Motion Picture Herald (Jan-Mar 1956)

GRADE Lower drawing illustrates sightline clearance which determines elevations of the ramp system as explained in text. 27 to 29 FT. Above drawing shows a single ramp in profile, indicating parking ramp (C-D) and driving ramp (D-C) of a single-ramp system with total width from 40 to 42 feet. lines, one can adapt a scheme of ramp elevations to the natural topography of the land so as to move as little earth as possible. If tlie land naturally slopes do^vmward toward tlie location selected for the screen (the most difficult condition to deal with) the ramp system can slope in that direction. If tlie slope toward the screen is upward, ramp gradients can conform to that natural contour. Also, ramp pitches can be bowled (lowest point somewhere near middle) if topogi'aphical conditions advise. The ramp plan on page 39, and the ramp dimensions given in the adjoining profile drawing, refer to the single-ramp system — cars enter the tier and drive forward into parking position beside a speaker post; then drive over tlie crest and turn across the drive-off slope to the exit drive. This is the system to use because it is more convenient and safer than the double-ramp system, which requires certain cars to back into parking position and into drive-out lane. The latter is occasionally employed for an absolute maximum capacity in area really too small for a drive-in. Parking positions are indicated by speaker posts — one post, from which two in-car speakers are suspended, serving two cars. These posts (galvanized pipe or seamless tubing with an inside diameter of or 2 inches) are set in bases of concrete (foundation blocks can be used, with one above another and the post cemented into the holes) at least 19 feet apart and preferably 20 feet. RAfAP DRAINAGE AND SURFACING Grading of the ramp area (and adjoining drives) must also provide for run-off of rain water into the theatre’s drainage system, by sloping the surface to one side or the other, according to the location of the drainage ditch or sewer. Flow can extend entirely across the ramps from one side to the other, or to both sides from the middle. This lateral sloping must carry far enough, and have a pitch great enough, to assure steady flow of rain water out of the area occupied by ramps and drives. A rate of pitch of about 6 inches to 100 feet should be sufficient in regions of normal rainfall. It is of course important that rain drained out of the ramp area be carried completely out of the drive-in tract with such efficiency that no pools of water are formed in which mosquitoes can breed. Of the methods of draining the ramps that of sloping each ramp along its lowest level from the middle toward each side has two advantages over the side-to-side system ■ — it reduces the lateral pitch to a minimum, and it minimizes erosion. Ramps must be surfaced for permanence of grading under hard wear. The surface should be built up of crushed stone (around 1^-inch) and topped with fine stone (quarter-inch). Road oil can be used as a binder, but an asphalt dressing is better. There should be at least two rollings. Ramps should be accurately graded from a system of elevations prepared by an architect or engineer who has made a competent topographical study of the property for the purpose of establishing proper sightlines. RADIAL PLAN OF RAMPS The ramps form arcs of uniform distance apart with the first one more or less (depending on maximum dimensions of the picture) on a radius of 125 feet from a point at the middle of the screen tower. This distance of the first ramp to the screen includes the first drive-out lane, for which a depth of 25 feet is sufficient. Drive-out lanes serving the second, third and fourth ramps are, of course, deeper, and should, indeed, be a little deeper than those for the ramps behind them since ramp feed should be from the rear (toward the screen), making the turning radius for the forward ramps relatively short. Hence, if the drive-out lane for each ramp behind the fourth is 27 feet deep, drive-out lanes for the second, third and fourth ramps should be 29 feet deep. A total depth for each ramp (car parking slope upward plus downward sloping drive-out lane) was originally set at 38 feet. That was before World War II. Automobile overhang has become considerably greater since then, advising 40 feet for drive-in ramp depths (42 feet for second, third and fourth ramps). Depth for the parked car remains constant at 13 feet. {See accompanying diagram of ramp dimensions.) This ramp system, regardless of total capacity, should form a segment of a circle preferably no greater than 85 degrees, with a questionable allowance of 90 degrees. Capacity is thus expandable only by increasing the number of ramps. With the ramp area within an angle of 85 degrees, and the first ramp approximately 125 feet from tlie screen, that front arc has a capacity of 28 cars, and 40 Better Theatres 1956 Market Guide