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1949 ARC SPOTLIGHT 411
twistlock receptacle, and the two heavier power wires are connected to individual electrical jacks.
A horizontal swing-lock lever, and a vertical tilt-lock lever mounted on the yoke, can be set to give the required amount of friction to suit the individual operator, when following a moving act. The spotlight can be swung through a full 360 degrees horizontal travel, tilted down to angles of 45 degrees or more, and tilted up to approximately 30 degrees.
LAMP AND OPTICAL SYSTEM MOUNTING CHANNEL A heavy-gauge-steel U-shaped channel is employed to give a precision mounting platform for the lamp and optical system units. Being 4*/2 feet in length this channel is rigidly reinforced to guard against any bending or twisting moments that might occur.
The lamp and optical system are mounted separately in this channel and each is held securely in optical alignment by three conveniently located screws. The channel is fastened to the base cradle by four easily inserted retaining screws. This makes the "Trouper" easily disassembled into two units for shipment.
LAMPHOUSE
The rigid lamphouse is designed to accommodate an alternatingcurrent high-intensity carbon arc. (Fig. 3.) The correct carbon trim is two 6-mm X 7-inch National alternating-current high-intensity, copper-coated carbons which operate at 45 amperes and 21 volts.
The carbons, having a burning rate of 4.3 inches per hour, are fed automatically from a lead screw, which is rotated by a 20-revolutionper-hour synchronous drive motor. At this rate, a full trim of carbons will burn for 1 Va hours. Tiiis precision method of feeding results in a constant arc gap, and essentially no carbon drift. The carbons are held securely in the jaws by a special heat-resistant leaf spring. By use of a lifting cam the spring is decompressed rapidly for changing carbons. Knobs, for manual striking of the arc, and focus adjustment of the arc, extend through the rear of the lamp in a convenient location.
A silvered, glass reflector, elliptical in shape, efficiently collects the arc-crater light and directs it to a circular aperture. The crater is magnified 73/s times its original size at this aperture. The physical dimensions of the reflector are 3x/4-inch focal length, 24-inch working distance, and 10V4-inch diameter.
Horizontal and vertical reflector tilt adjustment handles, project through the rear of the lamp, and assure quick alignment of the projected carbon crater on the aperture hole. To keep the reflector free