Tenants of modern office buildings fret if they wait more than 30 seconds for an elevator. This impatience cost Manhattan's Empire State Building nearly $400,000 for extra elevators. The space those elevators occupy takes more than four acres from the building's rentable space. The Empire State owners could have saved space & money by running 20 double-deck elevators to the 80th floor instead of the present 36 single-deck passenger cars which go that high. But the owners figured their building would quickly fill up with tenants whose rents would pay for the extra elevators and the lost floor space. More fundamentally, the owners were pressed for time in construction, feared that tenants might be reluctant to use double-deck cars.
The builders of Manhattan's newest, completed skyscraper, Cities Service's 67-story Sixty Wall Tower, installed double-deck elevators which seem to satisfy the tenantry. If ordinary single elevators had been used, the economical height of that building would not have been more than 48 stories.
To satisfy the tenants' demand for speed and the owners' need of profit is a complex problem which Carl F. Scott, Manhattan engineer, discussed in the current Engineering News-Record.
Elevators now run at between 900 and 1,200 ft. per min. The 67 (all told) cars in the Empire State Building can run, and the 74 in the Rockefeller Center building now being constructed will run, at 1.200 ft. per min. (14 mi. per hr.). Speed is scarcely felt, because the cars start and stop smoothly. But many passengers become uncomfortable as they ride. The air pressure atop the great tower buildings is about one-half pound per square inch less than at the street level. Elevator passengers feel the difference as an annoying pressure on the ear drums. They overcome the discomfort by pretending to swallow. That action opens the eustachian tubes, allows air pressure on the inner sides of the ear drums to equalize air pressure on the outer sides.
The cost of running an elevator up & down the Chrysler tower averages, all operating costs included, about 25¢ a round trip. Cars in that building run 320,000 mi., make 12,000,000 stops a year.
Electricity to run a car one mile (2½ tower round trips) costs 1¢. Other buildings find the costs about the same. Hence Mr.
Chrysler, John Davison Rockefeller Jr.
Rockefeller Center), Alfred Emanuel Smith (Empire State), Henry Latham Doherty (60 Wall) and their competitors want to carry as many people as possible each trip of their swift machines, and to get the passengers in & out as fast as possible.
Engineer Scott noted some ways this is done. Cars are wider than they are deep.
Door openings also are wide. This entices passengers to enter and step out smartly.
In lobbies signs show which elevators rise to certain heights. Starters are polite and intelligent. Cars stop precisely at floor levels. On each floor a light and a bell bring the tenant to the door of the ele- vator which will stop for him. Westinghouse Electric & Manufacturing Co., which with Otis Elevator Co. leads in U. S. ele- vator research* now attaches photo-electric cells to elevators. These prevent elevator doors closing on passengers, allow the doors to close the instant the passenger safely enters.