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Fig. 1. Outside configuration of 70mm Test Vehicle Recorder.
In Fig. 1 the outside configuration of the camera is shown. The large, heavy base-plate simplifies mounting the camera stably, even aboard aircraft. The lens is easily removed by taking out 6 screws. All adjustments of focus and aperture are clamped down for the aircraft use.
In Fig. 2 the camera is shown loaded with film, ready for the door to be closed. The 70mm film is wound on daylightloading spools. It can be seen that every adjustment interlocks with the door, so that the door cannot be closed and locked unless everything inside the camera has been adjusted correctly; also all parts must stay so adjusted until the door is opened again.
The number of moving parts has been reduced to a minimum. Attached directly to the motor shaft are an 8-in. diameter drum, a gear and a cam. The drum is the shutter; the gear drives the drive sprocket wheels and the take-up spool; and the cam operates the filmpulldown claws.
The shutter-drum has four openings approximately 1£ in. in height. This height gives excellent shutter efficiency and practically no focal-plane effect because of the large height of the openings.
It is the drum which limits the camera speed, for in preliminary tests the drum stretched out of shape at 580 frames/sec. However, the present shutter-drum and the present film-handling mechanisms have been operated at 510 frames/sec with no mishap.
The film-pulldown claws are operated from a cam. There are two sets of claws working alternately. Each of the two sets of claws is composed of four claws, two on each side of the aperture, making a total of eight claws. The timing of the claws is such that one set of four claws never pulls out of engagement with the film until the other set of four claws has made engagement. Thus the eight pulldown claws are controlling the exact position of the film at the aperture at all times almost as positively as positioning by registration pins.
In Fig. 3 the camera is shown with the aperture plate and the back pressureplate removed. Such removal is necessary for cleaning the camera, and it is advantageous in focusing of the actual image on ground film. On the aperture plate are two small lucite rods which transmit light from two neon timing lamps onto the upper two corners of the picture. There are also two small fiducial marks on the top margin, each one-half inch from the corner of the aperture.
In Figs. 2 and 3, under the "caution" sign and touching the inner edge of the film, can be seen a small metal plate which is the arm of a switch. This switch, called the finish switch, actuates a relay for turning off power to the motor after all the film has been exposed.
In Fig. 4 is a sample of pictures taken with the camera. The subject is an automobile running at 60 mph. Notice the two fiducial marks in the upper parts of the picture. The frame rate is approximately 300 frames/sec.
The advantages of this camera all seem to result from four characteristics :
1 . The camera has a high frame rate. Although several cameras record at
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June 1953 Journal of the SMPTE Vol. 60