Pulleys. - These are of two styles, side pulleys and overhead pulleys, the former being the style commonly used, and in fact, the only style used previous to about the year 1890.
The general shape of the common side pulley is shown in Fig. 419, although the end of the face plate is as often round as square.
These pulleys consist of a cast or wrought iron frame with a finished face plate and a cast iron wheel working on an axle. Slide pulleys are fixed in a mortise cut into the pulley stile, and the face plate is usually the only portion that is finished. Millions of very cheap iron pulleys are used every year, and unless the architect takes pains to specify the particular style and finish of pulleys he wishes used, he is quite likely to get a very inferior article. The essential points of a good pulley are that the wheel shall be of sufficient size, have a durable and smooth running axle with broad bearings and that the pulley shall have a neat appearance.
The common stock sizes of sash pulleys are 1 ¾, 2, 2¼, 2½ and 3 inches, the size referring to the diameter of the wheel. The Gardner pulleys are made up to 3½ inches, and the Norris pulleys are made in 2¾ and 4-inch sizes, but not 3½-inch. The 2-inch wheel is sufficiently large for sash not exceeding 3x3 feet with double strength glass, but for larger or heavier sashes, larger sizes should be used, principally for the purpose of throwing the sash cord further into the pocket so as to prevent the sash weight from striking the back of the pulley stile. One and three-fourth inch pulleys should not be specified except for very small windows.
Fig. 419. - Ordinary Axle Pulley.
For ordinary purposes a "steel axle" may be specified; in the better grades the axles are turned and are then called " noiseless" pulleys. For pulleys larger than 2 inches, it would be well to specify gun metal or phospho bronze pin, as these are less likely to break. There are also two or three kinds of anti-friction pulleys. The various grades of steel axle pulleys run about as follows: Plain face and wheel; lacquered or amber bronze face, plain wheel; bronze plated face (various finishes), nickel plated face, Bower-Barff face, bronze or brass face iron wheel; bronze or brass face, and bronze or brass face and wheel. A bronze or brass wheel would hardly be warranted except in very expensive work.
There are several variations in the shape of side axle pulleys, but they are mostly in the cheaper grades where special study has been made to reduce the labor of fitting them to the frame. Such pulleys are usually too cheap to specify. The principal variation from the common shape amongst good pulleys, is that of the Norris pulley, Fig. 420. In this pulley the face plate and case are cast in one piece, with a heavy beveled shoulder on the lower end which, when fitted into position, prevents the pulley from slipping down or out, so that the pulley does not depend upon screws to hold it in position.
Sash pulleys are made by a great many different firms, but only a few make a specialty of the better grades. The manufacturers of the Norris pulleys make probably the greatest variety, several of their grades being of great excellence of construction. They are made for cord, tape or chain, the chain wheels having a groove especially designed to fit the usual shape of chains.
The Gardner Sash-Balance Co., also makes a large line of sash pulleys especially adapted to their sash ribbon.