48 BULLETIN 440, U. S. DEPARTMENT OF AGRICULTURE. 
Grades and curvature may be heavier on spurs than on the main 
line where heavier loads must be handled. A geared engine can 
negotiate heavier grades and sharper curves than a rod engine. 
Narrow-gauge equipment can follow sharper curves than standard. 
Except where topographic conditions forbid, long main-line log- 
ging railroads are usually constructed to permit the use of rod engines. 
The maximum grades allowed are 3 or sometimes 4 per cent empty 
and 1 per cent loaded. The sharpest curves are usually 16° for 
standard gauge and 20° for narrow gauge. 1 In rougher regions 
even main lines can not be constructed for rod engines at a reasonable 
cost and geared engines must be used. The maximum grades ordi- 
narily employed are 5 per cent empty and 2 per cent loaded. A 
heavier grade than 5 per cent can be surmounted, but it is difficult 
to hold a heavy train on the down grade. The maximum curves 
used are from 25° to 30° for standard gauge and from 30° to 40° for 
narrow gauge. 
Logging spurs are usually constructed for the use of geared engines 
with a few cars at a time. The usual maximum grade for empties 
is 7 or 8 per cent, or even 10 per cent on short pitches, and the maxi- 
mum for loads about 4J per cent. The usual maximum curve for 
narrow-gauge spurs is 50°, though in some instances curves as sharp 
as 60° are used. The maximum for standard gauge is about 40°. 
One company using saddle-tank dinkey rod locomotives with a wheel 
base of 8 feet constructs its narrow-gauge logging spurs with maximum 
grades of 5 per cent empty and 2 per cent loaded and a maximum 
curvature of 50°. The maximum grades given above are of course 
compensated on curves at the rate of from 0.02 to 0.03 per cent per 
degree. 
All of the larger companies employ competent woods engineers 
to lay out their railroads. The engineers cooperate with the woods 
superintendent in determining roughly the routes of main-line exten- 
sions and spurs. The engineering force then makes preliminary 
and permanent location surveys and exercises general supervision 
over the construction. Upon the larger operations the engineer has 
a crew of a transitman and two helpers. The engineer is usually 
employed the year round and devotes his time in winter to mapping 
and cruising. During the summer considerable time of the engineering 
force is devoted to running land lines and other activities apart from 
railroad construction. The cost of engineering upon logging railroads 
varies from $200 to $400 per mile for main lines, depending upon the 
difficulty, and from $125 to $250 per mile for spurs. In the construc- 
tion of commercial railroads it is usually customary to figure engineer- 
ing as 5 per cent of the other costs. 
1 Straight connected saddle-tank locomotives with a short wheel hase can be operated over sharper curves 
than these. 
