The Rectangle.
Fig. 106.
The Rectangle.—The useful element of the Willis system known by this name is of iron cast in one piece ([Fig. 106]). The rectangles are used in the attachment of beds to each other under special conditions, or they are often attached to the stools or to brackets. Indeed their uses are multifarious, [see for examples Figs. 12], [58], [62], [89], [97], [102] and many others. The faces of the rectangle are 2½" broad. The outside dimensions are 6" and 9", and the thickness of metal is ⅝". Each side of the rectangle has the usual bolt slit ⅜" clear. Rectangles of a larger size are often found useful, their weight makes them effective stands ([see Figs. 35], [43], [52], [65]).
The Toothed Wheel.—The most convenient type of toothed wheel for our present purpose is that known as the cast iron ten-pitch. In all such wheels the number of teeth is simply ten times the number of inches in the diameter. For example a wheel with 120 teeth is 12 inches in diameter. A number of ten-pitch wheels large and small must be provided. The actual assortment that will be necessary depends upon circumstances. For most purposes it will be sufficient to have the multiples of 5 from 25 upwards to 120, and then a few larger sizes such as 150, 180, 200. Duplicates of the constantly recurring numbers such as 30, 60, 120 are convenient. Arm wheels are always preferable to plate wheels in lightness and appearance as well as in price. All wheels are to be 1" thick at the boss which is faced in the latter at each side, and bored with a hole full 1" diameter, in which a key groove is cut. A pair of mitre wheels such as are used in [Fig. 80] are sometimes useful.
The
Stud Socket.
Fig. 107.
The Pulley.—We have frequent occasion to use the pulley for conveying a cord, and a somewhat varied stock is convenient Thus light brass pulleys are used in the apparatus shown in [Fig. 3], and a stout pulley in [Fig. 71]. A cast iron pulley about 10" in diameter is seen in [Figs. 32] and [34]. It is bored 1" in diameter with a key groove, and the boss is 1" thick. Some small pulley-blocks similar to those used on yachts are often very useful.