UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 497 



Contribution from the Forest Service 



HENRY S. GRAVES, Forester. 



In cooperation with the University of Washington. 



sZ&^j-u 



Washington, D. C. 



PROFESSIONAL PAPER 



April 4, 1917 



TESTS OF WESTERN YELLOW PINE CAR SILLS, 

 JOISTS, AND SMALL CLEAR PIECES. 



By C. W. Zimmerman, Engineer in Forest Products. 



CONTENTS. 



Page. 



Introduction 1 



Material tested 2 



Methods of test 3 



Strength values shown by the tests 4 



Comparison of results of tests on large and 



small pieces 5 



' Relation between strength values 



Relation between physical characteristics and 



mechanical properties 



Seasoning 



Effect of seasoning upon strength 



Conclusions 



INTRODUCTION. 



Western yellow pine, Pinus ponderosa, is distributed over the 

 greater part of the western United States, but reaches it best devel- 

 opment in California. A variety of the species, known as scopulorym, 

 occurs in the Rocky Mountains. It is a smaller tree but has the 

 same botanical structure. Western yellow pine is long lived, attain- 

 ing an age of from 350 to 500 years. The wood is camparatively 

 weak, light, soft, and fine-grained. The heartwood is reddish-yellow, 

 and the sapwood almost white. In some regions the wood is quite 

 resinous; in others it is so free from resin that it is marketed as 

 I white pine." 



The tests described in the following pages were made for the pur- 

 pose of gaining a definite knowledge of the mechanical properties of 

 the wood. They began early in 1912, at the Seattle laboratory of 

 the Forest Service, U. S. Department of Agriculture, and have been 

 carried on in cooperation with the University of Washington. The 

 Western Pine Manufacturers' Association contributed the test mate- 

 rial. The tests were similar to those made by the Forest Service on 

 Douglas fir, western hemlock, western larch, and various other species, 

 so that a direct comparison-of mechanical properties can be made. 



67075°— Bull. 497—17 



