. Railroad construction : theory and practice : a textbook for the use of students in colleges and technical schools . htly downward. Anytendency to draw the spike will therefore cause the fibers topress still harder on the spike and thus increase the resistance. 248. Driving. The holding power of a spike depends largelyon how it is driven. If the blowsare eccentric and irregular in direc-tion, the hole will be somewhat enlarged and the holding power largelydecreased. The spikes on eachside of the rail in any one tie shouldnot be directly opposite, but shouldbe staggered Placing them direct-ly
. Railroad construction : theory and practice : a textbook for the use of students in colleges and technical schools . htly downward. Anytendency to draw the spike will therefore cause the fibers topress still harder on the spike and thus increase the resistance. 248. Driving. The holding power of a spike depends largelyon how it is driven. If the blowsare eccentric and irregular in direc-tion, the hole will be somewhat enlarged and the holding power largelydecreased. The spikes on eachside of the rail in any one tie shouldnot be directly opposite, but shouldbe staggered Placing them direct-ly opposite will tend to split the tie,or at least decrease the holdingpower of the spikes. The directionof staggering should be reversed inthe two pairs of spikes in any onetie (see Fig. 124). This will tend to prevent any twisting of thetie in the ballast, which would otherwise loosen the rail from thetie. 249. Screws and bolts. The use of these abroad is very ex-tensive, but their use in this country has not passed the experi-mental stage. The screws are wood -screws (see Fig. 125), [_ Fig. 124.— Fi<5. 125.—-Screw Spike. § 250. RAIL-FASTENINGS. 283 having large square heads, which are screwed down with a track-wrench. Holes, having the same diameter as the base of thescrew-heads, should be first bored into the tie, at exactly theright position and at the proper angle with the vertical. Alight wooden frame is sometimes used to guide the auger at theproper angle. Sometimes the large head of the screw bearsdirectly against the base of the rail, as with the ordinary designs employ a plate, made to fit the rail on one side,bearing on the tie on the other side, and through which the screwpasses. These screws cost much more than the spikes and re-quire more work to put in place, but their holding power is muchgreater and the work of track maintenance is very much , passing entirely through the tie, having the headat the bottom of the
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