. Annual report of the Director of Forestry. Forests and forestry. 298 REPORT OF THE PHILIPPINE COMMISSION. tried and abandoned, was designed to shear a section about 4 square inches in total shearing area from the block. A determination of the percentage moisture of each block tested was made by cutting thin wafers out of the block and weighing them before and after being dried in an oil kiln. Besides obtaining geneml deter- minations of the specific gravity of a beam, separate determinations of the smaller blocks were made. Bate of loading and computatimis,—The 200,000-pound testing machine
. Annual report of the Director of Forestry. Forests and forestry. 298 REPORT OF THE PHILIPPINE COMMISSION. tried and abandoned, was designed to shear a section about 4 square inches in total shearing area from the block. A determination of the percentage moisture of each block tested was made by cutting thin wafers out of the block and weighing them before and after being dried in an oil kiln. Besides obtaining geneml deter- minations of the specific gravity of a beam, separate determinations of the smaller blocks were made. Bate of loading and computatimis,—The 200,000-pound testing machine used is designed to test beams up to inches span. Power is transmitted by belt from the main shaft to a large pulley- wheel of the testing machine. By means of a friction wheel, a friction clutch, and a shifting gear four different speeds may be obtained. The time consumed for a single test varies from two to ten minutes, according to the nature of the test. Cross bending.—In this test the deflectograph is emploj'^ed, for which great credit is due to Mr. Neely, who designed it. In its essen- tials the deflectograph is a vertical pantograph, which multiplies the deflection of the beam five times. Besides eliminating the amount of work necessary to a cross-bending test, it enables the engineer to find accurately the deflection corresponding to any given load, a profile paper-carrying cylinder being designed to move through one of its divisions for eucli 1,000 pounds of load while the deflection is traced upon it. Power is applied by the slow friction wheel and the weigh- ing arm is kept balanced until failure occurs. This test gives the stress at elastic limit denoted by ''Se," stress at rupture denoted by ^'Sr," and modulus of elasticity denoted by ''; 8 Pe X s Se —' , ^',/ where ''Pe" is the assumed elastic limit, being the load 2 b d' ' ^ corresponding to that point on the deflection curve where the curva- ture is 50 per cent greater that at
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectforests, bookyear1902
