ASTM_F_779_-_12.pdf

Designation:F77912Standard Test Method forTorsion Characteristic of Alpine Skis1This standard is issued under the fixed designation F779;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 measurement of ski fore-body torsion and ski afterbody torsion of adult Alpine skis.1.2 No limitation to ski size is proposed.This test method isapplicable to all Alpine skis.1.3 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 of Terms Specific to This Standard:2.1.1 afterbody torsion angle,Athat angle,in degrees,towhich the running surface is rotated at Point A when a moment,Mt,is applied at Point A as shown in Fig.1.2.1.2 afterbody torsional spring constant,CAthe momentper degree of rotation of the ski afterbody when the ski isclamped in accordance with Fig.1 and the moment applied inaccordance with Fig.2.CANm/deg!5MtA2.1.3 forebody torsion angle,Fthat angle,in degrees,towhich the running surface is rotated at Point F when a moment,Mt,is applied at Point F as shown in Fig.1.2.1.4 forebody torsional spring constant,CTSthe momentper degree of rotation of the ski forebody when the ski isclamped in accordance with Fig.1 and the moment applied inaccordance with Fig.2.CFNm/deg!5MtF2.1.5 moment of torsion,Mtthe moment in newton-metresapplied to rotate the ski about its longitudinal axis when the skiis clamped according to Fig.1 and the moment is appliedaccording to Fig.2.3.Significance and Use3.1 This test method provides a means for determining thetorsional stiffness of Alpine skis.It is not intended to evaluatethe data with regard to the quality of the ski.4.Apparatus4.1 Clamping Fixture,to grip the ski as a vise with a flat,rigid jaw and three clamps with at least 150+50,0 mmspacing between them.One clamp is located at each end of thefixture and one in the center as illustrated in Fig.1.The clampsshould be at least 30 mm wide and cover the full width of theski.4.2 Torsion Head,shown in Fig.2,with low-friction mo-ment(0.2 Nm)and quasistatic loading system having aclamping fixture described in 4.1.Common devices for thisloading system are a weight on a cable wrapped around thehead,or a weight on a lever arm rigidly attached to the head.The torsion head clamping fixture should have a width of 10 61 mm and a length equal to or greater than the width of the ski.The base surface of the torsion head fixture to the ski baseshould be in the same plane as the clamping fixture(that is,camber forced out of ski in clamped position).4.3 Scale,to measure the torsion angle with an accuracy of0.5.5.Procedure5.1 Test skis at room temperature(23 6 5C)withoutspecific preconditioning.Torsion head and clamping fixture areadjusted such that the distance between them is C/2 6 2 mmshown in Fig.1.If the ski geometry does not allow point A orpoint F,or both,to be used as shown in Fig.1,move thelocation of point A or point F,or both,toward the center of theski;points A and F should be moved the minimum distancenecessary.Mount the ski to the clamping fixture so that the skiforebody or ski afterbody can rotate freely about Point M.Thetorsion head is attached to the ski at Point A or F 6 2 mm suchthat the longitudinal axis of the ski is in the center of the torsionhead.Apply a moment,Mt,of 20 6 0.2 Nm.(The momentshould be applied quasistatically.)The torsion angle must beread within 2 to 5 s after the torsion moment,Mt,is initiallyapplied.1This test method is under the jurisdiction of ASTM Committee F27 on SnowSkiing and is the direct responsibility of F27.30 on Skis and Boots.Current edition approved March 1,2012.Published March 2012.Originallyapproved in 1982.Last previous edition approved in 2006 as F779 93(2006).DOI:10.1520/F0779-12.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.Calculation6.1 Calculate the afterbody torsional spring constant,CA,innewton-metres per degree,in accordance with the followingequation:CA5MtA(1)6.2 Calculate the forebody torsional spring constant,CF,innewton-metres per degree,in accordance with the followingequation:CF5MtB(2)7.Report7.1 Report the following information:7.1.1 ASTM F779,7.1.2 Brand,model designation,manufacturers registrationnumber,size of ski,and the locations of points A and F relativeto the tip and tail of the ski,respectively,7.1.3 Afterbody torsional spring constant,forebody tor-sional spring constant,and7.1.4 Any deviations from this standard with explanations.8.Precision and Bias8.1 PrecisionThe precision of thi