1、Designation: F1832 07 (Reapproved 2011)An American National StandardStandard Test Method forDetermining the Force-Draw and Let-Down Curves forArchery Bows1This standard is issued under the fixed designation F1832; the number immediately following the designation indicates the year oforiginal adoptio
2、n 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 test method covers the procedure to be used todetermine the force-draw
3、 and let-down curves for archerybows.1.2 The values stated in inch-pound units are to be regardedas the standard. The SI units given in parentheses are forinformation only.1.3 This standard does not purport all of the safety con-cerns, if any, associated with its use. It is the responsibility ofthe
4、user of this standard to establish appropriate safety andhealth practices, and determine the applicability of regulatorylimitations prior to use.2. Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 ATA (archery trade association) draw length,nperpendicular distance from the point w
5、here the shootingstring of the bow contacts bottom of the nock slot of the arrow,to a vertical line through the pivot or low point of the hand grip(draw length pivot point), plus a standard dimension of 134 in.(44.5 mm).2.1.2 brace height, ndimension in inches (millimetres),from the grip pivot point
6、 (low point) of the grip to the nearestside of the bowstring, measured perpendicular to the bow-string, with the bow strung and in the undrawn condition.2.1.3 compound bow, ntype of bow that imposes a sec-ondary system of control of the force-draw characteristic on theusual limb geometry control sys
7、tem of the conventional bow.2.1.3.1 DiscussionThis secondary control system can becomposed of cam, levers, cables, or other elements, andcombinations thereof. The dual control system permits greatversatility in the design of the force-draw characteristic, andsimplifies the inclusion of let-off. In g
8、eneral, it is normal forcompound bows to have greater stored energy than conven-tional bows for a given level of peak or maximum draw weight.2.1.4 draw, vto move the shooting string of a bow fromthe rest or braced position toward the full drawn position byapplying force to said string.2.1.4.1 Discus
9、sionSuch action causes the limbs of thebow to bend and store energy. Moving the string from braceheight to the full draw position corresponds to the draw strokeof a bow.2.1.5 draw cycle, ncombination of the draw-stroke andthe let-down stroke, resulting in a full cycle from brace heightto full draw a
10、nd return to brace height.2.1.6 draw-stroke, ndistance in inches (millimeters) frombrace height to full draw.2.1.7 force-draw curve, ncurve that is plotted using theforce readings, taken at incremental values of draw lengthwhen drawing the bow, as the ordinate and the correspondingdraw length as abs
11、cissa.2.1.8 full draw, nposition assumed by the bowstring whenthe bow is drawn to a draw length corresponding to that fromwhich it will be released for the shot.2.1.8.1 DiscussionFor most standard test purposes fulldraw is specified as 30 in. (762 mm) ATA draw length forcompound bows, and 28 in. (71
12、1.2 mm) ATA draw length fornon-compound bows, but it can take any assigned value.2.1.9 let-down curve, ncurve that is plotted using theforce readings, taken at incremental values of draw lengthwhen relaxing the bow, as the ordinate and the correspondingdraw length as abscissa.2.1.10 let-off, ndiffer
13、ence between the peak or maximumdraw force reached during the draw stroke of a bow, and thelowest level of draw force reached subsequent to that peak.2.1.10.1 DiscussionQuantitatively, it is most frequentlyexpressed as a percentage of the peak force and is then referredto as percent of let-off.2.1.1
14、1 non-compound bow, nbow constructed in the tra-ditional manner, having two flexing limbs extending outwardlyin opposite directions from a handle.2.1.11.1 DiscussionA single shooting string of a lengthshorter than the bow, connects the extreme ends of the limbscausing them to assume a pre-stressed f
15、lexed condition. Draw-ing the bow causes additional bending and stressing of thelimbs, storing the energy necessary to propel the arrow. Control1This test method is under the jurisdiction of ASTM Committee F08 onSportsEquipment and Facilities and is the direct responsibility of Subcommittee F08.16 o
16、nArchery Products.Current edition approved June 1, 2011. Published July 2011. Originally approvedin 1997. Last previous edition approved in 2007 as F1832 07. DOI: 10.1520/F1832-07R11.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.of
17、 the force-draw characteristic of the bow is exercised entirelyby the static and dynamic geometry of the flexing limbs and thebowstring.2.1.12 peak draw force, nmaximum force reached whendrawing a bow.2.1.12.1 DiscussionFor conventional bows, the peakdraw force is usually reached at the full draw co
18、ndition. Forcompound bows, the peak draw force is reached part waythrough the draw stroke.2.1.13 power-stroke, ndistance in inches (millimetres)from full draw to brace height.2.1.14 static hysteresis, ndifference in pounds (newtons),measured under static conditions, between the draw force andthe let
19、-down force for any given draw length.2.1.14.1 DiscussionIntegrated over the full draw cycle ofthe bow, the static hysteresis is expressed as foot-pounds(joules) of energy.2.1.15 stored energy, nenergy required to draw a bowfrom brace height to full draw, usually expressed in foot-pounds (joules).3.
