Journal of the Society of Motion Picture Engineers (1930-1949)

486 MILLER November assurance of safety at 5500 revolutions per second, corresponding to 1.122 X 106 frames per second. It was not possible to operate the camera at such speed, however, because no solution was found to the problem of spattering oil from the journal bearing onto the camera lenses. Oil spattering was aggravated by the necessary evacuation of the rotor chamber. After some motion pictures of engine knock were obtained at 2 X 105 frames per second, the air-turbine drive was finally abandoned. Work was then started on an electromagnetic drive and suspension, modeled after an earlier development at the University of Virginia,9 but with some novel features. The photographs recently exhibited, taken at 5 X 10 5 frames per second, were obtained with the electromagnetic drive and suspension. I 23456 7 Fig. 6 — Selected frames from motion picture of engine knock. EXAMPLES OF PHOTOGRAPHS MADE WITH CAMERA Fig. 6 presents selected frames from a shot of engine knock obtained at 2 X 105 frames per second. These photographs have been discussed at length elsewhere. 1>5 The first frame of the series was exposed 25 X 10~6 second before knock started to develop, and the second frame only 5 X 10 ~6 second before the start of knock. Little change took place between the exposures of these two pictures because the combustion that precedes knock is too slow to produce much change in so short a time. Approximately the right-hand half of the piston top is seen in each frame of Fig. 6, looking downward through a glass window mounted in the cylinder head. The spark plug was at the left side of the chamber, far outside the field of view. Before the exposures of the first two frames the flame traveled all the way across the combustion chamber from left to right. In each of these frames, the black cloud