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1954-55 Theatre Catalog, 12th Edition, Page 153 (119)

1954-55 Theatre Catalog, 12th Edition
1954-55 Theatre Catalog
1954-55 Theatre Catalog, 12th Edition, Page 153
Page 153

1954-55 Theatre Catalog, 12th Edition, Page 153

throw. However, this factor is of even greater importance when rebuilding towers in already constructed theatres. In most cases the throw must generally be increased by locating the new tower farther from the booth in order to add the needed distance. It is for that reason that replacement towers built by the author have always been located behind the old tower. In those theatres having a short projection throw, the widening of a screen in its present location may very well be limited by the focal length of the lens required to do excessive magnification. Quite often this means going into the rather inefficient range of two or two and one-half inch focal length lenses.

Tower Trusses

The strength of the tower trusses is determined by simple engineering mathematics, and should be based on an assumed wind load of 30 pounds per square foot of surface plus-and this is very important#a factor of safety of at least 50 per cent. Some itbargain" towers are rated at 25 pounds per square foot and a 33 per cent safety factor,

The exhibitor may choose what ticalculated risk" he is willing to assume in


his strength rating, but as at the drugstore, the "giant economy size" is the best value. The New England hurricanes of September, 1954, had winds of 125 miles per hour, but there was not a single report of damage to the towers which the author had constructed in that area using the wind loads and safety factor described above. '

In this era of widening of old towers, a few jobs have come to our attention where strength has been disregarded by some local carpenter who can uvery cleverlyl, add height or add wings by wood framing beyond the original tower, without the use of new trusses to transmit the added wind area to the ground. Obviously, this is not getting something for nothing, but is simply reducing the strength rating to cause a failure at a much lower wind velocity. Therefore, what may seem like a very economical way to bring the wide screen to your drive-in might result in having the entire tower structure collapse in winds which had previously done no damage at all. In addition, by merely adding these

HERE is the skeleton of a new D-I wide screen lower. The two most important factors to be considered are curve and tilt, and wind load.

wings without making the proper provision for curvature, tilt and optics, it might be discovered that the front ramps are no longer useable, since it will be impossible to properly view the wider screen.


Two factors, then, must be taken in consideration in the purchasing of either a new or enlarged screen. First, the designer must understand the optical requirements. Tilting and curving alone are not enoughethe screen should be looked at as an engineered refiector prepared for each individual theatre, according to up-to-minute technical developments. Secondly, the wind resistance must be high enough to enable the tower to withstand the highest winds recorded in the particular area in which the drive-in is located. All this can be most easily accomplished through a specialist in theatre screen tower design and construction, for by his quantity of production from standard jigs, prices for quality can be held low. And as a bonus, there is the assurance that all technical and optical factors will be right.
1954-55 Theatre Catalog, 12th Edition, Page 153