352 STEEL HEAD FRAMES AND COAL TIPPLES. CHAP. X. 



of the drum at the hoist is 64 in., but the rope winds twice around the drum, so that the diameter 

 is 66 in. near the end of the lift. With proper allowance for bending stresses the working stresses 

 under the most severe conditions do not exceed the working load of 7.6 tons as given by the manu- 

 facturers of the wire rope. 



Estimate of Weight of a Steel Head Frame. A summary of a detailed estimate of the 75 ft. 

 steel head frame built by the American Bridge Company at Tonopah, Nev., is ;given in Table IV. 

 The details are 39.4 per cent of the weight of the main members. The rivet heads are 4.1 per cent 

 of the weight of the structure. 



For additional examples of steel head frames, see the author's "The Design of Mine Struc- 

 tures." 



COAL TIPPLES. The design of a coal tipple depends upon the quality of the coal, upon 

 whether the coal is hoisted from the shaft or is taken from a drift or tunnel, and upon the work 

 that it is necessary to do in order to prepare the coal for the market. The coal tipple for a bitumi- 

 nous mine in which the coal is hoisted from a shaft, consists of a head frame and a shaker structure 

 or tipple proper where the coal is weighed and screened. A coal tipple for an anthracite mine 

 ordinarily consists of a head frame with storage bins into which the coal is run without crushing 

 or screening; the coal being prepared for market in a separate breaker building. Where bituminous 

 coal is dirty or contains a large amount of refuse material it is sometimes cleaned in a washer 

 building, or is broken, sized and cleaned in a coal breaker. 



With a double compartment shaft the shaking structure, or tipple proper, is usually placed 

 with its axis at right angles to the center line of the two compartments. The hoisting ropes 

 may be either parallel to the axis of the tipple, in which case the head sheaves are parallel; or 

 may be placed at right angles to the axis of the tipple, in which case the sheaves are placed in 

 tandem. The coal may be run through rotary screens, or over shaking screens as is now the 

 common practice. Shaking screens are usually divided into sections and are driven by eccentrics 

 placed 1 80 degrees apart. The shaking screens do not ordinarily weigh more than two to three 

 tons empty or four to six tons when loaded, but are driven with a velocity of 100 to 150 strokes 

 per minute, with a length of stroke of from 4 to 12 in. and the shaking motion makes it necessary 

 to design the shaker structure with great care in order to reduce the vibration. The best modern 

 practice in the design of coal tipples is to make the head frame and the tipple, or shaker structure, 

 entirely separate and independent units. 



Sizing Coal. The object in sizing coal is to separate the dirt and slack from the coal, and 

 to obtain a product that can be burned more advantageously than unsized coal. A compact 

 coal will not admit the air and will burn on the surface, and it is therefore an advantage to have 

 the lumps of approximately equal size. The sizes and names of the different grades of coal differ 

 considerably in different localities. 



Types of Coal Tipples. Coal tipples may be classed under three types, depending upon the 

 manner in which the coal is brought to the tipple; (i) hoisting in cages or skips from vertical or 

 slightly inclined shafts; (2) cage hoisting on an incline either from a shaft, or on a bridge, or from a 

 tunnel; (3) conveyor hoisting either from the mine or from a head bin into which the coal has 

 been dumped from cars or skips. 



The design and operation of coal tipples will be illustrated by describing three steel coal 

 tipples, (i) Steel Coal Tipple for the W. P. Rend Coal Company vertical hoisting with self 

 dumping cages and shaking screens; (2) Spring Valley No. 5 Steel Coal Tipple vertical hoisting 

 in cages, with Ramsey transfer and shaking screens; and (3) Phillip's Coal Tipple vertical 

 hoisting with self dumping cages dumping into a storage bin. 



Steel Coal Tipple for W. P. Rend Coal Company. The steel coal tipple for the W. P. Rend 

 Coal Company, Rendville, 111., has the head frame covering four tracks, with provision for four 

 extra tracks on the opposite side of the center line of the head frame. The steel head frame is 

 79 ft. 6 in. from the collar of the shaft to the center of the sheaves. The sheaves are 8 ft. in 

 diameter and carry a i f in. hoisting cable. 