20、 Significance and Use3.1 This test method establishes the procedure to be used tomeasure the force necessary to draw an archery bow frombrace height to the full draw position, and the holding forcenecessary to retain the bow string when the bow is let-downfrom full draw to brace height. The force va
21、lues taken atincrements of draw length are then plotted versus draw lengthusing rectangular coordinates. The resulting curves are knownas the force-draw curve and the let-down curve.3.2 The force-draw curve is used to determine the energythat the limbs of the bow store when it is drawn. The area und
22、erthe curve between the positions of brace height and full drawcan be expressed as stored energy.3.3 The let-down curve is used to determine the energyrequired to restrain the bowstring as the bow is let-down fromfull draw to brace height. The energy represented by the areaunder the curve can be sub
23、tracted from the stored energy inorder to establish the static hysteresis of the bow system.4. Apparatus4.1 Force-Draw MachineA device capable of holding thebow with the restraining force located at the low point of thegrip while the bowstring is drawn from brace height to fulldraw. The force drawin
24、g the bowstring shall be positioned nearthe center of the bowstring so the restraining and drawingforces balance, thus stabilizing the bow during the operation.The device contacting the bowstring shall be a round orradiused section with a radius of18 in. (3.2 mm). The systemused to draw the bowstrin
25、g shall be capable of a smooth andsteady movement, and must maintain continuous unrelaxedforce so that no hysteresis effect is experienced.4.2 Force-Reading DeviceA scale or load cell shall beinterposed between the bowstring and the cable or rod used todraw the bowstring so that the force reading is
26、 direct and notcontaminated in any way. The force measuring device shall becapable of weighing to 0.25 lbf (1.12 N). A spring scale withadequate resolution may be capable of measuring the drawingforce for conventional bows but will provide questionablevalues when used for compound bows with precipit
27、ous let-off.4.3 Draw Length ScaleA graduated scale at least 36 in.(914.4 mm) in length having commercial accuracy shall beused to measure the draw length. It shall be indexed at a point134 in. (44.5 mm) forward of the low point or pivot point ofthe grip.5. Procedure5.1 Adjust the bow to the desired
28、peak draw force and drawlength. On most conventional bows it will not be possible toadjust draw force and draw length, however the bowstringlength should be twisted or untwisted to provide the recom-mended brace height.5.2 To derive data for the force-draw curve, mount the bowin the force-draw devic
29、e with the low or pivot point of the gripengaging the retaining surface of the device. Set the index ofthe linear scale 134 in. (44.5 mm) forward of the low point ofthe grip. Attach the drawing device to the bowstring at alocation near the center of the string, position the bowstring atbrace height,
30、 and draw the bow to the first incremental value ofdraw length. Record the force without relaxing tension toeliminate any effect of hysteresis. Continue to draw thebowstring, recording the force for each increment of drawlength until reaching one increment beyond the desired fulldraw position. The r
31、ecorded data will be the basis of theforce-draw curve.5.3 To obtain the data for the let-down curve, relax the forceretaining the bowstring until it returns to the full draw positionand record the corresponding force. It will be somewhat lowerthan the force recorded when the bow was drawn to the sam
32、eposition. The difference is an indication of static hysteresispresent. Continue to back down the bowstring, recording theforce readings at the identical increments of draw length usedwhen the force-draw curve was established. Do this until thebowstring has returned to brace height. The recorded for
33、celevels and the corresponding draw length values are the datafor the let-down curve.5.4 The force-draw and let-down curves are plotted onrectangular coordinate scales with the force values as theordinate and the draw length values as the abscissa. It iscommon practice to superimpose the let-down cu
34、rve on theforce-draw curve. The area under the curves may be deter-mined by any acceptable method. With appropriate conversion,it is usually expressed in units of energy, for example,foot-pounds (joules).6. Precision and Bias6.1 PrecisionThe precision of this test method for deter-mining the force-d
35、raw and let-down curves and the values ofthe energy represented is being determined.6.2 BiasNo statement on bias is being made at this timebecause no data is available on which to base an evaluation ofbias.7. Keywords7.1 brace-height; compound bow; draw-stroke; force-draw;let-downF1832 07 (2011)2AST
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