POWER SKIDDING 
251 
daily, the average being about five gallons of oil per thousand 
board feet of timber yarded. 
/ 
SPARK ARRESTERS 
The laws of most forested states require the use of some form 
of spark arrester on wood- and coal-burning skidding machinery. 
There are several types of spark arresters for stationary engines, 
C, 
Fig. 79. — The South Bend Spark 
Arrester adapted to Power Skid- 
ding Machinery. 
Fig. 80. — The Boomerang Spark 
Arrester. 
two of which are here described. A spark arrester will not com- 
pletely prevent the emission of live sparks from skidder power 
plants which are operated under forced draft, but the fire hazard 
can be decreased by properly screening the stack. 
The South Betid Spark Arrester^ is used almost exclusively 
on power skidders in the southern yellow pine region, and also 
to some extent in the Northwest. 
It has a round tapering shell (A) of sheet metal, an outlet (B) 
at the side for the discharge of sparks and cinders; and a sheet 
metal cover (C). A cone-shaped screen (D) attached to the 
sheet iron cover hangs within the stack, apex downward, and 
deflects the cinders into the spark receiver at the head of the out- 
1 See Fig. 79. 
