TR 890 C3 E72 33fl RUCTION OF DISABLED MEN IN MOTION PICTURE PROJECTION AN ELEMENTARY TEXT BOOK By JAMES R. CAMERON /nttrwtor of Projection The Red Crott Institute for C-ipped and Diiabled Men NEW YORK THE RED CROSS INSTITUTE FOR CRIPPLED AND DISABLED MEN 1919 GIFT OF MOTION PICTURE PROJECTION INSTRUCTION OF DISABLED MEN IN MOTION PICTURE PROJECTION AN ELEMENTARY TEXT BOOK By JAMES R. CAMERON Instructor of Projection The Red Cross Institute for Crippled and Disabled Men NEW YORK THE RED CROSS INSTITUTE FOR CRIPPLED. AND DISABLED MEN 1919 C3 ACKNOWLEDGMENT IS HEREBY MADE TO THE NICHOLAS POWER COMPANY AND MR. J. H. HALLBERG FOR THE LOAN OF SEVERAL CUTS AND PLATES USED IN THIS BOOK V COPYRIGHT, 1918 BY THE RED CROSS INSTITUTE FOR CRIPPLED AND DISABLED MEN MOTION PICTURE PROJECTION INTRODUCTION Fifteen to twenty years ago the motion picture was regarded as an amusement for children and little else. Today the industry is the fifth largest in the United States. The motion picture now commands the interest and attention of leaders in every field of endeavor and it is judged ky the high standards that are applied to the other arts. The development of the motion picture in mechanical and artistic perfection has brought about a correspond- ing demand for highly skilled projectionists. The poorly projected film, notwithstanding the thought, expense, and effort expended in its making, is stamped as a failure. The man who stands in the booth "and merely turns the crank" is as obsolete as the "Nickelo- deon." Into his place has stepped an artisan a man trained in applied electricity, optics, the theory of light, and the manifold complications that are entailed in successful projection. No man is permitted to operate the machine unless he has a city license, which means that he must pass a thorough examination before he can go to work. The need for schools to train motion picture projectors is greater at the present time than ever. Manufac- turers and exhibitors state that there is a scarcity of good projectionists, and they offer ready and profitable employment to qualified men. VI MOTION PICTURE PROJECTION The shortage of labor caused by the war pointed out the necessity as well as the wisdom of utilizing every possible unit of productivity. The experience of the European belligerents proved that it is possible to train cripples for trades in which their physical handicaps do not debar them from competing successfully with the able-bodied. Soon after America's entry into the war, a group of far-seeing men realized the need of pro- viding training for the cripples of industry so that the experience thus gained might serve as a basis for the re-education of the returned disabled soldier. The effort of these men culminated in the establishing in New York City of the Red Cross Institute for Crip- pled and Disabled Men, under the auspices of the American Red Cross. Departments of industrial sur- veys, research, employment and public education were inaugurated and the foundation of the first special non- commercial training school for the physically handi- capped in the United States was built. Classes in the manufacture of artificial limbs, mechanical drafting, printing, jewelry making, and oxy-acetylene welding were begun, and in May, 1918, a course in motion pic- ture operating was introduced with James R. Cameron as instructor. The choice of motion picture projecting as a trade for the cripple was based on the knowledge that it was one of the growing trades, that in England and France the cripple had made good as a projectionist, that the wages were good, that working conditions were favor- able, and that almost any man with both hands intact could, with a course of study of about two months in duration, acquire sufficient knowledge to enable him to MOTION PICTURE PROJECTION Vll enter an operating booth, and take charge of the machines. About twelve pupils responded to roll call during the first days of the class at the Red Cross Institute. Most all were leg cases, either paralysis or amputation. Most of the men had to support themselves while learning but they applied their energies to their task and made rapid progress. With one exception, all of the men who have taken up this course have passed the municipal examination, and have secured positions through the Institute, and what is more to the point, every one of them has made good on the job. The first graduate of the class earned sixty-two dollars during his first week of actual employment, and the salaries of the others averaged about thirty-five dollars per week. The course of study in the motion picture operating class in the Red Cross Institute is designed to be as thorough as possible. The pupil receives training in: (a) Elementary Electricity. (b) The Application of Electricity to an Arc Lamp. (c) The Construction, Care and Use of Electrical Ap- pliances, such as Transformers, Mercury Arc Rectifiers, Rheostats, Motor Generators, Storage Batteries, etc. (d) Optics Construction of Lenses. 0) Theory of Light. (/) Construction and Care of Projecting Machines. (g) Handling, Care and Repairing of Films. The aim of the course is not only to fit a man to take the city examination for a license, but to give him a Vlll MOTION PICTURE PROJECTION good working knowledge of actual projection. He must make a certain grade in his work both in theory and practice before the Institute permits him to apply for his license. The equipment at the disposal of the students in the Institute was generously loaned by the Nicholas Power Company, the Simplex Machine Company, the United Theatre Equipment Corporation through its President Mr. Hallberg, Mr. William Fox, Mr. B. F. Wyler, and others. It is valued at nine thousand dollars and consists of everything necessary to a mastery of the art of projection. The equipment includes the following: Power's Motor Driver Projection Machine. Simplex Machine installed in Asbestos Booth. Acme Portable Machine equipped with Mazda Lamp. Cosmograph Portable Machine with Pencil Arc. Hallberg Motor Generator. Hallberg Economizer. Hallberg Regulator for Mazda Lamp. Step-Up and Step-Down Transformers. Rheostats. Mercury Arc Rectifier. Stereopticons. Distributing Board fitted with the various House Wiring Systems, Ammeters and Voltmeters. Various makes of Screens. Film Measuring, Cleaning and Re-winding Machines. Vivatarg Apparatus. MOTION PICTURE PROJECTION IX VIVATARG APPARATUS A new motion picture projection machine whose mechanism is automatic and controlled by sound waves created by the voice, the clapping of hands, or other noises, reports by explosions, etc., was recently in- stalled in the Red Cross Institute. The sound waves are recorded by a telephone receiver connected to a system of control, which, instantly a sound is made by the voice, etc., brings the motion picture to a stop; after a pre-determined period of from one second to one hour, if desired, the picture on the screen resumes its motion. The Vivatarg is electrically operated and automati- cally controlled. It is especially useful in connection with lectures and practical demonstrations of surgical and dental operations and of the construction of special apparatus, for the picture can be brought to a sudden halt to enable the lecturer to explain his point in detail. To accomplish this, the inventor had three obstacles to overcome: (1) to stop the picture instantly at any given point; (2) to hold the picture still on the screen for any desired period; and, (3) to prevent the burning of the film while held stationary. The Vivatarg per- forms all three functions successfully. It is a mechan- ism that offers an almost unlimited field for experi- mentation. The Vivatarg in the Institute is one of three machines of the same type in existence. A FUTURE OF PROMISE From the beggar's cup, the pack of pencils, or the "blind alley" job of watchman or messenger to the X MOTION PICTURE PROJECTION position of motion picture projector from charity to self-support that is the road that many cripples have been encouraged to take. If the public will help the cripple to "come back," if they will regard him as a person with the same ambition and the same right to an opportunity to succeed as the normal man; if the employer will give the cripple a chance to make good on the basis of competency alone not charity the future that awaits those of our soldiers who return disabled is bright with possibilities. HARRY BIRNBAUM Red Cross Institute for Crippled and Disabled Men p t-( Xll MOTION PICTURE PROJECTION Powers Cameragraph No. 6B MOTION picfUKE 'PROJECTION ELECTRICAL TERMS It is necessary for the projectionist to thoroughly understand the following electrical terms : Electric Motive Force. Another name for voltage or pressure. Generally written E. M. F. The volt is the unit of E. M. F. Ampere. The unit of current strength. The quan- tity of current flowing through a circuit. Ohm. The unit of resistance. The term used to measure the opposition offered to the flow of an electric current. The amount of resistance offered by a column of mercury 106 centimeters in length by one square millimeter in cross section, at a temperature of zero centigrade. Direct Current. A current that flows in the one direc- tion. Written D. C. Alternating Current. A current that changes its flow of direction so many times a second according to the construction of the alternator. Written A. C. Conductor. Anything that will permit the passage of electricity. A wire. Rubber Covered Wire. A cable either solid or stranded with a rubber covering and an outer protective cover- ing of cotton braid. Used for mains for motion picture work. 2 MOTION PlCTtTRE PROJECTION Asbestos Covered Wire. A cable containing very fine strands of copper wire all twisted together and covered with an asbestos covering. Used wherever heat is gen- erated. On motion picture circuits used between the table switch and arc lamp. Stage Cable. A cable containing twin conductors each insulated from the other and the whole thing covered with a composition covering. Used for temporary purposes. B. X. Metal tubing containing two conductors, each conductor insulated from the other by a rubber covering, and both wires wrapped with a composition covering so as to completely fill the tubing. Ammeter. An instrument used in your circuit to measure the flow of amperes. Connected in series. Voltmeter. An instrument used in your circuit to measure the pressure or voltage. Connected in multiple. Laminated. Made up of a number of thin iron sheets. Current Frequency. The number of times alternating current changes its flow of direction a second. The changes are called cycles. Sixty Cycle A. C. This is when every part of the cir- cuit is 60 times positive and 60 times negative every second. The current changes its flow of direction 60 times a second. Induction. The property of a charged body on A. C. to charge a neighboring body running parallel to it without any tangible form of connection. MOTION PICTURE PROJECTION 3 Watt. The unit of power. The product of one ampere and one volt. Kilowatt. 