International projectionist (Jan-Dec 1950)

I E L Lr 1 i a n FIGURE 14 where its speed is greatest. At the opposite end of L the lever G points straight down, and its pin is close to shaft K, and K turns at its greatest speed. The condition is such that the speed variation is multiplied: not only has the speed of L been greatly increased, but at the same time L, through means of its lever G, increases the speed of K and, consequently, the speed of cam /. Double-Lever Arrangement Effect In Fig. 15 the parts have turned onehalf revolution from the position in Fig. 14. The first two levers have greatly slowed down shaft L, which in turn has slowed down the camshaft by means of the second pair of levers. By the use of this double system of levers the effective speed of the move-1 rrient can be changed without moving the camshaft; only the shaft L and its connected levers are moved up or down. This causes no complications, because the only connection to L is through the two pins H, which are free to move in their respective slots. Slight Speed Increase Possible The actual displacement of L from the in-line position was only a small amount. A larger displacement causes so great an increase in the spee'd of the move FIGURE 15 rt ment that the film simply cannot stand the terrific strain. This strain is not due to the conditions set forth in Figs. 3, 4, and 5 last month, because our present cam and star is actually a 3-to-l movement and operates as shown in Figs. 1 and 2. But even such a movement will, if the projector speed be increased enough, strain and eventually tear the sprocket holes. This is what happens when the movement is accelerated by a system of levers or through the use of elliptical gearing. Only a slight increase in speed is therefore permissible, and each increase calls for greater film tension to assure the film stopping in the proper position. Of course, the increased tension produces more strain on the film during the period in which it is started and accelerated. [TO BE CONTINUED] Latest Film-Flam Philology Bringing discussions on the use of the word "flammable" up to date, the National Fire Protection Association announces that many organizations have adopted "flammable" to designate materials that are easily ignited and burn with unusual rapidity. In law, however, the NFPA points out, the word ''inflammable" persists. "Now, after 25 years, the Congress of the United States has given official sanction to 'flammable,' " the NFPA reports in its Fire News. "It has just come to our attention," the News declares, "that in Chapter 39 of Public Law 772 the word 'flammable' is used in place of 'inflammable' with reference to Interstate Commerce Commission regulatory powers. The Civil Aeronautics Board adopted the word 'flammable' in their Revised Regulations. Projectionist Examination Questions 21. A unit of length used in electricity and which is equal to 1/1000 of an inch is called 31. The space on the film upon which the sound is photographically impressed is called 22. Films may be rewound in the 32. The smallest size wire which projection room proper provided may be used to supply a professional that... -j projector shall be 23. You have discovered that you are burning "upside down." To correct this trouble you would change the electrical connections at. 24. When your equipment, which operates on a 3-wire system, takes 55 amperes from one side of the system and 45 amperes from the other side, the current which flows in the neutral wire under these conditions will be 25. If your equipment takes 55 amperes at 120 volts, you would be using kilowatts. 26. The resistance of a copper wire one mil in diameter and one foot long at normal room temperature is known as 27. That wire of a 3-wire d-c system which is "positive" to one wire and "negative" to the remaining wire is called the 28. That property of a conductor which opposes the flow of current is called... 29. The amplifier that amplifies the currents set up in the photoelectric cell is called 30. R.p.m. is the abbreviation for 33. A motor-generator installed in the projector enclosure shall have the commutator end protected by , or by other suitable means. 34. The ventilation of the projection room shall be provided by means of a vent pipe having a cross-sectional area of at least.. 35. After striking the arc and permitting it to burn for a few minutes, you open the table switch. If the carbons glow with the same brilliancy, the current supplying the arc is 36. The metal out of which lamphouses are to be built shall not be smaller than sheet metal gauge. 37. A projector carbon having no core is called 38. The insulating material betwen the plates of a condenser is called the 39. The doors of magazines shall be designed to swing 40. If you connect a rheostat rated at 40 amperes and 120 volts in multiple with a rheostat rated at 80 amperes and 240 volts, the total resistance will be .ohms. 16 INTERNATIONAL PROJECTIONIST April 1950