TESTS OF KOCKY MOUNTAIN WOODS FOE TELEPHONE POLES. 17 
A comparison based on the fiber stress developed is equivalent 
to one based on uniform ground-line diameter. In practice, however, 
it is customary to specify top diameters. On a basis of measured 
tapers and the fiber stresses found by test, the loads may be calcu- 
lated for all shipments, using a uniform top diameter of 7 inches. 
Table 4 gives the calculated loads for such a comparison. The tapers 
used in the calculations were, for western red cedar, 0.098 inch per 
foot length; for the air-seasoned lodgepole pine, 0.077; for fire-killed 
lodgepole pine, 0.096; and for fire-killed Engelmann spruce, 0.130. 
These tapers do not include the flare of the butt. The length from, 
top to the load point was taken as 19.5 in all cases. Since the strength 
of a pole varies as the cube of its diameter, it is evident that differ- 
ences in taper will materially affect the strength. On a basis of equal 
top diameters it will be seen from Table 4 that — 
1. There is practically no difference in strength between air- 
seasoned lodgepole pine and western red cedar. In stiffness the 
lodgepole pine poles exceeded the cedar by about 25 per cent. 
2. The fire-killed poles, both lodgepole pine and Engelmann spruce, 
were practically equal to the cedar in strength at elastic limit and 
about 20 per cent below it at the maximum load. 
Table 4. — Strength of poles compared on a basis of 7-inch tops. 
Species. 
Seasoning condition. 
Load at elastic 
limit. 
Average. 
Ratio to 
red 
cedar. 
Maximum load. 
Average. 
Ratio to 
red 
cedar. 
Western red cedar . 
Lodgepole pine 
Do 
Engelmann spruce. 
Cut green and air seasoned. 
Fire killed 10 years 
do 
Pounds. 
7,800 
8,000 
7,470 
7,500 
Per cent. 
100 
103 
96 
96 
Pounds. 
12, 000 
11, 620 
9,500 
9,400 
Per cent. 
100 
97 
79 
78 
SMALL, CLEAR PIECES CUT FROM POLES. 
Table 5 gives the results of tests on small, clear pieces in bending, 
compression parallel to grain, compression perpendicular to grain, 
and shearing. For each pole the average strength values for all 
pieces taken from it are given, and at the bottom of the tables are 
the averages of all minor tests for the species. 
Table 6 gives the average strength values of minor tests sum- 
marized by species and condition of seasoning. An examination 
of the average results shows in general very comparable values for 
the fire-killed pine and spruce and for the cedar. The cedar, how- 
ever, falls about 16 per cent below the pine in shearing strength and 
the spruce about 12 per cent below it in crushing strength. The 
lodgepole pine from Montana showed a bending strength nearly 40 