1,000 watts (written K. W.) or 1.34 horse power as 746 watts equal one horse power. Circular Mil. The unit of area. A mil is the one- thousandth part of an inch and a circular mil is the area of a circle whose diameter is one mil. The cross section of wires is measured by circular mils. Short Circuit. Two wires of opposite polarity coming in contact with each other without any controlling device. Ground. Caused by the connection of an electrical conductor to a conducting medium other than that to which it belongs. Polarity. Pertaining to the two opposite poles of a circuit; the positive and negative. Transrerter. A motor generator set, an A. C. or D. C. motor connected to a D. C. generator. Secondary Coil. The coil of a transformer in which the current is induced, connected to the lamp. Primary Coil. The coil of a transformer that is con- nected to the source of supply. Inductor. A step-down transformer. Economizer. A step-down transformer. Converter. An apparatus used to change A. C. to D. C. or D. C. to A. C. Step-Down Transformer. A transformer that steps down the voltage and raises the amperage. 4 MOTION PICTURE PROJECTION Step-Up Transformer. A transformer that steps up the voltage and lowers the amperage. Arc Rectifier. An apparatus used to change A. C. to D. G. Auto Transformer. A transformer provided with only one coil instead of two. Part of the coil being traversed by the primary circuit and part being trav- ersed by the secondary circuit. Dimmer. An adjustable rheostat for increasing or decreasing the resistance in an incandescent lamp circuit. Insulation. Any material of high resistance through which electric current cannot pass. Rubber, mica, glass and porcelain are all insulating materials. Lug. A wire terminal. These lugs should always be soldered on the end of the wires except when such wires are to be used where heat is generated. A special lug is used under these conditions which is tightened on wire by the pliers. No solder should be used on lugs that are used on the rheostat or in lamp house. Watt Hour. The amount of work done by one ampere at a pressure of one volt in one hour. Ampere Hour. The amount of amperes flowing mul- tiplied by the time in hours. One ampere flowing for one hour equals one ampere hour. Two amperes flowing for one-half hour equals one ampere hour. One-half ampere flowing for two hours equals one ampere hour. Coulomb. The amount of amperes passing in a second. The product of amperes times seconds. MOTION PICTURE PROJECTION 5 Knife Switch. A switch with knife-like blades used on circuits carrying heavy currents. Negative. A term used to denote the pole of a source of electricity where the current enters. Safety Plug. A metal plug which is readily fusible when an abnormal current passes, used as a safety device. Negative Pole. The terminal of a source of electricity at which the current enters after having passed through the external circuit. Positive Pole. The terminal from which the current seems to start in traversing the external circuit. Series. An arrangement or connection of electrical devices in a circuit so that the current will pass suc- cessively from one to the next and so on through all, as distinguished from a parallel or multiple arrangement, in which each device is connected directly to the mains, or terminals of the source of supply instead of being connected thereto through the other devices. Insulating Tape. A ribbon of some flexible material impregnated with rubber or other suitable non- conductor and used for insulating wires, joints and exposed places. Positive Wire. The wire connected with the positive pole of a dynamo. Negative Wire. The wire by which a current returns to its source after completing the circuit. Induced Current. The current produced in a con- ductor by cutting magnetic lines of force. 6 MOTION PICTURE PROJECTION Graphite. A soft variety of carbon, sometimes -used for lubrication. Alternator. The name commonly given to an alter- nating current dynamo. Armature. The part of the dynamo in which the current is induced, and which may be either stationary or moving. It is placed near the poles of the field magnet. The armature proper of a dynamo is usually a mass of iron upon which are wound coils of insulated wire. Armature Core. The mass of iron or other magnetiz- ing material upon which the coils of an armature are wound. Switch Board. A board provided with switches which open,vclose, or interchange circuits. Wheatstone Bridge. A device for measuring resistance. Dynamo Brush. Strips of metal or a plate of metal or of carbon which bears upon the commutator of a dynamo and takes off the current to the circuit. Brush Holder. A device for holding the brush of a dynamo or motor in position. Commutator. That part of the dynamo or motor which changes the direction of the current. In a dynamo the current in a given section of the armature alternates, and must be made continuous on leaving it. This is done by the commutator, which consists of insulated metal bars connected with the armature wires and placed so as to feed into different brushes as the current changes. MOTION PICTURE PROJECTION 7 Transforming a Current. Changing the electric motive force of a current by its passage through a con- verter or transformer. Efficiency of Dynamo. The total electric energy developed by a dynamo, divided by the total mechani- cal energy required to drive the dynamo. Electric Efficiency. The useful electrical energy from any source, divided by the total consumed energy. Magnetic Field. The region of. magnetic influence surrounding the poles of a magnet. Filament. In an incandescent lamp the thread of wire or carbon which becomes luminous under the heating effect of an electric current passing through it. Magnetic Force. The force which causes the attrac- tions or repulsions of magnetic poles. Horse Power. (Written H. P.) A commercial unit for power or rate of doing work. A rate of doing work equal to raising 550 Ibs. one foot in one second, or 33,000 Ibs. one foot in one minute, always involves the three factors, force, distance and time. An electrical horse power is 746 watts. Leads. The conductors used in any system of electric distribution. Link' Fuses. Fuses for electric circuits formed by link-shaped strips of fusible metals. Magnet. A body possessing the quality of attracting or repelling other bodies. Pole Finding Paper. Paper used to tell the negative from the positive wire. 8^ MOTION PICTURE PROJECTION Motor Regulator. An adjustable rheostat used to regulate the speed of the motor. Speed Regulator. An attachment on machine (gen- erally a friction disc arrangement) used to regulate the speed of machine (not the speed of the motor). Fuse. A safety device used in your circuit to protect your line. Dynamo or Generator. Used to generate electricity. Motor Generator. A generator driven by a motor. Multiple. Multiple connection is when each lamp draws its own supply from the source of supply, and is not depending on any other lamp or set of lamps for supply. faW COIL* of -THE lN-TRlOf{ OF A OR 10 MOTION PICTURE PROJECTION Powers Cameragraph No. 6A Showing film threaded through machine MOTION PICTURE PROJECTION 11 PARTS ON THE HEAD OF MACHINE UPPER MAGAZINE CENTRIFUGAL MOVEMENT LOWER MAGAZINE IDLERS UPPER FIRE TRAP TENSION SPRINGS LOWER FIRE TRAP FILM RUNNERS UPPER FIRE SHIELD BALANCE WHEEL LOWER FIRE SHIELD TAKE-UP UPPER SPROCKET LENS LOWER SPROCKET GEARS INTERMITTENT SPROCKET SPINDLES INTERMITTENT MOVEMENT AUTOMATIC SHUTTER FLICKER OR LIGHT SHUTTER FRAMING DEVICE GATE COOLING PLATE PARTS ON LAMP HOUSE ARC LAMP DOWSER CONDENSERS SLIDE CARRIER FIRE PREVENTION DEVICES ON MACHINE UPPER MAGAZINE UPPER FIRE SHIELD LOWER MAGAZINE LOWER FIRE SHIELD UPPER FIRE TRAP AUTOMATIC SHUTTER LOWER FIRE TRAP COOLING PLATE 12 MOTION PICTURE PROJECTION Automatic Shutter. The shutter covering the film aperture in gate of machine and controlled by the centrifugal or governor movement, is so arranged that the shutter will remain up, so long as the machine is in motion, but should the machine stop for any reason then the shutter falls and cuts off the rays of light from the film in gate. (A fire prevention device.) Fire Trap. An arrangement of rollers on the upper and lower magazines through which the film is fed, used to prevent the flame, in case of fire, from entering the magazines. Flicker Shutter. A revolving shutter on head of machine just in front of the projection lens, its use being to cut off the rays of light from screen while the film is in motion in gate. Cooling Plate. The plate around the film aperture on gate which protects the gate itself from getting over- heated from the rays of light from arc lamp. Intermittent Movement. The movement that drives the intermittent sprocket, generally a four in one movement. Tension Springs. On gate of machine, used to give the proper tension to film while passing aperture. Take-up. Generally consists of a split pulley and tension spring, its use is to drive and control the speed and tension of the reel taking up the film in lower magazine. Governor Movement. The movement that works the automatic shutter, works by centrifugal force. MOTION PICTURE PROJECTION 13 Framing Device. An attachment on the machine which allows the operator to frame the picture on screen. Condensers. A lens or set of lenses used to gather the rays of light from the arc lamp and bring them to a fixed point of focus on aperture in gate. Dowser. On front of lamp house, used to cut off the rays of light from the head of machine. Back Focal Length of Lens. The distance from the back of the lens, to the film in the gate, while the film is in focus on the screen. v*C< *f?