TESTS OF WESTERN YELLOW PINE CAR SILLS, ETC. 5 



COMPARISON OF RESULTS OF TESTS ON LARGE AND SMALL 



PIECES. 



The ratios of the average strength values in bending of small clear 

 pieces to the average strength values of the sills and joists from 

 which they were taken are shown in Tables 8 and 9. These tables 

 indicate that the difference in strength between large timbers and 

 small clear pieces is considerably smaller for the air-seasoned than for 

 the green material. In other words, the increase in strength as the 

 result of seasoning is less in the structural sizes than in the clear 

 sticks. This is due to the development of defects in the large timbers 

 during seasoning. 



In the tests in compression parallel to the grain, only a slight differ- 

 ence was shown between the strength values of the large pieces taken 

 from the sills and those of the small pieces taken from both the sills 

 and joists. This is largely due to the fact that all of the specimens 

 used in these tests were free from defects. 



Table 4. — Results of bending tests of small clear sticks taken from western 

 yellow pine car sills, 2-inch by 2-inch by 30-inch beams, 28-inch span. 





Number 



of 



tests. 



Rings, 

 per 

 inch. 



Moisture. 



Weight per cubic 

 foot. 



Fiber 



stress at 

 elastic 



limit per 

 square 

 inch. 



Modulus 



of 

 rupture 



per 

 square 

 inch. 



Modulus 



of 

 elasticity 





As 



tested. 



Oven 

 dry. 



per 



square 

 inch. 



Green: 



Average 



52 

 1 

 1 



48 

 1 

 1 



14.9 



31.0 



7.5 



13.6 



28.0 



7.0 



Per cent. 

 36.1 

 126.1 

 24.9 



11.5 

 13.7 

 10.2 



Pounds. 

 35.5 



56.8 

 27.7 



29.6 

 39.3 

 24.0 



Pounds. 

 25.6 

 29.4 

 21.7 



26.6 

 34.6 

 21.7 



Pounds. 

 3,156 

 4,240 

 2,120 



6,705 

 9, 615 

 3,762 



Pounds. 

 5,831 

 7,615 

 3,910 



10,661 

 14, 840 

 7,350 



Thou- 

 sands of 

 pounds. 

 1,178 



Maximum 



Minimum 



Air seasoned: 



1,680 

 775 



1,442 



Maximum 



Minimum 



1,980 

 995 



Table 5. — Results of tests in compression parallel to grain on clear specimens 

 taken from western yellow pine car sills. 



Seasoning and size of sticks. 









Weight per cubic 



Number 



of 



tests. 



Rings 

 per 

 inch. 



Moisture. 





As 

 tested. 



Oven 

 dry. 



25 



14.1 

 21.0 



8.0 



Per cent. 

 43.2 

 80.9 

 27.4 



Pounds. 

 35.9 

 45.7 

 27.4 



Pounds. 

 25.0 

 28.8 

 21.4 



23 



11.5 



22.0 

 8.0 



12.5 

 14.4 

 11.3 



29.6 

 34.4 

 24.8 



26.3 

 30.5 

 22.1 



52 



14.9 



31.0 



7.5 



39.4 

 130.4 

 24.0 



34.9 

 57.1 

 27.4 



25.3 

 29.5 

 20.3 



47 



13.5 



28.0 

 7.0 



11.4 

 15.7 

 10.0 



29.9 

 38.5 

 24.2 



26.8 

 33.3 

 21.5 



Crushing 

 strength 

 at max- 

 imum 

 load per 

 square 

 inch. 



Green, 4 inch by 4 inch by 16 inch: 



Average 



Maximum 



Minimum 



Air-seasoned, 5 inch by 5 inch by 24 inch: 



Average 



Maximum 



Minimum 



Green, 2 inch by 2 inch by 8 inch: 



Average. 



Maximum 



Minimum 



Air-seasoned, 2 inch by 2 inch by 8 inch: 



Average 



Maximum 



Minimum 



Pounds. 

 2,830 

 3,910 

 2,195 



5,758 

 7,002 

 4,460 



2,896 

 3,890 

 2,240 



6,334 



8,160 

 4,770 



