194 BULLETIN 711, U. S. DEPARTMENT OF AGRICULTURE. 



(b) Frame-bent trestles are made of both round and sawed tim- 

 bers. If the former material has to be brought from a considerable 

 distance, it is advisable to use the latter, since it is easier to fit and 

 is more durable. On the longer main-line logging roads, most of the 

 frame trestles are built of sawed timber, the trestles on the spurs 

 being usually built of round timbers. Not infrequently, however, 

 the stringers used in connection with the construction of the trestles 

 on these latter roads consist of sawed timber. Where suitable pole 

 timber is available, a rough-timber trestle can be constructed more 

 cheaply than one with a sawed frame. 



The general app^rance of a frame trestle is much the same as 

 that of a pile trestle. The bents, which are spaced 13 to 16 feet apart, 

 consist of four legs made of round timbers 14 inches and up in diame- 

 ter or 10 by 10 inch or larger square tiiiibers. Each bent rests upon 

 a sill, which may be either a log or a 10 by 12 inch sawed timber. 

 Round or sawed timbers are used for caps and stringers. 



In computing the cost of frame trestles, the lumber used is com- 

 monly included at $12 per thousand feet. A convenient way of 

 figuring the cost of any trestle is at so much per 1,000 feet of th^ 

 material contained in it. This cost includes lumber, bolts, and other 

 supplies, and the labor of building the foundations and framing the 

 trestle. The cost of several representative standard-gauge frame 

 trestles recently constructed on logging railroads in this region is 

 given in Table 31. 



Table 31. — Cost of frame trestles. 



Length, 



Maxi- 

 mum 



Feet 



Total 



Cost per 



Cost per 

 linear 

 feet. 



feet. 



height, 

 feet. 



b. m. 



cost. 



M feet. 



620 



52 



105,000 



$2, 800 



$26.66 



$4.52 



652 



28 



60,000 



1,565 



26.08 



2.40 



762 



8 



68,000 



1,704 



25.06 



2.23 



202 



32 



28,000 



743 



26.54 



3.68 



140 



34 



19,000 



487 



25.63 



3.34 



238 



31 



31,000 



724 



23.35 



3.04 



272 



41 



45,000 



1,030 



22.89 



3.77 



144 



54 



30,000 



713 



23.76 



4.95 



TRACK MATERIALS. 



The following discussion has to do with standard-gauge material. 



Crossties. — Both sawed and hewn ties are used in constructing log- 

 ging railroads. Where the logging operator is also engaged in the 

 manufacture of lumber, and the sawmill is close to the logging camp, 

 most of the ties used are sawed. Independent loggers, as a rule, use 

 hewn ties exclusively. 



Sawed ties vary in size. The u.sual size, on standard-gauge roads 

 in the region is 7 by 9 inches by 8 feet. Ties 7 by 8 inches by 8 feet 