*f* \J r> -"*- \ v^ Right and wrong way to set D. C. arc. I. Lower carbon not far enough forward. II. Correct setting. III. Lower carbon too far advanced 14 MOTION PICTURE PROJECTION WORKING PRINCIPLE OF ELEMENTARY PROJECTION MACHINE By turning the operating crank A, counter clockwise, the main shaft J5, is driven through the 4 to 1 reduction chain drive D, a steady turning motion being caused by the fly wheel (7, this in turn operates the upper steady feed sprocket E, through the 4 to 1 reduction gear F, thus the teeth of E sprocket which mesh with the per- forations in the film, feed the film at a constant rate, the film being held against E by pressure roller G. A film loop or length of loose film is thus maintained between E and the steady drum H. The film is fed past the film gate intermittently by the intermittent sprocket I, operated by the Geneva movement K, the latter producing a quick quarter turn of /, followed by a relatively long rest during which the main shaft B makes one revolution. The barrel shutter Z, by a 2 to 1 gear with the main shaft and 'proper timing, operates to cut off the light rays from the screen during each movement of the intermittent sprocket I, and to admit the light during the intervals that I remains stationary. The synchronous operation of the intermittent sprocket and the shutter is very clearly shown in the diagram. A lower steady feed sprocket M, which operates at the same speed as the upper sprocket E, maintains a lower feed film loop N, and feeds the film to the lower reel 0. Because of the increasing diameter of the roll of film due to winding the film on reel 0, the velocity of rota- MOTION PICTURE PROJECTION 15 UPPER REE REEL BOX UPPER FEED FILM LOOP, RREEL EL BOX 10 MOTION PICTURE PROJECTION tion of must be allowed to vary; this is accomplished by means of the belt drive P, the belt permitting slippage below the maximum speed. It should be carefully noted that the total revolutions made by each of the three sprockets E, /, and M , is the same, the only difference being that the motion of E and M is constant while that of I is intermittent. Showing effect of arc being connected upside down MOTION PICTURE PROJECTION 17 THE INTERMITTENT MOVEMENT PRELIMINARY REMARKS Too much prominence cannot be given to the inter- mittent movement of Power's Cameragraph. Before entering into a technical description of this movement, it will be well to give a brief outline of the fundamental principles upon which the art of moving picture pro- jection depends. An understanding of these principles will enable one to better appreciate the very important part that Power's Cameragraph has played in the evo- lution of the moving picture. The moving picture is accomplished by flashing a great number of stationary photographic views before the eye in such rapid succession that the eye is deceived into the belief of having beheld actual motion. The photographic views, which are usually taken at the rate of sixteen per second, are printed in direct suc- cession upon a ribbon of transparent film one and three-eighths inch in width and between one and two thousand feet in length. Each view is condensed into a rectangular space approximately one inch wide and three-fourths inch high. When the film is run through the projector at normal speed, sixteen of these views are shown each second. It would appear from this that each view is shown for one-sixteenth of a second. Such is not the case, how- ever. Each view is held stationary before the lens for only a part of this minute period of time, and the 18 MOTION PICTURE PROJECTION remainder of the period is consumed while the film is being moved down a distance of three-fourths of an inch, so as to bring the succeeding view in line with the lens. Figure 1 During every such movement of the film, the main blade (or wing) of a revolving shutter, passes in front of the lens, thus preventing any trace of the movements from reaching the screen. If this was not done, the picture would be greatly marred by streaks of light known as " travel ghost." An additional wing (and sometimes two) is inserted in the shutter wheel for the MOTION PICTURE PROJECTION 19 purpose of doing what is technically known as "equal- izing the light." We will not discuss this matter of light equalization as it has no direct bearing upon the point that we wish to bring out. It is the necessary passage of these wings in front of the lens that prevents an attainment equalling theo- Figure a retical perfection wherein each view would appear on the screen for its entire allotment of one-sixteenth of a second without interruption of any kind. It would probably be possible to devise a way to move the film so rapidly that the eye could not perceive any trace of the movement, and thus the necessity of using the revolving shutter would be eliminated, but we are prevented from doing this by the very important fact that wear and tear on the film must be taken into 20 MOTION PICTURE PROJECTION consideration. The movement of the film must not be made so rapidly nor in such a jerky manner as to cause the film to rip or pull apart. Power's Cameragraph accomplishes this movement more rapidly than any other projector now in practical use. The nature of the movement is such as to keep wear and tear on the film reduced to a minimum. The mechanical parts which control the movement are of greater durability than those used in any other pro- jector. These great advantages, which are to be had only with Power's Cameragraph, have done their full share in placing this projector in its present preeminent position as the leader in the art of picture projection. TECHNICAL DESCRIPTION OF THE INTERMITTENT MOVEMENT The term "intermittent movement" is used to desig- nate that part of the mechanism of a moving picture projector, which performs the important function of stopping the film at regular intervals, so that the photo- graphic views may be successively held in line with the lens. In Power's Cameragraph this movement consists primarily of four elements, namely : a diamond shaped cam, a locking ring, a pin cross and a sprocket. Photo- graphic views of these parts will be found on page 18. The cam and locking ring are formed together on the face of a solid steel disc. The four pins of the pin cross are formed from the end of a solid cylinder of steel. The remainder of this cylinder is turned down to the proper diameter to act as a spindle upon which the sprocket is securely fastened. The sprocket has two MOTION PICTURE PROJECTION 21 rows of teeth to mesh with the holes that are perfor- ated on each side of the film. Figures a, 6, c, and d, show these elements in action. A portion of the back of the cam-ring disc has been cut away so as to expose the workings of the movement during one revolution of the disc. The curved arrows Figure b indicate the direction in which the parts are revolving. The sprocket is in mesh with a short strip of film. Portion e of this film, which lies between the heavy black cross lines, represents one of the photographic views to be projected upon the screen. In Figure a, the four pins of the pin cross are shown in engagement with the locking ring. Pins 1 and 2 are at the outer circumference and pins 3 and 4 are at the inner circumference of the ring. Although the ring is 22 MOTION PICTURE PROJECTION revolving, it cannot impart motion to the pin cross as the pins are securely locked by contact with the inner and outer surfaces of the ring; consequently the pin cross, the sprocket and the film are at rest. It is during this period of rest that the photographic view is being projected on the screen. Figure c In Figure 6, the pins are disengaging from the locking ring. The cam is just starting to engage with pin 1. As the engagement takes place the pin is pushed for- ward and upward, thus imparting a rotary motion to the pin cross spindle. The sprocket, being fastened to this spindle rotates with it, thus pulling the film downward. In Figure c, pin 1 has almost reached the apex of the cam. Pin 2 is traveling into slot /, pin 3 is describing MOTION PICTURE PROJECTION 23 an arc in the space between the ends of the locking ring, and pin 4 is traveling out of slot g. As pin 1 slides over the apex of the cam, pin 4 engages with the curved surface h at the end of the locking ring, and the pin is thrown forward and upward until it slides on to the outer surface of the locking ring. Figure d In Figure d, pin 4 has just reached the outer surface of the ring. The four pins are immediately locked as the locking ring travels into the space between them. In contrast to the pin position in Figure cr, pins 1 and 4 are now at the outer circumference and pins 2 and 3 are at the inner circumference of the locking ring. It can readily be seen that the pin cross spindle has made a quarter revolution, and that view 1 J 0'J Ques. What is meant by the safe carrying capacity of wires? Ans. All wires will heat when a current of electricity passes through them. The greater the current or the smaller the wire, the greater will be the heating effect. Large wires are heated comparatively more than small wires because the latter have a relatively greater radi- ating surface. Ques. What parts of a dynamo are liable to be short circuited? Ans. The terminals, brush holders, commutator, armature coils and field coils. Ques. Suppose on looking over your motor you found that there were several ridges on the commutator, where would you look