52 BULLETIN 440, TJ. S. DEPARTMENT OF AGmCULTURE. 



from 50 to 60 cents per linear foot, exclusive of stumpage. From 

 400,000 to 450,000 feet board measure of logs are required per mile. 



Two types of frame trestles are in use on logging railroads, namely, 

 rough timber and sawed timber trestles. Rough timber is usually 

 used on spurs or lines which wUl be in use for a short time only, be- 

 cause it decays more quickly than sawed timber. Its durability is 

 increased, however, by peeling the poles. Where suitable pole tim^'^r 

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

 than one with a sawed frame.. Rough timber trestles are commonly 

 built with bents 15 feet apart from center to center. Each bent con- 

 tains a log for a siU and four smaller logs for posts. Rough timbers 

 are used for caps and stringers, but the bracing is done with sawed 3 

 by 8 inch planks. The usual method of building such a trestle is to 

 place a Dolbeer donkey at the site and skid the sUls, posts, and caps 

 in from the near-by timber. The bents are then built on the ground 

 and raised to a vertical position by the donkey engine. In one in- 

 stance a crew of 18 men working in this manner constructed a stand- 

 ard-gauge rough timber trestle 255 feet long, with a maximum height 

 of 38 feet in eight working days, at a labor and supply cost of $416. 

 The log scale of the material involved was as follows: Caps, 2,700 

 feet; stringers, 6,900 feet; posts, 9,420 feet; sUls, 10,400 feet; total, 

 29,420 feet. In addition, 4,800 feet of braces were required. Allow- 

 ing $1 per 1,000 stumpage on the rough timber and $12 per 1,000 as 

 the cost of braces, the total cost is $503. Thus, for this example, the 

 cost per 1,000 is $14.80, and the cost per linear foot is $1.97. 



Sawed timber trestles are hkewise constructed with bents 15 or 16 

 feet apart. Each bent rests upon a sill which may be either a sawed 

 10 by 12 inch timber or a cedar log. Four 10 by 10 inch posts are 

 used in each bent, the two outside having a batter of 2 or 3 inches per 

 foot. Each bent has a 10 by 12 inch cap 12 feet in length. Three 6 

 by 16 inch stringers are placed under each rail to suppc.t the ties. 

 The bents are brace, with 2 by 8 inch or 3 by 8 inch sway and 

 coUar braces and froi- 3 by 8 inch to 4 by 8 inch stringer braces. 

 These dimensions are for standard-gauge logging trestles The caps 

 and sills are shorter in narrow-gauge trestles and some of the braces 

 may be lighter; therefo_ , from 5 to 10 per cent less timber is required. 

 Otherwise the cost is very little less for a narrow-gauge trestle, because 

 the work of erection is about the same. 



The cost of frame trestles is usually figured at so much per 1,000 

 feet board measure of the lumber used. This cost is made to include 

 lumber, bolts, and other supplies, and the labor of building the foun- 

 dations and framing the trestle, the lumber being usually charged ir 

 at $12 per 1,000. The costs of several representative standard-gaug- 

 frame trestles recently constructed on logging roads ire given i: 

 Table 7, 



