ASTM_F_498_-_12.pdf

Designation:F49812Standard Test Method forCenter Spring Constant and Spring Constant Balance ofAlpine Skis1This standard is issued under the fixed designation F498;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of centerspring constant,forebody spring constant,and afterbody springconstant of Alpine skis.In addition,it covers a method fordetermination of the spring constant balance.1.2 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.Terminology2.1 Definitions:2.1.1 afterbody spring constantthe load,in newtons,re-quired to deflect point A a distance of 1 cm.CA5FAfm(1)2.1.2 center spring constantthe load,in newtons,requiredto deflect point M a distance of 1 cm.CM5FMfm(2)2.1.3 deflection fthe displacement of the ski under load Fmeasured at points A,B,or M normal to a line between supportpoints or the clamping plane.2.1.4 forebody spring constantthe load,in newtons,re-quired to deflect point B a distance of 1 cm.CB5FBfB(3)2.1.5 load Fthe force applied normal to the support pointsor the clamping plane,at points A,B,or M.The onlycomponent of load F is shown in Fig.1.2.1.6 point Athe support point for the afterbody of the skiwhen the center spring constant is measured or the loadapplication point when the afterbody spring constant is mea-sured.2.1.7 point Bthe support point for the forebody of the skiwhen the center spring constant is measured or the loadapplication point when the forebody spring constant is mea-sured.2.1.8 point Mthe load application point when the centerspring constant is measured and the clamping point when theforebody spring constant or the afterbody spring constant ismeasured.It is located at the midpoint between points A and B.2.1.9 ski size,xplthe projected length with the ski bodypressed flat against a plane surface,measured between the skitail and the ski tip,commonly referred to as chord length.Thedeveloped or material length is the length from tip to tail alongthe bottom contour of the ski.2.1.10 spring constanta measurement of the stiffness of aski in bending,expressed as a ratio of force to deflection.2.1.11 spring constant balancethe ratio of afterbodyspring constant divided by forebody spring constant.B 5CACB(4)3.Preparation of Apparatus3.1 Center Spring Constant EquipmentEquip supports Aand B with low-friction rolls of 2.0 6 0.1 cm diameter.Applythe load with a dynamometer or calibrate the measurement ofload with an accuracy of 60.5 N.Measure the deflection witha suitable instrument with an accuracy of 60.005 cm.Applythe load with a cylindrical contact ram having a radius of 1.06 0.1 cm and extending over the width of the ski.3.2 Forebody and Afterbody Spring Constant EquipmentProvide a clamping fixture to grip the ski as a vise with a flatrigid jaw and three clamps with at least 15-cm spacing betweenthem.Locate one clamp at each end and one in the center.Clamps should be at least 3 cm wide covering the width of theski.Apply the load with a cylindrical contact ram having aradius of 1.0 6 0.1 cm and covering the width of the ski.4.Procedure(See Fig.2)4.1 Center Spring ConstantPlace the supports at points Aand B.The location of point A is 5 6 1 cm from the tail of theski.If the ski geometry does not permit this point to act as asupport,move the location of point A toward the center of the1This test method is under the jurisdiction of ASTM Committee F27 on SnowSkiing and is the direct responsibility of Subcommittee F27.30 on Skis and Boots.Current edition approved March 1,2012.Published March 2012.Originallyapproved in 1977.Last previous edition approved in 2006 as F498 77(2006).DOI:10.1520/F0498-12.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 ski until it can act as a support.The location of point B is adistance of C(C=xpl 25 cm(6 1 cm)from point A orequivalent to 20 6 1 cm from the tip of the ski.If the skigeometry does not permit this point to act as a support,movethe location of point B toward the center of the ski until it canact as a support.Apply a load of 300 6 2 N to the ski.Readdeflection within 2 to 5 s after load application with anaccuracy of 60.05 cm.4.2 Afterbody Spring Constant and Forebody SpringConstantMount the ski to the clamping plate in a way thatthe ski forebody or ski afterbody can be bent freely from pointM.Apply a load of 50 6 0.5 N at point A or B normal to theline extended from the clamping plates.Read deflection within2 to 5 s after load application and measure it normal to