Skip to main content

Full text of "Metallurgy Of Cast Iron"

See other formats

KV1I.S   OF   i.'ASTlNU    TKST   UAKS   K1.AT.                489
streng'tll could be obtained than if the bar was turned the reverse side up. I have found in experimenting" with a larg-e number of bars one-half inch square, one inch square, and one and one-eighth inches diameter, with supports twelve inches apart, that I obtained on an average 30 pounds more strength for a one-half inch square bar, 100 pounds in the one-inch bar, and 150 pounds in the one and one-eighth inch round bar. I wish these figures to be accepted only as an average of many tests of bars of the respective si/cs g'iven, and with which, as a rule, the results have been very erratic.
I have found in a one-half-inch square bar as much as 50 pounds difference in testing" the two sides and in the one-inch square and one and one-eighth inch round 1 have found a few bars which showed from ^oo to 400 pounds difference, thereby presenting' proof that casting" flat any form of size of bar admits of errors and jug'g'lery and is wholly wrong'.
I would state that in experiment ing* with testing" on the lower and upper sides of test bars, the}-should always be moulded in the same flask, poured from the same ladle and from the same gate. To prove my position on this question, I would lirst rail attention to conditions which can be found by any who arc sufficiently interested to experiment in this line. In Pig;. 109, next pag'e, is shown a side elevation of a bar resting* on pointed supports A B, 12 indies apart, the distance which the author used in his experiments. The point of load is shown at, I >, The position of the bar is the same as when east or lying" in its mould. In exam inę ing such a bar it will be found that the metal at the lower side or shell 1C E is generally denser, or of a closer gram, than that composing' the upper half of the Chapter I,XX,, par,*-*; :;y.| in r,.s.j. and attacked the usual formulae for loaded beams asound burs..........................*fi$7 "