for the cause? Ans. The brushes are not set right or the tension of brushes on commutator is too great. Ques. How would you go about setting a Simplex flicker shutter? Ans. When setting the shutter, set the framing lever in center, move the shutter adjusting block to a point equidistant between the two pins by means of the knob on the back of the mechanism facing towards lamp house. Four teeth on intermittent sprocket represents one full move of one section on star, moving the sprocket two teeth either backward or forward would mean center. Now adjust shutter as follows: On a three wing shutter the center of the blade with the word "Simplex" stamped on it should be on center with the lens; on a two wing shutter the center of either blade will cover the lens. The position can best be determined L02 MOTION PICTURE PROJECTION by the set screw on the spider, which should face the operator in a horizontal position. In setting shutter always keep as close to the lens as possible. Ques. What is a D. C. to D. C. motor generator? Ans. It is a D. C. motor connected to a D. C. genera- tor, used to give a D. C. controlled light at arc, thereby doing away with the use of rheostats. When we take into consideration the fact that a rheostat on 110 volt circuit wastes from 35% to 50% of the current, and on 220 volts, rheostats wastes from 65% to 75% it will be easily seen why a D. C. generator should be installed in place of rheostats. Ques. Show by figures what would be the saving if you installed a Hallberg D. C. generator and discarded your rheostats, taking it for granted that you were drawing 80 amperes at the arc on a 110 volt circuit? Ans. With rheostats we would be consuming 110 volts times 80 amperes or 8,800 watts while with the generator we would be consuming 1 10 volts times 57 amp- eres (this being the amount of current generator draws from line) or 6,270 watts. With rheostats we consume 8,800 watts per hour while with generator we only consume 6,270 watts per hour, the generator showing a saving of 1,530 watts per hour. Ques. State what advantage a motor generator has over rheostats aside from the question of current saving. Ans. You do away with the heat generated by the rheostats. Ques. What is a Hallberg 4 in 1 automatic regulator? Ans. Consists of an adjustable transformer with separate line and lamp coils. The primary coil is MOTION PICTURE PROJECTION 103 wound in two sections each section insulated from the other. Each section is wound for 110 volts. For 110 volts you connect the two sections in multiple while for 220 volts you connect the two sections in series. It is used for moving picture circuits when using the mazda lamp instead of arc. (See page 33.) Ques. What is meant by stealing the arc? Ans. When two arcs are connected to one source of supply, as when two arcs are connected to one genera- tor, and where the striking of the second arc automati- cally puts out or draws from the first arc. Ques. What is meant by the strength of a current? Ans. The quantity of electricity which flows past any point of the circuit in one second. Ques. What is the difference between a dynamo and an alternator? Ans. A dynamo generates D. C. while an alternator generates A. C. Ques. Suppose you had one 110 volt 25 ampere rheostat connected on a 110 volt circuit D. C. and you had one 110 volt 25 ampere rheostat connected on a 110 volt circuit A. C. at which arc would you draw the most amperage and why? Ans. On the A. C. arc because with A. C. you have to feed the carbons closer together than on D. C. and* that draws a little more amperage. Ques. How does a dynamo create current? Ans. It does not create current but generates an induced E. M. F. which causes a current to flow through a circuit. 104 MOTION PICTURE PROJECTION Ques. How should a knife switch be installed? Ans. So that gravity tends to open same. Ques. Is it possible to reverse the rotation of a motor, if so how? Ans. Yes, by reversing the current through the fields or the current through the armature. Ques. What is the difference between a D. C. and an A. C. rheostat? Ans. Rheostats are made for either A. C. or D. C. There is no difference between them. Ques. How many rheostats would you use on 220 volts and how would you connect same? Ans. One 220 volt rheostat in series with your line or two 110 volt rheostats in series with each other and in series on your line. Ques. With 55 volts coming in, how many rheostats would you use, and how would you connect same? Ans. Use two 110 volt rheostats in multiple with each other and in series on your line. Ques. What effect does it have by connecting rheo- stats in multiple and rheostats in series? Ans. Rheostats in series gives you the sum of their resistance, for instance if they each offered 4 ohms resistance and we connected same in series with each other we would have 8 ohms resistance on our line. If we connected the same two rheostats in multiple we would only then have approximately 2 ohms resistance. Ques. Why don't they use copper coils instead of iron in a rheostat? Ans. Because iron offers more resistance than copper, copper being a good conductor. MOTION PICTURE PROJECTION 105 - Ques. Is all the resistance offered in your rheostat? Ans. No, everything on your line offers resistance, all substance offers resistance to the passage of elec- tricity through them, the amount of resistance de- pending on the substance and its size, that is on its length and cross section. Ques. Do metals offer more or less resistance when hot? Ans. The resistance of all metals increases with an Increase of temperature, while carbons and insulating materials decrease with an increase of temperature. Ques. Is it possible to get a short circuit in the rheostat ? Ans. Yes, when the arc lamp is burning, as you then have two polarities in rheostat. Ques. How many kinds of current are there and state what they are. Ans. Two, direct current and alternating current. Ques. What is meant by direct current? Ans. Direct current is a current that always flows in the same direction; always leaves the dynamo through the positive pole and returns through the negative pole. Ques. What is alternating current? Ans. Alternating current is a current that changes its flow of direction so many times a second. Each part of the circuit being so many times positive and so many times negative every second. 106 MOTION PICTURE PROJECTION Ques. What is current frequency? Ans. The number of times alternating current changes its flow of direction in a second. (These changes are called cycles). Ques. Which current is the best for moving picture work and why? Ans. Direct current, gives a better arc, more easily controlled, and is not so noisy as A. C. Ques. Is it possible to change A. C. into D. C.? Ans. Yes, there are various machines on the market for this purpose transverters, arc rectifiers and motor generator sets. Ques. Suppose you had 110 volts D. C. coming into the theatre and you had one 110 volt rheostat on your line, and then the current was changed from D. C. to A. C. what changes would you make on your line and state reasons why. Ans. Would take off the rheostat and install an economizer (step-down transformer) this would give me a saving of about 66% (makers claim) . Ques. Suppose you changed a rheostat for an econ- omizer on a 220 volt line, would there be a saving? If so, about how much? Ans. About 80% (makers claim). Ques. State an easy way to test whether you have A. C. or D. C. at arc lamp, and if you are on D. C. whether you are connected right (positive line con- nected to top carbon). Ans. First strike the arc and let it burn a second or two, then throw off the switch and open lamp house MOTION PICTURE PROJECTION 107 door, if both carbons remain red for the same length of time we have A. C. but should one carbon remain red longer than the other we have D. C. The top carbon should remain red longest, so if the bottom remains red longer than the top one we know that we are burning upside down. (Positive line is connected to bottom carbon instead of to top.) Ques. Suppose you find you are burning upside down, where on your line would you make the change? Ans. At table switch, arc lamp or wall switch. Ques. Could you change polarity at the rheostat if you were burning upside down? Ans. No, as you have only one polarity at the rheostat. Ques. What is meant by constant current type of a current rectifying device? Ans. Where two arc lamps are connected to one apparatus like a transverter or a motor generator, and where the voltage and not the amperage is doubled when both arcs are struck. For instance if we had one arc operating at 55 volts and 50 amperes and we struck the second arc we should then have two arcs operating at 50 amperes 110 volts (approximately). Ques. What is a three wire system? Ans. A distribution system invented by Edison, where two dynamos are connected in series and the third or neutral wire is taken from a point common to both dynamos. Ques. How many rheostats would you use if you were using the two outside wires of a three wire system? 