ASTM_F_2845_-_14.pdf

Designation:F284514Standard Test Method forMeasuring the Dynamic Stiffness(DS)and CylindricalCoefficient of Restitution(CCOR)of Baseballs andSoftballs1This standard is issued under the fixed designation F2845;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This procedure describes a method of measuring thedynamic stiffness(DS)and cylindrical coefficient of restitution(CCOR)of baseballs and softballs providing similar impactforces and ball deformation as are observed in a bat-ballcollision.1.2 This procedure is for a ball that is intended for the gameof baseball or softball.1.3 The test method is based on ball speed measurementsbefore and after impact with a cylindrical test surface and theimpact force between the ball and impacted surface.1.4 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 baseball or softball,nany ball defined by the rulesfor the game of baseball or softball,respectively.3.1.2 cylindrical coeffcient of restitution(CCOR),ntheratio of the rebound to incoming speed of a ball impacting asolid rigid cylinder.3.1.3 dynamic stiffness(DS),na normalized measure ofthe ball impact force having units of stiffness(lb/in.or kN/m).It is obtained by dividing the square of the peak force betweenthe ball and impact surface by the ball mass and the square ofthe incoming ball speed.4.Summary of Test Method4.1 A load cell or array of load cells is mounted between acylindrical solid steel impact surface and a rigid wall.The ballspeed is measured before and after impact with the impactsurface and the force is measured throughout the impact event.5.Significance and Use5.1 1 The ball dynamic stiffness is a measure of a ballshardness.Its measurement is conducted to represent bat-ballimpact forces.It is normalized by the ball weight and speed tominimize the influence of manufacturing and test variationsfrom the measure.5.2 The cylindrical coefficient of restitution is a ball prop-erty of relative velocity change caused by impact with acylindrical surface.5.3 This test method compares the performance of baseballsand softballs after impact with a cylindrical test surface.5.4 Sports associations can use DS and CCOR measure-ments in specifications for official baseballs and softballs.6.Apparatus6.1 Strike Plate:6.1.1 Load CellAdevice capable of measuring force up to10 kip(45 kN)within 61%.The peak load-cell reading afterball impact due to oscillation shall not exceed 5%of themeasured peak impact force.6.1.2 Impact SurfaceA 4 6 0.1-in.(102 6 2-mm)longsolid steel half cylinder.For softballs,the diameter of the half1This test method is under the jurisdiction of ASTM Committee F08 on SportsEquipment,Playing Surfaces,and Facilities and is the direct responsibility ofSubcommittee F08.26 on Baseball and Softball Equipment.Current edition approved March 1,2014.Published March 2014.Originallyapproved in 2010.Last previous edition approved in 2011 as F2845 11.DOI:10.1520/F2845-14.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 cylinder is 2.25 6 0.01 in.(57.2 6 0.3 mm).For baseballs thediameter of the half cylinder is 2.62 6 0.01 in.(66.7 6 0.3mm).6.1.3 MountingThe load cell and impact surface shall besecured to a massive rigid wall and fastened sufficiently secureto prevent movement during ball impact.Thread-lockingliquids help prevent fasteners from coming loose and reduceload-cell oscillations.6.2 Ball Throwing DeviceA ball throwing device capableof delivering the ball through the electronic speed monitorwithin 61 mph(60.5 m/s)of the desired speed.Balls shall beoriented to impact the strike surface between the stitches.6.3 Electronic Speed Monitors3An electronic ball-speedmeasuring system consisting of two vertical light screensmounted 12 6 0.03 in.(305 6 0.8 mm)apart,and ap