22 



HARDWOOD RECORD 



September 10, 1921 



%!'3ff:PO>^R^LOGGING-i4A!Z) 



m^.As j^BER Handling 



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.114^-- iTT. ,.£s ~'niIEf^; 



Selection of a Motor Track for Logging 



Some iuteresting ideas on the seleefion ol' iiiotur trueks i'or lod- 

 ging are givcu by Frederick Malcolm Knapp, a student in the Col- 

 lege of Forestry, University of Washington, in a brochure recently 

 issued on Motor Truck Logging Methods. Mr. Knapp 's very thor- 

 ough thesis is based on experiences and conditions in the Pacific 

 Northwest, but the information pertaining to the choice of trucks 

 should be of value to the Uimbernu'n of any territory. 



Mr. Knapp points out that in general two jilans are fcdlowed 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 i)lan is to build a flexible body so that 

 the chassis will "give" rather than resist when subjected to hard 

 strains. Although the rigiilly built truck may be entirely satis- 

 factory 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 oper- 

 ated over good paved roads. When only ordinary unpaved public 

 roads are avail.able, flexibility is one of the most important chara- 

 teristics 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 i)art, as the roadbed then is more likely to 

 be free from holes and irregularities. 



" .\11 makes of trucks are more or less alike in general construc- 

 tion, diifering only in minor details, so that the jiersonal 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 th<' truck and less by the trailer, 

 giving better traction to the drive wheels, Init necessitating extra 

 strong rear springs .anil axles. 



What Power Transmission 



''The type of jiowei' transmission best suited to the use of the 

 logging truck is a question that has received a great deal of atten- 

 tion. There are three general methods of transmitting the power: 

 (1) By chain, (2) by worm drive, and (.'i) 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 drive vehicle, a 

 bre.-ik 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 ch.-iiti drive also allows the replacement of the sprocket 

 with one of a larger or smaller diameter, thereby giving a higher 

 or lower ge.-ir ratio, which cannot be done with the worm gear. 

 This seems to be of some advantage to an operator when changing 

 his setting from one with a short haul and steep grades where a 

 low^ gear ratio is re(|\iired, to one where the haul is long and fairly 

 level, and where speed in transit is an advantage. 



"On the other hand, in starting on slippery grades or wherever 

 the traction is poor, the worm drive will give better traction than 

 a chain drive, because there is difficulty in taking up the slack that 

 is always present in the chain before letting in the clutch fully. 

 The slightest jerk giviMi to the wheels when the slack is taken up 

 is likely to cause them to spin, thereby losing all the tractive power 

 of the drive wheels. In the worm gear there is no slack to take 

 up and the power can be applied more gradually, thus reducing 

 the chances of spinning the wheels and losing the traction. The 



question of the weight of the truck \ised for logging iiurposes 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 trueks using state or country 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 2,400 to 3,000 feet, B. M., of Douglas fir, deiiending upon the 

 locality. In such cases, it is an advantage to have a lighter truck, 

 say one of .3'/l> tons capacity. By adding additional leaves to the 

 rear springs *of a truck of this capacity it may be made to carry a 

 larger loail than it would be possible to put on a 5-ton truck and 

 still comply with the law. The pulling power of the 3%-ton truck 

 and the .'5-tiin 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 ad- 

 vantage of the lighter weight truck is speed. The 3^i-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. 



"Whenever the legal weight limit does not enter into the [irob- 

 leni, as in operating over a pole or plank road for the entire dis- 

 tance, it is, of course, advantageous to carry the largest loads pos- 

 sible. In such cases a 5-ton truck with an 8%-ton trailer is the 

 most profitable investment. This allows a much larger load to be 

 carried in proportion to the overhead charges. The disadvantage 

 of the 5-ton truck is that it is very heavy, and unless the roads are 

 good it w'ill easily sink into the ground and cause trouble. A com- 

 mon fault of the 5-ton truck today is the overweight of the front 

 end, which is too heavy for the width of tire on the front wheels. 

 This can be very easily overcome by the use of wider tires. 



lafe and Depreciation 



"The life of a truck is directly pro]iortiiiual to the care that it 

 receives, hence, a good driver is a most important consideration. 

 If the right man can be secured his wages should be a secoudarj' 

 consideration. 



"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 overrate 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 

 unpaveil jniblic road. The matter of depreciation, then, will de- 

 pend largely ui)on the type of road over which the truck is to 

 operate. In general, a four-year depreciation charge, less 25 per 

 cent 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 the year is only half of 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 deprecia- 

 tion charge is that methods of logging arc changing constantly 

 and that trucks in that time may be improved upon to such an ex- _ 

 tent that the use of the old equijuuent would be unprofitable and 

 iueflicient." 



