The Engineering Experiment Station of the University of Washington was established in December, 1917, in order to coördinate investigations in progress and to facilitate the development of engineering and industrial research in the University. Its purpose is to aid in the industrial development of the state and nation by scientific research and by furnishing information for the solution of engineering problems.

The control of the Station is vested in a Station Staff consisting of the President of the University, the Dean of the College of Engineering as ex-officio Director, and seven members of the Faculty. The Staff determines the character of the investigations to be undertaken and supervises the work. For administrative purposes the work of the Station is organized into seven divisions—

1. Forest Products
2. Mining and Metallurgy
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5. Electrical Engineering
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7. Physics Standards and Tests

The results of the investigations are published in the form of bulletins. Requests for copies of the bulletins and inquiries for information on engineering and industrial problems should be addressed to the Director, Engineering Experiment Station, University of Washington, Seattle.

BULLETIN
UNIVERSITY OF WASHINGTON

ENGINEERING EXPERIMENT STATION

MOTOR TRUCK LOGGING METHODS

BY
Frederick Malcolm Knapp
Student in the College of Forestry,
University of Washington.

SEATTLE, WASHINGTON
PUBLISHED QUARTERLY BY THE UNIVERSITY
APRIL, 1921

Entered as second class matter, at Seattle, under the Act of July 16, 1894.

CONTENTS

INTRODUCTION

HISTORY OF TRUCK LOGGING

Motor trucks in the logging industry are a comparatively recent development. As nearly as can be determined, the first use of a truck in a logging operation was made in this region by Palms and Shields near Covington, Washington, in the spring of 1913. Since that time various types of road construction suitable for heavy trucks have been devised and the use of the motor truck for logging has steadily increased until at the present time there are about six hundred trucks operating in the woods in the Northwest.

The first real progress in the use of the motor truck for logging purposes came with the development of the trailer. Although the motor truck has been brought to its present high state of perfection in eastern factories the problem of adapting it to the hauling of massive logs was solved in Seattle, Washington, with the perfecting of a trailer which could carry unprecedented loads and stand up under the speed attained by a motor truck. In the early attempts to design a trailer, it was found that too great tractive effort on the part of the truck was required if the trailer was patterned after older types with simply increased dimensions in all of its parts. Through successive improvements the modern form of heavy duty trailer was finally evolved. It has solved a serious problem by permitting the hauling of heavier weights with the aid of the trailer than is possible with the use of the truck alone. With the help of the trailer and an adjustable reach, the motor truck has successfully entered the logging field.

In the Pacific Northwest tracts of timber of sufficient area well situated for economical logging by old established methods are no longer plentiful. Almost every logging chance which exists today presents its own peculiar conditions and individual problems. An operator must therefore analyze the situation thoroughly before arriving at a decision as to the most economical logging methods that will apply in any particular case. Even in different sections of the same operation it is often necessary to use different methods. Since proper cost accounting systems are not usually kept by logging companies, particularly the smaller concerns, these companies often do not know that they are losing money upon one part of an operation because the success of the whole absorbs this loss.

The use of a motor truck has proved to be practicable in many instances, and bids fair to become of increasing importance. It will therefore be advantageous for every operator to inquire into its possible applications. It should be emphasized, however, that the motor truck is not economically adapted to all conditions. There have been many failures. Each projected application of the motor truck in the logging field must be thoroughly analyzed and if a doubt as to its successful performance exists, expert advice should be sought.

TRANSPORTATION OF LOGS—RAILROADS VERSUS MOTOR TRUCKS

The principal methods of transporting logs are by rail, by motor truck and by animal power. The last of these methods is, for obvious reasons, impracticable in the Northwest, and so needs no further comment. While it is impossible to give specific details in a general discussion of this kind to show where the motor truck may be more economically suited to the conditions at hand than the railroad, a comparison of the fundamental principles involved should enable any operator familiar with logging to determine whether or not to use the truck for his particular chance.

