Further details of the bottom seat and the cap are shown in

Fig. 4, in which the unit is the same as in Fig. 3, and the proportions are as follows:

a = 1" (constant).

b = 1.65 d-.5".

c = .08 d.

d = .1 d.

The foundation, or bed casting, is shown in Fig. 5, and has

dimensions to suit the pedestal shown in Fig. 3. Its proportions are as follows:

The diameter of the crank shaft journal d = unit.

Hangers.

A hanger is used when a shaft bearing is to be suspended from the ceiling. The following figure shows a form of a hanger made by a leading manufacturing company.

The frame of the hanger is divided and the parts are connected by bolts. With such a form, the shaft may be more easily removed than when the hanger frame is a solid piece.

The units for determining the leading dimensions of a shaft hanger are the diameter d of the shaft and the drop D of the hanger.

The following proportions are suitable for shafts ranging from 14" to 4" in diameter:

Thread of plugs, .5" pitch for all sizes.

NOTE.-To find R1, draw the arc J; also, draw the arc Q tangent to P; then, draw a straight line tangent to these arcs, and R, will be the distance along the center line determined by B included between this tangent and the upper face of the hanger. Having found R1, make R equal to it.

The radius T, is made equal to the thickness at the middle. The steps of the ball and socket bearings are of cast iron and

are bored to fit the journal without using either lining, or brasses. The ball and the recesses in the ends of the plugs, into which the ball is fitted, should be faced. The screw threads on the plugs may be cast on the plugs or turned, the latter being preferable. It is customary to use two threads per inch for all sizes of plugs.

BELT PULLEYS.

The accompanying table gives the dimensions of a set of cast iron belt pulleys ranging from 6" to 72" in diameter, as made

by a well-known manufacturing company. These pulleys are so designed that the number of patterns may be kept within reasonable limits, and at the same time have the dimensions correspond as nearly as possible with well established rules.

The letters over the columns of dimensions given in the table correspond tothe letters in the figure.

In all cases the number of arms is 6, and the

arms increase in size toward the hub, the taper being " per foot. Pulleys that run at high speeds must be carefully balanced, i. e., the center of gravity of the pulley must correspond with the center of the shaft, otherwise there will be a heavy stress on the shaft and bearings. Since it is seldom possible to make the pulley exactly symmetrical, the difference in weight of the heavy side is compensated for by weights riveted to the inside of the rim. and on the light side.

It is usually considered unsafe to run a cast iron pulley, gear wheel or fly-wheel at a higher rim speed than 100 feet per second. Since the centrifugal force increases in direct proportion to the cross-section of the rim, it is evident that it is useless to try to provide against it by putting more material in the rim.