TESTS OF EOCKY MOUNTAIN WOODS FOR TELEPHONE POLES. 7 



FIRE-KILLED LODGEPOLE PINE AND ENGELMANN SPRUCE. 



Twenty poles each of fire-killed lodgepole pine and Engelmann 

 spruce were cut near Norrie, Colo., on a north slope at an elevation 

 of about 10,000 feet. The area had been burned over by a light fire 

 about 10 years ^ previously. The poles were largely free of bark, 

 though a majority had patches here and there, showing that no serious 

 weathering of the surface had taken place. 



METHODS OF TEST. 



Figure 4 shows the method employed in testing. The poles were 

 supported about 1 foot from each end ui bearing blocks (e, e) resting 

 on rocker supports (/, d) 23 feet apart. The load was applied by a 

 universal testing machine 'through a bearing block {t) 5 feet from the 

 butt end of the pole, or 4 feet from the center line of the butt support. 

 The rocker support {d) rested on a pier (c) buUt on the floor. The 

 rocker support (/) rested at the center of the auxiliary beam (^), one 

 end of which was supported by a rail (b) and two piers (a, a). The 

 other end of the auxiliary beam {g) rested on a roller Qc) in the center 

 of the weighing platform Qh) of the machine. As the load was gradually 

 applied at t the pole deflected, and the scale at n, at the center of the 

 span, moved down with respect to a taut spring {'p) stretched be- 

 tween pins driven into the pole on the neutral axis directly over the 

 supports. The deflection of the pole at the load point was read on a 

 scale (m), which gave the movement of the machine head (0 with 

 reference to the platform Qi). 



Corresponding readings of the applied load, the deflection at the 

 load point, and the deflection at the niiddle of the span were taken 

 at convenient intervals, and plotted as shown in figure 5, until the 

 pole was broken. The settling of the pole in the bearing blocks and 

 deflection of the auxiliary beam (^) introduced slight errors in ^.e 

 deterniination of the deflection. The total error was estimated as 

 less than 3 per cent within the elastic limit, and the only calculated 

 results affected by this (which was practically constant for all the 

 poles) are the stiffness factor and elastic resilience, both of which 

 are comparable only with results from tests of the same nature. 



From each pole after test a 30-inch section ol clear wood was taken 

 and cut into 2 by 2 inch sticks. These were tested in bending, in 

 compression parallel to the grain, compression perpendicular to the 

 grain, and shearing. The method employed in making these minor 

 tests is discussed fully in Forest Service Circular 38 (revised). The 

 purpose of these tests was to deterniine the influence of defects on 

 the strength of the poles. 



The poles in each of the four lots were given consecutive numbers 

 starting with 1, in order to distinguish between the individual poles 

 of each lot. 



1 The date of the fire was obtained from local residents. 



