412 METALLURGY OF CAST JRON.
above described and seen in Fig. 85. This done, the first sand mould is removed from its ladle shank and another set in to replace it. This in turn is also filled with metal, and instead of pouring this into a chill it is poured into the stationary sand mould, after which it is then removed and placed with its mate. We now have two moulds, one a chill and the other a sand mould, that will have a sunken space at the neck K, Fig. 84. To learn the amount of shrinkage that has taken place, the shrunken and unfilled spaces at the necks of the chill and the dry sand castings are now filled with molten metal and separated from the main casting, views of which pieces are seen at E and H, Fig. 84. The straight portion at H is that created by the shrinkage, which takes place as the metal is being poured, and the portion at E, which is irregular in outline, is that created by the shrinkage of the molten metal in cooling to a solid, to leave a cavity in the main body of the roll as seen at the right of Fig. 63, page 338, after the moulds have been poured and are released by splitting the end of the roll at K. The piece at E is the other end up from that shown before being removed from the roll K. A little study of the sections E and H will show that their total weight (by fine apothecary scales), minus any thin wafer sheets of iron that might be found sticking to the walls of the dry sand mould, that had not run out as metal to test the shrinkage, would be the shrinkage of that iron under the conditions in which it had been poured.
By referring to Table 86, page 411, it will be seen that we have, in castings measuring about two and a quarter inches diameter by seven inches long (the actual form and size being seen at M, Fig. 84), weigh-ss.of ^