Motor Truck Logging Methods Part 2

[5] Operating Cost of Motor Truck Computed. Timberman. Feb., 1918.

Page 60.

Objection to the trailer that it tends to shorten the life of the truck is hardly worth consideration. According to a careful a.n.a.lysis it has been estimated that the use of the trailer does not shorten the life of the truck by more than one year, which is of little consequence when the saving due to the size of the load that can be carried is taken into consideration.

_Description of the Trailer_: The frame of the trailer is constructed of heavy steel channel bars which support the twin bunks used for logging, and for the substructure to carry the body when used for other service.

The steel frame is supported by semi-elliptic springs held by shackles similar to those of the truck. The springs rest securely upon the axle, are clamped to it by U-bolts, and are relieved from side stresses by radius rods which connect the axle to the frame.

The trailer is coupled to the truck by a reach which is pa.s.sed through guides secured to the hounds of the trailer. The latter may slide upon the reach and is held in the desired position with reference to the truck by means of clamps. The hounds are located fore and aft of the axle and are connected to it by steel plates. The square reach is more favored generally by loggers than the round type for the reason that it can be more easily adjusted, particularly the round reach that is cut in the woods, which is irregular and has to be clamped very tightly in order to make it stay in place. Holes bored through the square reach makes the adjustment easy. Combination steel and wood reaches, the sides being of channel iron and the center of wood, are favored by some operators.

The twin bunks of the trailer carry the load in balance upon the axle independent of the reach, thereby relieving the reach of all vertical stress. (See ill.u.s.tration below). The rear bunk is just an ordinary wooden affair designed only to help support the weight of the logs. The front bunk is of the same construction as the one on the truck (described above) and serves to hold the load in place.

[Ill.u.s.tration: Type of trailer adapted for heavy Pacific coast logging.]

The trailer is guided through the reach directly to the axles, thus relieving the springs and frame from side stresses. The springs and their suspension from the frame permit a limited movement of the frame and the load independent of the wheels and axles and vice versa. This enables the wheels to pa.s.s over an obstruction or drop into a hole without subjecting the trailer to shocks that would otherwise ensue.

Other types of trailers are used to a limited extent. The trailer described above was evolved by local engineers and is in almost universal use in motor truck logging operations.

_Brakes._ All trailers should be equipped with brakes when negotiating heavy grades. A device connecting the trailer brakes to the truck permits a ready control from the driver's seat on the truck. The brake outfit is easily attached to the truck and consists of a ratchet and lever which winds a one-quarter inch cable on a small drum. The cable winds around a second drum which is attached to the frame of the truck about six feet back of the driver's seat. A third drum in the center of the cha.s.sis attached to the shaft of the second drum winds a cable which goes to an equalizing bar just in front of the trailer brake. As the ratchet and drum are tightened, the motion is transmitted through the second and third drums to the equalizing bar. Two arms extend from this bar to roads which when pulled forward, move a bar attached to the road in such a way that the brake band in the inside of the brake shoe is extended against the shoe, applying the brakes evenly to each wheel no matter how uneven the road-bed or how sharp the curve. A spring attached to the reach clamp pulls back the equalizing bar when the brakes are released. A heavy spring on the drum in the center of the shaft on the truck allows for curves so that an even pressure is always maintained.

The use of a trailer equipped with brakes will do away with the numerous devices for snubbing a load of logs down a grade not steeper than twelve per cent. Grades up to this degree of steepness are safe to operate over in dry weather without added braking power if the trailer is properly equipped.

A simple and it is claimed an effective air brake for motor trucks and trailers is now being marketed by an air-brake concern of San Francis...o...b..t it has not yet been tried out in the logging industry. "Braking action is secured by means of a diaphragm and pressure plate. The diaphragm is directly connected to the brake-band lever. No air compressor is used in this system. A small air receiver or storage tank takes the spent gases from one of the cylinders by utilizing the outlet afforded by a priming c.o.c.k. The brakes are applied by a control system mounted on the steering column. By means of a quickly adjusted hose connection, air can be applied to the wheels of the trailer using the control which governs the braking of the truck. The air pressure in the storage tank is automatically maintained by means of an acc.u.mulator valve which closes when the tank pressure reaches 150 to 175 pounds. If the tank should be empty at the top of a long grade, sufficient pressure is generated by the compression of the engine to operate the brakes.

Opening the throttle to full emergency position will apply maximum braking effect without sliding the wheels."[6]

[6] Air Brakes for Trucks. Timberman. March, 1920. Page 48g.

This system has not been tried out under the conditions as found in the woods but if it can be made to work satisfactorily it will be a big improvement over the old system as the driver will then have instantaneous control over the load at all times.

LIFE AND DEPRECIATION

The life of the trailer is about the same as that of the truck, and in depreciation, a period of four years is usually allowed. The maintenance and upkeep of the trailer is very low. It rarely gives out and with the ordinary usage requires only a few minor repairs every two or three years.

COST DATA

The items of expense are here segregated in such a manner that they may be used as a basis for figuring the cost of hauling logs under average conditions. These costs are for the truck and trailer as a unit. If a road has to be built, the overhead charge of the road per thousand feet of timber hauled over it together with the cost of upkeep must be added to the figures given below in order to know the total cost of transportation per thousand feet.

