The Moving Picture World (April 1908)

284 THE MOVING PICTURE WORLD Lessons for Operators. • By F. H. Richardson, Operator, Chicago. CHAPTER VI—THE CARBONS. There are as many different ideas regarding the kind, degree of hardness and set of carbons as there are hairs on a dog's tail, and the advocates of each will advance ' plausible arguments in support of their particular pet theory every time. For ordinary work, where from twenty-five to forty-, five amperes of current are used, five-eighths cored and the same size solid below is, in the writer's judgment, best for direct current. Five-eighths cored above and half-inch solid below will fill the bill for alternating, but care should be exercised not to get the solid too hard or they will burn red, thus producing poor light. A me- dium grade of hardness is best for both direct and alter- nating. Many prefer five-eighths cored both above and below for alternating, and better results will be produced if it is desired to use two craters than with the solid below. For low'voltage and weak current, smaller, very soft carbons should be used. There is no set rule, how- ever, that can be made to fit all conditions, and if your light is not all it should be, try other carbons. Don't be afraid to experiment until you get what is best for your particular case, and above all things don't be satis- fied until you get the result you desire. It can be gotten all right and it is simply up to you, Mr. Operator, to get it. Setting the carbons is a question upon which scarcely any two operators agree, but let it, in the first place, be thoroughly understood that practically all available light comes from the small cup-shaped depression (crater) that forms on the upper carbon with direct current and on both carbons with alternating current. With this in mind it will readily be seen that the operator who wants the best light will bend his energies and exercise his ingenuity in so setting his carbons that these craters will be of good size, well shaped and as nearly as possible squarely face the condenser lens, the latter being of prime importance. It is up to the individual operator to ex- periment until these results are as nearly perfect as may be obtained. An angle that would in one case produce the desired result will be found to be all wrong in an- other. In general, however, the writer has found that, where direct curjent is used, setting the carbons in line wrfli each other and angling the whole back about twenty- five degrees from the perpendicular; setting the tip of the upper carbon about one-eighth to three-sixteenths of an inch behind the center of the lower tip, gives the best results. But very excellent light may be obtained by set- ting the lower straight up and down and angling the top carbon sharply back. But in any case, with direct cur- rent, always set the upper carbon tip back of the lower as above directed. This is for the purpose of forcing the crater to form on the face of the upper tip instead of at its center, in which case much of the light would be lost. With alternating current no set rule may be given with any degree of assurance, since there are so many varier ties of this current. Let it be said right here, however, that excellent projection light may be had from alter- nating current, though getting it requires skill and pa- tience. It must be borne in mind that with alternating current,,craters form both on the upper and lower tips, "this for'the' reasons'that the current flows both ways and <each- <carbofl ■• fe-aiternately -positive and negative several J^pusand^t^pes.-per ^ninute. By angling both carbons ahead a portion of the light from both craters may be obtained, but by this method it is practically impossible to maintain good craters and it is a very open question whether a part of the light from two comparatively poor craters is better than all that from one good one which may be obtained T>y setting them about the same as for direct current, save that the tips are always centered with each other for alternating 3 current. Personally the writer prefers the latter method, but this is a question each one must decide for himself when he is so unfortunate as to be^compelled to handle alternating. By the latter method better craters are maintained, but no light at all will be available from the lower. Always be sure your carbons are in exact line side- wise. If they are not, they will be likely to "sputter" . and the crater cannot be made to squarely face the con- denser. As a general thing, if the spot shows oblong, the long axle of it leaning, it indicates carbons out of line side wise. Carbons should always be carefully pointed, and time spent in doing this well, is well expended, since it enables one to get a good light-almost from the start . with new carbons. The careful operator will, on re- ceiving a bundle of carbons, at once point them all and place them in a suitable receptacle ready for instant use. The best method of doing this is as follows: Rest the end to be sharpened on edge of a bench, holding with left hand. Then rotate slowly toward you, filing the point with a medium wood-rasp. This will quickly pro- duce a perfect point. A flat place a quarter of an inch should be left—that is to say, don't file clear down to a sharp point. With direct current it is well to file a flat place on one side of the upper carbon point to assist the crater in forming quickly. To cut carbons into lengths, first notch a quarter of an inch deep on one side, then strike sharply over edge of bench opposite notch and the carbon will break square off at the notch. By this method the careful man may sharpen and cut into lengths a full bundle of carbons in half an hour and not spoil a single one.' Don't buy cheap carbons. They are an abomination. Get the best money will buy, every time —it pays. THE CONDENSER. Condenser lenses are made of standard diameter, i, l /i inches, but of varying focus, and it is of prime impor- tance that lenses of the right focus be used. The sizes most commonly used are 6>y 2 and 7J4, and from these two, several combinations may be had. Both lenses may be 6j4, both 7*4, or a 6}/ 2 in front and a 7 r / 2 behind, or vice versa. The shorter the throw the lower the number of focus required. In ordering condenser lenses the first time, always order from some reliable optical firm, giving exact length of throw and size of picture. Ascertain just what he supplies you with arid you may then order where you will and always-be right if you order the same thing. The lenses are subjected to the fierce heat of the arc lamp and will occasionally break, even with the most careful management. When you hear an operator boast- ing that he "never breaks a condenser," just tell him that Mr. Richardson says he is a prevaricator—that sounds better than the other word and means the same thing. Of course, however, breakage may be very largely augmented by ignorance or carelessness. But glass that is subjected constantly to alternate heating and cooling will occasionally break, no matter how careful one may be. There is, however, a wide divergence of opinion as to how best reduce breakage to a minimum. Many good, competent operators will assure you that breakage 1 caused by draft, but you will find others running wiw