522
iMETALLUROY OF CAST IRON.
by standing" patterns on their end to ram them up on the plan illustrated on page 527. In gating and pouring such bars the metal is best dropped from the top through a cope, and not allow it to strike the sides of the mould, and when two or more bars are moulded in one flask, their top pouring "gates" should be all con- y
nected to one pouring basin, made deep enough so as to keep the "gates" full of metal when the FIG' I25'
bars are being poured. By careful work, plain bars can N N ke cast on end by this plan that
r
FIG. 126.
will prove sound when broken. Plans for single bars are described, page 509, and plans for two or more plain bars being cast together are seen in Fig. 129, page 527.
Let it ever be remembered that, at the best, a test bar can only be used to make relative comparisons in the physical -qualities of mixtures, and to properly secure these a size and form of a bar must be used that is not sensitively affected by the dampness of a green sand mould, and degrees in fluidity of metal. This demands that a bar be of round form, not less than one and one-eighth inches in diameter, and that such is best cast on end, as is displayed by reading Chapters LVL, LIX. and LXV.
A
FIG. 127.hes wide and the holes in the end of the flask at II, Figs. 123 and 124, made one and fifteen-sixteenths inch diameter, also the one and one-eighth inch or one and five-eighths inch test bar patterns to have a swell of one and fifteen-sixteenths inehcs diameter at the point where it would rest, or fill the hole II when the bars are being moulded.