As already stated in "Pattern Making" on page 42, pulley patterns in a complete state are rarely used. Instead a ring, a pattern for the spokes, and loose hubs arc used for making all widths of face for a given diameter. The ring is of cast iron turned smooth. It has holes drilled near the edges in which lifting hooks may be placed for drawing. If one-half the face of the pulley is to be less than the total width of the ring the latter is first set on the moulding board as for ordinary patterns.

Moulding Pulleys 100441

Fig. 69.

This is illustrated in Fig. 69 where the dotted line a b represents the face of the moulding board. The amount by which the total width of the pattern exceeds the half width of the pulley face is represented by the distance between the dotted line a b and the full line A It. The line A B will be the parting line between cope and drag. The drag is raised from the moulding board by a frame or wedges of this width. Ram some sand in the bottom and lay in the pattern for the spokes. This pattern is usually solid. It must be imbedded in the sand on the moulding board so that its center is exactly in line with the parting line A B. The hub with the core print is then put on and the sand of the drag rammed as in the case of any ordinary pattern. When the drag is turned the sand is cut away to the parting line. The surface of the parting line is then sleeked off. This leaves the ring projecting above the surface of the parting line by the distance c h as shown by the hatched section of the pattern at the left of Fig. 69. The lifting hooks are then inserted in the ring and it is drawn out of the sand of the drag until it occupies the position ef as shown by the hatched section on the right of Fig. 69. The friction of the sand is depended upon to hold up the ring. If the depth f g is insufficient to do this, the ring is not drawn to the full height at first. After raising the ring the cope is put in position and rammed as usual. Great care must be taken that the rammer does not strike the ring. Before ramming, the top section of the hub is put on.

If the ring is not drawn to its full height at e for the first ramming of the cope, the sand of the latter is rammed about it, and the pattern raised again. The ring is sometimes moved four or five times before the full width of the face is made. After ramming in this way, the cope is lifted off and the ring usually comes with it in the sand. The cope is turned for finishing and the ring withdrawn. The hub and spoke patterns are removed in the ordinary manner. The mould is usually filled from the hub.

In case the width of the ring is less than half the width of the pulley face, the ring is drawn up in the ramming of the drag in the same manner as already described for the cope. When the drag is turned, it is drawn in the opposite direction as stated.

When the width of the ring is greater than the total width of the pulley face there is more difficulty. The mode of procedure for the ramming of the drag is the same as in the first instance. In ramming the cope, it is placed on and rammed nearly to the top of the ring. The sand is then cut away to such a level that the ring is just embedded in cope and drag by the width of the pulley face. The ring is then drawn out of the sand. The annular hole thus left in the sand of the cope is covered by a series of flat dry sand cores. When these are set the ramming of the cope is continued. After this has been done the cope is lifted and the spoke and hub patterns removed.

Spur gears with different lengths of teeth may be moulded in this same way from but one pattern by a partial withdrawal of the pattern and successive ramming.