114 BULLETIN 711, U. S. DEPARTMENT OF AGRICULTURE. 
(2) The life of yarding engines is frequently shortened through 
working them far beyond their efficient capacity, also through insuffi- 
cient maintenance. 
(3) It is frequently prolonged through unprofitable care. 
(4) The industry has not kept cost records in such form as to 
enable one in a given case to say confidently when the efficient life 
has been passed. 
Most operators place the efficient life of ground yarding engines at 
eight years. One of the leading operators of the region figures that 
it is economical to work his yarding engines hard for four years, sell 
them, and buy new ones. Possibly he works them harder than any 
other operator. If he can sell his engines at the end of four years 
for one-half of their original cost, which he hopes to do, it would 
seem that he figures on a life of about eight years. 
For the purpose of arriving at the amount that should be written 
off annually for depreciation on this class of equipment, in connection 
with the appraisal of national forest timber, the efficient life of 
yarding engines has been placed at eight years, with a scrap value of 
10 per cent of the original cost. 
ESTIMATING THE COST OF YABDING. 
The following hypothetical statement will serve to summarize the 
several items of expense in yarding and to show an estimated cost 
of yarding per thousand feet on the basis of an output of 60,000 feet 
per day per engine. It will also serve as a guide in estimating the 
total cost of yarding, including labor, supplies, repair parts and mate- 
rial, maintenance, depreciation, and supervision. 
Table 20. — Estimated total cost of ground yarding. 
Items. 
Total daily 
cost. 
Cost per 
1,000 feet. 
Labor cost 
Wire rope 
Rigging: 
Blocks, hooks, and rollers 
Fuel oil 
Lubricants, waste, and packing 
Depreciation on logging engine 
Maintenance of logging engine 
Woods water system 
Foreman, scaler, timekeeper, and bookkeeper. 
Total 
S39. 60 
SO. 66 
, .136 
.03 
.02 
.132 
.01 
.06 
.04 
.02 
.04 
1.14S 
The labor cost is based on an average daily output of 60,000 feet, 
which takes into account both productive and unproductive time. It 
is assumed that no extra yarding engine is used, which means that the 
regular yarding crew moves the engine from one setting to another. 