108 MOTION PICTURE PROJECTION Ans. Two 110 volt rheostats in series with each other, as between the outside wires we would have 220 volts. Ques. Suppose you were drawing 50 amperes off one side of a three wire system and 40 amperes off the other, how many amperes would be flowing in the neutral wire? Ans. As the amount of current in the neutral wire is the difference between the amperage drawn off either side, we would have a flow of 10 amperes in the neutral wire. Ques. Suppose that we were drawing 45 amperes off either side of a three wire system what would be the amount of amperage flowing in the neutral wire? Ans. If we were drawing 45 amperes off each side of the system, the system would be balanced and there would be no flow of current in the neutral wire. Ques. What are the advantages of a three wire system? Ans. The saving of copper is the advantage of the system, as by its use the size of the conductors may be reduced, by increasing the pressure at which the cur- rent is transmitted, without increasing the voltage of the lamps. If for example the neutral wire is made the same size as the two outside wires, the total weight of the copper for the three wire system, will be three- eighths (3-8) of that required for two, two wire systems for the same load, distance and percentage of loss. Ques. What are the disadvantages of a three wire system? Ans. The system is more complicated, the cost of the switches, panel boards, etc., is increased, that the MOTION PICTURE PROJECTION 109 system is more subject to disturbances, if for example- the fuse on the neutral wire should melt, the lamps on the system might be considerably damaged in case the two sides of the system were not balanced. Ques. Can you connect between the positive and neutral wire for moving picture work? Ans. Yes, you will then need one 1 10 volt rheostat. Ques. Which wire on a three wire system is grounded ? Ans. The neutral wire. Ques. If we were connected on the positive and neutral wires of a three wire system, and we got a ground on the lower jaw of arc lamp, would that blow the fuse. Ans. No, all metal machines must be grounded, and by so doing the lamp house becomes the same polarity as the neutral wire. Therefore the ground being on lower jaw which is neutral and the same polarity as lamp house, it may not blow the fuse. Ques. What is a transformer, how is' it made and how does it work? Ans. A transformer consists of two copper coils, the primary and the secondary, and a laminated iron core. The two coils are insulated from one another and from the core. The primary coil is connected to the source of supply and the secondary is connected to the lamp. As a matter of fact these coils are each usually made of several sections. The voltage induced in the secondary coil is equal to the voltage impressed on the primary coil multiplied by the ratio of the number of turns in the secondary to the number in the primary coil, less a 110 _ MOTION PICTURE PROJECTION certain drop due to impedance of the coils and to magnetic leakage. This drop is negligible on no load. Step-up transformers are used to raise the voltage. Step -down transformers are used to step down the voltage. The efficiencies of transformers are high, varying from 94% to 95% at one-fourth load to 98% at full load for sizes above 25 K. W. The current enters the transformer through the primary coil and the alternations of the current in this coil sets up a magnetic field in the transformer. The secondary cuts the lines of magnetic force and carries off a new current to the arc lamp. Ques. Does a transformer change the current from A. C. to D. C.? Ans. No, it gives off a magnetized A. C. current to arc lamp. Ques. Can you use a transformer on direct current? Ans. No. Ques. Why do they make the core of a transformer of a soft metal like iron, instead of steel? Ans. Because the softer the metal the more easily it is to magnetize and it will lose its magnetism quicker after the current has been shut off. Ques. State in one word how an economizer or trans- former works. Ans. Induction. Ques. What is meant by induction? Ans. A charged body running parallel to another body (it being a conductor) tends to charge the neigh- boring body without any tangible form of connection. MOTION PICTURE PROJECTION 111 Ques. How are the coils in a transformer or econo- mizer connected, in multiple or series? Ans. They are not connected, they are insulated from each other. Ques. What is the difference between an economizer, an inductor and a step-down transformer? Ans. None, they are all the same and answer the same purpose. Ques. Where on your line would you connect your economizer and why? Ans. Between the table switch and the arc lamp, so that by pulling the table switch you put the arc and the economizer out of commission at the same time, whereas if economizer was connected between the table switch and the wall switch it would be necessary to pull both switches or at least pull wall switch to put both out of commission. Ques. How many working parts are there in a transformer? Ans. None. Ques. Where is the difference between a step-up and a step-down transformer? Ans. In the ratio of the coil windings. Ques. What is a transverter? Ans. A motor generator set, an A. C. motor con- nected to a D. C. generator gives a D. C. current at arc lamp. Or a D. C. motor connected to a D. C. generator that gives a controlled D. C. current at arc lamp. 112 MOTION PICTURE PROJECTION Ques. What is a mercury arc rectifier used for? Ans. To change A. C. to D. C. Ques. What is the difference between a motor, a motor generator and a generator? Ans. A motor transforms electrical into mechanical power. A generator transforms mechanical power into electrical power. A motor generator is a device consis- ting of a motor mechanically connected to one or more generators. Ques. What is the difference between a starting box and a speed regulator? Ans. Motor starting rheostats or starting boxes are designed to start a motor and bring it gradually from rest to full speed. They are not intended to regulate speed and must not be used for that purpose. Failure to observe this caution will result in burning out the resistance which in a motor starter is sufficient to carry the current for a limited time only, whereas in a speed regulator, sufficient resistance is provided to carry the full load current continuously. Ques. What is meant by self induction? Ans. A characteristic of alternating current circuits, where the current tends to create a counter E. M. F. Self induction varies greatly with conditions depending upon the arrangement of the circuit, the medium sur- rounding the circuit, the devices or apparatus supplied or connected in the circuit, etc. For example, if a coil having a resistance of 100 ohms is included in the cir- cuit, a current of one ampere can be passed through the coil with an electric pressure of 100 volts, if direct current is used; while it might require a potential of MOTION PICTURE PROJECTION 113 several hundred volts to pass a current of one ampere if alternating current is used, depending upon the number of turns in the coil, whether it is wound on iron or some other non-magnetic material. Ques. State six reasons for the film jumping on the screen. Ans. Dirt on sprockets, especially the intermittent sprocket, losing the bottom loop, not enough tension in gate of machine, sprocket shaft not true, shaft bushings badly worn, holes in the films worn. Ques. Suppose you blow the fuse when you strike the arc, where would you look for the trouble? Ans. In the rheostat. Ques. Suppose you blow the fuse when you close the table switch, where would you look for the trouble? Ans. Between the table switch and the arc lamp. Ques. If you strike the arc and only get a spark and carbons refuse to hold arc where would you look for the trouble? Ans. Loose connection or oxidized connection in rheostat or on line. Ques. Is it possible to get a fire on the machine, if so how? Ans. Yes, bad patches in film opening up while going through machine, torn sprocket holes on each side of film, take-up refusing to work, automatic shutter failing to work, film breaking in gate between upper and intermittent sprocket, dirt and pieces of film gathering in film aperture in gate. 114 MOTION PICTURE PROJECTION Ques. State what you would use to test for ground or open circuit in rheostat. Ans. A bell set. Ques. How yould you test for ground and how for open circuit in rheostat? Ans. First test bell set by connecting both terminals together, if you get a ring then set is all right and proceed as follows : Place one of the terminals of bell set on the frame of rheostat and the other terminal on the first coil or plate of rheostat, if you get a ring, then rheostat is grounded. If you do not get a ring then rheostat is free from ground. If grounded, to locate which plate or coil is causing the ground, proceed as follows : Place terminal of bell set on frame and other terminal on first coil, if you get a ring, disconnect first coil then test the second and so on till bell stops ringing. As soon as bell stops ringing it signifies that, the coil that you disconnected last is the coil that was grounded. To test for open circuit, place the terminals of bell set on the terminals on rheostat and if you get a ring then rheostat is O.K. Ques. If you were drawing 30 amperes on a 110 volt circuit, how many kilowatts would you be using? Ans. Volts times amperage equals watts, so 110 x 30 equals 3300, and as there are 1,000 watts in a kilowatt that means that we have 3 3-10 K. W. Ques. How would you measure a No. 6 rubber cov- ered stranded wire? Ans. First, scrape off the insulation, then measure one of the strands with a B. & S. wire guage, we would find that this strand would be a No. 14, then by referring MOTION PICTURE PROJECTION 115 to the wire table we would find that a 14 wire contains 4,107 circular mils, then we count the strands in the cable and we find there are seven, so we multiply 4,107 by 7 which equals 28,749, then we again refer to wire table to find the nearest number to 28,749 which is 26,250 and looking across wire column we find that this is a No. 6 wire. Ques. State how you would test lamp house for grounds? Ans. Take test lamp and after making sure that there was current in the lamp house (by placing test lamp terminals on carbons) would proceed as follow: Would place one terminal of test lamp on the upper carbon and the other terminal on lamp house, if test lamp lights, then the lower jaw must be grounded, if we do not get a light then lower jaw is O.K. Then we place one of the test lamp terminals on the lower jaw or carbon and the other terminal we place on metal of lamp house, if we get a light then the upper jaw is grounded, if we do not get a light then the upper jaw is O.K. If machine was grounded we would of course remove ground wire before making the test as above. Ques. Name three essential parts of a dynamo. Ans. Armature, commutator, field coils. Ques. What is the object of the field magnets? Ans. To provide a field of magnetic lines of force to be cut by the armature inductors as they revolve in the field. Ques. What is an armature? 