ASTM F2398-11(2015)

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Designation: F2398 − 11 F2398 − 11 (Reapproved 2015) An American National Standard
Standard Test Method for
Measuring Moment of Inertia and Center of Percussion of a
Baseball or Softball Bat
This standard is issued under the fixed designation F2398; 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
1.1 Method for determining the moment of inertia (MOI), the center of percussion (COP), and the balance point (BP) of baseball
and softball bats. These physical properties are used in Test Method F1881, Test Method F1890, and Test Methods F2219.
1.2 The MOI, COP, and BP are measured in the laboratory on test equipment meeting the requirements defined in this test
method.
1.3 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.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
F1881 Test Method for Measuring Baseball Bat Performance Factor (Withdrawn 2014)
F1890 Test Method for Measuring Softball Bat Performance Factor
F2219 Test Methods for Measuring High-Speed Bat Performance
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 balance point (BP), n—the distance to the center of mass measured from the knob end of the bat.
3.1.2 center of percussion (COP), n—also known as the center of oscillation. Forces and impacts at this location will not induce
reactions at the pivot point, 6 in. (152 mm) from the knob end of the bat.
3.1.3 cycle, n—one complete oscillation of a pendulum supported at the pivot point, 6 in. (152 mm) from the knob end of the
bat.
3.1.4 moment of inertia (MOI), n—also known as the mass moment of inertia, the measure of the bat’s resistance to changes
in its rotation rate about the pivot point, 6 in. (152 mm) from the knob end of the bat.
3.1.5 period, n—the time required for a pendulum to oscillate through one complete cycle.
4. Significance and Use
4.1 This test method offers a laboratory means to measure the inertial properties of bats, specifically weight, balance point,
center of percussion, and MOI, in support of other test methods including the ASTM standards referenced in this document.
4.2 Use of this test method can provide sports governing bodies the means to establish rules regarding the physical properties
of bats, specifically MOI.
This test method is under the jurisdiction of ASTM Committee F08 on Sports Equipment, Playing Surfaces, and Facilities and is the direct responsibility of Subcommittee
F08.26 on Baseball and Softball Equipment.
Current edition approved April 1, 2011Oct. 1, 2015. Published May 2011November 2015. Originally approved in 2004. Last previous edition approved in 20102011 as
F2398 – 10.F2398 – 11. DOI: 10.1520/F2398-11.10.1520/F2398-11R15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
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F2398 − 11 (2015)
5. Apparatus
5.1 Bat MOI Test Apparatus:
5.1.1 Ruler, suitable for measuring lengths up to 42 in. (1067 mm) to the nearest 0.03 in. (0.8 mm).
5.1.2 Weight Scales, suitable for measuring weight up to 48 oz (1361 g) to the nearest 0.0035 oz (0.1 g).
5.1.3 Electronic Timer, suitable device sufficiently accurate for measuring time to the nearest 1 μs (0.000001 s).
5.1.4 Pendulum Stand—A frame with a pivoting bat collar-clamp large enough to allow a bat held in a vertical position to swing
freely (see Fig. 1).
5.1.5 Bat Collar-Clamp—A lightweight clamp or collar that can hold the weight of a bat and provide a fixed pivot location. The
2 2
clamp shall be rotationally balanced and have a maximum MOI of 4 oz-in. (73 kg-mm ) measured about the bat pivot location
(see Fig. 1). The MOI of the clamp shall not change with the diameter of the bat being tested.
6. Calibration and Standardization
6.1 Calibration Rod—The calibration rod shall be 1 6 0.01 in. (25.4 6 0.25 mm) in diameter by 34 6 0.1 in. (864 6 2.5 mm)
long, solid aluminum.
6.2 Target Calibration MOI—Measure the length and the weight of the calibration rod. Compute the target calibration rod MOI
using Eq. 1:
2 2
L L
c c
I 5 W 1 2 d 1I (1)
H S D J
T c c
12 2
where:
...