BRIDGES
In most cases the construction of bridges is unnecessary on account of the steep grades the trucks can take and because they can negotiate sharp curves, which make it easier to avoid expensive bridge work. Where they are absolutely necessary a serviceable bridge is made of cribwork.
The Esary Logging Company of Camano Island, Washington, operates over a crib bridge 175 feet long and 15 feet high. The sub-structure of this bridge is made of logs laid alternately crosswise in tiers. Six by twelve inch plank are laid diagonally on the cribbing and four by twelve inch plank are placed on crosswise to the road on top. This makes a bumpy surface. A better one could be made with cross-ties placed on the cribbing with fore and aft planking on top. A guard rail is placed on all bridges.
Short bridges up to eighty or ninety feet in length are constructed by the use of two large logs hewn flat on the upper surface. The logs should be at least thirty-six inches in diameter and perfectly sound. They are placed at the proper gauge and the regular road on cross-ties constructed on top. On such short stretches this type of bridge has been operated over without supports. It is not used, however, for long stretches. The long bridges are, of course, constructed of bents or piling but are very seldom used in connection with motor truck transportation on account of the expensive construction and because they are usually unnecessary.
TURNING DEVICES AND TURNOUTS
When the truck and trailer reach the place where they are to be loaded, some method must be used to turn them around. Various means are used to accomplish this. One is the motor truck turn-table. The turn-table should be slightly longer than the length of the truck and trailer combined. It is constructed of heavy plank and timbers so that each track is about 16 inches wide and tapers in thickness from about 14 inches at the center to 4 inches at the ends. The two tracks are held together at the center and each end by heavy timbers. A heavy timber is sunk to the level of the road and at the center two circular saws are laid. A king bolt through the center brace of the turn-table and through the two saws into the sunken timber provides a pivot upon which the table turns. When properly balanced and with a little oil between the surfaces of the saws, the turn-table can be operated by hand with very little effort. It is usually placed at the end of the road. A turn-table can be loaded on the truck and trailer when it is desired to move it, so that as the road is extended into the timber, a means of turning the truck can be obtained close to the point where the logs are to be loaded. This device can be built at a cost of from $75 to $125 and is very serviceable. The main objection to its use is that the setting has to be just right to make it work satisfactorily and it is sometimes difficult to get a spot that is level enough. It is always a difficult problem and a different one for each set-up.
The use of the "back around" is more common with truck loggers at present because it is easier to build. The back-around is simply a pocket or short spur along the road above the landing ground which is planked solid. The truck and trailer are backed into this far enough so that the truck can pull ahead in the opposite direction. This method of turning the truck requires only a little extra clearing and grading and is less expensive and more easily constructed than a turn-table.
