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Show 6 INTER-MOUNTAI- MINING REVIEW. N power and light to mines and mills in that dis electric hoists in mines under his management, trict, at distances varying from two to fifteen and serves this purpose admirably. miles. The direct current at 500 or even 1,000 The choice of the best kind of motor depends volts being too expensive for that distance, they considerably on the size of the hoist, its locaturned to the alternating current; and the only tion, and the nature of the work. For an un- alternating current available at that time balanced hoist of moderate size, especially if this was adopted. placed under ground and exposed to dirt and being a single-phasseries wound street-ca- r Several mills were run by syn- water, the iron-cla- d e, chronous motors quite successfully, but of power to miscellathe application neous purposes, requiring and frequent starts and stops, was impracticable with this system, for the reasons heretofore The plant has recently been changed to the multiphase alternating system, using two phase generators and motors, and an arrangement of transformers to change the into three-phas- e current for transmission, on account of the saving of 25 per cent, in copper effected by the three-phs- e system, as This plant is compared with the speed-regulatio- ns ex-explain- ed. two-pha- se two-phas- e. type is well adapted, as it is strong, well protected and designed to stand heavy work on intermittant service. In this motor, efficiency, low heating and absolute freedom from sparking are to some extent sacrificed for compactness and lightness. For large hoists, which are generally located in comparatively clean, dry Work almost' conplaces, and, if tinuously, hoisting and lowering, and in which high efficiency is more important than in small hoists, the stationary type of motor is usually preferable. is one of the most im- The over-balance-d, speed-controll- er . now lighting the town of Telluride used in the electric hoists at tho Free Silver Alta Argent and Della S. mines at Aspen, and tho Silvpr Lalre mines at Silver ton, and will doubtless be employed more generally in the future than in the past. The Alta Argent hoist, in addition to being overbalanced, is arranged in a novel manner. The hoist, with its motor, is placed on a sub- stantial platform above the head of the incline, is out of the way of the operator, who is located, with the controlling levers, just below the hoist and on the level where the cars are run off. This gives more room for handling the cars as they are raised, and enables the hoist operator to do this wrork. The largest electric hoist in the world is on the Free Silver shaft at Aspen, Colorado. It is flat rope hoist, an overbalanced double-reemotor, capable equipped with a of developing 120 H. P. continuously and 150 to 175 II. P. intermittently. An auxiliary 60-P, . l, 100-K- 4-p- ole H. m doing other work, is arranged so and supplying motors for running a number of mills in that vi- that it counter-shaf- mines plant, Colorado, Sil-verto- n, In 1894 Edward G. Stoiber, owner of the Silver Lake mines, installed the first multiphase plant in this part of the country, doubled its capacity in 1895, and is now 4xJ-inc- h still further increasing it. This plant is on the 500 three-phas- e I .'t ! pound ore (hung from cage in sinking) about car 2,400 pounds, and ore about pounds, 3, and bailer, containing cubic feet of water, about 900 111 sys- SILVER LAKE MINE AND MILL Silverton, Colorado, (Electric Power Plant,) Altitude compressor, pumps, blowers, machine shop and lights. Thedistance of transmission is 3 miles. Of the large number of electric mining plants installed in the Rocky Mountain district during the past eight years, the foregoing are selected in tracing the development of electric power, as they illustrate all of the systems that have been tried. Electricity is being applied to the operation of every kind of machinery used in mines. Hoists. The first application of electric power, and one of the simplest, was to hoisting ; the rotary motion of the electric motor being easily adapted to this work. Most of the earlier machines consisted of or street car motors, geared to hoists. This type is very satisfactory far small or medium-sizemachines, as the friction-gea- r is an assistance to the in smooth starting. For large hoists a positive geared motor is more reliable; but it is desirable to interpose a friction-dutc- h or equivalent device at some point between armature and drum, as a safeguard in case of excessive strain on gearing, caused by the inertia of the armature when the drum is stopped by a too sudden application of the brakes. D. W. Burton, of Aspen, has designed a slipping pinion, which is used on the V-fricti- on d motor-controll- er : 2 bucket and flat-fricti- on f flat rope, 1,375 ELECTRIC MINING MACHINERY. .1 and pounds per foot The cage weighs and runs mill, hoist, air i t weighing tem, . be assist the large motor if necesEach reel sary. has 1,500 feet of Silver Lake f can geared to the hoist cinity. I, ordinarily 13,200 Feet. portant features of an electric hoist. On many of the earlier hoists the commuted field, thrown into various combinations of different resistances by a cylinder-switcwas employed; this form of control being at that time widely used in street car service. This controller gave quite satisfactory results when assisted by but with positive gearing it would not give a sufficiently gradual start. On most hoists a variable resistance in armature-circui- t is employed; and by making this resistance sufficiently high, a perfectly smooth start may be obtained, even with slack rope. The most satisfactory rheostatic controller, especially for heavy work, is one in which the resistance is cut in and out by a cylindrical switch with magnetic blow-ou- t, which avoids the troublesome effect of arching at contacts, when the current is broken. In some cases it is practicable to use a double motor equipment, with series parallel controller, such as is now employed almost exclusively in h, friction- -gearing, pounds. Two counter weights are used, the one for cage and bucket weighing 2,450 pounds, and the one for cage and car 2,675 pounds, the two being com-armature Two bined when bailing. pinions are provided (the motor sliding on rails), one for ordinary hoisting giving a speed of 600 feet per minute, and the other for bail-ing at 1,000 feet per minute, which, with the maximum load of about 10,000 pounds (bailing) f would require over 300 H. P. net, exclusive of friction in gearing and rope, were it not for the j overbalanced arrangement. Actual tests have shown that the average current consumed in p 1 is only about hoisting with counter-weigd of the amount required when the hoist is unbalanced. ht one-thir- some Pumps. The electric pump presents a what more difficult mechanical problem thanof the hoist, on account of the conversion un rotary in reciprocating motion, and the and portance, in most cases, of compactness Tha protection of the motor against water. solvw been has the satisfactorily problem a By overbalancing hoist, making the o number the is large however, proved by eight equal to the dead load plus about half in so0, the live load, the work in hoisting and lowering electric pumps of various kinds and size can be made approximately equal, and the cessful operation. maximum current and size of motor can be reThe sinking pump is the most difficult to duced to considerably less than half of what sign, on account of the small space nilabl would be required for doing the same work for the motor, and the necessity of enclosing1 numeron with an unbalanced hoist. This principle is in a practically water-tigcase; but street-ca- r works. counter-w- de- - ht j |