ASTM F2398-04
(Test Method)Standard Test Method for Measuring Moment of Inertia and Center of Percussion of a Baseball or Softball Bat
Standard Test Method for Measuring Moment of Inertia and Center of Percussion of a Baseball or Softball Bat
SCOPE
1.1 This test method covers a method for determining the moment of inertia (MOI) and balance point (BP) of baseball and softball bats. These physical properties are used in calculations in other key ASTM standards.
1.2 The MOI 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 the 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.
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An American National Standard
Designation: F 2398 – 04
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 F 2398; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Significance and Use
1.1 This test method covers a method for determining the 3.1 This test method offers a laboratory means to measure
moment of inertia (MOI) and balance point (BP) of baseball the inertial properties of bats, specifically weight, balance
and softball bats. These physical properties are used in calcu- point, center of percussion, and MOI, in support of other test
lations in other key ASTM standards. methods including the ASTM standards referenced in this
1.2 The MOI and BP are measured in the laboratory on test document.
equipment meeting the requirements defined in this test 3.2 Use of this test method can provide sports governing
method. bodies the means to establish rules regarding the physical
1.3 The values stated in inch-pound units are to be regarded properties of bats, specifically MOI.
as the standard.
4. Apparatus
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 4.1 Bat MOI Test Apparatus:
4.1.1 Ruler, suitable for measuring lengths up to 42 in.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- (1067 mm) to the nearest 0.031 in. (0.79 mm).
4.1.2 Weight Scale, suitable for measuring weight up to 48
bility of regulatory limitations prior to use.
oz (1360 g) to the nearest 0.0035 oz (0.1 g).
2. Terminology
4.1.3 Electronic Timer, suitable device sufficiently accurate
2.1 Definitions of Terms Specific to This Standard: for measuring time to the nearest 1 μs (0.000001 s).
2.1.1 balance point (BP)—the distance to the center of mass 4.1.4 MOI Stand—A frame with a pivoting bat collar-clamp
measured from the distal end of the bat knob. large enough to allow a bat held in a vertical position to swing
2.1.2 center of percussion (COP)—also known as the center freely (see Fig. 1).
of oscillation, the length of a simple pendulum with the same 4.1.5 Bat Collar-Clamp—A part of the MOI stand that
period as a physical pendulum, as in a bat oscillating on a allows quick accurate mounting of the bat without a variable
pivot. Forces and impacts at this location will not induce axial MOI effect due to the clamp with a maximum MOI of 4
2 2
reactions at the pivot point. oz-in. (0.8 kg-cm ) measured about the bat pivot location. A
2.1.3 cycle—one complete performance of the oscillation of lightweight clamp or collar that can hold the weight of a bat
the bat, specifically, one full swing of the bat. and provide a fixed pivot location. Collar shall be rotationally
2.1.4 moment of inertia (MOI)—a measure of mass distri- balanced (see Fig. 1).
bution relative to an axis of rotation. It is the product of the
5. Calibration and Standardization
mass multiplied by the square of the distance to the mass,
5.1 Calibration Rod—A calibration rod tested at two differ-
summed over the entire bat.
2.1.5 period—the time required for a pendulum to oscillate ent pivot locations shall be used to determine if the MOI stand
is capable of accurately measuring the MOI of a bat. The rod
through one complete cycle.
shall be a 1-in. (25.4-mm) diameter by 24-in. (609.6-mm) long
steel rod weighing 85.65 oz (2.43 kg). The MOI of this rod
This test method is under the jurisdiction of ASTM Committee F08 on Sports
measured with the pivot location at 8 in. (20.32 cm) should be
Equipment and Facilities and is the direct responsibility of Subcommittee F08.26 on
2 2
5487 oz-in. (1003 kg-cm ) and at a pivot location of 2 in.
Baseball and Softball Equipment and Facilities.
Current edition approved May 1, 2004. Published May 2004.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F2398–04
FIG. 1 - MOI Fixture
2 2
(50.8 mm) should be 12 682 oz-in. (2319.5 kg-cm ). Devia-
where:
2 2
tions of more than 50 oz-in. (9.15 kg-cm ), after accounting for
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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