3000 FOOT CAPACITY, OUTFIT COMPLETE

The following figures are for a 3-ton logging truck with a 5-ton trailer. The figures are based upon a 275 working day year.

Cost of equipment (as a basis) $6700.00 Less resale value at expiration of 4 years at 25% of the original cost $1675.00 Less cost of tires, 2--36" 6" $140.50 4--40" 12" 776.00 916.50 -------- -------- Total $916.50 $2591.50 2591.50 -------- Basis for computing $4108.50

RUNNING EXPENSES PER MILE

Per Mile Tires, based on a cost of $916.50 and a life of 8000 miles $ .1145 Gasoline, four miles to a gallon @ $ .28 per gal. .07 Oil and grease .02 General repairs .03 -------- Total running expenses per mile $ .2345

FIXED CHARGES PER 275 WORKING DAY YEAR

Depreciation, based on 25% per year on $4108.50 $1027.12 Interest on money invested at 6% (figured on truck less cost of tires) 347.01 Driver at $7.00 a day 1925.00 License 27.00 Insurance, Fire, Theft and Liability based on $1 a hundred on 90% of the value of the new truck for fire and theft, and a flat rate of $33.75 for liability 90.75 ------- Total fixed charges for 275 day year $3416.88 Total fixed charges per day 12.418

TOTAL EXPENSES

30 40 50 60 70 miles miles miles miles miles Uniform variable charges $7.035 $9.38 $11.725 $14.07 $16.415 Fixed charges 12.418 12.418 12.418 12.418 12.418 Total charges (per day) 19.453 21.798 24.143 26.488 28.833 Total cost per mile, loaded one way only .648 .545 .482 .441 .412 Total cost per 1000 ft. per mile with 3000 ft. to the load .216 .181 .160 .147 .137

4000 FOOT CAPACITY, OUTFIT COMPLETE

The following figures are for the 5-ton logging truck equipped with an 8-ton trailer, based on a 275 working day year:

Cost of equipment (as a basis) $7600.00 Less resale value at expiration of four years at 25% of original cost $1900.00 Less cost of tires:

2--36-in. 6-in $140.50 4--40-in. 14-in 923.00 -------- Total $1063.50 1063.50 -------- $2963.50 2963.50 -------- Basis for computation $4636.50

RUNNING EXPENSES PER MILE

per mile Tires, based on cost of $1063.50 and a life of 8000 miles $.129 Gasoline, 3 miles to the gallon @ $.28 per gal. .08 Oil and grease .02 General repairs .035 ------ Total running expenses per mile $.264

FIXED CHARGES PER 275 DAY YEAR

Depreciation, based upon 25% per year on $4636.50 $ 1157.13 Interest on money invested at 6% (figured on equipment less cost of tires) 392.19 Driver at $7.00 a day 1925.00 License 27.00 Insurance, fire, theft and liability, based on $1 a hundred on 90% of the value of the new truck for fire and theft, and a flat rate of $33.75 for liability 101.75 ------- Total fixed charges for 275 day year $3603.07 Total fixed charges per day 12.92

TOTAL EXPENSES

30 40 50 60 Uniform variable charges per miles miles miles miles mile $.247 $ 7.92 $10.56 $13.20 $15.84 Fixed charges per day 12.92 12.92 12.92 12.92 Total charges per day 20.84 23.48 26.12 28.76 Total cost per mile loaded one way only .694 .587 .522 .479 Total cost per 1000 feet per mile with a 4000 foot load .173 .146 .130 .119

The above costs will be found to be approximately correct for average operations. They will vary somewhat with the road conditions, loads, grades, and the efficiency of the driver. These variations, however, will be slight. They will not amount to more than one cent per thousand feet per mile of haul. The investment pays the owner six per cent and provides renewals for all time. The interest charge is based on the total cost of the equipment less the cost of the tires. The tire cost is deducted in figuring the interest charges because this item is covered under running expenses. The resale value of the truck at the end of four years is not deducted from the interest charge, because this sum is tied up for that length of time. Renewal for the equipment is taken care of by the creation of a sinking fund based on an average life of four years. Theoretically, on a 5-ton truck, $1157.13 is put aside each year for four years at the expiration of which time the aggregate of these savings together with the resale value of $1900, automatically provides for the purchase of new equipment.[7]

[7] Timberman. Feb., 1918. Page 60.

A fifty-mile haul may be used as an ill.u.s.tration for figuring the total running expense of the 5-ton truck. This means that the truck makes trips enough to total fifty miles for the day's run. The cost per mile, including gasoline, oil and repairs is 26.4 cents. It will, therefore, cost $13.20 for the fifty miles. To this amount must be added $12.92, daily overhead charge, making a total of $26.12 for fifty miles traveled or 52.2 cents a mile. With an average load of four thousand feet the cost will be 13.0 cents per mile per thousand feet. A glance at the table will show that the greater the mileage and the larger the load, the less will be the overhead expense and consequently the cost per mile per thousand feet. To these items must be added the cost and maintenance of the road if one has to be built.