ASTM F2845-10
(Test Method)Standard Test Method for Measuring the Dynamic Stiffness (DS) and Cylindrical Coefficient of Restitution (CCOR) of Baseballs and Softballs
Standard Test Method for Measuring the Dynamic Stiffness (DS) and Cylindrical Coefficient of Restitution (CCOR) of Baseballs and Softballs
SIGNIFICANCE AND USE
1 The ball dynamic stiffness is a measure of a ball’s hardness. Its measurement is conducted to represent bat-ball impact forces. It is normalized by the ball weight and speed to minimize the influence of manufacturing and test variations from the measure.
The cylindrical coefficient of restitution is a ball property of relative velocity change caused by impact with a cylindrical surface.
This test method compares the performance of baseballs and softballs after impact with a cylindrical test surface.
Sports associations can use DS and CCOR measurements in specifications for official baseballs and softballs.
SCOPE
1.1 This procedure describes a method of measuring the dynamic stiffness (DS) and cylindrical coefficient of restitution (CCOR) of baseballs and softballs providing similar impact forces and ball deformation as are observed in a bat-ball collision.
1.2 This procedure is for a ball that is intended for the game of baseball or softball.
1.3 The test method is based on ball speed measurements before and after impact with a cylindrical test surface and the impact force between the ball and impacted surface.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation:F2845–10
Standard Test Method for
Measuring the Dynamic Stiffness (DS) and Cylindrical
Coefficient of Restitution (CCOR) of Baseballs and
Softballs
This standard is issued under the fixed designation F2845; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.2 cylindrical coeffıcient of restitution (CCOR), n—the
ratio of the rebound to incoming speed of a ball impacting a
1.1 This procedure describes a method of measuring the
solid rigid cylinder.
dynamic stiffness (DS) and cylindrical coefficient of restitution
3.1.3 dynamic stiffness (DS), n—a normalized measure of
(CCOR) of baseballs and softballs providing similar impact
the ball impact force having units of stiffness (lb/in. or kN/m).
forces and ball deformation as are observed in a bat-ball
It is obtained by dividing the square of the peak force between
collision.
the ball and impact surface by the ball mass and the square of
1.2 This procedure is for a ball that is intended for the game
the incoming ball speed.
of baseball or softball.
1.3 The test method is based on ball speed measurements
4. Summary of Test Method
before and after impact with a cylindrical test surface and the
4.1 A load cell or array of cells is mounted between a
impact force between the ball and impacted surface.
cylindrical solid steel impact surface and a rigid wall. The ball
1.4 The values stated in inch-pound units are to be regarded
speed is measured before and after impact with the impact
as standard. The values given in parentheses are mathematical
surface and the force is measured throughout the impact event.
conversions to SI units that are provided for information only
4.2 Method A—The cylindrical impact surface for softballs
and are not considered standard.
is 2.25 6 0.01 in. (57.2 6 0.3 mm) in diameter. The ball
1.5 This standard does not purport to address all of the
inbound speed is 95 mph (42.5 m/s).
safety concerns, if any, associated with its use. It is the
4.3 Method B—The cylindrical impact surface for baseballs
responsibility of the user of this standard to establish appro-
is 2.62 6 0.01 in. (66.7 6 0.3 mm) in diameter. The ball
priate safety and health practices and determine the applica-
inbound speed is 115 mph (51.4 m/s).
bility of regulatory limitations prior to use.
5. Significance and Use
2. Referenced Documents
2 5.1 1 The ball dynamic stiffness is a measure of a ball’s
2.1 ASTM Standards:
hardness. Its measurement is conducted to represent bat-ball
E177 Practice for Use of the Terms Precision and Bias in
impact forces. It is normalized by the ball weight and speed to
ASTM Test Methods
minimize the influence of manufacturing and test variations
E691 Practice for Conducting an Interlaboratory Study to
from the measure.
Determine the Precision of a Test Method
5.2 The cylindrical coefficient of restitution is a ball prop-
3. Terminology erty of relative velocity change caused by impact with a
cylindrical surface.
3.1 Definitions of Terms Specific to This Standard:
5.3 This test method compares the performance of baseballs
3.1.1 baseball or softball, n—any ball defined by the rules
and softballs after impact with a cylindrical test surface.
for the game of baseball or softball, respectively.
5.4 Sports associations can use DS and CCOR measure-
ments in specifications for official baseballs and softballs.
This test method is under the jurisdiction of ASTM Committee F08 on Sports
Equipment and Facilities and is the direct responsibility of Subcommittee F08.26 on
6. Apparatus
Baseball and Softball Equipment.
6.1 Strike Plate:
Current edition approved May 1, 2010. Published June 2010. DOI: 10.1520/
F2845-10.
