CROSS TIES 291 



(d) Open-crib piling, where ties are placed in alternate layers 7 one 

 way and 2 the other. This is known as 7 by 2 piling. Variations of it, 

 such as the 9 by 2 and 7 by i, 8 by i, and 8 by 2 are also used. This is 

 the most common form and is now specified by most of the progressive 

 railroad systems of the country. Ten tiers or layers of ties resting on 

 stones or cull ties, with 45 ties to the pile is a common form. It permits 

 of free circulation of air and experiments have shown it to give the 

 best results. The 7 by i method is commonly used with hardwoods 

 whereas the 7 by 2 method is used with softwoods. 



When green ties or those that have been in the water are exposed to 

 too rapid drying by warm temperatures, direct rays of the sun and strong 

 wind currents, the ends of the ties, due 

 to more rapid evaporation of moisture, 

 are likely to shrink and check. Many 

 ties are culled on inspection when 

 checked too severely. Close piling will 

 tend to decrease the checking, together 

 with piling in the shade and other simi- 

 lar precautionary measures. However, 



in all cases, a few ties, especially those Fig. 78.-Method of using "S" irons to 

 ' 1 ■ 1 • 1 prevent the further opening of checks 



of certain species which season with ;„ ^j^gg ^^^^ 



difificulty, will split and check. Many 



railroads are now following an old European practice, which consists of 



driving " S " irons 'n the ends of the ties, across the incipient check to 



prevent further opening. Their use is shown in the accompanying 



diagram. 



Oak ties should be given a minimum period of seasoning of eight 

 months after cutting in the late winter, but they should preferably be 

 exposed under favorable conditions of seasoning for fully twelve months. 

 Other dense and heavy hardwood ties, such as beech, birch, maple, 

 sycamore, and locust should receive the same length of seasoning period. 



Yellow- pine, Douglas fir, western larch, and tamarack ties should be 

 seasoned from five to eight months; hemlock, jack pine, cedar, cypress, 

 redwood and chestnut ties from four to six months. ' If accurate moisture 

 determinations cannot be conveniently made, seasoning should be con- 

 tinued until their weight is constant. 



LIFE OF UNTREATED TIES 



Until comparatively recent years, nearly all cross ties were placed in 

 service in railway tracks in the untreated condition. White oak, chest- 



