Power: 227.5 p.s.i. x 2 (plungers) x 124 sq. in. (plunger area) 56,420 lb.
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Excess to overcome friction 5,090 lb.
Footnotes:
[1] Translated from Jean A. Keim, _La Tour Eiffel_, Paris, 1950.
[2] The foundation footings exerted a pressure on the earth of about 200
pounds per square foot, roughly one-sixth that of the Washington Monument,
then the highest structure in the world.
[3] A type of elevator known as the "teagle" was in use in some multistory
English factories by about 1835. From its description, this elevator
appears to have been primarily for the use of passengers, but it
unquestionably carried freight as well. The machine shown in figure 7 had,
with the exception of a car safety, all the features of later systems
driven from line shafting--counterweight, control from the car, and
reversal by straight and crossed belts.
[4] The Otis safety, of which a modified form is still used, consisted
essentially of a leaf wagon spring, on the car frame, kept strained by the
tension of the hoisting cables. If these gave way, the spring, released,
drove dogs into continuous racks on the vertical guides, holding the car
or platform in place.
[5] A notable exception was the elevator in the Washington Monument.
Installed in 1880 for raising materials during the structure's final
period of erection and afterwards converted to passenger service, it was
for many years the highest-rise elevator in the world (about 500 feet),
and was certainly among the slowest, having a speed of 50 feet per minute.
[6] Today, although not limited by the machinery, speeds are set at a
maximum of about 1,400 feet per minute. If higher speeds were used, an
impractically long express run would be necessary for starting and
stopping in order to prevent an acceleration so rapid as to be
uncomfortable to passengers and a strain on the equipment.
[7] Two machines, by Otis, in the Demarest Building, Fifth Avenue and 33d
Street, New York. They were in use for over 30 years.
[8] Although the eventually successful application of electric power to
the elevator did not occur until 1904, and therefore goes beyond the
chronological scope of this discussion, it was of such importance insofar
as current practice is concerned as to be worthy of brief mention. In that
year the first gearless traction machine was installed by Otis in a
Chicago theatre. As the name implies, the cables were not wrapped on a
drum but passed, from the car, over a grooved sheave directly on the motor
shaft, the other ends being attached to the counterweights. The result was
a system of beautiful simplicity, capable of any rise and speed with no
proportionate increase in the number or size of its parts, and free from
any possibility of car or weights being drawn into the machinery. This
system is still the only one used for rises of over 100 feet or so. By the
time of its introduction, motor controls had been improved to the point of
complete practicability.
[9] Mechanical transmission of power by wire rope was a well developed
practice at this time, involving in many instances high powers and
distances up to a mile. To attempt this system in the Eiffel Tower,
crowded with structural work, machinery and people, was another matter.
[10] According to Otis Elevator Company, the final price, because of
extras, was $30,000.
[11] In _Pall Mall Gazette_, as quoted in _The Engineering and Building
Record and the Sanitary Engineer_, May 25, 1889, vol. 19, p. 345.
[12] From speech at annual summer meeting of Institution of Mechanical
Engineers, Paris, 1889. Quoted in _Engineering_, July 5, 1889, vol. 48, p.
18.
[13] Located near the Tower, built for the Paris fair of 1878.
[14] Improved oil-well drilling techniques were influential in the intense
but short burst of popularity enjoyed by direct plunger systems in the
United States between 1899 and 1910. In New York, many such systems of
200-foot rise, and one of 380 feet, were installed.
[15] An obvious question arises here: What prevents a plunger 200 or 300
feet long and no more than 16 inches in diameter from buckling under its
compressive loading? The answer is simply that most of this length is not
in compression but in tension. The Edoux rams, when fully extended,
virtually hung from the upper car, sustained by the weight of 500 feet of
cable on the other side of the sheaves. As the upper car descended this
effect diminished, but as the rams moved back into the cylinders their
unsupported length was correspondingly reduced.
[16] M. A. Ansaloni, "The Lifts in the Eiffel Tower," quoted in
_Engineering_, July 5, 1889, vol. 48, p. 23. The strength of steel when
drawn into wire is increased tremendously. Breaking stresses of 140,000
p.s.i. were not particularly high at the time. Special cables with
breaking stresses of up to 370,000 p.s.i. were available.
Transcriber's Notes:
Passages in italics are indicated by _underscore_.
The original was printed in two columns per page.
Illustrations have been moved to the nearest paragraph break.
The following misprints have been corrected:
"Trevethick's" corrected to "Trevithick's" (page 5)
"then" corrected to "than" (page 14)
"smiliar" corrected to "similar" (page 31)