In general the choice between railroad and motor truck logging depends, fundamentally, upon two things: (1) comparative cost, and (2) adaptability. Sufficient motive power and rolling stock can be obtained much more cheaply for motor truck logging than for a railroad. There are, of course, many situations where the locomotive and car costs, as well as those of constructing a logging railroad, are obviously prohibitive, and the question revolves entirely upon the adaptability of the motor truck to existing conditions. There is no question at all that the logging railroad is not adapted to small, isolated and scattering tracts, and to certain portions of larger operations. There are almost innumerable tracts situated close to public highways, or where temporary roads can be built, which may be very serviceable during the summer months, giving ample time to clean up the timber before wet weather sets in. In such instances, road construction and maintenance costs are of very minor importance. In the larger operations and in the use of the motor truck as an auxiliary to railroad logging, there are many opportunities for the reduction of logging costs. However, it is impossible to discuss these problems specifically in a paper of this kind. They will need to be worked out on the ground with each case as a distinct problem. The fundamental problems covered in this paper will serve as a basis for the more detailed problems that must be solved on the ground.

Wherever the item of road construction is important, it may be stated in general that the time required and the cost of building roads for motor trucks are very much less than for a logging railroad. This is due to the lesser importance of grades, curves, ballasting, bridges and other construction work, all of which is much cheaper and takes less time. In case a pole road is built the material found adjacent to the right of way can be utilized for what it costs to fell it.

From the standpoint of adaptability the motor truck is very flexible. It can operate on grades and curves that are impossible with the railroad. The whole logging equipment, including the donkey engine, can be loaded on the truck and trailer and easily moved from one setting to another. By replacing the log bunk with a platform the truck can take out all the smaller marketable material, such as shingle bolts, poles and cordwood. The modern truck can also be provided with the necessary equipment for use in snaking out the logs in stands of small timber and when used with a winch and an “A” shaped boom, will load itself. If the truck becomes mired in a mud hole, the winch may be used to pull it out. Finally, the item of fire risk is practically negligible.

COSTS

In order to arrive at definite figures as a basis for a comparison between railroad and motor truck transportation costs, the following case is cited as an example representing average good conditions:[1] A 5-ton truck with trailer was used, operating on a seven and one-half mile haul over ordinary unpaved roads. An average of four trips a day were made and the actual running expense for hauling was $.901⁄2 per thousand feet. Adding to this the overhead expenses of interest, depreciation, etc., the total cost of hauling was $1.44 per thousand feet. The statement of this cost is as follows:

Actual Cash Outlay in Hauling 128,420 Board Feet of Logs

Total Expense of Hauling 128,420 Board Feet of Logs

Variable Charges

Following is a recapitulation of the work performed by a 5-ton logging truck, Jan. 20 to Jan. 31, 1916, inclusive. The logs were hauled from O’Neill’s Camp on the Bothell-Everett road 71⁄2 miles and dumped into Lake Washington at Bothell.

Many loggers who have used both the steam railroad and the motor truck claim that the latter is preferable in some cases and often is the only method by means of which logs can be gotten to the mill at a reasonable cost. Where the stand is scattered and of poor quality, the building of a railroad is not practical. In such a case the motor truck may offer the only solution.

The motor truck makes the best showing when hauling from one “side.” With a two or three side operation the railroad is by far the more practical. It must be remembered, however, that the railroad and the motor truck are not competitors in the logging industry—they are allies.

ROLLING STOCK EQUIPMENT

In general two plans are followed in building a motor truck. The first is to build a rigid truck so that it will resist all shocks and distortions that come from rough and uneven roads. The second plan is to build a flexible body so that the chassis will “give” rather than resist when subjected to hard strains. Although the rigidly-built truck may be entirely satisfactory for most forms of trucking, it is practically impossible to build one on the rigid principle that will stand up under the heavy strains to which a logging truck is subjected unless it is to be operated over good paved roads. When only ordinary unpaved public roads are available, flexibility is one of the most important characteristics to look for when selecting a truck. Where the operator is hauling over his own pole or plank road this consideration does not play so important a part, as the road bed then is more likely to be free from holes and irregularities.

