ELECTRICITY IN MINING 40 



at 2.62 cents, showing a saving by oloctric haulage of .'J.OO 

 cents. 



A special featun^ of electric haulage in mines is the use 

 of gathering locomotives. In most coal mines the cars are 

 gathered or collected from the working faces of the rooms 

 by mules or horses, though in some low veined mines where 

 it is necessary to use very small cars they are pushed between 

 the working faces and the room necks by the miners them- 

 selves. They are then collected by locomotives and hauled 

 in trains to the tipple or shaft bottom. In many cases it 

 has been difficult to enlarge the entries sufficiently to accom- 

 modate the mule, because of the cost of brushing the roof or 

 taking up the bottom, especially where a hard slate or rough 

 limestone has to be dealt with. One means of obviating this 

 difficulty has been found in the use of compressed air loco- 

 motives, but electricity has been found particularly suitable 

 for this class of work. Locomotives used for this purpose 

 are equipped with a reel which carries a flexible insulated 

 cable. One end of this cable is connected to the trolley line, 

 and the current is conveyed to the controller on the loco- 

 motive through a contact at the reel. The reel is geared 

 up with the axles or truck of the locomotive, so that the cable 

 can be paid out or coiled up. The gathering locomotive 

 system can be pushed to a considerable distance from the end 

 of the regular trolley circuit. 



In metalliferous mines, as distinguished from coal mines, 

 the locomotive is usually smaller. An instance of such work 

 is to be foimd in the haulage system of the United Gold Mines 

 company, of Victor, Colo. — the Cripple Creek district — where 

 one 8 ton locomotive with a draw bar pull of about 3,500 

 pounds and a speed of from 8 to 10 miles per hour is used. 

 This locomotive is equipped with a single high speed motor 

 placed in the center and on top of the frame, the motor shaft 

 being connected to the drivers by gears. Current for this 

 locomotive is generated at a water power plant 12 miles 

 distant b)^ a 3 phase alternating current d3'namo, transmitted 

 at a pressure of 13,000 volts, stepped down and rectified at 

 a substation, and delivered to the trolley at 550 volts direct 

 current. 



Vol. 6-4 



