SUMMARY 



Producers and users of utility poles have long been plagued by the twisting of some poles 

 after installation. Between 1952 and 1960, six studies were made with the cooperation of four 

 pole -producing companies to determine (1) frequency of spiral grain in poles, (2) how to detect 

 spiraling in unpeeled poles, and (3) the part that spiral grain plays in the twisting of poles. The 

 five studies reported in this paper were all of western larch, but the results are believed to be 

 generally applicable to other species. 



The study of cause of twisting of poles soon pinpointed spiral grain as a major cause. In 

 290 poles in four power transmission lines, left spiral grain occurred about three times as 

 frequently as right spiral, and poles usually twisted in the same direction as their spiral grain. 

 Left-spiraled poles usually twisted more than right -spiraled poles, and all severe twisting was 

 associated with severe spiral grain on the pole's surface. Well-seasoned poles twisted less 

 than unseasoned or briefly seasoned poles. 



Results of a study aimed at finding a practical method of detecting spiral grain in poles 

 before debarking were disappointing. Neither of two methods tried gave consistent success. 



The study of frequency of spiral grain (based on 800 poles) showed two-thirds with left 

 spiral and one -third with right spiral. However, the spiral was so slight in 48 percent of the 

 poles that they could be classed as straight grained. Severe spiraling was chiefly left hand. 

 Variation in slope of grain along the pole's length was common, and maximum divergence from 

 the longitudinal occurred most frequently near the top. 



The position of a tree on a slope had no apparent effect on either the direction or severity 

 of spiral grain, but both direction and severity of spiral grain appeared to be highly correlated 

 with stand density. Trees in open stands (with long crowns and rapid growth rate) tend to have 

 grain that spirals to the left; the opposite was true for trees in very dense stands. 



The study to determine correlation between pole twisting and spiral grain showed that 

 straight -grained poles and those with right-hand spiral twisted less than poles with left-hand 

 spiral, irrespective of amount of seasoning. Left-spiraled poles twisted most, and twist was 

 in the same direction as spirality. Dissection showed that right -spiraled poles generally 

 contained left spiral grain inside the pole that counterbalanced the tendency toward right-hand 

 twist. Left-spiraled poles contained no such counterbalancing force. 



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