116 MOTION PICTURE PROJECTION Ans. A collection of inductors mounted on a shaft and arranged to rotate in a magnetic field with provision for collecting the current induced in the inductors. A simple loop or turn of wire may be considered as the simplest form of armature. Ques. What is a commutator? Ans. A device for causing the alternating currents generated in the armature to flow in the same direction in the external circuit. It consists of a series of copper bars or segments arranged side by side forming a cylin- der and insulated from each other by sheets of mica. Ques. How do armature and field magnets differ in dynamos and alternators? Ans. In the dynamo the field magnet is the station- ary part and the armature revolves. While in an alter- nator the reverse is the case. Ques. Name five parts of a dynamo. Ans. Bed plate, field magnets, armature, commu- tator, brushes. Ques. The primary coil of a transformer is supplied with a current of 25 amperes at 2,000 volts, the pressure received from the secondary is 250 volts. What is the current from the secondary coil, taking it for granted that the transformer is 100% efficient? Ans. Input equals output. Input is 2,000 times 25 equals 50,000 watts. Watts divided by volts equals amperes, so 50,000 divided by 250 equals 200. Therefore the current from the secondary is 200 amperes. Ques. What is the name of the coil in which the current is induced? Ans. The secondary. MOTION PICTURE PROJECTION 117 Ques. Does a transformer take any current when the switch on the lamp side of same is open? Ans. Yes. A no-load passes through the primary. Ques. What is meant by an oil cooled transformer? Ans. A transformer filled with mineral oil to help keep the transformer cool, never used on moving pic- ture work, the fire risk is too great. Ques. What would cause the breaking of a brand new film while passing through the machine, taking it for granted that the film was handed to you in perfect condition, and that you had just run some six or seven reels of film through the machine without mishap? Ans. Caused by the emulsion coming off the new film and adhering to the tension bars in gate of machine, which would give undue tension to the film. Ques. What is meant by fading a picture? When and how is it done? Ans. Fading is done by the gradual cutting off of the light (either when taking or projecting the picture) . The operator fades one reel into the other when chang- ing from one machine to the other. This is accom- plished by the dowsers on the machines, by slowly closing one and at the same time slowly opening the other. Ques. On which coil of an economizer is the greatest wattage? Ans. As transformers are not 100% efficient there is a loss in transforming the current, this loss amounts to approximately 5% and as the output equals the input less the loss, it will mean that we have more wattage on the primary than on the secondary. 118 MOTION PICTURE PROJECTION Ques. What is the proper rate of speed of showing a 1,000 feet of film? Ans. About fifteen to seventeen minutes. Or about sixteen pictures to the second. Ques. if the machine is running at proper speed (sixteen pictures to the second) about how long is each picture held on the screen? Ans. For one-sixteenth part of a second less the time it takes the intermittent sprocket to move the film. Ques. Mention some of the different makes of moving picture machines. Ans. Powers, Simplex, Standard, Motiograph, Baird, Edison, Lubin, Pathe, Kinemacolor, Cameron. Ques. Which would show the greater saving, a D. C. economizer or rheostats? Ans. The initial cost of the D. C. economizer would be greater than that of rheostats, but the working cost of the D. C. economizer would show a great saving over that of the rheostats. Ques. Why are flicker shutters made with two or three blades when only the largest blade is used to cut off the picture from screen while the film is in motion in gate of machine? Ans. The second and third blades are on to equalize the light. Ques. What is a wire gauge? Ans. A gauge used to measure wires. Ques. What is the difference between Greenfield and B. X.? Ans. Greenfield is a metal tubing without wires while B. X. is the same tubing with wires. .MOTION PICTURE PROJECTION 119 Ques. What is the difference between a D. C. con- verter and a rotary converter? Ans. A D. C. converter converts D. C. to D. C. while the rotary converter converts A. C. to D. C. Ques. What is meant by a circuit? Ans. The path in which the current flows. Ques. What is a closed circuit? Ans. When all switches, etc., on a line are closed giving the current a continuous path. Ques. What is meant by insulation? Ans. Some non-conducting material on or around a conductor to prevent the escape of current. Ques. Show by sketch how a lens is set and how it works. Ans. See page 75. Ques. What is a circuit breaker? Ans. A switch which opens automatically when the current or pressure exceeds or falls below a certain fixed standard. Ques. What effect has it by connecting dynamos in series and dynamos in multiple? Ans. Dynamos in series increase the volts, dynamos in multiple increase the amperes. Ques. Name a number of good conductors, fair con- ductors and non-conductors. Ans. Silver, copper, mercury and aluminum are good conductors. Water, the body, and dry wood are partial conductors and mica, slate, glass are non- conductors. 120 MOTION PICTURE PROJECTION Ques. What is the inverse of resistance? Ans. Conductivity. Ques. State one of the disadvantages of using A. C. for motion picture work. Ans. Both carbons form a crater and the arc keeps traveling around carbons making it difficult to get a good steady light on screen. Ques. Of what use is the field magnet in a dynamo? Ans. To provide a field of lines of force to be cut by the armature inductors. Ques. State one of the advantages of A. C. over D. C. as far as transmission goes. Ans. Reduces the cost of transmission by using high voltage and transformers. Ques. What is the armature? Ans. A collection of inductors mounted on a shaft and arranged to turn in a magnetic field for collecting the current induced in the inductors. Ques. What is a commutator? Ans. A device for causing the alternating currents generated in the armature to flow in the same direction in the external circuit. Ques. Which end of the lens faces arc? Ans. The flat or lesser convex end. Ques. What would you use to scrape off the emul- sion from tension bars? Ans. Copper or any soft metal. Ques. Where is the most luminous part of an arc? Ans. In the crater of the positive carbon. MOTION PICTURE PROJECTION 121 Ques. What causes hissing of an electric arc? Ans. Feeding carbons too close together, feeding it a higher current than that required for the length of arc employed. Ques. What is the reason of using a cored carbon in the positive jaw of arc? Ans. To reduce the voltage required to maintain the arc by lowering the boiling point or the vaporizing temperature of the crater. Ques. State the advantages of rubber as an insulator. Ans. It is flexible, fairly strong and waterproof. Ques. Can you use a bell set to find ground in lamp house? Ans. Yes. Place one terminal of bell set on upper carbon and other terminal on lamp house frame, if bell rings then the upper jaw is grounded, if no ring then upper jaw is O.K. Then place one terminal of bell set on lower carbon and other terminal on lamp house if bell rings then the lower jaw is grounded, if you do not get a ring then lower jaw is O.K. Ques. How often would you test lamp house for grounds? Ans. Before show each day. Ques. Suppose you found that either the upper or lower jaw was grounded, where would you first look for the trouble? Ans. Probably the mica insulation has worked out of jaws of lamp. 122 MOTION PICTURE PROJECTION Ques. Describe fully what is meant by an electric arc. Ans, Suppose two carbons are connected in an elec- tric circuit, and the circuit closed by touching the tips of the carbons together (striking your arc); on separ- ating these carbons again the circuit will not be broken, providing the space between be not too great, but will be maintained through the arc formed at this point. The current is assumed as passing from the upper carbon (positive) to the lower carbon (negative). We find in a direct current arc that most of the light issues from the tip of the positive carbon, and this portion is called the crater of the arc. The lower carbon becomes pointed as the upper one hollows out to form the crater. The negative carbon is also incandescent, but not to the same extent as the positive. Between the carbons there is a band of violet light (the arc proper) -and this is sur- rounded by a luminous zone of a golden yellow color. The carbons are worn away or consumed by the pas- sage of the current. The positive carbon being con- sumed about twice as quick as the lower. With alternating current the upper carbon becomes positive and negative alternately, and there is no chance for a good crater to be formed, both carbons giving off the same amount of light and being consumed at about the same rate. Ques. What is a voltmeter used for and how would you connect same? Ans. Use to measure the pressure or voltage, con- nected in multiple on your line. Ques. What is an ammeter and how is it connected? Ans. Used to measure the current or amperage, con- nected in series on the line. MOTIOX PICTURE PROJECTION 123 Ques. State what care you would take of film while it is in your charge. Ans. Would examine all film before showing, keep each reel in a metal box or can, and keep all these cans in another metal box constructed without solder and with a self-closing door. Ques. Name three causes of sparking at your motor. Ans. Dirt, uneven brushes and broken segment in the commutator. Ques. Under what conditions can you rewind film in the booth? Ans. Never rewind films in booth while arc is burn- ing, or while audience is in theatre. Ques. What would you do in case of fire in the booth ? Ans. Stop motor and switch off arc, drop the booth shutters, turn on the house lights, notify manager and try and extinguish fire. Ques. What precautions would you take to prevent fires? Ans. Keep all films in fireproof cans, only have the film on the way to the machine exposed at any time, keep booth free from all pieces of film and all combus- tible material, see that take-up and automatic shutter work O.K., keep lamp house free from all grounds, keep all electrical connections tight, keep machine clean and in good running order, have a bucket of water and one of sand near at hand in booth, place all hot carbons into a bucket of water when you take them from arc lamp. Ques. How would you adjust the take-up without stopping the machine? 