CAR CONSTRUCTION.
Car Bodies. In cities there are three general types in common use; namely, box cars, suited for winter use only; open cars, suited for summer use only; and semi-convertible cars, which can be adapted to either summer or winter use. The open and box cars are the older types. The semi-convertible car is usually provided with a center aisle, and cross seats on each side of this aisle. The windows are large, so that they can be lowered or raised in summer to make something approaching the character of an open car. The car bottom, which forms the basis for the entire car structure, is constructed with longitudinal sills either of steel or of wood combined with steel. One form of construction employs as the main supports two steel channel bars extending the full length of the car. Steel I-beams are sometimes used. Where wood is used in combination with steel for longitudinal sills, the steel is usually in the form of flat steel plates between the timbers. Most cars seat about one passenger per foot of length over all.
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.
Steel Car Framing. As a result of the demands of the officials of the New York Subway for cars of greater strength and less subject to danger from fire, much progress has been made in the last few years in the construction of cars with steel framing. Steel construction is much more expensive than that in which the framing is of wood and is considerably heavier. The advantages lie partly in the fact that it is more durable, but the great reason for the interest with which the new style of construction has been received is that the danger of collapse and consequent injury to passengers, in case of accident, is greatly diminished.
Car Weights. The total weight of a street car with a body 16 feet long over corner posts mounted on a single truck with two motors is approximately 14,000 pounds. Of this the body weighs about 4,500 pounds, the truck 4,400 pounds, and the motors and the electrical equipment the remaining 5,100 pounds. The weights of the separate parts of a certain interurban car measuring 52 feet 6 inches over the bumpers mounted on double trucks, one of which carried two motors, is body 34,065, motor truck 9,565, trail truck 6,670, electrical equipment 12,800; total 63,100.
An interurban car of about the same size as the one just mentioned but equipped with four motors gave the following weights: Body with controller and resistance grids 39,000 pounds, trucks 19,130 pounds, motors 15,420 pounds; total 73,550 pounds.
Car Painting. A great deal of attention is given to the proper painting of cars. A car painted with care and proper materials always presents an attractive appearance, while one carelessly painted is readily noticeable. New cars go through an elaborate painting process. The time required is from two to three weeks. The following scheme may be regarded as an example of a good process:
A coat of primer is given the car the first day. On the third day all irregularities are puttied up smooth. On the fourth and fifth days a heavy primer is applied, one coat on each day. A coat of filler is given on the sixth day and allowed to harden the following day. The next paint applied is termed a guide coat. This is of a color different from the preceding ones and serves as a guide for the rubbers, who on the following day go over the car with mineral wool, fine sandpaper, or pumice stone, and rub it until the guide coat is worn away. This assures an even and smooth surface. On the tenth day the car is allowed to stand. A coat of the color desired is applied, one on each of the following three days. On the fourteenth and fifteenth days the car is striped with the desired ornaments and lettered. This is usually done in aluminum or gold leaf. The car is then given three coats of varnish on alternate days, and the work is completed. The best practice brings the cars in once each year to be revarnished.
TYPICAL HIGH GRADE TRACK CONSTRUCTION.
J. G. White & Co.
ELECTRIC RAILWAYS.
PART II.