2 BULLETIN 497, TJ. S. DEPARTMENT OF AGRICULTURE. 



MATERIAL TESTED. 



The logs from which the test material was taken were cut near 

 Springdale, Stevens County, Wash., during September, 1911, and 

 sawed into car sills and joists at a mill at Spokane, Wash., during the 

 same month. Representatives of the Forest Service selected the sills 

 and joists; and, upon the arrival of the selected timbers at the Seattle 

 laboratory, an inspector of the Pacific Coast Lumber Manufacturers' 

 Association graded the sills in accordance with the association's ex- 

 port rules for 1911. 



The material tested was of two classes : 



(1) Car sills and joists representative of the various commercial 

 grades found on the market. The car sills were 5 by 8 inches by 16 

 feet; and the joists, 2 by 10 inches by 16 feet. 



(2) Small, clear pieces cut from the uninjured portions of the 

 tested beams. Tests on these were made to determine the relative 

 strength of wood free from knots and other natural defects, as com- 

 pared to that of the various grades of market material. 



METHODS OF TEST. 1 



BENDING. 



Two methods of applying the load were used in these tests : " Third- 

 point" loading was used for testing the large beams and center- 

 loading for the small, clear sticks. In the " third-point " method the 

 load is applied at two points, each one-third the length of the span 

 from the end supports. This method of loading represents as nearly 

 as practicable the conditions to which the beam will be subjected .in 

 structural use. Plate I shows the method of loading and of pre- 

 venting buckling in the joist tests. 



COMPRESSION PARALLEL TO THE GRAIN. 



In the tests in compression parallel to the grain the load was ap- 

 plied to the upright specimens. The specimens Avere of two sizes, 

 5 by 5 by 24 inch sticks taken from the car sills and 2 by 2 by 8 inch 

 sticks taken from both car sills and joists. 



COMPRESSION AT RIGHT ANGLES TO THE GRAIN. 



The tests in compression at right angles to the grain consisted in 

 applying the load to an iron plate 4 inches in width and extending 

 across the upper side of 5 by 8 by 20 inch specimens lying horizontal 

 on the platform of the machine. 



MOISTURE DETERMINATIONS. 



From each test piece a moisture disk 1 inch in thickness was cut 

 and dried to a constant weight at 100° C. The moisture disks taken 



1 The methods of making the various tests on western yellow pine and the. definitions of 

 the different strength factors referred to are fully discussed in. Forest Service Circular 38, 

 «' Instructions to Engineers in Timber Tests." 



