Journal of the Society of Motion Picture Engineers ( Volume: 45, Issue: 2, August 1945)

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The Calculation of Accelerations in Cam-Operated Pull-Down Mechanisms

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Publisher: SMPTE
Doc Type: Journal Article
Article Type: research-article
Abstract: The maximum force between a cam and its follower depends on the mass of the driven elements and the maximum accelerations imparted to them by the cam. The magnitudes of these forces affect the wear on the surfaces and the tendency of the mechanism to be noisy. If the follower works on one side of the cam only, contact being maintained by a spring, the required spring tension is determined by the acceleration. Some cams can be designed to give a predetermined motion and if the motion can be simply expressed mathematically, the acceleration can be easily calculated. Other types of cam are made up of a series of circular arcs and the motion of the follower is determined by certain geometrical relations. For any given design, the position of the follower can be calculated point by point of the cam rotation, by solving triangles, or graphically. But to determine velocities by measuring slopes of the position curve, and accelerations by measuring slopes of the derived velocity curve, gives only rough approximations. Determination of velocity by writing and then differentiating a mathematical equation for follower position in terms of cam position, appears to be possible only for the simplest case, but if the problem is taken in 2 steps, first to find the follower position by the solution of one or 2 triangles, and then for a given position, to find the velocity and acceleration from formulas given in the paper, the calculations are not difficult, and the degree of precision may be whatever is required.
Publication Date: 1945-08-01
DOI: 10.5594/J12852
Link: https://doi.org/10.5594/J12852
Author(s): Edward W. Kellogg

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Edward W. Kellogg; The Calculation of Accelerations in Cam-Operated Pull-Down Mechanisms, Journal of the Society of Motion Picture Engineers ( Volume: 45, Issue: 2, August 1945); SMPTE, 1945. Available at https://doi.org/10.5594/J12852

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Edward W. Kellogg; The Calculation of Accelerations in Cam-Operated Pull-Down Mechanisms, Journal of the Society of Motion Picture Engineers ( Volume: 45, Issue: 2, August 1945); SMPTE, 1945. Available at https://doi.org/10.5594/J12852

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<span class="citation">Edward W. Kellogg; <cite>The Calculation of Accelerations in Cam-Operated Pull-Down Mechanisms</cite>, Journal of the Society of Motion Picture Engineers ( Volume: 45, Issue: 2, August 1945); SMPTE, 1945. Available at <a href="https://doi.org/10.5594/J12852" target="_blank" rel="noopener">https://doi.org/10.5594/J12852</a></span>

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<li>
Edward W. Kellogg; <cite id="bib-10-5594-j12852">The Calculation of Accelerations in Cam-Operated Pull-Down Mechanisms</cite>, Journal of the Society of Motion Picture Engineers ( Volume: 45, Issue: 2, August 1945); SMPTE, 1945
<span class="doi">10.5594/J12852</span>
</li>