Film Sprocket Design

THE analogy between motion picture film running over sprockets, and the metallic link belts or power transmission chain running with chain sprockets can exist only when the pitch of the film is identical with the pitch of the sprocket teeth on which it is being run. In the manufacture of power transmission chain and sprockets every effort is made to maintain identical pitch in both chains and sprockets. Commercial accuracy of metal power transmission chain admits of a tolerance of approximately 1/32″ to 1/16″ per foot. This is equivalent to approximately ¼ to ½ of one per cent, but in a chain there is always elongation corresponding to negative shrinkage in the case of film. The tools for locating holes in chain members being accurate as to center distance all discrepancy in pitch is equal to the accumulated tolerances in working fit of pins and holes. This may be compensated for to a certain extent in cutting the teeth of the sprockets. But even though the conditions are not perfect, the chain will accommodate itself to the sprocket in a measure and give satisfactory results.

Print ISSN

0096-6460

Published

1923-10

Content type

Original Research

DOI

10.5594/jj00013