CHAPTER X. 

 STEEL HEAD FRAMES AND COAL TIPPLES. 



Types of Head Works for Mines. The design of the head works for a mine depends upon 

 the material which is to be hoisted, upon the depth of the mine, the inclination of the shaft, the 

 rate of hoisting, the amount to be hoisted at one time, the treatment of the ore or coal after being 

 hoisted, and upon the material used in the construction of the structure. Head works for mines 

 may be divided into three classes: (i) head frames; (2) rock houses; (3) coal tipples. 



The first head frames were constructed of timber; the most common type being the 4-post 

 head frame. The square or rectangular mine tower was cross-braced and the sheave supports 

 were made of heavy timber. The back brace was inclined and was placed between the hoisting 

 rope and the line of the resultant of the stress in the hoisting rope. 



Sheave 



FIG. i. 



Steel head frames vary in design to suit local conditions and the ideas of the designer. The 

 A-frame in Fig. I is the most satisfactory type where conditions permit of its use. It is simple 

 in design and economical of material; the stresses are statically determinate, and it can be easily 

 and effectively braced, making a very rigid frame. The 4-post frame in Fig. 2 is the type to use 

 when it is necessary to hoist from several compartments of a shaft not in a single line. It is also 

 used for coal tipples and double compartment shafts. The 4-post frame is not so economical of 

 material as the A-frame; is more difficult to brace effectively, partly for the reason that part of 

 the bracing in the tower must be omitted to permit the dumping of the ore or coal, and in addition 

 the stresses are statically indeterminate. The frame shown in Fig. 3 is a modification of the 

 A-frame used for an inclined shaft. Several early head frames in the coal fields of Pennsylvania 

 were built on the lines of the frame shown in Fig. 4. This type of frame has no points of merit 

 and is practically obsolete. 



For an elaborate discussion of the design of head frames, coal tipples, and other mine struc- 

 tures, see the author's "The Design of Mine Structures." 



METHODS OF HOISTING. In hoisting from inclined or vertical shafts, the hoisting 

 engine is placed at some distance from the mouth of the shaft, the cable passes up over the sheave 

 at the top of the head frame and into the shaft. The rope, if round, is carried on a smooth or a 

 grooved hoisting dium, and if flat, is carried on a hoisting reel. The maximum working load on 

 the rope occurs when the loaded skip or cage is being hoisted from the bottom of the shaft. The 

 working load then consists of the skip or cage, the load, the accelerating force, the weight of the 



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