Gasoline-Driven Rock-Drill. (Engineering and Mining Journal, N.Y., 27 April 1905, p. 827.) An illustration and a description show and explain the construction of a new pattern of rock-drill. The special feature of this drill is that it is operated by a gasoline motor, which is selfcontained. The peculiar advantage claimed for this type of drill, which is comparatively light and easy to transport from point to point, lies in its self-contained power. When it is not in actual operation, the working-expenses cease, unlike steam- and airdriven machines, for which steam or air-pressure must be kept up. The motor is of the two-cycle, air-cooled type with cylinders of 4-inch bore by 4-inch stroke. By cranking the fly-wheels in the ordinary manner, the piston is made to draw in a charge of the gas mixture, compressing it in the front chamber. At the proper point it is transferred to the rear chamber, where the compressed charge behind the piston is exploded by an electric spark. The forward movement of the piston drives a hammer to strike an anvil to which the "bit" is attached, the action being that of hammer and drill as in hand work. The cross-head is arranged with buffer behind the hammer, which buffer, together with the connection with the fly-wheels by means of the connecting-rods, carries the piston over the centre, returning it to receive the new charge. A ratchet-fork engages the cross-head at one end, and at the other end, by means of a pawl having its axis eccentric with the axis of the rotating ratchet-wheel, rotates the entire chuck and bit. The commutator and spark-plug are connected by wires to an electric battery in the power-box. By depressing the commutator lever, the spark is advanced and the drill speeds up. The working-speed is 1,500 blows a minute, which is said to give high cutting-power. The weight of the drill proper, exclusive of clamp, is 325 lbs. As to power plant, the ordinary steam-engines, boilers, buildings and compressor plant are replaced by a small power-box weighing 75 lbs., containing batteries and spark-coil for ignition purposes, and a copper gasoline-holder containing one day's supply of gasoline, nearly 3 gallons per 8-hour shift. G. G. A. Shaft-Sinking by the Jetting Process. GEORGE C. MCFARLANE. (Engineering and Mining Journal, N.Y., 11 May 1905, p. 901.) The Author describes a method of sinking through thick beds of quicksand and boulders, in which a strong inflow of water has to be dealt with, based on his experience in boring through such strata. The plan, which he has outlined in a sketch, contemplates sinking a round shaft-lining of steel-jacketed concrete, provided at the lower end with a cutting shoe. The sinking with this contrivance is to be accomplished by rotating the shaft-lining and forcing the cuttings to the surface by pumping the water and compressed air down the inside of the shaft. The water, escaping under the shoe and rising to the surface around the outside of the shaft-lining, will carry off the cuttings and allow of the easy rotation of the sinking shaft-lining. A necessary condition of success is that a steady stream of water or compressed air be forced down the shaft when the lining reaches the quicksand. If the current were stopped for only 2 or 3 minutes, the sand would settle around the shoe and make it difficult to rotate the lining, or even to start the current of water again. The sinking apparatus includes a double engine with a worm keyed on to the crank-shaft. This worm drives a large wormwheel which is grooved on the underside and rests on a series of balls travelling on a circular bed-plate bolted to the concrete foundation. Four powerful hydraulic jacks are bolted to the worm-wheel. The lugs of a heavy clamp ring on the shaft-lining rest on each pair of jacks. The jacks raise and lower and also transmit the rotary motion to the shaft-lining. The latter consists of two steel shells, respectively 15 feet and 19 feet in diameter, built up of-inch and -inch tank-steel plates. At the lower end the shells are riveted to a heavy cast-iron shoe with inserted tool-steel teeth. That the lining may offer a smooth surface to the descending and ascending current of wash-water and suspended sand and detritus, the plates should be riveted to butt-straps, the rivet holes in the plates being countersunk, and the rivets plugged down to fill the countersink and cut off flush with the plate while hot. The seam between the plates should be split caulked. A line of 4-inch extra heavy gas-pipe is carried up from the shoe between the two linings. The 2-foot space between the shells is filled with Portland cement concrete. The shaft would be excavated by hand through the comparatively dry surface