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Feb., 1950
ROSS : HEATING OF FILMS AND SLIDES
51
The air is therefore obtained from the studio compressed air supply and the equipment is shown in Fig. 9. It was found that noise occurs wherever there is a marked drop of pressure. All the air passes at full pressure (70 lbs. per sq. in.) through the air filter, which removes water and dust. The pressure is reduced by an ordinary control valve which is surrounded with a small blimp. The extremely loud hissing sound in the air is removed by a most effective silencer, which is itself blimped. The air, now at only 2 to 6 lbs. per sq. in. pressure, passes to the slide holder and a gauge indicates the air flow. Flexible pipes are provided to enable the slide to be tilted, lifted and panned. The air becomes slightly more noisy on passing the slide at such high speed, but another silencer removes this and the air is practically silent as it exhausts into the room.
Results in Operation
This slide holder is fitted to a process projector delivering 60,000 lumens through a 3 in. x 2-2 in. gate, incorporating the heat-absorbing cell and watercooled condenser lens described above. It is possible to project ordinary slides of any density for many hours without any damage. The equipment is so silent that it is possible to use it for all shots without troubling the soundrecording, and it is not necessary to arrange any sound reducing flats or blankets between " — *_ compressed air
the projector and /?==*! 1=>—
the microphone.
Fig. 9. Schematic diagram of arrangement for supplying air to slide cooler from studio compressed air supply. Pressure is reduced at the control valve, and silencers remove the
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Supply silencer
EXHAUST SILENCER
EXHAUST.
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SLIDE HOLDER
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The quantity of air used is measured to be 50 cu. ft. per min., giving a calculated air velocity about 340 m.p.h. The total amount of heat extracted from the slide is 360 watts, as measured experimentally.
Acknowledgments.
Throughout this work the greatest assistance has been given by Dr. B. V. Bowden, of Sir Robert Watson-Watt & Partners, and many of the ideas and calculations are his. Help has also been given for Part I by Dr. F. S. Hawkins and Mr. H. H. W. Losty of G.E.C. Research Laboratories. The combined heat absorbing cell and lens, described in Part I, and the optical system of the high-performance process projector mentioned in Part II, were designed by Mr. A. Warmisham and his staff, and made by Taylor, Taylor & Hobson, Ltd. Facilities for practical tests have always been given by the personnel of the process projection staff at Pinewood Studios and help has been given by my colleagues in the Technical Director's Department, J. Arthur Rank Productions Ltd.
REFERENCES
Spectral Characteristics of Light Sources for Fading and Degradation Tests. B. S. Cooper & F. S. Hawkins. /. Soc. Dyers & Colourists. In the Press. See also Spectral Distributions and Colour-Temperatures of the Radiant Energy from Carbon Arcs. F. T. Bowditch & A. C. Downes. /. Soc. Mot. Pic. Eng., 30 (April, 1938), p. 400. Illumination in Motion