A Mechanical Rock- Worm 



This apparatus gnaws its way through 

 soHd rock, using neither drill nor dynamite 



" BIT 



FOR the past fifteen years inventors 

 have been developing a rock-tunneling 

 machine that could bore its way 

 through hard rock more quickly, cheaply 

 and safely than the rock drill and dynamite. 

 At the present time one of these machines, 

 developed by Oliver O. App, is demon- 

 strating its possibilities in the subway 

 excavation under the Grand Central 

 Terminal, in New York city. 



It is designed to cut away the rock by 

 the action of a number of 

 pneumatic hammers, fitted '^iR n 



with chisels, which turn on 

 a longitudinal axis. It 

 represents a dis- 

 tinct improve- 

 ment over for- 

 mer apparatus 

 of its kind in 

 the character of 

 the cutting and 

 the action of 

 the hammers. 

 When a chisel 

 is not bearing 



against the rock, the hammer does not act. 

 But as soon as the tool contacts firmly 

 with the rock face the hammer operates. 



The harder the rock the more air is sup- 

 plied automatically. If the rock is soft, 

 less air is applied; if sufficiently soft, the 

 hammer is inactive, and the rock or dirt 

 is cleaved off by the rotation of the tool. 

 In short, the blow delivered is proportional 

 to the hardness of the rock to be cut. 



Until this cooperation between chisel and 

 hammer was obtained, the tunneling ma- 

 chine was not a success. Even in its present 

 stage of development it is doubtful if it 

 represents an improvement over the rock 

 drill and blast method. In tunneling 

 through soft rock and dirt it is, obviously, 

 a great improvement over all existing ap- 

 paratus. But when it is working in hard 

 New York gneiss, for instance, the spokes- 

 men for the rock drill and blast method say 

 their way is safer and cheaper. In three 

 eight-hour shifts in which the total operat- 

 ing time was thirteen hours, the machine 

 made an advance of nearly nine feet. The 

 pneumatic rock drill has better records 

 than that to its credit. It remains for the 



future to determme whether or not the 

 machine will supersede the rock drill. 



The carriage of the machine consists of 

 a two-wheel main truck at the rear and a 

 two-wheel guide truck at the front. The 

 wheels, rest on a light track of standard 

 gage. The front and rear halves are sepa- 

 rate. The front, carrying the revolving 

 head, is moved forward one inch per revolu- 

 tion, by means of two lead-screws. After 

 the front has advanced two or three feet 



the rear is moved 



ROD FOR CONTROLLING 

 AIR SUPPLY TO PISTON 



DRia BIT ANVIL 



CHUCK 



Detail showing the component parts 

 of the hammer and chisel element 



Up by means of 

 gearing. 



The head, 

 which supports 

 the tool carrier, 

 consists of a hub 

 and four arms 

 placed ninety 

 degrees apart. 

 Two arms carry 

 four hammers 

 each ; on each of 

 the other two 

 arms are three 

 fourteen hammers are 

 the chisels cut in 



hammers. These 

 so arranged that 

 concentric circles. 



The power to operate the machine is 

 furnished by a compressed-air engine 

 located on the forward part of the carriage. 

 A spray of air and water falls over the face 

 of the rock to lay the dust. The broken 

 rock is delivered on a belt conveyer that 

 "discharges into muck cars at the rear. 



The hammer and chisel element, which 

 is illustrated herewith, is a new design. In 

 one of the old rock-cutting machines a 

 three-inch cylinder, with piston, valves, 

 and springs at each end of the cylinder, 

 was tried. In the present machine a four- 

 inch valveless cylinder carrying a thirty- 

 two-pound hammer twelve inches long is 

 used. The hammer is reciprocated by the 

 action of compressed air, the distribution 

 of which is effected entirely by the passing 

 of the hammer over ports in the cylinder 

 wall, there being no distributing valves 

 whatever. The hammer strikes a steel 

 chisel-holder, into which the chisel is firmly 

 inserted. Oil for lubrication enters the 

 cylinders with the air. 



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