soil, and the lining be built on from the top and lowered by the jacks to keep pace with the excavation. On reaching the water-bearing strata a stationary bulkhead would be placed in the lining near the top and the column pipe in the lining fitted with a tee and nipple projecting into the shaft just under the bulkhead. The nipple would be capped by a gatevalve, the stem of which would pass through a stuffing-box in the bulk-head. Air- and water-pipes provided with downward opening check-valves, pass down the centre of the shaft and lead into a single pipe, which is turned and polished where it passes through the bulkhead. Water is pumped down, and as the revolving lining slowly bores into the earth the water passing under the shoe washes away the cuttings and carries them to the surface. When the strata are heavily laden with water the wash-water will not rise to the surface. Then the valve on the column pipe must be opened and compressed air forced down one of the pipes. The air thus made to pass down the column pipe and escaping under the cutting shoe will mix with the water and cause it to rise to the surface. A core of earth will be left in the shaft, to be excavated later in the usual manner. The strata outside the shaft will be undisturbed, because the wash-water will rise in a small annular space between the lining and the sides of the hole, and any enlargement of this space will reduce the velocity of the uprising current and cause it to deposit some of the suspended material. In all other systems of sinking the tendency is for sand and water to run into the shaft, leaving cavities which often cause destructive slides. The shaft-lining should be sunk to a good hard stratum and the water sealed off by forcing down the column pipe a mixture of Portland cement and bran, while the lining is being slowly rotated, using a very small quantity of wash-water. Then the jacks are to be released and the lining allowed to settle down on the mixture. The bran will swell and form a water-tight joint. The Author estimates the total cost of sinking a round shaft 15 feet in diameter from 150 to 300 feet deep by this system at £35 per foot. G. G. A. Pumping Data. R. GILMAN BROWN. (Engineering and Mining Journal, N.Y., 18 May 1905, p. 947.) The Author has collected records of pumping recently kept at the Brunswick Mine, Grass Valley, California, where very large quantities of water have to be raised, and has deduced therefrom the efficiency of three systems of lifting water, namely, the airlift, the electric pump, and the Cornish pump, each of these systems being installed in accordance with the most advanced knowledge in this field of engineering. For the air-lift, the air was supplied by a pair of duplex single-stage compressors driven by electricity and giving a united displacement of 9.91 cubic feet. of free air per revolution, the speed being constant at 110 revolutions per minute. These compressors, placed 50 feet from the collar of the shaft, delivered the air through a receiver and a 4-inch air-column to the mine. The column for the air-lift was of 7-inch tubing, with flanged joints. The interior air-pipe was 2 inches in diameter. As the final result of the experience gained with this system, it was found that constant volume of compressor delivery, i.e., constant speed of motors, and frequent changing of submersion and lift, are not conducive to economical work. By "submersion" is meant vertical depth of the bottom of the air-pipe below the surface of the water, and by "lift," vertical height of the discharge above that surface. Exact adjustment of air-volume and pressure to submersion and lift are essential to good efficiency. The best results-only about 10 per cent.-appear to have been obtained when the ratio of submersion to lift was 1.25 to 1.75. But under the conditions usual in work of this kind such adjustment cannot be made. For regular air-lift work, as from deep wells, 32 per cent. to 35 per cent. is spoken of as possible. However, in spite of the very low efficiency, this method cost less in power and plant combined than any other that could have been applied. The electric pumps installed were of the Aldrich type. The two main pumps were five-plunger, single-acting, 6 inches in diameter by 12 inches stroke, with a rated displacement of 66.7 cubic feet per minute. One of these was driven by two 40-HP. 440-volt induction motors through a single set of reduction gears. The other was a duplicate, except that it was driven by one 50-HP. motor. The respective heads for these pumps were 376 feet and 290 feet. The current was brought into the mine by leadcovered, armoured, three-conductor cables. Including the conduction loss and two series of lamps, these