BULLETIN OF THE 



No. 77 



Contribution from the Forest Service, Henry S. Graves, Forester. 

 May 7, 1914. 



(PROFESSIONAL PAPER.) 



ROCKY MOUNTAIN MINE TIMBERS. 1 



By Norman de W. Betts, 

 Engineer in Forest Products, Forest Products Laboratory. 



STRENGTH. 



OBJECT OF THE TESTS. 



Approximately one-fourth of the timber cut in Colorado during 

 1911 was consumed by the mining industries of that State. A num- 

 ber of different species are used, and their relative strength is of con- 

 siderable importance both to miners and producers of mine timbers. 

 Native Douglas fir, the so-called "red spruce" of the Rocky Mountain 

 region, has been the wood most suitable for use in mines, but it is 

 no longer available for a very large part of the supply. The forests of 

 lodgepole pine and Engelmann spruce, containing also several minor 

 species, must furnish the bulk of the material. The Forest Service, 

 in cooperation with the University of Colorado, has tested these dif- 

 ferent timbers to determine their relative strength. 



Since the timbers are used both green and air-dried, the influence 

 of moisture on their strength is of interest, and material was tested 

 in order to bring out this relation. 



The relative value of fire-killed timber and of timber cut from 

 growing trees has been the subject of much discussion. Since con- 

 siderable dead timber is used in the mines, and a large supply is avail- 

 able, tests on this kind of material were included, with the idea of 

 determining its strength in the round form for comparison with 

 material cut green. 



MATERIAL. 



The material tested 2 consisted of round beams and of props and caps 

 representative of the market run of timber used in the coal mines. 

 The props were from 5 to 6 inches in diameter and 6 feet long; the 

 caps from 5 to 6 inches in diameter and 8 feet long; the beams nomi- 

 nally 8, 10, and 12 inches in diameter and 16 feet long. Table 1 

 gives a list of the material tested, and shows the form and number of 



i This paper is of interest to miners and producers of mine timbers and will be suitable for distribution in 

 Idaho, Montana, Wyoming, Colorado, Nevada, Arizona, and New Mexico. 



2 The material for the tests described in this report was in part donated by the Northern Coal & Coke Co. 

 of Denver and in part obtained from several national forests located in Colorado. The tests were made at 

 the timber-testing station of the Forest Service, which is conducted in cooperation with the University of 

 Colorado, at Boulder. 



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