There are two distinct classes of aerial tram ways; namely, single rope systems and double rope systems. The single rope system is the simpler in construction and for limited capacity not exceeding eight tons per hour and an aver age condition of route, is economical in both construction and operation. This system con sists of a moving endless rope to which are attached in various manners the carriers, bug gies or buckets. The entire line is supported by sheaves placed on towers which are located according to the profile of the ground. At each terminal the cable passes around a horizontal sheave or series of sheaves, generally one of them being provided with grips in its periphery for driving or controlling the tramway. When divisible material is carried, mechanical loaders are used and the buckets are arranged so that they discharge automatically. This is all ac complished while the line continues in operation. Bulky material can be loaded and taken away from the carriers while the tramway continues in motion, owing to its slow speed. The double rope system is always preferable to a single system owing to the fact that a separate track rope or cable is used upon which the buckets travel, the other rope being exclusively for hauling. This diminishes and divides the strains developed greatly increasing the life of the cable and plant. The double rope system will fulfil almost any requirements in the tramway line and may be built practically any length. The practicability of long lengths of tramway is fully demonstrated by the tramway built for the North American Copper Company at En campment. Wyo., which has a total length of over 16 miles and is built in four sections, making it the longest tramway in this country. Another notable cableway is that of the Saline Valley Salt Company at Bishop, Inv) County, Cal. It is 6'),025 feet long and carries 20 tons of salt per hour from the floor of the valley over the Inv° Mountains 6,330 feet above that level to the line of the Southern Pacific Railroad on the other cite The track cables are and inches for the loaded side and 7i inch for the returning empties. The traction rope is y. inch in dotter!, r The ionizct ca},le+A ay in the world is owned by the Argen•ine Republic and runs from the mining district of Ilejicana, 11,500 feet high in the Cordilleras to the railroad station at Cliik cito. The distance is 21.54 miles. The cables are 1 7/16 inches and the lower lq inches in diameter. The hauling cable is 11/16 of an inch in diameter. The buckets have a capacity of 1,100 pounds each, and are spaced 1.500 feet apart. The cable is run at 400 feet per minute. The entire cableway is in eight sections, and is operated, or rather controlled by five engine plants. Once the cable is started by loadingit runs continuously. Lubrication is
by an oil car which is run over the line occasionally. The double rope system is capable of carrying capacities as great as 200 tons per hour and in fact even greater, when conditions demand it. The double rope system in general consists of two tracks or standing cables., upon which the loaded and empty carriers travel respectively and an endless traction rope for propelling them. The track cables are stretched at high tension, one end being anchored solidly and the other being fastened to a tension device. All of the cables are supported by towers, which are located according to the shape of the ground over which the line passes.
In all of the above classes, the traction rope passes around a sheave or a series of sheaves at either terminal; one, however, being generally provided with in its periphery for clamp ing the cable in order to secure the necessary friction for driving or controlling the tramway In long lines, tension stations are provided at intervals, for dividing the tension and take up on the track ropes. Double rope systems may be subdivided into three classes. One in which the carriers are attached and detached to and from the traction rope by means of a friction or compressing grip. The second in which the carriers are permanent fixtures to the traction cable, the loading of same being effected by mechanical loaders while the buckets are auto matically tripped at the discharging point. And the third in which the traction cable has per manent fixtures attached to it in the shape of clips or buckets. The buckets in this system are automatically attached and detached to and from the same at either terminal of the line by means of a locking device. This latter system is furthermore designed so that the bodcets are automatically discharged at the unloading end without any attendants to look after them. A simple self-operating tramway which is known as a two-bucket tramway may sometimes be used to advantage where the grade is steep and where the capacity is moderate. This as true for short lines. It consists of two cables stretched parallel to each other, upon each Wag operated a bucket, the two buckets connected to a traction rope whicharound a sheave or series of sheaves at end of the lure When the loaded bucket descends by gravity, it pulls up the empty bucket on the opposite cable and vice versa. This type is sometimes used on level ground or even up-grade simply by applying power to the line for operating. The most suitable system of tramways to be used in any case depends upon the profile of the ground, nature of the material to be transponed and terminal requirements and these Ions should be investigated thoroughly before decid ing upon any particular construction.