pumps, when under full load, have given a power efficiency of 72.3 per cent., based on a 100-per-cent. displacement of the plunger. The actual displacement was found to be 94.5 per cent. of the theoretical displacement, so that the actual horse-power in water raised was 69 per cent. of the power delivered to the conductors at the collar of the shaft. In the Cornish pump system the stroke was 6 feet, the maximum number of strokes per minute being 8.75. There were one plunger 14 inches in diameter under 128 feet head, one plunger 12 inches in diameter under 250 feet head, one plunger 12 inches in diameter under 287 feet head, and one plunger 12 inches in diameter under 230 feet head. The pump was driven by water under 288 feet kinetic head, the first speed reduction being by belt, and the second by gear. The rod was of Oregon pine 12 inches square supported by rollers in the usual way. There was an angle-bob at one of the levels where the shaft changes dip, a balance-bob at a lower level, and an ordinary counterbalanced operating bob at the surface. The records for a month showed an efficiency of 53.7 per cent. on the basis of full displacement. The water actually thrown, however, amounted to only 75 per cent. of the displacement, because of the necessity for drawing back water from the columns into the pumps for considerable periods to keep the pumps "solid." This is a serious drawback to the use of the Cornish system. The real efficiency works out about 51 per cent. The Author adds that it seems highly improbable that efficiencies as high as 69 per cent. can be obtained by other than electrically-driven pumps, with the possible exception of pumps using re-heated compressed air. G. G. A. Electric Pumping on the Comstock. CARL GEORGE P. DE LAVAL. (Engineering and Mining Journal, N.Y., 16 March 1905, p. 516.) For years past continuous and expensive work has been going on to explore the Comstock lode. The efforts made in the last 26 years to cope with this great task have brought into operation in that locality all the latest improvements in pumping machinery, and the great and rapid development which has taken place may there be seen to advantage. At the present time, attention is being directed to electrical pumping. A short time ago plant of the most modern type, consisting of three Riedler electric pumping-engines driven by 200-HP. induction motors, was put down at the Consolidated California shaft. These pumps raise 4,500 gallons of water per minute under a head of 430 feet. The power is generated by M'Cormick turbines connected directly to Westinghouse threephase generators of the revolving armature type. Each pair of wheels will develop about 1,400 HP. under a head of 84.5 feet. Regulation is effected by Lombard governors. The generator potential of 500 volts is raised to 24,000 volts by Westinghouse oil-insulated transformers, and the current is transmitted, over a double circuit of copper wire, a distance of 35 miles. The mining companies purchase power of the Electric Light Company, the price being about 288. per HP.-month. About 2,000 HP. of apparatus has been installed on the Comstock, but this will soon be increased to 5,000 HP., a contract having been made with the Comstock Pumping Association for the delivery of electric power up to a maximum amount of 5,000 HP. In order to supply this, a second generating-station is to be provided where the power will be obtained from water-wheels working under a head of 141 feet. For the maximum of 5,000 HP. the rate will be 188. per month, with proportional rates for less amounts. This is based on motor readings. All motors of 50 HP. and over are operated directly on 2,240 volts; all smaller motors on 440 volts; and the lighting circuit is 220 volts, three-wire system, excepting in one mine where it is 110 volts. The Riedler pumps are of the mechanically operated valve type, and run at 110 revolutions per minute. But experience has proved that high-speed pumps do not require positively closed valves, and that such valves cannot be worked at more than 150 revolutions, while properly constructed poppet-valves work satisfactorily at 300 revolutions. The Author has designed pumps which, he states, are now running at 600 feet to 800 feet without positive mechanism, showing that "water-hammer" from backward flow at the end of the stroke, which causes the valve to seat hard, can be prevented without mechanically-moved valves, if the pump is properly proportioned in relation to water-spaces, air-chambers, and passages. In determining the type and design for their Ward shaft the Association was able to select the plant from the best types of pumping machinery in the world, and to consider the electric |