Fig. 61. Side Elevation and Plan of Car.
Fig. 62. Cross-Section of Car Body.
Many more difficulties are met in the construction of passenger cars for electric railways than in steam coach construction. The electric car must have low steps and platforms and turn short curves. The difficulties are largely in the floor framing of the car. The platforms at each end are usually eight to ten inches lower than the floor of the interior. As the car must frequently be designed to pass around curves of small radius, often of only thirty or forty feet, sufficient clearance must be provided for the swing of the trucks. This necessitates that the trucks of a double truck car be set far enough back towards the center of the car to clear the dropped platform timbers, shown in [Fig. 63]. In the illustration shown, [Fig. 61], the truck centers are but 21 feet 8 inches apart, while the ends overhang the truck centers 11 feet 4½ inches. It is difficult to support this overhanging weight properly. The difficulty is increased by the fact that the rear platform is often crowded with passengers having an aggregate weight of one ton or more. Trusses manifestly cannot be employed to give rigidity to the long platform. This is usually given in cars of wood construction by reinforcing the platform timbers with steel plates as shown in the figure. In order that the dropping tendency of the platform shall not bow up the body of the car between the trucks this portion must be braced rigidly. The space below the windows and above the side sill is utilized for this purpose. The side sill is moreover strengthened by having steel plates bolted to it.
Fig. 63. Reinforcing Plates.
The longitudinal members of the body framing are termed sills. These are usually of long leaf yellow pine. Various combinations of wood and steel are employed for sills, an example of which is seen in Figs. [61] and [62]. The sills are kept the proper distance apart by “bridgings” or cross sills mortised into them at intervals and by “end sills.” The whole framing is tied together by the rods running parallel to the bridging. These tie rods are often provided with turn buckles for tightening when occasion may require. The outer sills are termed side sills; those nearest the center of the car, the center sills or draft timbers; while those between are called intermediate timbers.
The remaining portion of the car is constructed much after the manner of a steam coach. The posts between the windows are mortised into the side sill at the bottom and into a top sill at their upper end. They are laterally braced by a belt rail immediately under the window opening, both the belt rail and the posts being gained out so that the rail fits flush with the posts. A wide letter board gained into the post just below the side plate adds to the bracing of the side of the car, as does also an iron truss usually one-fourth to one-half inch thick and two to three inches wide which is gained into the posts on the inside running just under the windows between the truck centers, and then descends to pass through the side sills and fasten by a bolt underneath.
The roof consists of the upper and lower decks. That portion over the platform or vestibule is termed the hood. Rigidity is given to the whole upper portion of the car by the end plates resting on the corner posts and extending between the side plates at either end of the car body proper, and by steel carlins which conform to the peculiar shape of the roof and extend between the side plates. The steel carlins are usually placed over alternate side posts. Bolted on either side of them and placed at intervals of about twelve inches between are wood carlins. The wood carlins of the lower deck extend from the side plate, to which they are fastened by screws, to the top sill, which is immediately below the windows of the upper deck. Above these windows is the top plate, supporting the carlins of the upper deck, which extend between and a few inches beyond the two top plates. Poplar sheathing three-eighths or one-half inch is nailed over carlins and on this heavy canvas usually of six or eight ounce duck is stretched tightly. Several coats of heavy paint on the canvas and a trolley board for supporting the trolley stand complete the roof. On the underside of the carlins the headlining, usually of birch or birdseye maple, is secured. This forms the interior finish of the ceiling of the car.