296 FOREST PRODUCTS 



of our more progressive railway systems and especially those with frequent 

 and heavy traffic are installing the latest accepted forms on all newly 

 laid track and tie renewals. 



The passing of trains over the track results largely in an un- 

 dulating or pumping action in its effect on the ties. In addition to 

 this motion, which is responsible for the cutting of the ties by the rails, 

 there is strong lateral pressure tending to spread the rails, especially on 

 curves. The latter action causes a displacement of the spikes. Eventu- 

 ally the spikes are bent backward and pulled out. The grinding action 

 of the rail on the tie causes it to cut and finally check until together with 

 the necessary respiking the tie is literally worn out. 



FIG. 80. The effect of the nail spike and the screw spike on wood fibers of ties. The former 

 works loose more readily and is less firm than the screw spike. The latter is almost 

 universally used in Europe and is being gradually adopted in this country. The D., L. 

 & W. Railroad has used it with great success. 



This discussion, therefore, may be summarized under the following 

 heads of (i) spikes and (2) tie plates: 



i. Spikes. The function of spike is to hold the rail in place and pre- 

 vent spreading. In driving the ordinary nail spike the fibers are crushed 

 to a considerable extent so that it is more or less easily pulled out by the 

 pumping and lateral pressure jars. Tests 1 carried out by Prof. W. K. 



1 From "Holding Force of Railroad Spikes in Wooden Ties,," by W. K. Hatt. 

 Forest Service Circ. 46, 1906. 



