Bunks. All trucks for use in log hauling are equipped with a patent bunk over the rear axle on which the logs rest (see [illustration] on page 13). This is essentially a steel I-beam (A) which grips the logs so that they will not slip. At each end of the bunk are V-shaped iron chock-blocks (B) held by chains which run under the I-beam and are fastened by an iron gooseneck hook (C) so that the load is kept from spreading. These blocks may be adjusted to any width of load. The whole bunk is mounted on a swivel so that it will turn with the logs when rounding a sharp turn in the road. When dumping the logs at the landing, each block is loosened from the opposite side so that the danger of the logs rolling off on the men is greatly lessened.
Tires. Solid rubber tires are generally conceded to be the best suited for the heavy duty required in logging. The use of steel tires is rapidly declining. The jar on the equipment is in itself enough to condemn their use. Rubber tires double the mileage of a day’s work, more than double the life of the equipment, allow the weight of the equipment to be cut in half, and work well on dirt, cement, or any other type of road. The saving on the life of a pole or plank road by the use of rubber tires is also an item of considerable importance. There are three general types of solid rubber tires in use on the logging truck: the so-called giant tires, the duals, and the non-skid or caterpillar tires. It is a question as to which of the three is the best. Traction for the drive wheels and also for the trailer wheels, if the latter are equipped with brakes, is the problem to be solved.
The duals are satisfactory with light loads and easy grades, on cement, brick, or other perfect surface road, but when the haul is heavy and the braking difficult on account of heavy grades, the larger single-tread giant tires are more efficient. During dry weather it is safe to work with the single-tread tires on grades as high as nine or ten per cent, but in wet weather a seven per cent grade should be the maximum unless some extra means are taken to secure traction, and even then the wheels will skid if particles of soil get on the surface of a plank road, unless chains are used or the wheel is wrapped with a light cable.[4] For very heavy-duty trucking, where resiliency and long service are prime considerations, the giant type is rapidly superseding the old dual type as the former contains more rubber and gives more mileage with the least truck vibration.
[4] West Coast Lumberman. October, 1919. Page 25.
The non-skid or caterpillar tire may well be used on heavy grades or where the traction is very poor, the general opinion being that it gives a firmer grip on the road and makes it safer to handle the truck in wet weather.
There is no standard width of tread for truck wheels. The widths usually used on the drive wheels of the logging truck and the wheels of the trailer are twelve and fourteen inches, respectively. The use of tires of smaller width on either trailer or truck cannot be recommended. The wider the tires on the trailer, the better it is both for the life of the equipment and for ease in handling the load. When the surface of the giant tires becomes worn down so that the grooves become very shallow, it is desirable to have the tires re-grooved. They will last a great deal longer if this is done and will also give better traction on the road. The groove makes the tire lobes act separately on the uneven places in the road so that only one lobe is subjected to the strain of the irregularities instead of the whole tire. This is also true with reference to the strains that are set up internally due to the twisting of the rubber.
LAWS GOVERNING THE OPERATION OF MOTOR VEHICLES
The Laws governing the operation of motor vehicles upon the public highways of the State of Washington are contained and summarized in Senate Bill No. 220, Session of 1921 of the Legislature of the State of Washington. They include the following provisions governing the operation of motor trucks and trailers:
(a) Chapter 153 of the laws of 1913 and Chapter 142 of the laws of 1915 are repealed.
(b) Motor truck vehicles weighing less than 1,500 pounds must pay an annual license fee of ten dollars ($10.00); Trucks weighing more than 1,500 pounds and not to exceed 6,500 pounds, ten dollars ($10.00) plus forty cents per hundredweight for all in excess of 1,500 pounds and in addition thereto fifty cents per hundredweight at the rated carrying capacity. Motor trucks weighing more than 6,500 pounds must pay a license fee of ten dollars ($10.00) plus fifty cents per hundredweight for all in excess of 1,500 pounds and in addition thereto fifty cents per hundredweight at the rated carrying capacity. Trailers used as trucks shall be classified and rated as, and shall pay the same fees as hereinbefore provided for motor trucks of like weight and capacity.