ASTM F2398-04e1

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An American National Standard
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Designation:F2398–04
Standard Test Method for
Measuring Moment of Inertia and Center of Percussion of a
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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.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
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´ NOTE—Figure 2 editorially corrected in July 2004.
1. Scope 2.1.5 period—the time required for a pendulum to oscillate
through one complete cycle.
1.1 This test method covers a method for determining the
moment of inertia (MOI) and balance point (BP) of baseball
3. Significance and Use
and softball bats. These physical properties are used in calcu-
3.1 This test method offers a laboratory means to measure
lations in other key ASTM standards.
the inertial properties of bats, specifically weight, balance
1.2 The MOI and BPare measured in the laboratory on test
point, center of percussion, and MOI, in support of other test
equipment meeting the requirements defined in this test
methods including the ASTM standards referenced in this
method.
document.
1.3 The values stated in inch-pound units are to be regarded
3.2 Use of this test method can provide sports governing
as the standard.
bodies the means to establish rules regarding the physical
1.4 This standard does not purport to address all of the
properties of bats, specifically MOI.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Apparatus
priate safety and health practices and determine the applica-
4.1 Bat MOI Test Apparatus:
bility of regulatory limitations prior to use.
4.1.1 Ruler, suitable for measuring lengths up to 42 in.
2. Terminology (1067 mm) to the nearest 0.031 in. (0.79 mm).
4.1.2 Weight Scale, suitable for measuring weight up to 48
2.1 Definitions of Terms Specific to This Standard:
oz (1360 g) to the nearest 0.0035 oz (0.1 g).
2.1.1 balance point (BP)—thedistancetothecenterofmass
4.1.3 Electronic Timer, suitable device sufficiently accurate
measured from the distal end of the bat knob.
for measuring time to the nearest 1 µs (0.000001 s).
2.1.2 center of percussion (COP)—alsoknownasthecenter
4.1.4 MOI Stand—Aframewithapivotingbatcollar-clamp
of oscillation, the length of a simple pendulum with the same
large enough to allow a bat held in a vertical position to swing
period as a physical pendulum, as in a bat oscillating on a
freely (see Fig. 1).
pivot. Forces and impacts at this location will not induce axial
4.1.5 Bat Collar-Clamp—A part of the MOI stand that
reactions at the pivot point.
allows quick accurate mounting of the bat without a variable
2.1.3 cycle—onecompleteperformanceoftheoscillationof
MOI effect due to the clamp with a maximum MOI of 4
the bat, specifically, one full swing of the bat.
2 2
oz-in. (0.8 kg-cm ) measured about the bat pivot location. A
2.1.4 moment of inertia (MOI)—a measure of mass distri-
lightweight clamp or collar that can hold the weight of a bat
bution relative to an axis of rotation. It is the product of the
and provide a fixed pivot location. Collar shall be rotationally
mass multiplied by the square of the distance to the mass,
balanced (see Fig. 1).
summed over the entire bat.
5. Calibration and Standardization
5.1 Calibration Rod—Acalibration rod tested at two differ-
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This test method is under the jurisdiction ofASTM Committee F08 on Sports
ent pivot locations shall be used to determine if the MOI stand
EquipmentandFacilitiesandisthedirectresponsibilityofSubcommitteeF08.26on
is capable of accurately measuring the MOI of a bat. The rod
Baseball and Softball Equipment and Facilities.
shall be a 1-in. (25.4-mm) diameter by 24-in. (609.6-mm) long
Current edition approved May 1, 2004. Published May 2004. DOI: 10.1520/
F2398-04E01. steel rod weighing 85.65 oz (2.43 kg). The MOI of this rod
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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F2398–04
FIG. 1 - MOI Fixture
~6Wt ! 1 ~24Wt !
measured with the pivot location at 8 in. (20.32 cm) should be
6 24
BP 5 (1)
2 2 F G
~Wt 1 Wt !
5487 oz-in. (1003 kg-cm ) and at a pivot location of 2 in.
6 24
2 2
(50.8 mm) should be 12682 oz-in. (2319.5 kg-cm ). Devia-
where:
2 2
tionsofmorethan50oz-in. (9.15kg-cm ),afteraccountingfor
BP = BP from distal end of the bat knob,
the MOI of the clamp fixture, shall be rectified before bats are
Wt = Weight of the bat measured 6 in. from the knob,
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tested.
Wt = Weight of the bat measured 24 in. from the knob,
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and
6. Procedure
W =Wt+Wt = total weight of the
...