On a compound the nocking point does not travel in a straight line during the draw, and how far it strays depends on the bow's geometry
4 studies
The summary today
The mechanics are there and carefully worked out, but they come from a single author and from models checked on a handful of bows. One formula, valid for compound, recurve and longbow alike, says that with the nock set above the geometric centre of the string, as it nearly always is, the nocking point rises throughout the draw, and rises more the further it sits from that centre. On a single-cam compound the uncorrected path would stray 21.8 mm from the straight line; with the cam tracks corrected by the manufacturer the measured path stays within 1.5 mm, the best of the many bows the author says he measured. As early as 2009, presenting a dynamic model, the same author had measured a path within a millimetre of a straight line on another single cam bow. Geometry decides: a longer bow axle to axle strays less, the unbraced limb angle matters little, and only single and hybrid cams have the degrees of freedom to straighten the path, while twin and binary cams do not. A second paper by the same author adds that it is the nocking-point path, more than string force or the rest spring, that governs how the arrow behaves, and an independent model from 2012 finds a transverse component of about 9 per cent in the force at full draw. The registry counts this work as modelling, because the measurements on bows serve to check the calculation rather than standing as a test of their own; and nobody has yet looked at the target, meaning a group or a score comparing a corrected bow with an uncorrected one.
Also phrased as: "nock travel"; "nocking point travel"; "the nocking point rises during the draw"; "straight-line nock travel"; "cam timing and nock travel"
In practice
Among compound archers it is said that the nocking point belongs level with the rest mounting hole, and that cams out of time send arrows low when you pull harder into the stops.
Evidence
-
2009
Context Model Published later
In the paper presenting his dynamic model of the compound, the author measures the path of the nocking point while drawing an Archery Research AR34 single cam: it stays within 1 mm of a straight line perpendicular to the string at rest, and the riser flexes less than 1.5 mm over its whole length. The measurement serves to justify an assumption of the model, the one that allows only half of the bow to be analysed; it is given in a single line, with no graph, and concerns one bow.
A compound archery bow dynamic model, suggesting modifications to improve accuracy · J L Park
-
2010
For Model Published later
A geometric calculation of the nocking-point path in the vertical plane, checked on real compound bows: on a single-cam bow of a reputable make with 0.865 m axle to axle, the maximum deviation from the straight line would be 21.8 mm without correction, while with the cam tracks corrected by the manufacturer the measured path stays within 1.5 mm, the best of the many bows the author measured. With the nock above the geometric centre of the string the nocking point rises continuously throughout the draw, and on a twin-cam bow the measured path closely follows a parabola with its turning point at brace height.
Compound-archery-bow nocking-point locus in the vertical plane · J L Park
-
2010
For Model Published later
In the same paper the deviation grows with the distance of the nock from the geometric centre of the string, falls markedly as the bow gets longer axle to axle, and is barely affected by the unbraced limb angle. Counting the degrees of freedom of the cams, only single and hybrid cams can straighten the path at the design stage; on twin and binary cams all that is left is to bring the nock closer to the centre of the string, and on a corrected single or hybrid cam the intended position is level with the rest mounting hole.
Compound-archery-bow nocking-point locus in the vertical plane · J L Park
-
2010
Context Model Published later
The path the arrow actually experiences adds the bow's rotation during the power stroke, small but always present, to the geometric one: on the single-cam bow studied the nocking point first drops below the line, then crosses above it more quickly and stays almost constant over the last stretch, when the arrow is already moving fast. Placing the arrow pass exactly at the geometric centre would remove the problem, but it puts the hand well below the centre of the bow, which then feels top-heavy and is usually not preferred.
Compound-archery-bow nocking-point locus in the vertical plane · J L Park
-
2011
Context Model Published later
A dynamic model of an arrow shot from a compound bow, with a sensitivity analysis: changing the string force along the arrow or the rest spring alters the arrow's behaviour little, while changing the nocking-point path alters it markedly. It does not measure the path again: it explains why it matters.
The Behaviour of An Arrow Shot from a Compound Archery Bow · J L Park
-
2012
Context Model Published later
A mathematical model of a compound bow's asymmetry in the vertical plane, checked with photographs on an experimental bow at full draw (0.738 m): the force is not directed along the arrow but has a transverse component of 9.4 N against 104.5 N longitudinal, about 9 per cent, and the slope of the line from grip to nock is 0.088 measured against 0.090 simulated. It shows that the asymmetric geometry shifts the forces in the vertical plane, but it does not follow the nocking point through the draw.
Compound archery bow asymmetry in the vertical plane · Ihor Zanevskyy
Status history
- 2009 Not studied The first measurement of the path arrives in passing, in the paper presenting a dynamic model of the compound: on a single cam bow the nocking point stays within a millimetre of a straight line perpendicular to the string at rest. The author needs it so that only half of the bow has to be analysed, and the question itself is not asked: nobody has yet calculated how far the path strays from a straight line, or what that depends on.
- 2010 Transferred The first work on the question calculates the nocking-point path with a formula valid for compound, recurve and longbow, and checks it on real bows: on an uncorrected single cam the deviation from the straight line would reach 21.8 mm, while with the cam corrected by the manufacturer 1.5 mm is measured. A longer bow axle to axle strays less, the unbraced limb angle matters little, and only single and hybrid cams can straighten the path. The measurements serve to check the model rather than standing as an equipment test of their own, and there is a single author: the claim rests on a model, hence transferred.
- 2011 Transferred The same author publishes the dynamic model of an arrow shot from a compound: in the sensitivity analysis the arrow's behaviour depends above all on the nocking-point path, far more than on string force or the rest spring. It explains why the path matters, but it does not measure it again and does not come from an independent group: the status stays transferred.
- 2012 Transferred A second author models the compound bow's asymmetry in the vertical plane and checks it with photographs on an experimental bow: at full draw the force has a transverse component of about 9 per cent. It is an independent model pointing the same way, but it does not follow the nocking point through the draw and does not reach the target: transferred.
Related
Related articles
Research lines
Cite
Campagna, M. (2026). On a compound the nocking point does not travel in a straight line during the draw, and how far it strays depends on the bow's geometry (Version 3). In Evidence Registry. Retrieved 16 October 2026, from https://matteocampagna.com/en/registry/equipment/compound-nocking-point-path
@misc{campagna2026_incoccopercorsocompound,
author = {Campagna, Matteo},
title = {On a compound the nocking point does not travel in a straight line during the draw, and how far it strays depends on the bow's geometry},
year = {2026},
howpublished = {Evidence Registry, matteocampagna.com},
url = {https://matteocampagna.com/en/registry/equipment/compound-nocking-point-path},
note = {Version 3; accessed 2026-10-16}
}
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