POWER SKIDDING 
225 
line, where the log is lowered to the ground by slackening the 
main cable. As logging progresses the outer block through which 
the haul-back line passes is changed so that the trolley and main 
cable always can be pulled away from th(^ center of the run. 
Logs may be successfully side-lined for 150 feet. 
More power is needed to elevate the logs than is required in some 
other overhead systems, since both the weight of the main cable 
^hree Sheave Tree Jack 
\24 In. Auto-Lubricating Sky-Line Block 
14 In. Auto-Lubricating Sky-Line Block 
From Bui. 711, U. S. Dept. of Agriculture. 
Fig. 70. — The North Bend System of Overhead Logging. 
and of the logs must be raised. The daily capacity of a machine 
of this type is from 50,000 to 100,000 board feet, depending upon 
slope conditions, log size, and length of span. 
Previous to a change in runs, the tail tree spar in the next 
run to be logged is chosen and properly guyed. When logging 
on one run is completed the main cable is pulled to the head- 
spar tree. One end of the haul-back line is then attached to a 
small cable, called a straw line, which has previously been pulled 
out over the new run and when the straw line is pulled in, the 
haul-back line is drawn out through a block on the tail spar 
tree and back to the head spar. 
North Bend System.^ — This is used both for yarding and for 
1 See Fig. 70. 
