42 



BELL SYSTEM TECHNICAL JOURNAL 



Fig. 9 — Crossarm section between pinholes. 



The significance of ;- and a in these formulae, and of the other symbols used 

 in the computations that follow will be clear from a glance at Fig. 9. 



1/2 b 



D = 4.09375" 



b = 3.1875" 

 ^b = 1.59375" 

 r = 4" 



r- = 16.000000 

 (1/2 by- = 2.540039 

 p- = 13.459961 

 p = 3.668782" 

 d 

 A 



Sin a = 



= 0.39843750 



a = 23° 28' 49.93" 

 a = 0.40981266 radians 

 2 a = 46° 57' 39.86" 

 Sin^ a = 0.063252925 

 Sin 2 a = 0.73089017 

 Cos a = 0.91719548 

 Sin a Cos a = 0.36544507 • 

 = /)+(/)-;-) = 3.7625" 

 = 0.7099 sq. ins. [Area of T by Formula (2)] 

 = 3.8018" [By Formula (3)] 

 = .V - /> = 0.1330" 



I BB= 10.2654 [By Formula (1)] 

 Ax- = 10.2601 



IT = 0.0053 

 (Note: WTiile the results of this and the following computations are shown 

 to four decimal places, the actual work was done by machine and carried 

 to eight decimal places as mentioned in the text.) 



Since the width of the section in this computation and the radius of its 

 roof is the same as for the minimum 33^" x 4" section at the end of the arm, 

 the top segments of the two are identical, and the only value that will differ 



