TRANSMISSION OP POWER BY ALTERNATING CURRENT AfA 



ver, towers are cheaper than steel poles, especially in this 

 country, where labor high. 



1 towers are a development of the windmill tower so com- 

 mon in this country. They are ordi- 



narily composed of four main 

 members braced by light cross-mem- 

 bers. They are stronger and more 

 rigid than either the wooden or the 

 steel pole. As they are made of a 

 comparatively tew standard niem- 



riveted or bolted together, the 

 labor costs are comparatively low. 

 Owing to the spread of the four 

 main members, they are able to re- 



lic high torsional stresses >\\c\\ 

 as would result from the breaking 

 of the conductors on one side. 

 Towei-s may be set in concrete 

 bases. This is necessary if the 

 ground is mar>hy. A less expen- 

 sive method is to rivet pla 

 feet on the bottom and bury the 

 lower supports directly in the 

 ground. The towers are usually 

 shipped "knocked down" and are 

 assembled on the spot by the ere.-t- 



ingerew. Figure 370 shows a trans- 

 mi ion tower of unusual height 

 which supports the power lit 



Kastern Connecticut Power 

 < 'ompany at a river crossii 



A cheaper form of transmission 

 line structure M the flexible tower. _ 132000 _ volf 



This form of tower is based on the nmiii 



,,n,,,ipl, , I,, , if the stresses in ,. 



adjacent -pan- are e<|iial. the stru<-- 



ly as a prop which support- t he line but which need 

 not resist longitudinal forces. Me\ii.le t\\. (71) are merely 



A-fra; ,mied to wilh-land the ma \IIIIMIII transverse - 



