ASTM F1832-07(2011)
(Test Method)Standard Test Method for Determining the Force-Draw and Let-Down Curves for Archery Bows
Standard Test Method for Determining the Force-Draw and Let-Down Curves for Archery Bows
SIGNIFICANCE AND USE
This test method establishes the procedure to be used to measure the force necessary to draw an archery bow from brace height to the full draw position, and the holding force necessary to retain the bow string when the bow is let-down from full draw to brace height. The force values taken at increments of draw length are then plotted versus draw length using rectangular coordinates. The resulting curves are known as the force-draw curve and the let-down curve.
The force-draw curve is used to determine the energy that the limbs of the bow store when it is drawn. The area under the curve between the positions of brace height and full draw can be expressed as stored energy.
The let-down curve is used to determine the energy required to restrain the bowstring as the bow is let-down from full draw to brace height. The energy represented by the area under the curve can be subtracted from the stored energy in order to establish the static hysteresis of the bow system.
SCOPE
1.1 This test method covers the procedure to be used to determine the force-draw and let-down curves for archery bows.
1.2 The values stated in inch-pound units are to be regarded as the standard. The SI units given in parentheses are for information only.
1.3 This standard does not purport 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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Standards Content (Sample)
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Designation: F1832 − 07 (Reapproved 2011) An American National Standard
Standard Test Method for
Determining the Force-Draw and Let-Down Curves for
Archery Bows
This standard is issued under the fixed designation F1832; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.1.4 draw, v—to move the shooting string of a bow from
the rest or braced position toward the full drawn position by
1.1 This test method covers the procedure to be used to
applying force to said string.
determine the force-draw and let-down curves for archery
2.1.4.1 Discussion—Such action causes the limbs of the
bows.
bow to bend and store energy. Moving the string from brace
1.2 The values stated in inch-pound units are to be regarded
height to the full draw position corresponds to the draw stroke
as the standard. The SI units given in parentheses are for
of a bow.
information only.
2.1.5 draw cycle, n—combination of the draw-stroke and
1.3 This standard does not purport all of the safety
the let-down stroke, resulting in a full cycle from brace height
concerns, if any, associated with its use. It is the responsibility
to full draw and return to brace height.
of the user of this standard to establish appropriate safety and
2.1.6 draw-stroke, n—distance in inches (millimeters) from
health practices, and determine the applicability of regulatory
brace height to full draw.
limitations prior to use.
2.1.7 force-draw curve, n—curve that is plotted using the
2. Terminology
force readings, taken at incremental values of draw length
when drawing the bow, as the ordinate and the corresponding
2.1 Definitions of Terms Specific to This Standard:
draw length as abscissa.
2.1.1 ATA (archery trade association) draw length,
n—perpendicular distance from the point where the shooting
2.1.8 full draw, n—position assumed by the bowstring when
string of the bow contacts bottom of the nock slot of the arrow,
the bow is drawn to a draw length corresponding to that from
to a vertical line through the pivot or low point of the hand grip
which it will be released for the shot.
(draw length pivot point), plus a standard dimension of 1 ⁄4 in.
2.1.8.1 Discussion—For most standard test purposes full
(44.5 mm).
draw is specified as 30 in. (762 mm) ATA draw length for
compound bows, and 28 in. (711.2 mm) ATA draw length for
2.1.2 brace height, n—dimension in inches (millimetres),
non-compound bows, but it can take any assigned value.
from the grip pivot point (low point) of the grip to the nearest
side of the bowstring, measured perpendicular to the
2.1.9 let-down curve, n—curve that is plotted using the force
bowstring, with the bow strung and in the undrawn condition.
readings, taken at incremental values of draw length when
relaxing the bow, as the ordinate and the corresponding draw
2.1.3 compound bow, n—type of bow that imposes a sec-
length as abscissa.
ondarysystemofcontroloftheforce-drawcharacteristiconthe
usual limb geometry control system of the conventional bow.
2.1.10 let-off, n—difference between the peak or maximum
2.1.3.1 Discussion—This secondary control system can be
draw force reached during the draw stroke of a bow, and the
composed of cam, levers, cables, or other elements, and
lowest level of draw force reached subsequent to that peak.
combinations thereof. The dual control system permits great
2.1.10.1 Discussion—Quantitatively, it is most frequently
versatility in the design of the force-draw characteristic, and
expressed as a percentage of the peak force and is then referred
simplifies the inclusion of let-off. In general, it is normal for
to as percent of let-off.
compound bows to have greater stored energy than conven-
2.1.11 non-compound bow, n—bow constructed in the tra-
tional bows for a given level of peak or maximum draw weight.
ditional manner, having two flexing limbs extending outwardly
in opposite directions from a handle.
2.1.11.1 Discussion—A single shooting string of a length
This test method is under the jurisdiction of ASTM Committee F08 onSports
Equipment and Facilities and is the direct responsibility of Subcommittee F08.16 on
shorter than the bow, connects the extreme ends of the limbs
Archery Products.
causing them to assume a pre-stressed flexed condition. Draw-
Current edition approved June 1, 2011. Published July 2011. Originally approved
ing the bow causes additional bending and stressing of the
in 1997. Last previous edition approved in 2007 as F1832 – 07. DOI: 10.1520/
F1832-07R11. limbs, storing the energy necessary to propel the arrow. Control
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1832 − 07 (2011)
of the force-draw characteristic of the bow is exercised entirely capable of weighing to 0.25 lbf (1.12 N). A spring scale with
by the static and dynamic geometry of the flexing limbs and the adequate resolution may be capable of measuring the drawing
bowstring. force for conventional bows but will provide questionable
values when used for compound bows with precipitous let-off.
2.1.12 peak draw force, n—maximum force reached when
drawing a bow.
4.3 Draw Length Scale—A graduated scale at least 36 in.
2.1.12.1 Discussion—For conventional bows, the peak draw
(914.4 mm) in length having commercial accuracy shall be
force is usually reached at the full draw condition. For
used to measure the draw length. It shall be indexed at a point
compound bows, the peak draw force is reached part way
1 ⁄4 in. (44.5 mm) forward of the low point or pivot point of
through the draw stroke.
the grip.
2.1.13 power-stroke, n—distance in inches (millimetres)
5. Procedure
from full draw to brace height.
2.1.14 static hysteresis, n—difference in pounds (newtons), 5.1 Adjust the bow to the desired peak draw force and draw
mea
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