Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1909 Excerpt: ...at distances 6 feet apart placed horizontally across the shaft and nailed to the wall-plates; corner rackings are nailed to the wallplates on either side of the buntons to keep them secure (see Figs. 96 and 97). On the completion of the first section of timbering as above, the sinking of the shaft is resumed and continued as long as is considered safe, then the sides of the further section will be similarly supported. On completion of the shaft the guides or conductors will be put in, being carried up from the bottom in 20 or 30 feet lengths and fixed to the buntons, care being taken to have all screw bolts well counter sunk. Various forms of joints or mortices are adopted in shaft-timbering, some of which are illustrated in Fig. 98. It should be borne in mind, however, that it is unwise to impair the strength of the timber by the removal of too much wood. The making of elaborate joints has also a tendency to cause the timber to split, for which reason dove-tailing or wedge-shaped joints are undesirable. When the sides are unsafe, lagging or plank-sheathing should be placed between the barring and the sides-Lead sheeting Fig. 99.--Detail of Joint in German Tubbing. of the shaft, especially if the barring is not placed flush, set with set. "English" and "German" Tubbing as used in Hand-Sunk Shafts.--The so-called English tubbing, consisting of small segments supplied in the rough, and, when erected, their joints being, as already described, wedged with wood, is still largely used; but the "German" type of tubbing (Figs. 99 and 100), made in larger segments, often 5 feet high, with thin sheet lead between the joints, and bolted together, is becoming increasingly popular. These segments are carefully machined, so that the surfaces...
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