244 EXPERIMENT STATION RECORD. 



The use of wooden poles for overhead power transmission, C. Wade (Jour. 

 Inst. Elect. Engin. [London}, 39 (1901), Ao. ISo, pi). SOJ,-Sr)S, pis. 3, figs. 22).— 

 lu this paper, read before the Institution of Electrical Engineers in May, 1907, 

 an account, together with the discussion which followed, is given of experinients 

 dealing with the strengtli, breaking load, wind pressure, deflection, etc., on singh; 

 poles and double A-shaped poles. The tests were conducted by the author 

 assisted by Professor Goodman of Leeds University. The methods of i)roceilure 

 are described and illustrated and the tabulated results, together witli the 

 method of reducing them, are given in an appendix by Professor Goodman. Tlie 

 discussion which followed is also reported. 



In general the results showed the superiority of an A-shaped pole over a 

 single pole for high-tension work, both as regards economy and strength, the 

 "A" pole being shown to be at least four and one-half times as strong as a 

 single pole. 



The usual breaking point of a single pole when tested to destruction was 

 about 5 ft. above ground level or about 10 ft. from the butt. Hence, the diame- 

 ter of the pole at this point is the most important dimension to consider in esti- 

 mating for certain loads. The weakest point of an "A" pole is at the top, 

 where the stress due to windage and weight takes place. The member of the 

 pole which is under tension tends to elongate and force itself away from the 

 member in compression. 



Tests made of ditferent methods of constructing "A" poles are also described. 

 In "A" poles spread to different widths at the bottom, the spread which gives 

 strength combined with cheapness of erection was found to be about 4 ft. on a 

 32 ft. pole or a taper of about one-eighth. 



One advantage of wooden poles in general, as shown by the test, is their great 

 flexibility and recuperative power after severe deflections from the perpendicu- 

 lar caused by abnormal stresses. Some single poles which were projected free 

 for a length of 35 ft. were deflected under pressure from 13 to 15 ft. before 

 breaking, and when released showed a very small permanent set. 



Judging from the data secured in these experiments, it is believed that the 

 factor of safety usually required in high-tension work can be greatly reduced. 



Treating' wood that is refractory to treatment and also subject to decay, 

 D. Allkrton i Engin. Xcivs, 59 (190S), Xo. 8, p. 1S2). — An abstract of a paper 

 read at the amiual meeting of the United States Wood Preservers" Association 

 at Kansas City in January, 1908, and dealing with creosoting experiments with 

 Douglas fir recently conducted for the purpose of deriving a method to secure 

 the maximum penetration of creosote with a specified amount of preservative 

 to the cubic foot. • 



Three methods were tried in preparing the timber for injection, viz, steam- 

 ing the timber with dry steam and afterwards applying a vacuum, repeating 

 this method at short intervals, and boiling the timber in creosote. In each case 

 with green timber the excess of water was removed with difficulty, the fiber 

 was injured, and not over 7 lbs. of creosote could be injected to the cubic foot, 

 whereas 10 lbs. per cubic foot is the specified amount for piling. The fiber was 

 also injured when seasoned timber was treated and the same difficulty experi- 

 enced in injecting the oil. 



A method was finally adopted in which seasoned fir is placed in a sealed retort 

 and steam turned into the coil, the creosote being introduced at a temperature 

 of 170° F. A temperature of 175 to 180° is maintained about an hour, when 

 pressure is started gradually in order to allow the injected oil to fill the ex- 

 panding and heated cells. P>y gradually increasing the pressure this oil is 

 forced still farther in by the increased pressure of the oil behind. When piling 



