26 BULLETIN 67, U. S. DEPARTMENT OF AGEICULTURE. 



CONCLUSIONS. 



The tests on poles and specimens cut from them show that — 



1. Air-seasoned lodgepole puie poles cut from Hve timber in Mon- 

 tana were fully equal in strength to the cedar poles tested. In actual 

 stress developed they were superior, but on account of the greater 

 taper of the cedar poles this advantage was lost in a comparison based 

 on equal top cUameters, the dimension usually specified. 



2. Cedar poles were superior to the pine and spruce poles cut from 

 a fire-killed area in Colorado in maximum load developed. The three 

 shipments were, however, practically equal at the elastic Hmit. Were 

 the native poles to be used in place of cedar without change of specifica- 

 tions, it would follow that the factor of safety would be reduced one- 

 fifth for conditions at failure, but would remain the same for stresses 

 at the elastic limit. 



3. The fire-killed pine, after standing 10 years, did not show deteri- 

 oration to any appreciable extent when compared to seasoned lodge- 

 pole pine cut from representative live trees in Wyoming and Colorado. 

 The advantage in strength of the material from the lodgepole pine 

 poles from Montana can be accounted for by the fact that it was above 

 normal in weight — at least for lodgepole pine from the southern part 

 of its range. " . 



4. The ratio between the strength of the poles and the strength of 

 the clear material cut from them is not constant for the different 

 kinds of wood. This "efficiency" factor varied from 0.74 to 0.48 of 

 the strength of the clear wood when the comparison is made as tested, 

 and from 0.98 to 0.65 when compared on the basis of values estimated 

 to represent the same moistm-e condition in the small pieces as existed 

 in the poles when tested. The values were highest for the cedar and 

 lowest for the spruce, the pine representing an average for the three 

 species. 



POLE TESTS BY THE PACIFIC TELEPHONE & TELEGRAPH CO. 



The Pacific Telephone & Telegraph Co. made tests on 81 poles of 

 western red cedar and Port Orford cedar at the pole yards of the 

 Western Electric Co. near Kichmond, Cal. These poles were 25 

 and 30 feet in length, with 6, 7, and 8 inch top diameters, and 35 feet 

 in length, with 7, 8, and 9 inch tops. 



The method employed in these tests makes it impossible to make 

 any accurate comparisons of stress values with those obtained in the 

 Forest Service tests. In the telephone company's tests stresses are 

 figured for the point of failure, while the Forest Service tests are 

 figured for the load point or ground line, theoretically the point of 

 greatest stress. 



In the telephone company's tests the poles were tested horizontally, 

 with 6 feet of the butt end of the pole held firmly between four 12 