All makes of trucks are more or less alike in general construction, differing only in minor details, so that the personal whims of the buyer will largely determine the kind he will select. It is advantageous to have as long a distance as possible between the driver’s seat and the bunk over the rear axle, in order to allow more of the load to be carried by the truck, and less by the trailer, giving better traction to the drive wheels, but necessitating extra strong rear springs and axles.

The type of power transmission best suited to the use of the logging truck is a question that has received a great deal of attention. There are three general methods of transmitting the power: (1) by chain; (2) by worm drive, and (3) by internal gear drive. Each has its advantages. It is claimed by many that the chain drive saves many hours of “shut-down time” due to the fact that if anything breaks in the transmission, it will be a link in the chain as this is the weakest point. It is then only a matter of a few minutes to insert another link. With the worm driven vehicle, a break in the transmission requires an expensive shut-down before the matter can be repaired. The worm drive, on the other hand, very seldom breaks if proper care is used.

The question of the weight of the truck used for logging purposes is not as important now as it will be in the future. Laws are being passed in nearly every state limiting the maximum weight to be carried on each wheel by trucks using state or county roads so that the total weight of the truck without load will be important. When operating over state or county roads the load is limited to from 2400 to 3000 feet, B. M., of Douglas fir, depending upon the locality. In such cases, it is an advantage to have a lighter truck, say one of 31⁄2 tons capacity. By adding additional leaves to the rear springs of a truck of this capacity it may be made to carry a larger load than it would be possible to put on a 5-ton truck and still comply with the law. The pulling power of the 31⁄2-ton truck and the 5-ton truck is practically the same so that the difference in dead weight between the two may be carried in a profitable manner by adding four or five hundred feet B. M. of logs. Another advantage of the lighter weight truck is speed. The 31⁄2-ton truck is geared to make from 14 to 16 miles an hour, while the 5-ton truck is usually limited to from 10 to 12 miles an hour.

LIFE AND DEPRECIATION

The charge to be made for the depreciation of a truck is an uncertain question. Some loggers figure on the basis of four and a half years, others on as much as seven years. The depreciation charge on a truck used in the logging industry should depend largely upon the type of road over which it is operated. Loggers in general over-rate the life of their equipment because they do not fully realize the severity of the work. Over a fore and aft plank road or a cement road, where the jar and vibration are reduced to a minimum, the wear and tear on the equipment is very much less than where the truck is operated over a cross-plank road or an unpaved public road. The matter of depreciation, then, will depend largely upon the type of road over which the truck is to operate. In general a four-year depreciation charge less 25% sale value at the end of that time should be used as a basis for figuring costs unless the hauling conditions are very favorable. Only under very rare circumstances should more than four years be allowed. It should be remembered that the depreciation on a truck is very heavy during the first year, and the sale value at the end of a year is only half the original price. Many truck operators now hauling over good roads who are depreciating on the basis of five years say that a four-year depreciation would be more nearly correct. Another factor in favor of a four-year depreciation charge is that methods of logging are changing constantly and that trucks in that time may be improved upon to such an extent that the use of the old equipment would be unprofitable and inefficient.

INSURANCE

Fire and theft insurance is based upon the list price of the truck and body when new and the usual premium for the logging truck is one dollar for every hundred dollars of insured value. Theft rates on the trailer are based on a flat charge of twenty-five cents per hundred dollars of insurance taken, regardless of age, list price, etcetera.

Collision insurance is based upon the list price of the equipment and covers full value at the time of loss of the damage to the truck by colliding with anything movable or immovable.

The liability rate for logging trucks is $33.75 and is based upon occupation alone. This covers the public as well as the employee and is limited to $5,000 for one person and $10,000 for two persons or more.

The property damage rate for logging trucks is $13.50, and covers the damage done to the property of others. It is arrived at in the same way as liability insurance. The usual limit for property damage is $1,000.

TRUCK EQUIPMENT

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.