CROSS TIES 



295 



dally true of the softer woods, which are readily cut by the rail when heavy 

 axle loads and frequent trains are the rule. Those species which ordina- 

 rily decay rather quickly, such as loblolly pine, hemlock and beech, should 

 not be protected with tie plates if laid untreated as they will decay before 

 they wear out. Other soft but durable woods such as redwood, northern 

 white cedar, western cedar, southern juniper, etc., unless protected 

 by means of tie plates and screw spikes will wear out before they fail 

 from decay. 



As mentioned in the first part of this chapter, among the prime requi- 

 sites that determine the desirability of any wood for tie purposes are 

 hardness or ability to resist impact, ability to resist spike pulling and 

 lateral displacement and sufficient strength to resist strains due to center 

 binding. A composite expression of these properties to show the relative 

 mechanical value of the principal woods used for cross ties has been 

 devised by the U. S. Forest Products Laboratory. Proportionate weight 

 has been given to the various properties involved and the following table 

 constructed:^ 



TIMBERS ARRANGED IN ORDER OF THEIR MECHANICAL VALUE AS TIES 



The protection of cross ties against mechanical wear is afforded by 

 means of improved forms of spikes and by the use of tie plates. Various 

 forms of screw spikes and tie plates have been tried out with very satis- 

 factory results by the European state railways and to-day practically 

 all their trackage is protected by both screw spikes and tie plates. Many 



* See " Woods Suitable for Cross Ties," by R. Van Metre in Annual Proceedings of 

 American Wood Preservers' Association, 1916. 



