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TRANSPORTATION ON LAND BY VEHICLES: -THE ROADS 



Climax engine in operation on a trestle, over wooden rail. Climax Mfg. Co, Corry, Pa. 



are found below the stringers. They are mortised at one end into the abutments or bulkheads, at the 

 other end into the corbels supporting the caps and stringers. 



IV. Bent (trestle) bridges (notably for railroads). Bents are either "pile trestle bents" or "frame trestle 

 bents." 



Piles are timbers (oak, longleaf pine, Douglas fir) driven into the ground by pile drivers. Pile trestles 

 are trestles wherein the vertical members or supports consist of piles. By "bent" is understood a group 

 of bridge members forming a single vertical support. They are designated as "pile bent" when the 

 principal members are piles, and as "frame bent" when the principal members are framed timbers. 



The timbers are best joined by mortises 5 inches deep and 3 " ■ 8" wide. The posts, sway-braces and caps 

 of wet spans should be boxed up so as to prevent the twisting influence of mud and debris lodged in the 

 meshes of the bents. 



The foundation for frame trestles may consist of piles, wooden subsills, or masonry. 



By "sill" is understood the lower horizontal member of a frame bent. 



By "subsills" are understood timbers bedded in the ground and meant to support frame bents. 



Sills for frame trestles should scale 12" '■' 12", and should be securely drift-bolted or anchor-bolted 

 to the foundation. 



The vertical members of the bent of a frame trestle are the "posts" Posts should scale 12" X 12", 

 and should be secured with drift bolts or dowels. The outside posts should have a batter of 1 in 4. 



By "caps" are understood the horizontal connecting members upon the tops of piles or posts. Caps 

 should scale 12" / 14", should be 14 feet long, and should be drift-bolted to posts or piles with '/,-inch 

 drift bolts. 



The spans between the bents are usually 14 feet between centers. Stringers, the longitudinal members 

 extending from bent to bent, should be laid with broken joints, and should be bolted together with '/(-inch 

 bolts and cast-iron back spools. The stringers are secured to the caps with 2 drift bolts for each cap. 

 The cross section of the stringers is best at 8 by 16 inches. 



Cross braces are members extending diagonally from bent to bent in vertical planes. 



