62 



Tl NNKI.1NG 



Fio. 29. Strut- 

 ting of Timber 

 Posts and Rail- 

 tray Kail Caps. 



FIG. 30. Strutting 

 made entirely of 

 Railway Rails. 



and expensive. The advantages which iron strutting is claimed 

 to possess over the more common wooden structure are : its 

 greater strength ; the smaller amount of space which it takes 

 up ; and the fact that it does not wear out, and may, therefore, 

 be used over and over again. 



Iron Strutting in Headings. In strutting the headings the 

 cross frames have a crown bar consisting of a section of old 

 railway rail carried either by wood or iron side posts. When 

 wooden side posts are used their 

 upper ends have a dovetail mor- 

 tise, and are bound with an iron 

 band, as shown by Fig. 29. The 

 base of the rail crown bar is set 

 into the dovetail mortise and 

 fastened by wedges. When iron 

 side posts are employed they 

 usually consist of sections of rail- 

 way rails, and the crown bar is 

 attached to them by fish-plate connections, as 

 shown by Fig. 30. The iron cross frames are set up as the 

 heading advances, and carry the plank lagging or poling- boards, 

 exactly in the same manner as the timber cross frames previ- 

 ously described. 



Full Section Iron Strutting. The iron strutting devised by 

 Mr. Rziha for full section work is shown by Fig. 31. Briefly 

 described, it consists of voussoir-shaped cast-iron segments, 

 which are built up in arch form. Fig. 32 shows the construc- 

 tion of one of the segments, all of which are alike, with the 

 exception of the crown segment, which has a mortise and 

 tenon joint which is kept open by filling the mortise with sand. 

 The segments are bolted together by means of suitable bolt- 

 holes in the vertical flanges, and when fully connected form an 

 arch rib of cast iron. This arch rib, A, Fig. 31, carries a series 

 of angle or T-iron frames bent into approximately voussoir 

 shape, as shown at B, Fig. 31. Above these frames are inserted 



