26. The Whiting System.—This is a system of hoisting with round ropes, in which two rope wheels placed tandem are used in place of cylindrical or conical drums. As shown in [Fig. 15], for a two-compartment shaft the rope passes from one cage a up over a head-sheave c, down under a guide sheave d, and is then wound three times about the rope wheels e and f, to secure a good hold, then around a fleet sheave g, and back under another guide sheave h, up over another head-sheave i, and down to the other cage b. When the system is to be used for a single-compartment shaft, one end of the rope carries the cage and the other end carries a balance weight, which is run up and down in a corner of the shaft. A balance rope below the cages, as shown, is generally used, though it is not essential to the working of the system, as it is in the Koepe system. When sinking a shaft, a balance rope cannot be used as it interferes with the work at the bottom of the shaft.
Fig. 15
The drums or wheels e, f are light, inexpensive, and narrow, thus permitting short sheave shafts and small foundations. They are lined with hardwood blocks, each lining having three rope grooves turned in it. The main wheel e is driven by a hoisting engine, which may be either first or second motion. The following wheel f is coupled to the main wheel by a pair of parallel rods, one on each side, like the drivers of a locomotive. As the rope wraps about the wheels e, f three times, there are six semi-circumferences of driving contact with the rope, as compared with the one semi-circumference in the Koepe system, and there is no slipping of the rope on the wheels. The following wheel f is best tilted or inclined from the vertical an amount equal, in the diameter of the wheels, to the pitch of the rope on the wheel, so that the rope may not run out of its groove and may run straight from one wheel to the other without any chafing between the ropes and the sides of the grooves.
The capacity of the wheels e, f is unlimited, while grooved cylindrical drums, conical drums, and reels will hold only the fixed length of rope for which they are designed.
As shown by the dotted lines, the fleet sheave g is arranged to travel backwards and forwards, in order to change the working length of the rope from time to time to provide for an increased depth of shaft, and for the changes in the length of rope due to stretching and when the ends are cut off to resocket the rope. The fleet sheave g is moved a distance equal to half the change in the length of rope.
27. Hoisting from intermediate levels can be readily done with the Whiting system; for instance, if the cage a is at the top and cage b at the bottom, and hoisting is to be done from some upper level, it is only necessary to run the fleet sheave g out, and thus shorten the working length of the rope until cage b comes up to the upper level. It can then be loaded and go to the top. While cage b goes to the top, cage a descends to the same level, where it can be loaded while cage b is being unloaded, and can then go directly to the top without any of the lost time, as is the case in the Koepe system.
The system permits a perfect balance of rope and cage, so that the work to be done by the engines is uniform, except for the acceleration, and consists only in lifting the material and overcoming the friction.
There is no fleeting of the rope, so the rope wheels can be placed as close to the shaft as may be desired.
28. This system was tried as early as 1862 in Eastern Pennsylvania, but it was not used extensively because hoisting from great depths was not necessary, since, for depths of less than 1,000 feet, cylindrical and conical drums are quite satisfactory. In the Lake Superior copper region, there are now three Whiting hoists, two of which are probably the largest hoisting plants in the world. Each plant consists of a pair of triple-expansion, vertical, inverted-beam engines, driving direct a pair of 19-foot drums. The high-pressure cylinders are 20 inches in diameter, the intermediate cylinders 32 inches, and the low-pressure cylinders 50 inches, and all six of them have a 72-inch stroke. The rope used is a 2¼-inch plow-steel rope and hoists 10 tons of material at a trip, in one case from a depth of 4,980 feet, the deepest shaft in the world. Several plants on the Whiting system have been built in England, and two or more are working in South Africa.