A Note on the Projection Life of Film

Tests with intermittent sprockets of different diameters have shown that the maximum projections which can be attained depends greatly on a diameter within the range of 0.943 inch to 0.965 inch diameters, about a 2½ per cent range. The sprocket pitch for best wear is greater than the apparent match between static perforation measurements and sprocket dimensions. This is in accord with the view that the elastic characteristics of the base are important at this point in the projection cycle. Tests with different pressures on the film gate show that this setting is an important factor affecting wear at the intermittent sprocket. The way by which perforations tear is different under the following two conditions: (a) film pitch less than best match for sprocket pitch, and (b) film pitch greater than best match for sprocket pitch.

Print ISSN

0097-5834

Published

1943-10

Content type

Original Research

DOI

10.5594/J09808