the end of the century.

By the last quarter of the century, a continuous series of improvements in the valving, control systems, and safety features of the steam machine had made possible an elevator able to compete with the subsequently appearing hydraulic systems for freight and low-rise passenger service insofar as smoothness, control, and lifting power were concerned. However, steam machinery began to fail in this competition as the increasing height of buildings rapidly extended the demands of speed and length of rise.

The limitation in rise constituted the most serious shortcoming of the steam elevator (figs. 8-10), an inherent defect that did not exist in the various hydraulic systems.

Since the only practical way in which the power of a steam engine could be applied to the haulage of elevator cables was through a rotational system, the cables invariably were wound on a drum. The travel or rise of the car was therefore limited by the cable capacity of the winding drum. As building heights increased, drums became necessarily longer and larger until they grew so cumbersome as to impose a serious limitation upon further upward growth. A drum machine rarely could be used for a lift of more than 150 feet.[5]

Another organic difficulty existing in drum machines was the dangerous possibility of the car—or the counterweight, whose cables often wound on the drum—being drawn past the normal top limit and into the upper supporting works. Only safety stops could prevent such an occurrence if the operator failed to stop the car at the top or bottom of the shaft, and even these were not always effective. Hydraulic machines were not susceptible to this danger, the piston or plunger being arrested by the ends of the cylinder at the extremes of travel.

THE HYDRAULIC ELEVATOR

The rope-geared hydraulic elevator, which was eventually to become known as the “standard of the industry,” is generally thought to have evolved directly from an invention of the English engineer Sir William Armstrong (1810-1900) of ordnance fame. In 1846 he developed a water-powered crane, utilizing the hydraulic head available from a reservoir on a hill 200 feet above.

The system was not basically different from the simple hydraulic press so well known at the time. Water, admitted to a horizontal cylinder, displaced a piston and rod to which a sheave was attached. Around the sheave passed a loop of chain, one end of which was fixed, the other running over guide sheaves and terminating at the crane arm with a lifting hook. As the piston was pressed into the cylinder, the free end of the chain was drawn up at triple the piston speed, raising the load. The effect was simply that of a 3-to-1 tackle, with the effort and load elements reversed. Simple valves controlled admission and exhaust of the water. (See fig. 11.)

Figure 11.—Armstrong’s hydraulic crane. The main cylinder was inclined, permitting gravity to assist in overhauling the hook.
The small cylinder rotated the crane. (From John H. Jallings, Elevators, Chicago, 1916, p. 82.)

The success of this system initiated a sizable industry in England, and the hydraulic crane, with many modifications, was in common use there for many years. Such cranes were introduced in the United States in about 1867 but never became popular; they did, however, have a profound influence on the elevator art, forming the basis of the third generic type to achieve widespread use in this country.

The ease of translation from the Armstrong crane to an elevator system could hardly have been more evident, only two alterations of consequence being necessary in the passage. A guided platform or car was substituted for the hook; and the control valves were connected to a stationary endless rope that was accessible to an operator on the car.

The rope-geared hydraulic system (fig. 13) appeared in mature form in about 1876. However, before it had become the “standard elevator” through a process of refinement, another system was introduced which merits notice if for no other reason than that its popularity for some years seems remarkable in view of its preposterously unsafe design. Patented by Cyrus W. Baldwin of Boston in January 1870, this system was termed the Hydro-Atmospheric Elevator, but more commonly known as the water-balance elevator (fig. 12). It employed water not under pressure but simply as mass under the influence of gravity. The elevator car’s supporting cables ran over sheaves at the top of the shaft to a large iron bucket, which traveled in a closed tube or well adjacent to and the same length as the shaft. To raise the car, the operator caused a valve to open, filling the bucket with water from a roof tank. When the weight of water was sufficient to overbalance the loaded car, the bucket descended, raising the car. On its ascent the car was stopped at intermediate floors by a strong brake that gripped the guides. Upon reaching the top, the operator was able to open a valve in the bucket, now at the bottom of its travel, and discharge its contents into a basement tank, to be pumped back to the roof. No longer counterbalanced, the car could descend, its speed controlled solely by the brake.

The great popularity of this novel system apparently was due to its smooth operation, high speed, simplicity, and economy of operation. Managed by a skillful operator, it was capable of speeds far greater than other systems could then achieve—up to a frightening 1,800 feet per minute.[6]

Larger Image
Figure 12.—Final development of the
Baldwin-Hale water balance elevator, 1873.
The brake, kept applied by powerful springs,
was released only by steady pressure on a lever.
There were two additional controls—the
continuous rope that opened the cistern valve to fill
the bucket, and a second lever to open the
valve of the bucket to empty it. (From
United States Railroad and Mining Register,
Apr. 12, 1873, vol. 17, p. 3.)

Larger Image
Figure 13.—Vertical cylinder,
rope-geared hydraulic elevator with 2:1
gear ratio and rope control (about 1880).
For higher rises and speeds, ratios of
up to 10:1 were used, and the endless