124 MOTION PICTURE PROJECTION Ans, If the belt was slipping would use a little rosin or tighten up the tension screw, or use the idler pulley if machine was equipped with one. If take-up refused to revolve the bottom reel, would stop machine and fix. Ques. Why do they ground an all metal machine? Ans. For safety, Ques. How would you find the amount of resistance offered by any conductor? Ans. The resistance of any conductor is equal to its length in feet divided by the area in circular mils mul- tiplied by the resistance per mil-foot (which is 10.5 ohms) . Ques. What is the international ohm? Ans. The resistance offered by a column of pure mercury 106.3 centimeters in length by one square milli- meter in cross section at a temperature of zero centi- grade. Ques. What percentage of light is lost between the arc lamp and the screen? Ans. Take the crater of arc as 100%, only 33% of this is picked up by the condensers on D. C. (On A. C. the percentage is much less). Then there is a 16% reflection loss (4% at each of the four glass- to-air surfaces of condensers) plus an absorption loss of 9% (absorption loss being reckoned as 6% per inch, and assuming the condenser combination to have an axial thickness of 1^2 inch) or in other words the light fall- ing upon the condensers is subjected to a reduction of 25% in passing through them. Thus only 25.75% passes on to the film being projected. About 50% of MOTION PICTURE PROJECTION 125 this light will be lost passing through the film, so that only 12.85% is sent on to projection lens. In its pas- sage through the objective lens the light is further re- duced some 25% in intensity (4% reflection loss at each of the six glass-to-air surfaces) therefore but 9.65% emerges from lens. This is again cut 50% by the flicker shutter, leaving only 4.80% of the original amount emanating from arc lamp for the illumination of the screen picture. Other factors such as the dis- tance to screen and the effective aperture of the ob- jective also enter, so this is only a rough approximation. Ques. What is a six to one intermittent movement? Ans. A movement with which each picture on the film is moved into place before the aperture of the projector in an interval of time equal to one-sixth of the period required for a complete revolution of its driving member (cam). Ques. Is both voltage and amperage used up in arc lamp, or is the voltage used up and amperage returned; or is the voltage returned to dynamo and amperage used up at arc? Ans. The voltage is used up forcing the amperage through the resistance. The amperage returns to dynamo. This can be proved by connecting an am- meter in your circuit. Ques. What would be the result if you lost your bottom loop? Ans. Film would jump or break. Ques. What regulates the speed of the reels in the upper and lower magazines. 126 MOTION PICTURE PROJECTION Ans. The top reel is regulated by film tension and the lower is regulated by the tension spring and split pulley. Ques. Of what use is the flicker shutter on head of machine? Ans. To cut off the rays of light from screen while the film is in motion in gate. Ques. What causes the film to remain stationary in gate of machine? Ans. The intermittent movement. Ques. What is it that works the automatic shutter? Ans. The centrifugal movement. B. and S. Gauge MOTION PICTURE PROJECTION 127 Head of Powers' No. 6 128 MOTION PICTURE PROJECTION MOTION PICTURE PROJECTION 129 COPY OF THE RULES ISSUED BY THE DEPARTMENT OF WATER SUPPLY, GAS AND ELECTRICITY NEW YORK CITY The Operator's License and copy of these rules shall be displayed in a conspicuous place in the booth while the public is in or has access to the premises. No operator shall conduct an exhibition except where to his knowledge a permit or license of the department of licenses is exhibited on the premises. The apparatus and its construction shall be tested by the operator prior to each performance. No defec- tive apparatus, or apparatus of a type not approved by this department shall be operated. No apparatus with a lamp served with oxy-hydrogen or acetylene gas shall be approved. It is forbidden to overfuse (see electrical code, section 418 of the Code of Ordinances) or to make any electrical connections not sanctioned by the aforesaid chapter (see section 438). The operator shall report promptly every defect in the apparatus or its connection, the correction of which he is unable to secure. Badly torn films shall not be used and their presence in the booth shall be reported as soon as practical. The booth at all times shall be kept clean. No pieces of film or loose combustible material shall be allowed to remain in the booth, unless kept in a metal box pro- 130 MOTION PICTURE PROJECTION vided with a close fitting cover constructed without the use of solder. The door of the booth shall be kept closed while the public has access to the premises. No person shall be allowed in the booth except the manager or owner of the premises, a licensed operator, a person specially authorized by the commissioner in writing, or any duly accredited officer of the city. The interior of the booth shall remain readily acces- sible to the persons mentioned in the foregoing section. The door of the booth shall not be latched on the inside nor the handle removed from the outside, nor shall any signalling device be permitted which is operated from the front of the house. No film other than that on the machine or on the rewinder shall be exposed in the booth at any time. No smoking is permitted in the booth at any time. No matches, fire or open light is permitted in the booth while the public is on or has access to the house or premises. Every fire, together with the apparent cause thereof, shall be promptly reported. Advance report shall be made of the installation of a moving picture machine for a one night exhibition. The apparatus shall at all times be in charge of a licensed operator. It is forbidden to operate while under the influence of liquor or drug or to read while operating. Certificates shall not be loaned or transferred. MOTION PICTURE PROJECTION 131 POINTS TO REMEMBER To find the positive or negative polarity when con- nected up, strike the arc and let same burn for a second or two, then throw off the switch and look to see which of the carbons cool off first. Whichever remains red the longest is the positive and this should always be the carbon in the top jaw of lamp. If you find that the lower carbon remains red longer than the top, then your lamp is burning upside down, or in other words the positive line is connected to the lower jaw instead of the top. This can be remedied by changing the wires at arc, wall, wall-switch, or table- switch. Should both carbons remain red the same length of time you have alternating current. The Department of Water Supply, Gas and Electric- ity call for the use of link fuses in the operating booth on the machine line. Cartridge fuses are not allowed. Always see that all connections are tight and that lamp house, etc., is free from grounds. Examine the lamp leads every so often, remember that copper oxidizes when overheated. See that you have enough carbon in holders to run the reel through. When buying or fitting condensers and mounts for same, remember to leave room in mounts for the expansion and contraction of condensers. Remember that cold draughts will break your condensers. 132 MOTION PICTURE PROJECTION To Set the Flicker Shutter. To set the flicker shutter, loosen up the set screw so that shutter revolves freely on the shaft, now turn shutter till single set screw is in groove of shaft and then tighten, now loosen the two screws on the collar and open the gate of machine. Turn the balance wheel till you see that the intermittent movement is just about to revolve, then the large blade of shutter should just be coming up to cover lens, and should be so fixed that the blade of shutter is cover- ing the front of lens as long as the intermittent sprocket is in motion. Another way to set it is as follows : Turn the balance wheel till two teeth of the intermittent sprocket has passed a given point, this represents one-half of a picture or in other words that the picture has completed one- half of its movement, now set the large blade of the flicker shutter dead over the front of lens. Always set the flicker shutter as close to the lens as possible leaving enough room to focus the lens. Always keep carbon holders clean so that carbons make good contact. Always have a spare belt (driving and take-up) near at hand. Keep your fingers off the glass surfaces of lenses. Oil machine often a little at a time, keep oil off the floor of the booth. Keep oil off the friction discs. Never use oil on the arc lamp. Use graphite. Renew motor brushes, whenever necessary, and keep grease cups filled. Use your head more and the "One minute please" slide less. MOTION PICTURE PROJECTION 133 EXAMINATION QUESTIONS 1. Name some of the different lenses used in moving picture work. 2. Under what conditions can you rewind films in the booth? 3. To which end of the table switch (lamp or line) would you connect the primary coil of a transformer? 4. How is a transformer constructed and how does it work? 5. How would you judge what size fuse to use on a line? 6. How is a rheostat made, and what is it used for? 7. Name three kinds of wires used in moving picture work. 8. What is meant by induction? 