THE A. tf. A. COMMITTEE'S REPORT. 577
tensile test of cast iron, is of the opinion that the transverse test is the more desirable, and certainly within reach of even the smallest foundry. We further would suggest to the mechanical engineers of this country the desirability of standardizing the speed at which the various tests should be performed, and also the urgent necessity of studying the impact test in its various phases. We deem these questions outside of the province of this association, our work being the selection of methods for getting at the true value of the material we sell, without prejudice or favor.
In selecting the test bars for the purpose of specification, we have followed the cardinal principle of selecting the largest cross section for the iron consistent with a sound physical structure, and within the range and structural limits of an ordinary testing machine. The following are the sizes of bars selected for tests as a result of our investigations:
For all tensile tests a bar turned to .8 inch in diameter, corresponding to a cross section of J^ square inch. Results, therefore, multiplied by two, give the tensible strength per square inch.
For transverse test of all classes of iron for general comparison, a bar i % inches diameter, on supports 12 inches apart, pressure applied in middle, and deflection noted. Similarly for light machinery, stove plate, and novelty iron a i % -inch diameter bar; that is to say, for irons running from 2 per cent, in silicon upward, or from 1.75 per cent, silicon upward where but little scf ap is in the mixture.
For dynamo frame, cylinder, heavy machinery, and gun metal irons, similarly a 2-inch diameter bar is recommended; that is, for irons running from 1.50 toiu daily practice, in addition,