Fig. 32
Fig. 33
[Fig. 33] shows the construction of the ordinary timber gallows frame used at many ore mines.
[Fig. 34] shows a steel A frame, of which the principal dimensions are as follows: height to sheave center 48 feet; base 33 feet 10 inches by 56 feet. Legs a and b are made of laced channels, as are also the central upright posts and cross-braces. The forward inclined legs are made of I beams. The weight of the frame is 98,000 pounds without the sheaves. The advantages claimed for this type of design are that it gives a very strongly braced frame while using a minimum of material. Also, in cases of overwinding, the cage goes over the top of the frame without injury to the frame, and should men be overwound they would fall only the height of the frame instead of being crushed against the top.
35. Square Type Without Inclined Brace.—[Fig. 35] shows a steel frame in which the tendency to be overturned by the pull of the rope is resisted by a nearly vertical tension leg as explained in [Art. 32]. Each leg of the frame is built of channel bars connected by lattice bracing, as shown, and the legs are stiffened by horizontal channel cross-bars similarly braced and also by diagonal tie-rods, provided with turnbuckles.
Fig. 35