When cast-iron wheels are worn to an improper shape or have flat spots upon them, due to the sliding of the wheels with the brakes set, an emery wheel grinder must be used to grind them down, as nothing else is hard enough to have any effect on the iron.
Fig. 48. Standard M. C. B. Flange.
When steel-tired wheels are worn, they can be put in a lathe and the surface of the tire turned off, as this surface is of metal soft enough to be workable with ordinary tools.
Fig. 49. Brake Shoes and Levers.
The types of wheel tread and wheel flange in use vary greatly among different electric railways. There is a standard Master Car Builders’ wheel tread used on steam railroads, which is shown in [Fig. 48]. Electric railways, however, are usually obliged to use a smaller flange and narrower tread. Street railway special work, such as switches and crossings, usually has too shallow a flange way to permit a standard M. C. B. flange to pass through. Some street railways use flanges as shallow as ⅜-inch, although ¾-inch is most common on city work. The width of the tread on street railway cars, that is, the width of the wheel where it bears on the rail, is usually from 1¾ inches to 2¼ inches. There is a tendency, however, on electric railways, on account of the increasing number of interurban cars which must use city tracks, to build tracks that will accommodate wheels approaching the M. C. B. standard of steam roads. A few roads have adopted wheel treads and flanges very near to the M. C. B. standard.
AUTOMATIC AIR BRAKE CAB EQUIPMENT.
Westinghouse Air Brake Co.
Brake Rigging. The brake rigging on a single-truck car may be arranged in a variety of ways, but should be such that a nearly equal pressure will be brought to bear on the brake shoes on all four wheels. A typical arrangement of brake shoes and levers for single-truck cars is shown in [Fig. 49]. The rods R terminate in chains winding around the brake staff upon which the motorman’s handle or hand wheel is mounted.