The cost of rails is frequently the largest single item in the cost of constructing a railroad, the cost of the ties usually being less than one-half the cost of the rails. This familiar fact is apt to cause the engineer to lose sight of the fact that the relative cost for maintenance is reversed. For the last three years the average cost of maintaining ties on the railroads of the country has been over three times the cost of maintaining the rails. The amount actually spent in 1910 was over $55,000,000, or over 3% of the total operating expenses. The enormous number of ties annually consumed in track maintenance is so depleting the forests of the country that the price of timber has advanced very greatly during the last few years, and it has become a question of national importance which is engaging the attention of the United States Government. Therefore any method which will increase the life of a wooden tie is a matter of great importance, not only to the railroads but also to the community in general, since the whole lumber industry has been very largely affected by the use of timber for railroad-ties.

105. Methods Of Deterioration And Failure Of Ties

The failure of ties is due to some one or to a combination of a large number of causes. First, the wood may decay.

Second, the wood may be so soft that the holding power of the spikes may be small and this requires that the spikes must be frequently re-driven in order to hold the rails. Since the tie must be placed symmetrically under the rails, the available area for driving spikes is very limited, and it sometimes happens that an otherwise sound tie must be taken out because it has been "spike-killed." Third, the tie may be so soft that it is crushed by the concentrated pressure of the rail-flange and especially by the pressure of the outer flange of the outer rail on curves. This form of destruction is largely obviated by the comparatively inexpensive device of tie-plates.