where M = bending moment in foot-pounds, W = greatest load in pounds on one point of bearing on drum, and l = distance in feet between points of bearing.

The drum is to be designed according to the specifications for ordinary plate girders. The web thereof shall have stiffeners on both sides at all points of concentration. These stiffeners must have perfect contact with the top and bottom flanges. The section required for these stiffeners is to be determined by considering the entire concentration on one point of bearing to be carried by the said stiffeners, which act as a column, fixed at both ends, with an unsupported length equal to the depth of drum. Stiffeners, each consisting of two angles, placed on opposite sides of the web must be used at intermediate points at distances not exceeding either the depth of web or three (3) feet six (6) inches.

Brackets to support the pinions gearing into the rack are to be provided on the drum. They shall be built of rolled-steel sections, and made amply strong in all directions and in every particular so as to resist the greatest thrust, wrenching, or torsion that can possibly come from the shaft. In no case are these brackets to be made of castings. The use of turned bolts for attaching the brackets to the drum will not be permitted where it is possible to drive rivets, as such bolts do not afford sufficient rigidity to prevent the connections from working loose sooner or later. The splices in the web and flanges of drum must be such as to develop the full strength of same; and the abutting ends of web and flanges must be planed smooth, and have continuous contact.

The drum must be made perfectly round, so that the centre line of web at any height will conform to the circumference of a circle; and, to preserve this form and brace the drum thoroughly, rigid radial struts are to be run from the centre casting to the drum, taking hold of the latter at each point of concentrated loading, and at intermediate points when the bearings are spaced more than eight (8) feet between centres. These radial struts must be made of four angles with solid webs  or  angle  lacing.  At  the  centre  they  are  to  be  riveted  to  circular  plates  fitting  closely  around  the  centre  casting,  thus