Solutions of common salt have been used in the same manner, but it is claimed that the corroding action on the iron of the calcium chloride is not as great as that of a salt solution.
TRUCKS.
Electric railway cars are classified generally as double-truck and single-truck cars. Double-truck cars are those that have a truck that swivels at each end of the car. A single-truck car is one having four wheels.
Fig. 43. Brill 21-E Car Truck.
Single Trucks. A great many types of single trucks have been designed. It would be out of the question to discuss them all here. In general, however, it may be said that truck builders have aimed to make a truck frame in itself a complete unit independently of the car body, so that the car body will simply rest upon the trucks and there will be no strain on the car body in maintaining the alignment of the truck. Most single trucks, therefore, consist of a rectangular steel frame, either cast or forged, riveted or bolted together. This frame holds the journal boxes in rigid alignment. Usually a spring is placed between each journal box and the truck frame. This spring may be either spiral or elliptic. The principal springs, however, are between the truck frame and the car body. Most truck builders have used a combination of spiral and elliptic springs between the car body and truck frame, as this combination is considered to give better riding qualities and greater freedom from teetering or galloping than either spiral or elliptic springs alone. [Fig. 43] shows a Brill single truck, which illustrates all of the features enumerated.
Swivel Trucks. Swivel trucks, commonly called double trucks, are made in many forms, but the most common is that known as the M. C. B. type of truck. This truck is similar to the standard truck which is in universal use on steam railroad passenger cars in the United States. Different truck builders have introduced many variations in this general type of truck, in adapting it to electric service. Some modifications from the steam railroad standard truck were necessary to accommodate the electric motors and to permit in some cases a low-hung car body. Such trucks are made in a great variety of sizes.
Fig. 44. St. Louis Car Company Truck.
Fig. 44 shows one of these trucks built by the St. Louis Car Company. In this type of truck the car body is fastened to the truck only by the kingbolt on which the truck swivels. This kingbolt is placed in the center of the truck bolster. There are also side bearings between the car body and the ends of the bolster, to prevent tipping of the car body when it is unbalanced. The arrangement of this part of the truck is shown in [Fig. 45]. Under this bolster are elliptic springs which rest on what is called the spring plank. This spring plank is hung from the rectangular frame of the truck by links which allow a side motion. This side motion gives easier riding, especially upon entering and leaving curves. All trucks having this feature are known as swing bolster trucks. The weight, being transmitted to the transom and truck frame through the swinging links just referred to, is then taken by the equalizer springs that support the rectangular truck frame on equalizing bars, which equalizing bars rest on the journal box at either end and are bent down to accommodate the springs located between them and the truck frame. The truck frame holds the journal boxes in alignment by means of guides which permit an up-and-down movement without movement in any other direction, just as on all other types of truck. It is thus seen that there are two sets of springs between the car body and car journals; one set of spiral springs between the equalizing bar and truck frame; and one set of elliptic springs between the spring plank and the bolster. All shocks must be transmitted first through the spiral springs and then through the elliptic springs. The motors used on this type of truck usually have nose suspension, the nose of the motor resting either on the bolster of the truck or on the truck frame.