The carrying pulleys are arranged in vaults located at distances 25 ft. apart. A trans verse yoke holds the track and slot rails in place. It has a long and flat face, resting on foun dations which are independent of the conduit construction. The pulleys are mounted in pairs. The duplicate cables are carried around grooves at different elevations. A conical wheel with spiral grooves pays the outer cable (when in use) down and out to its normal line after the passage of the grip. The grip is arranged on the front end of the car, and is provided with a stationary and a movable jaw. At each end of the jaws is a pair of small carrying pulleys, for supporting the cable and raising it from the grip jaw when the car is at rest. Spools are mounted at each end of the jaws, for ejecting the cable, in ease the rope should strand. The grip is reversible, and the cable may be received from either side. The mechanism foroperat ing the jaws is attached to or made part of the grip car, being independent of the grip proper, and the grip may he operated from either end of the car, so that no adjustment of the jaws is required while in transit.
The construction of the driving machinery is as follows : Each pair of driving drums is operated independently through the medium of friction clutch, so that each cable may be individually set in motion or stopped. The driving drums have grooves varied in diameter to meet the contraction of the rope as it is relieved of the strain of operating the road. The incoming cable, having the whole strain, passes into the first groove, and when relieved of a small percentage of the strain, passes to the second groove. The latter groove allows a slight contraction in the cable to take place, and this contraction continues throughout the succes sion of wraps.
The drains are tilted in opposite directions for the purpose of guiding the cable direct into the grooves when two or three wraps are made. whereas were it not for this tilting of the drains the rope would be carried diagonally from one drain to another, causing much trouble by elating the grooves and wearing the cable. The principal improvement is in the arrange ment of the gearing to meet the angle of these d ruin shafts ; the shafts being tilted. the gears have straight teeth, while the intermediate pnd also the driving gears have angular teeth which meet the line of the straight, tooth of the tilted gear.
After being wrapped around the drums, as stated, the cables pass to the tension wheel, which is on a car, and traverses a track in rear of the driving machinery, and then it is carried out into the street again.
On the Tenth Avenue Cable Road, of New York City, two Wright engines, 28 x 48, are employed. The driving drums have five grooves each, and are about 12 ft. in diameter ; the
first groove on the first drum being the largest. The first groove on the second drum is in. less in circumference. and all other grooves are reduced successively in the same ratio. Each pair of driving drums has an independent pair of driving gears, and in the center between the drums a pair of 8 x 8 upright engines are located. These engines are used to move the rope slowly for examination, to take out an old cable or put in a new one, and also are utilized when repairs are made to the main machinery.
It is found that with cables of about 4 miles in length that there is a movement of the tension car of front 4 to 5 ft., so that from 8 to 10 ft. of rope must be disposed of every few minutes. An automatic variable tension device is provided, decreasing or increasing the tensile strain on the contraction of the rope, and so governing the movement of the car.
The Brooklyn Bridge ( 'able Road.—The cable railway over the Brooklyn Bridge presents the most favorable conditions ever encountered for this mode of propulsion. The road is comparatively short and the traffic is heavy. The track is separate from the roadway, so that the cable, grip. etc., need not be sunk in a conduit, but run over the track bed. The power plant with which the bridge railway began business eight years ago was a modest affair. One set of winding drums and a pair of engines sufficed. The work required rarely exceeded 200 ho•se-power. In 1333, the increasing traffic demanded additional power, and an entirely new power plant was put in. It consists of three Wright engines, one 30 in. diameter of cylinder by 48 in. stroke of piston, the second 26 in. diameter by 48 in. stroke, and a third 22 in. diameter by 36 in. stroke. A fourth is to be put in, 38 in. diameter by 48 in. stroke.
During the hours of heavy traffic, the work calls for an average expenditure of energy equivalent to 400 or 450 horse-power, and sometimes this runs up to 700 horse-power. As it takes less than 100 horse-power to run the machinery and cables, it is evident that this is the most efficient cable road known, only about 20 per cent. of the power being absorbed in running the cable and machinery, while in street roads 50 per cent. is always allowed for this, and the actual percentage so expended frequently exceeds that figure. The variations in the power exerted are sudden and enormous. Sometimes a preponderance of trains on the down grade will send the engines racing around with throttles shut, and instead of absorbing power will give it out.