IEEE Power & Energy Magazine - November/December 2015 - 90

he pointed out that, since electricity
made telegraphy possible, the building
should also use this latest technology in
its vertical transportation system.
although limit switches and car
safety circuits were not yet installed,
for several days the first express elevator had been running up and down the
shaft without a problem. So, on impulse,

Frank Sprague had invited his whole
crew to join him on the elevator's first
passenger ride. although of only modest build and bearing, Frank Sprague
still seemed to stand out in any crowd.
Even when working, he usually wore
a suit with a vest, dress shirt, and tie,
and a hat jauntily perched at a rakish
angle on his head. His square face was

figure 1. The drawing for the Sprague screw-type elevator patent U.S. No.
716,953, issued to Frank J. Sprague on 30 December 1902 (image courtesy of
John L. Sprague).
90

ieee power & energy magazine

dominated by a slightly hooked nose,
bushy red mustache, and penetrating
eyes that glittered with intelligence. He
was demanding and drove his men relentlessly, but no more so than he drove
himself. Utterly fearless, he repeatedly
undertook seemingly impossible tasks
with relish and invariably delivered on
what had been contracted. as a result,
he elicited fierce loyalty in those who
worked for him such that they would
follow him wherever he wanted to go.
The structure they faced was a rectangular metal cage that seemed to rise
above them forever, inside of which
was a metal passenger car. The drive
mechanism consisted of a large horizontal steel bar threaded like a screw
and driven by a heavy electric motor.
On the threaded shaft was a large nut
that moved along it as the motor rotated the shaft. attached to the nut was
a series of lifting cables and multiplying sheaves so that a short travel of the
nut created a large movement in the
cables that ran to more sheaves at the
top of the elevator shaft and then down
to the top of the passenger car. another
cable ran from the top of the car to a
counterweight so that the lifting cables
only had to overcome the difference in
weight between the car and the counterweight. On the way down the motor became a dynamo powered by the
weight of the descending car and returned electric power to the system (see
Figure 1).
although it has never been clear
why, when the rest of the group entered
the elevator car, one remained behind
in the basement. It began as a relaxed
joy ride when Frank Sprague operated
the control lever and the car shot upwards at 400 ft/min. However, as they
neared the 14th floor and he tried to
stop the car, nothing happened. apparently the controller contacts had
welded together. With no safeties in
place, the stunned group envisioned
crashing into the overhead sheaves and
then tumbling down to certain death as
the entire elevator structure collapsed.
However, sensing that something was
very wrong, at the last second the man
in the basement opened the master
november/december 2015



Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - November/December 2015

IEEE Power & Energy Magazine - November/December 2015 - Cover1
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IEEE Power & Energy Magazine - November/December 2015 - Cover3
IEEE Power & Energy Magazine - November/December 2015 - Cover4
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