WHEELED VEHICLES 199 
expense is warranted in hauling valua})le logs than those of 
average (jiiahty. For example, veneer mills in the Central Hard- 
wood Region have hauled logs on round trips of 85 miles, with 
average loads of from 900 to 1000 feet log scale and the service 
was stated to be as cheap as railroad transportation and much 
quicker. 
T]ir(H> general types of trucks are used, namely, light trucks, 
UKHlium trucks with a rated capacity of from 3 to 4 tons, and heavy 
trucks rated at 5 tons or more. The light truck represents the 
lowest initial investment but owing to its limited capacity and 
less rugged construction, it is not adapted to heavy or steady 
log-hauling work. The medium-weight truck is adapted to 
conditions where the size of the load is limited by state or county 
road regulations. Many operators rely upon public roads for 
their main lines and build side roads from them to the timber. 
Limits have been set to the amount of timber which may be car- 
ried over public roads on one unit, in those sections in which 
hauling by motor trucks has become extensive. This limit varies 
from 2400 to 3000 board feet in different counties in the Douglas 
fir region. The heavy trucks are preferred on operations on 
which private roads, only, are used since maximum loads, ranging 
from 3000 to 5000 board feet, can be carried on each trip. 
Many makes of trucks are used, including four-wheeled drive, 
and both chain and gear rear-wheel drive. Loggers prefer a 
machine with a wheel base of from 160 to 170 inches, since 
this gives a good balance to the load, and a truck so built can be 
handled on turns and at the loading places easier than one which 
is longer. The frames of trucks with larger wheel bases may 
give trouble, when overloaded, by tending to buckle. A motor 
truck for log hauling should have stronger springs, gears and 
bearings than are placed on ordinary commercial vehicles of the 
same size, because of the severe usage to which the machine is 
subject. Solid, single-tread rubber tires, 12 or 14 inches wide, 
are used on the rear wheels of practically all logging trucks and 
on trailers and are safe for use on dry pole or plank roads having 
9 per cent grades. They will skid on a wet road on grades in 
excess of 7 per cent unless the tires are wrapped with ^-inch 
wire cable, or similar cable is fastened crosswise on the traction 
surface. On good roads and favorable grades, logging trucks 
travel from 10 to 12 miles per hour. 
