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1948-49 Theatre Catalog, 7th Edition, Page 412 (399)

1948-49 Theatre Catalog, 7th Edition
1948-49 Theatre Catalog
1948-49 Theatre Catalog, 7th Edition, Page 412
Page 412

1948-49 Theatre Catalog, 7th Edition, Page 412

Low Operating and Replacement

The Motiograph-Hall lamps are designed to use either currently available 9 mm. or 11 mm. high intensity positive carbons. When completely developed 10 mm. carbons become available, they can be used also. The cost of 9 mm. positive and 5/16" negative carbons is said to be very little more than the cost of the 8 mm. positive and 7 mm. negative carbons used in reflector-type arc lamps in the 65-70 ampere range. By similar contrast the cost of such carbons is said to be about one-third of the cost of the Super H. I. 13.6 positive and 7/16" negative carbons used in condenser-type lamps operating in the 140-180 ampere range. As another consideration the 16" diameter reflectors, manufactured by Bausch & Lomb to exacting specifications, are said to be only slightlyhigher in replacement cost than the smaller sized reflectors used in reflector-type high intensity lamps in the 65-70 ampere range, and very much less costly than either the glass or quartz condensers used in condenseretype lamps operating in the 140-180 ampere range.

Simplicity of Operation

Once the arc is struck, the projectionist need only watch a pilot light on the lamphouse, which indicates lamp performance. This light dashes when the current varies 2% above or 1% below normal. When such variations happen, the control equipment adjusts the arc gap to optimum operation. Constant adjustment of the manual controls by the projectionist is largely eliminated.

Nor is there any need for the projectionist to periodically adjust the reflector. The reflector in its holder is per manently mounted and forms the rear door of the lamphouse. This method of mounting the mirror and securing it to prevent movement keeps the redector, the aperture and the lens in perfect optical alignment.

If the automatic focusing device should fail to operate for any reason, the projectionist can operate the burner mechanism by means of a conveniently located knob in the operating side of the machine. At initial installation time the entire carriage is naturally positioned so that the light spot will be of the correct dimension and centered on the aperture. In the event the burner mechanism should be removed and subsequently replaced so that the relation of the spot to the aperture is disturbed, manual adjustment to raise or lower the carriage or to move it from side to side can be made by two additional knobs

located on the operating side of the lamp.


The moving portions of the lamp conSist of comparatively few parts; and all of these have been carefully machined and made wear-resistant. The arc burner mechanism is built as a complete unit which can be readily removed if servicing is required.

The spacious housing is constructed Wlth smooth inside surfaces to facilitate cleaning. In addition, a false bottom is


provided which extends under the entire burner mechanism. It can be readily removed.

The positive carbon contacts are made of bronze. This alloy possesses the best heat conductivity among metals and a1loys, consistent with resistance to oxidation and scaling. The contact surfaces are lined with pure silver 1/16th of an inch thick. Both silver and bronze will readily conduct current and dissipate heat rapidly, without scaling.

The lamphouse is comprised of a formed heavy gauge sheet steel base to which two sturdy aluminum castings are attached by polished steel rods. These castings form the front and back of the housing. Both doors are double-walled to effectively insulate the outside surfaces from the high are temperature. The usual ruby glass observation ports and are image projector are provided.

Production Background

The new lamps are being built by Motiograph craftsmen under the personal supervision of Theodore 0. Hall who has had a lifetime of experience as a designer of projection light sources. The new models are designed and engineered to give maximum performance.

They are precision built and easy to operate and adjust.

Experimental models of lamps were in actual operation in drive-in theatres for over a year at a number of points throughout the country prior to fullscale production. The experience acquired in these installations enabled the designer and the manufacturer to eliminate the minor difficulties which are occasionally part and parcel of a newly designed product.


The Motiograph-Hall 75/115 High Intensity Arc Lamp, tested and validated under actual operating conditions in conventional and drive-in theatres in 1948, is scheduled for plant production in 1949. Although an inexorable press time prevents any further report on the new lamp in the present edition of THEATRE CATALOG, detailed engineering and fabrication data will be collected and made available in the 1949-1950 edition. In the follow-up article, the editors plan to supplement the introductory material presented above with a complete technical data survey, including tabulated results of the new lampls performance during its first and experimental year in the field.

IT IS A COMPACT UNIT with the Motiograph projection-sound system but can be adapted to others.
1948-49 Theatre Catalog, 7th Edition, Page 412