9. State the difference between an auto transformer and a step -down transformer. 10. How would you ground an all metal machine, and after you have same grounded would you expect to get a light with test lamp if you connected it between either carbon of arc lamp and the lamp house frame? 11. Name three causes of sparking at your motor. 12. What would happen if the neutral fuse on a three wire system was to melt, providing the system was balanced? 13. Explain fully what is meant by a D. C. econo- mizer. 14. Show by sketch the setting of a D. C. arc and a jack-knife setting. 134 MOTION PICTURE PROJECTION 15. Which fuse would you remove first on a three wire system and give reason why? 16. Where is a transverter used on A. C. or D. C.? 17. What is meant by stealing the arc? 18. Is the primary coil of an economizer connected in series or multiple on your line? 19. Is there any difference in the construction of a step-up and a step-down transformer, which is used for moving picture work? 20. Describe fully what regulates the speed of a Powers, Simplex and a Standard machine. 21. Do you get A. C. or D. C. from the secondary coil of a transformer? 22. Does the resistance of metals and carbons in- crease or decrease with an increase of temperature? 23. What is a rectifier used for? 24. Name the fire prevention devices on the head of machine. 25. What controls the size of the picture on the screen? 26. What precautions would you take before starting your show? 27. How many sets of fuses would you use on your line and what would you call them? 28. Of what use are the condensers? 29. Suppose when you struck the arc the fuse melted where would you look for the trouble? 30. How are the coils in a transformer connected, in multiple or series? 31. What would you do in case of fire? 32. Show by sketch how a lens works and how it is put together? MOTION PICTURE PROJECTION 135 33. What is the carrying capacity of a No. 6, a No. 8, a No. 14 rubbeer covered wire? 34. Name the mechanical and electrical safety de- vices on the machine and on the line. 35. What precautions must you take when on a three wire system? 36. Give an easy way to test for A. C. or D. C. 37. What is the back focal length of a lens? 38. Name the advantages and disadvantages of a three wire system. State how a three wire system is obtained. 39. What would you use to change D. C. to A. C.? Is this ever done for moving picture work? If so, state when? 40. What is a keystone effect on screen? 41. What is ohms law? 42. What is a converter and where is it used? 43. What is the difference in construction between a step-down transformer, an economizer, and an in- ductor? 44. What is meant by current frequency. Do we get current frequency on D. C.? 45. What is a kilowatt, and a circular mil? 46. Show by sketch two rheostats connected in mul- tiple with each other and in series on your line. State where you would use them. 47. With two 110 volt 25 ampere rheostats connected in series, how much resistance (in ohms) will they offer in our circuit? 48. What is an electric arc? 49. Explain how you would test lamp house and rheostat for ground. 136 MOTION PICTURE PROJECTION 50. What size wire would you use for motor connec- tions and what size fuse? 51. Show by sketch two machines connected to one source of supply. 52. On which line, positive or negative, would you connect your rheostat? 53. What is the difference between A. C. and D. C.? 54. State what combination of carbons you would use if you were drawing 50 amperes D. C. 55. Name the principal parts of a dynamo. 56. How do you get the equivalent focus of a lens? 57. Explain what the flicker or light shutter is used for. 58. What is a lug? 59. Name six causes of the film jumping on screen. 60. What is the difference between a short circuit and a ground? 61. State if there would be any saving, if you in- stalled an economizer in place of a rheostat on 110 volt A. C. circuit. 62. State how you would go about measuring a stranded and a solid wire. 63. With two 1 10 volt 25 ampere rheostats connected in multiple, how much resistance in ohms would they offer on our line? 64. Show by sketch a complete circuit from the main fuses in cellar up to arc lamp, taking it for granted that you have 220 volts D. C. to work on. 65. Show by sketch a complete circuit using a trans- former. 66. Suppose the output of a transformer was 2,500 watts, 50 volts, what would be the amount of amperage? MOTION PICTURE PROJECTION 137 67. If you connected three 110 volt 50 ampere rheostats in series,and connected them on a 220 source of supply what approximate amperage would this give you at arc lamp? 68. What would be the ohmic resistance of three 110 volts 30 ampere rheostats, connected in series? 69. What is the voltage, if we have 4 1-2 ohms re- sistance on line and are getting 35 amperes at arc lamp. 70. Connected between the neutral and positive wire of a three wire system and with 4 2-5 ohms resistance on circuit, what amperage have we at arc lamp? 71. When and how is fading done? 72. On which coil of a transformer, the primary or secondary, is the most wattage and give your reason for this. 73.; State fully what precautions you would take so that you could project a picture free from frame-ups. 74. By what would you judge the proper rate of speed in projecting pictures, how long should it take you to run off a 2000 foot reel? 75. What is the wattage on a mazda lamp used for moving picture projection work? 76. How would you measure a stranded wire? 77. Name six parts on a motor generator and state their uses. 78. What size fuse would you install providing you were connected up on a 220 volt circuit and had two 110 volt 25 ampere rheostats on your line? 79. Name three causes of your film breaking. 80. What lubricant would you use on the following parts of the machine? (a) Arc lamp? (6) Intermittent movement? , (c) Gears? (d) Motor bearings? 138 MOTION PICTURE PROJECTION 81. Which would be the cheaper to install and which the cheapest as far as operating cost, a D. C. economizer or rheostats? 82. What would cause the breaking of a brand new film while passing through machine? Is there any way to help overcome this? 83. What is meant by a travel ghost, how would you remedy same? 84. State the working principal of a Powers inter- mittent movement. 85. Why are flicker shutters made with more than one 'blade? 86. Of what use is the loop setter and on which make of machine will you find same? 87. Is it possible to take out a travel ghost while the machine is in motion, if so how would you go about it? 88. What is a pin cross and where on the machine is it situated? 89. How should fuses be installed? 90. State one of the disadvantages of A. C. current for moving picture work. 91. Is it possible to use cored carbons on D. C.? 92. Name three good conductors, three fan* conduc- tors and three non-conductors* 93. What is meant by conductivity? 94. State how you would repair a torn film. 95. How would you determine the amount of am- perage that would flow over a circuit in a given time? 96. What effect would it have on your rheostat, if you changed from D. C. to A. C.? 97. How would you find the saving of a D. C. economizer or a motor-generator set, over that of a rheostat? MOTION PICTURE PROJECTION 139 98. Are there any precautions that should be taken with new film to prevent the breaking of same while passing through the machine? 99. Suppose you start the machine and you find lower reel is not taking up, where would you look for the trouble? 100. What is meant by the armature? Does the armature revolve in a dynamo and alternator? 101. What are the brushes in a motor made of? 102. How are the coils or plates of a rheostat con- nected, in series or multiple? 103. What is meant by series connection and multiple connection? 104. Suppose the film broke while passing through the machine, state exactly what you would do. 105. Is an ammeter and voltmeter connected in series or multiple on your line? 106. What is meant by reflection and refraction? 107. Why do we get double the voltage and not double the amperage, when connected between the two outside wires of a three wire system? 108. What is meant by chromatic aberration? 109. What is a friction disc speed regulator? 110. What is an ampere-hour. 111. State the uses of following parts of the machine: (a) Flicker shutter (g) Fire traps (6) Balance wheel (h) Framing device (c) Speed regulator (i) Objective lens (d) Intermittent movement (j) Condensers (e) Tension bars (k) Dowser (/) Centrifugal movement (I) Take-up 140 MOTION PICTURE PROJECTION 112. State how you would clean the lenses of the machine, and what you would use for this purpose. 113. Why not use a cartridge fuse in the booth cut out? 114. What would be the result supposing you con- nected two 110 volt 25 ampere rheostats in multiple, on a 220 volt circuit? 115. What is meant by a balanced circuit? 116. How many volts will a No. 6 wire carry? 117. What is stage cable, rubber covered wire, and asbestos wire? 118. State in your own way how we are deceived into the belief of motion while watching pictures oil the screen. 119. What is an achromatic lens? 120. What is a ground? What is a short "circuit? 121. State how it is possible to get a fire on head of machine. 122. Does a transformer change A. C. to D. C.? 123. How would you go about cleaning the head of machine? What would you use for this purpose? 124. What is meant by the arc lamp burning upside down? How would you remedy this? 125. What is a frame-up? 126. State how an objective lens is put together and say exactly what it does. 127. WTiat is the principle of the revolving shutter and how would you time it? 128. What would happen if a coil in your rheostat melted out? 129. Show by sketch two machines connected to a three wire system, using rheostats, and mark the polarity of the wires. THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO SO CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE. LD 21-100m-7,'33 393283 UNIVERSITY OF CALIFORNIA LIBRARY