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850 HANDBOOK OF PROJECTION FOR
CARBON CLAMPS.— Two sizes of negative carbon holders, or clamps, are supplied with the Peerless equipment. One is for seven and one for eight millimeter diameter carbons. Select the right one suited to your work, and place the shank thereof in the carbon holder support casting, AL-91, Fig. 315J, securing it in place by means of clamp screw, AL-92, Fig. 315J, in such position that the flat side of its front end will be down.
The lamp bed track with carbon holders, as a whole, are adjustable forward and backward independent of the reflector and it is by this movement that the Arc Crater is adjusted to its correct position in relation to the reflecor.
THE POSITIVE CARBON CLAMPING DEVICE is adjustable to fit any size carbon within range of the amperage for which the lamp is designed. Screw, AL-51, Fig. 315J, is an eccentric, and by turning it clamp AL-50 is either raised or lowered. To turn it you have but to loosen the nut at its rear end. You may then set the clamp in position to grasp any desired diameter of carbon, merely by turning the screw head to the desired position and holding it there while you tighten the nut at its back end. By removing the nut on the rear end of screw AL-51, you may pull the whole thing out, if you wish, and see just how it is made and how it operates.
CAUTION. — When you have adjusted the carbon clamp lever as to height, be sure and tighten nut down solidly, so that the eccentric will not slip when a carbon is clamped into its holder. Better lubricate the screw of the nut with powdered graphite, as it will be subject to some heat.
INSERTING CARBONS.— Having the negative carbon holder in place and properly adjusted, and the positive carbon clamp adjusted for the diameter of carbon you will use, by means of the positive crater position indicator pull bar, AL 123; Figure 315K; bring indicator pointer arm, AL 122, downward; place the positive carbon in position in the holder and clamp it when the end is just even with pointer No. AL-120. The positive carbon crater indicator designates the exact focal point of the reflector, which is the position in which the positive crater should be carried.
After this has been completed, pull outward on bar No. AL123, Fig. 315K to throw No. A-122 indicator pointer arm out of the path of light reflected by the reflector; bring the tip of the negative carbon to within about three sixteenths of an inch of the positive and, assuming that the lamp has been connected through the proper current controlling device, you