COMPARISONS OF STRENGTH IN SPECIALTY MIXTURES.*
This chapter is a revised extract from a report of the
author's labors as a member of the Western Foundry-men's Association Testing Committee, and presents a series taken from about one hundred tests which he personally obtained, of irons such as are used for gun metal, chill rolls, car wheels, heavy machinery, light machinery, stove plates and sash weights, a list which can be seen to cover very nearly all mixtures or "grades" necessary to cast iron founding.
Each founder in casting a set of these test bars from the patterns which the author furnished made three one-half inch square, three one inch square, three one and one-eighth inch in the rough, and three one and one-eighth inch turned. . These one and one-eighth inch round bars in the rough and turned are of an area as nearly equal to one square inch as it is practical to make them. The turned bars were cast with a swell on so as to measure about one and five-eighth inches in diameter for about four inches of their length in the center. This swell was turned down until the bars measured close to the size of .their companion, one and one-eighth rough bars. The comparison between
* Read at the meeting of the Western Foundrymen's Association, at Chicago, Wednesday evening, Oct. 24, 1894.two bars two inches square and forty-eight inches long were moulded together in the same mould. One was poured with the metal as '' hot'' as could be obtained from the cupola, and the other with the same ladle cooled down to pour the metal as '' dull'' as possible and still obtain a full-run bar. Two sets of these experiments were made, but no difference was found in their contraction. The fact of there being no visible difference in the contraction of the two-inchameter and made a dry sand mould, using" a piece \