NEW STAXDARD SPf.CIFI CATIONS FOR WOOD POLES 



523 



poles were tabulated, and as might have been anticipated, the occur- 

 rences of large knots or large groups of knots were found to increase 

 with the length of pole. This led to a division of the data into a 

 group for short poles and one for long poles of each species. Figure 2, 

 for southern pine, is a typical illustration of the curves drawn from the 

 data. It shows, first, the per cent of poles that have single knots of 

 the given diameters, (.4) for poles up to 45 feet long, and (B) for poles 

 50 feet and longer; and second, the per cent of poles having groups of 

 knots with the indicated sums of diameters in any 12 inch section, 

 separately plotted for the same two cases. The limits set by this 

 study for single knots and for groups of knots in a twelve inch section 

 are shown in Table 4. 



TABLE 4 

 Specification Limits for Knots 



Southern 

 Pine 



Chestnut 



Western 

 Red 

 Cedar 



Northern 

 White 

 Cedar 



Single Knots 



Poles 45 ft. and under * 



Poles 50 ft. and over *. 

 Croup of Knots 

 {12 in. Sections) 



Poles 45 ft. and under. . 



Poles 50 ft. and over . . . 



(Diameter — -Inches) 



3 and 4t 

 5 



10 



4 



5.5 



(Sum of Diameters — Inches) 



7 10 



9 10 



2.5 

 4.5 



9 



11 



* Except for Northern White Cedar where the length division points are 35 ft. 

 and 40 ft. 



t 3 inches for Classes 4 to 10; 4 inches for Classes 1 to 3. 



The standards referred to above which have been prepared and 

 approved under the procedure of the American Standards Association 

 are nine in number. One prescribes the ultimate fiber stresses for 

 poles of northern white cedar, western red cedar, chestnut and south- 

 ern pine, and four prescribe the dimensional classifications for each of 

 the above species according to lengths and circumferences as shown 

 in Table 2. These five are American Standards. The situation with 

 respect to checks and dead timber led to recommending the remaining 

 four specifications covering material requirements as American Tenta- 

 tive Standards. They are the first American standards for wood poles 

 and their adoption on the sound basis outlined marks an important 

 step toward simplified practice in an essential public utility com- 

 modity. 



The application of the results of the work, as is true of other well- 

 conceived standardization projects, should yield many engineering 



