The main core box for the cylinder is made in the same way as has been already described for Fig. 227.
The steam-chest core box is shown in Fig. 249, in which P is a side view, one side of the box being removed to show the valve seat v, and the core prints x, z, and y, which form recesses in the core into which the upper ends of the two steam-inlet cores and the central exhaust-passage core are placed. Q is an end view of the box with one end removed, and R is a view looking into the box from above.
For the core forming the exhaust passage, two half-core boxes, one right and one left will be necessary. One-half of this box is illustrated at S, Fig. 260, as also a sectional view at T. The dotted lines show the manner in which the passage is widened to retain the full size of the opening throughout.
Fig. 250. Exhaust Port Con Box.
Only one core box will be needed for the two steam ports. Three views of the box are given in Fig. 251. At G one aide is removed, giving a side view of the construction of the box. 17 shows a cross-section through G with the end u removed, and F is a view from above. The core is swept off on the upper side for the length of cc, and the bar ee as well as the end u must he movable so that the core can be taken from the box. Both ends of the core change from circular into straight parts just at the entering of the cylinder and at the entering of the steam chest.
The entire set of patterns is simple and easy of construction if carefully made drawings are furnished to work from; the time and labor required depending entirely upon the size of the cylinder. Separated Steam Chest. In some slide-valve cylinders, the steam chest is cast separate and bolted to the cylinder, thus affording free access to the valve seat v and a better opportunity for finishing and fitting. In this case, the main cylinder core and the two steam-inlet cores are made together in the same box, as illustrated in Fig. 252, in which one side of the core box is cut away to a depth of one-half of the length of the steam-port openings, or to the line cc, which must be just one-half of the inside width of the box, as shown at H and at F, Fig. 251. The part which has been cut away is replaced by the three blocks a, a, and b, which are shaped to give the required size and form to the steam-port cores. These blocks are fastened by dowels, loosely, to the main part of the core box, and, after the core has been rammed up, the whole box and core is turned over on its face and the main part of the box is lifted off, after which the two loose blocks a and a can be drawn away endwise and the block b can also be lifted out with ease.