6.1.1 Load Cell—Adevicecapableofmeasuringforceupto
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10 kip (45 kN) within 61 %. The peak load-cell reading after
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ball impact due to oscillation shall not exceed 5 % of the
Standards volume information, refer to the standard’s Document Summary page on
measured peak impact force.
the ASTM website.
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F2845–10
FIG. 1 Test Apparatus
6.1.2 Impact Surface—A 4 6 0.1-in. (102 6 2-mm) long 8.1.1 Test balls shall be stored in an environmentally
solid steel half cylinder of diameter prescribed by MethodAor controlled space for at least 14 days immediately before
B. testing.
6.1.3 Mounting—The load cell and impact surface shall be 8.1.2 Temperature is to be maintained at 72 6 4°F (22 6
securedtoamassiverigidwall,andfastenedsufficientlysecure 2°C).
to prevent movement during ball impact. Thread-locking 8.1.3 Relative humidity (RH) is to be maintained between
liquids help prevent fasteners from coming loose and reduce 40 and 60 %.
load-cell oscillations. 8.1.4 Temperature and relative humidity are to be measured
6.2 Ball Throwing Device—A ball throwing device capable and recorded hourly within 0.5°F (0.3°C) and 2 % RH over
of delivering the ball through the electronic speed monitor conditioning and test durations.
within 61 mph (60.14 in./s, 60.5 m/s) of the desired speed.
9. Procedure
Balls shall be oriented to impact the strike surface between the
stitches.
9.1 Select the desired test method according to 4.2 or 4.3.
6.3 Electronic Speed Monitors —An electronic ball-speed
9.2 Set the ball throwing device to the test target speed
measuring system consisting of two vertical light screens
within 6 1 mph (60.14 in./s , 0.5 m/s). Results from shots
mounted 12 6 0.03 in. (305 6 0.8 mm) apart, and a
above or below this speed range will not be used.
photoelectric sensor located at each screen that triggers a
9.3 A minimum 1-min rest period is required between each
timing device on ball passage to measure the time for the ball
shot. A non-contact temperature sensor shall be used to verify
to traverse the distance between the two vertical planes before
the ball temperature remains within the specified test-room
and after impact with the strike plate. Accuracy shall be 60.1
temperature range.
mph (60.014 in./s , 60.05 m/s).
9.4 The ball shall be rotated after each impact among its
6.4 Data Acquisition—Thesignalfromtheloadcellshallbe
four ears or surfaces with maximum spacing between the
sampledatafrequencyofatleast100kHzwhileitisincontact
stitches.
with the ball.
9.5 Verify proper alignment by observing the rebound path
of the ball after impact. The ball rebound angle after impact
7. Preparation of Apparatus
with the impact surface should be within 6 5° of the inbound
ball path.
7.1 Mount the cylindrical impact surface and load cell on a
rigid wall. Verify all fasteners are tightened according to 9.6 Compare the impulse from the ball speed and impact
force.
laboratory procedure to minimize load-cell oscillation.
7.2 Position the speed monitors so that the first speed 9.6.1 Calculate the impulse from the impact force by:
monitor (light screen) is 12 6 0.1 in. (305 6 2 mm) from the
L 5 F~t!dt (1)
F *
strike plate (see Fig. 1).
where:
8. Conditioning
L = force impulse, lb-s (N-s), and
F
8.1 Ball Conditioning and Test-Room Conditioning:
F(t) = force measurement during impact, lb (N).
9.6.2 Calculate the impulse from the ball speeds by:
m
L 5 V 1 S! (2)
~
3 S
Thesolesourceofsupplyoftheapparatus(IBeamSensororequivalent)known c
L
to the committee at this time is Automated Design Corporation, 1404 Joliet Road,
Suite B, Romeoville, IL60446, http://www.automateddesign.com/. If you are aware
where:
of alternative suppliers, please provide this information to ASTM International
L = speed impulse, lb-s (N-s),
S
Headquarters.Your comments will receive careful consideration at a meeting of the
m = ball mass, oz (g),
responsible technical committee, which you may attend.
F2845–10
10.1.6 For each impact (including invalid impacts) ball
V = incoming speed, mph (m/s),
inbound speed, rebound speed, CCOR, peak force and DS.
S = outgoing ball speed, mph (m/s), and
10.1.7 Any important observations including but not exclu-
c = unit conversion factor, 350.99 US (1000 SI).
L
sively, damage to the ball, unusual noises or vibrations and the
9.6.3 Calculate the impulse ratio by:
number of invalid impacts for each ball.
L
S
K 5 (3)
10.1.8 Respective calibration dates for load cells and veloc-
L
F
ity timers.
where:
K = impulse ratio,
11. Precision and Bias
L = speed impulse, lb-s (N-s), and
S
11.1 The precision of this test method is based on an
L =
...
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