Journal of the Society of Motion Picture and Television Engineers (1950-1954)

he moving pairs of reflectors on the pinning disk to the first refocusing lens. Phe side bridge carries the three mirrors ocated in the optical path between the wo refocusing lenses. The three mirrors upported by the side bridge can be noved in a direction parallel to the axes f the two refocusing lenses by adding r removing spacer blocks between the iridge and the housing. Side plates orm light-tight covers for the optical ystem. The lower two mirrors mounted on he side bridge must be adjustable to a 0° angle with great accuracy. The nounting of only one of these mirrors s attached directly to the side bridge, he other mounting is hinged to the irst, and is positioned by a differential crew, providing an exceedingly fine djustment. A simple optical check, vithout the need of any optical instrunents but the human eye, permits the ine adjustment needed. The mounting for the second reocusing lens is somewhat complicated y the need of incorporating the final nirror of the system, and the cylindrical ens near the film. As the angular velocity of the spinning isk is very constant during the period >f one rotation during which photographs re exposed, no provision is needed for stablishment of repetition rate on the hotosensitive film itself. A reading of he tachometer, recorded at the time he photographs are exposed, is satisactory. However, a special spark plug, lot indicated in the figures, has been built nto the camera housing for establishment f chronological identity between one or nore frames of the high-speed pictures ind corresponding datum points in >ther records, such as a photograph of a :athode-ray trace. The design conditions imposed severe equirements upon the drive for the pinning disk, involving a top speed of 12,000 rpm, a reasonably short acceleration period for the 50-lb disk, an effective means of braking, and the need for smooth acceleration and deceleration throughout. An estimate of the power required to drive the disk in air yielded a prohibitive value of 40 hp. Operation of the disk with at least a partial vacuum therefore appeared necessary. No encouragement was received from the manufacturers of seals for the transmission of power through the rotating shaft from atmosphere into the evacuated chamber. Although the use of a highfrequency synchronous motor within the evacuated space, cooled by circulating water, showed promise, this solution was considered to be somewhat too developmental. Finally a hydraulic system was chosen, to be supplied by Vickers, Inc. This system is standard, with the exception of the use of a needle valve in the discharge line of the hydraulic piston motor as a means of braking. The 10-hp electric motor drives a constant-delivery vane pump. Both motor and pump are mounted on a 30-gal reservoir. A pressure-relief valve in the line from the vane pump to piston motor is set at 1,000 psi. The flow-control valve provides a satisfactory flow rate of fluid, regardless of load. The hydraulic piston pump, 5 in. in diameter, is rated at 5 hp at 3600 rpm. In operation, the electric motor is started and the flow-control valve is set for a flow rate corresponding to the desired spin velocity of the disk. The pressure gauge in the line between vane pump and piston motor verifies the establishment of driving pressure and the cutoff of driving pressure when operating speed is reached. The camera disk accelerates with this arrangement to 6,000 rpm in 3 min., with a 25-in. vacuum in the chamber. Deceleration time from 6,000 rpm is also about 3 min. Miller and Scharf: Isotransport Camera 141