core in the mould, the ends of the core are extended to form “core prints,” which rest in corresponding recesses in the mould. The steam and exhaust posts are formed from cores of this type, and the hollow cylindrical bore of the cylinder is formed by another large core.
All these cores are made of “loam,” composed of clay and sharp clean sand mixed together with cow-hair, which helps to bind the core, but more particularly makes it porous, so that the gases formed when pouring can escape.
Fig. 9 shows a view of the large iron foundry at the Great Western Railway locomotive works at Swindon. The moulds on the floor in the foreground on the left-hand side show single outside cylinders in various stages of the work. Two of these finished cylinders are being lifted by cranes. In the middle of the floor is a half pattern of a pair of inside cylinders, in front of which is an iron core barrel, on which the loam core for the bore of one of the cylinders is plastered, and finally “strickled,” i.e., the core barrel with the wet loam on it is rotated and the excess of loam swept off by means of a straight lath of wood until the core is of the proper diameter. After having been dried in a drying chamber, the barrel core is placed in its proper position in the mould. To hold it in position there are “core prints” formed in the mould. The pattern in the middle of the floor shows two of these “prints” on the front face.
All moulds must be rammed and “vented”
