LOGGING IN THE DOUGLAS FIR REGION. 
77 
D equals diameter of flange, in inches. 
d equals diameter of barrel, in inches. 
L equals length between the flanges, in inches. 
C equals constant, varying for each size of line. 
Value of C. 
Size of line. 
Constant. 
Size of line. 
Constant. 
4.16 
2.67 
1.86 
1.37 
1.05 
.828 
.672 
.465 
.342 
262 
207 
11 inches 
.167 
138 
ll inches 
.116 
If inches 
099 
1 J inches 
.085 
1| inches 
074 
2 inches 
.066 
Using the above formula, the drum capacity is obtained by multiplying the 
sum of one-half the diameter of the flanges and one-half the diameter of the 
barrel by the difference between one-half of the diameter of the flanges and one- 
half the diameter of the barrel by the length between the flanges and the con- 
stant for the size of the line required. Five-eighths inch line is almost uni- 
versally used for trip lines. The main line varies from 1 inch to If inches in 
diameter. 
In computing the proportion between the main drum and the trip-drum rope 
capacities it is assumed that the main line is li inches and the trip line f inch. 
( d ) As a matter of relative comparison only, the speed of any line is the speed 
of the line when the drum is one-half full of cable and engine is running at a 
piston speed of 600 feet per minute. 
(e) Standard logging engine. — What is known as a standard logging engine 
is a two-drum machine complete with boiler, hood, stack, spark arrester, and 
one gypsy head. Patented spark arresters, straw-line and loading drums, and 
the like, are additional equipment, and usually are furnished at extra cost. In 
the case of narrow drum yarders where a true lead is necessary on the drums, 
one main line and one trip line fair-leader should be furnished with each engine. 
(/) Boilers. — The working pressure of boilers 48 inches or larger in diameter 
should not be less than 175 pounds. Boilers are rated by their inside diameters 
and the over-all length of effective shell. Any extension below the water leg 
for the ash pan or any extension above the tube sheet for the breeching is not 
considered part of the effective shell. 
(g) Pulling power. — The pulling power of any drum can be obtained by the 
following formula : 
rXGXPXA 
W= 
R 
W= Weight or pull on cable. 
P=Full boiler pressure. 
A=Area of one cylinder. 
r= Radius of crank. 
R= Radius of drum. 
G=Gear ratio drum. 
The size of yarding engines varies in different camps. An operator 
who has given more than the usual amount of attention to this 
question, and who has a reputation for consistently securing large 
yarding outputs, made the following recommendations, based on 
uphill yarding: 
