105
60 mph
100
95
90
85
Basic Single Wall
Very high performing
composite bat
ASTM 2219 vs. ASTM 1890
110
BBS (mph)
105
100
95
90
85
80
ASTM 2219
ASTM 1890
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BBS (mph)
ASTM F2219 era study
110
105
100
95
90
85
80
Effect of bat MOI
100
95
BBS (mph)
90
85
80
Field
2219
75
1890
70
6863
7982
9085
9988
Bat MOI (oz in^2)
10871
Ball Compression (90 mph)
114
112
110
Multi-wall Al
Composite
BBS (mph)
108
106
104
102
100
98
96
94
375 lb
525 lb
Ball Compression
Results from Charlotte field study, 2002
ASTM F2219, 2003
115
Alum.
98
Comp.
96
110
94
92
BBS (mph)
Batted Ball Speed, 25 percentile (mph)
100
90
88
105
100
86
84
95
82
80
0
100
200
300
400
Compression (lbs)
500
600
90
40/300
40/375
44/375
47/525
Ball Conditioning
1.4
9 days
1.2
Weight Change (%)
•Increase RH by 20%
Ball compression
decreases 40 lbs
1
0.8
0.6
0.4
0.44 COR, 375 lb balls
30% to 50% RH
0.2
0
0
50
100
150
1/2
Time (min )
200
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