TIMBER PHYSICS. 



OO 1 



remarkable since the important influence of moisture was recognized and emphasized by both 

 French and German experimenters more than forty years ago. 1 



These facts were fully appreciated by the engineers of our country, as is well shown by the 

 numerous, often emphatic, approvals and recommendations of the timber-physics work undertaken 

 by the Division of Forestry, and by the eagerness with which wood consumers generally seized on 

 all information of this kind as fast as the Division of Forestry could supply the same. 



Southern and ^Torthern Oak. 



Though fully planned before, the work in timber physics was really begun in order to decide 

 an important controversy as to the relative value of Southern and Northern grown oak. 



A representative committee of the Carriage Builders' Association had publicly declared that 

 this important industry could not depend upon the supplies of Southern timber, as the oak grown in 

 the South lacked the necessary qualities demanded in carriage construction. Without experiment 

 this statement could be little better than a guess, 2 and was doubly unwarranted, since it condemned 

 an enormous amount of material, and one produced under a great variety of conditions and by at 

 least a dozen different species of trees, involving, therefore, a complexity of problems difficult 

 enough for the careful investigator, and entirely beyond the few T unsystematic observations of the 

 members of a committee on a flying trip through one of the greatest timber regions of the world. 



A number of samples were at once collected (part of them supplied by the carriage builders 1 

 committee) and the fallacy of the broad statement mentioned was fully demonstrated by a short 

 series of tests and a more extensive study into structure and weight of these materials. From 

 these tests it appears that pieces of white oak from Arkansas excelled well-selected pieces from 

 Connecticut both in stiffness and endwise compression (the two most important forms of resistance). 



Besulta of tests on Northern and Southern white oak made in Washington University Laboratory, St. Louis, Mo., by Prof. 



J. B. Johnson, 1880. 



Test pn ee. 



Bending and cross breaking Size of test piece 1| by 



lg by 24. 



Compression. 



Stillness. 



Ultimate 

 strength. 



Resistance to 

 shock. 



Endwise 



Transverse 



Shearing. 



Longitudinal 



8 Modulus 

 ol elas- 



t> tie lty j t> 



Wheie pio< urorf | ¥o. l% "§f e pounds I ^ f e 



Avei ago 



A voi age 



per 

 square 



9 | 990,000 

 5 1,280,000 



Modulus 

 3. W. L, 



2. b 1H 

 pounds 



per 



square 



inch. 



Itange 

 No 



3 1 1J5 000 



6 ' 1,120,000 

 10 920, 000 



13, 7G0 

 18, 50 J 



16, 130 



12 300 

 12,700 



4 | 1,020 000 



12, 500 



Modulus 

 inch- 



Modulus 



pounds 



per 



pounds xt," square 



per cubic 

 inch 



inch. 



Siyelff by! 



5 melieh. i 



Modulus Modulus 



Kange P°"" <ls . Itange l»°"J» lU 

 >J„ te Pe* xr,* P^I 



No 



59 

 92 



6,160 

 5,480 



pei 



square 



inch. 



3, 400 

 3,100 



No 



70 



47 

 55 



11 



>, 820 



3, 250 



4,740 

 4, 980 



2, 500 



2 800 



51 



Aveiaise .. 



11 850, 000 



7 1, 140, 000 



5 995, 000 



11, 400 

 12, 300 



11,850 



83 

 45 



b 

 10 



4, 860 



2,650 



5, 2 JO 



4, 820 



,025 



2 700 

 2,500 



2,600 



1 Foi a more complete history see Bulletin 6 of Division of Forestry. 



2 See Report of the Division of Forestry, 1890, page 209 



[W. = total load at center m pounds 

 W L * Avhere L -~~ le:i:1 gth "* inches, 

 syomi^, s modulus of elasticity. K=r fprni's < D. = deflection in inches 



* u, o, n. i ^ —.foreadth ln niches. 



h — height m inches. 



pe 



squai < 



inch 



1, 375 



1, 560 



1,46b 



1 09K 



1 225 



4 1, 175 



2 J, 510 



1, 458 



B. 







3 1 



8 1 



4 1 



"1,870,000 



1, 100, 000 

 1, 385, 000 



Ji/e 1| by Ig by 18 



inches. 







6,800 , 

 7,800 1 

 6,800 



Size. 1 



11 

 2 

 9 



g cube 











8 

 9 



6 



2 



11 



12, 380 

 14, 690 

 11, 240 



9 

 3 



11 



27 

 82 

 19 



4 

 1 

 5 



2,000 

 3, 200 

 2,300 



10 

 5 



800 



1,260 



825 





Z j 



1, 351, 667 



2 



12, 770 



4 



43 



2 



7, 133 | 



4 



2, 500 



5 



9b2 





Average 



10 

 11 







1 

 2 



1, 653, 000 

 1, 581, 000 



4 

 10 



13, 030 



11, 590 



8 

 10 



30 

 22 



3 

 2 



6,900 



7, 700 | 



7,300 



6 



10 



2, 600 

 2, 100 



8 

 9 



1,050 

 940 





1 



1,617,000 



4 



12, 310 



5 



26 



1 



5 



2,350 



4 



995 















