32 RAILWAY CONSTRUCTION. 



threads and of forcing open the upper or detached segments, give 

 an enormous holding and retaining power to the lock-nut, and 

 enables it to withstand the train vibrations for a very long time 

 without any perceptible slackening. In case of line repairs the 

 nut can be readily unscrewed, and taken off the bolt. 



Round iron spikes, as in Figs. 323 and 324, and round wooden 

 trenails, as in Fig. 325, are both used for fastening cast-iron 

 chairs to the sleepers. The spikes are made with a slightly 

 taper neck, of size rather less than the hole in the chair, to avoid 

 risk of breaking the casting when driving the spike down. 

 Trenails are made out of well-seasoned hard wood, and are 

 compressed by machinery. When driven into the sleeper, they 

 expand by exposure to the atmosphere, and hold the chair very 

 securely in position; but being only wood and of very small 

 scantling, they are subject to early decay. The head, which is 

 the only part in sight, may be perfectly sound, while the part 

 between the chair-seat and top of sleeper may be quite rotten 

 and useless. It would be very risky to depend upon trenails 

 alone ; one spike at least should be used to every chair. In some 

 cases an extra large trenail is used with an augur-hole down 

 the centre, through which either an iron spike is driven or a bolt 

 is passed and screwed into a crab-nut on the under side of the 

 sleeper. This arrangement will work well for a time, but there 

 will be a great deal of play in the spike or bolt when the trenail 

 becomes much decayed. 



The spikes represented in Figs. 326, 327, and 328, are much 

 used with flange rails. They are square in section, and finished 

 with either blunt or sharp points, as shown. The top of spike is 

 made with a doghead and side-lugs to facilitate the easino- or 



O . <-* O 



withdrawal when necessary for renewals of sleepers, or altera- 

 tions in line. By inserting the curved double claw end of a 

 platelayers' crowbar, the spike can be raised without injuring 

 the sleeper; but if it is required to be driven into the same 

 sleeper again, a new hole must be bored, as the old hole will be 

 too slack to be of any service. Augur-holes must be bored in 

 the sleepers for the above spikes. For new roads, these holes 

 can be bored by machinery when cutting the grooves for rail- 

 seats; but when carrying out alterations or repairs, a large 

 number of spike-holes must be bored by hand-augurs, an opera- 

 tion both slow and laborious. With the hand-boring there is 

 the danger that the hole may not be made deep enough, owing to 



