SPRING, CARRIAGE. Various methods are adopted for lessening the concussion occasioned by the rolling of a wheeled carriage over a rough road. One of the simplest means is that often adopted in light carts, of suspending the seat from the sides of the body by leather straps or lashings. Next to this is the use of straps to suspend tbe body itself, an expedient which seems to have been occasionally resorted to from a very early period. To remedy the defects of the primi tive slung carriage, it was desirable to the pillars from which the straps were sus pended somewhat elastic. This could not be' readily effected with wood, because the pillars were necessarily short, and therefore stiff. Hence arose the use of elastic steel supports, which have gradually assumed the form now well known as C-Springs. These were for merly used for almost all kinds of carriage springs ; but the great improvement of our roads has made way for the introduction, in all stage coaches, and in many private carriages,. of the more compact straight and elliptic springs.
Carriage-springs are usually formed of se. vend thin plates of steel, of various lengths, so Laid and fastened together that the spring' shall be thick in the centre, or at the end by which it is fixed, and thin, or consisting of only a single plate, at the end or ends where the greatest play is required. The steel used is of coarse quality, and has little carbon in its composition.
Coach-makers apply distinct names to a great many varieties of springs. The straight spring, if single, or acting only on one side of the point at which it is fixed, is technically named the Single-Elbow Spring. The Double-:
Elbow-Spring is a straight spring, acting on both sides of the fixed point. Elliptic Springs, which are usually but 'little curved, are used single in some carriages, between the axle and the framework. Elliptic springs are often used in pairs under the name of Nut-Cracker Springs, the two springs being hinged together at each end, so as to form a long pointed ellipsis. C.Springs, which are chiefly used in private carriages, usually consist of two-thirds of a circle, lengthened out into a tangent ; the tangent being laid horizontally; and bolted down to the framework of the carriage. - Tele= graph Springs are combinations of straight springs in sets of four. Tilbury-Springs are another combination of straight springs used for the two-wheeled carriage called a tilbury. Dennet-Springs are a combination of three straight springs, two of them placed across the axle, and attached at their fore ends to the shafts or the framing- of the body, and the third placed transversely, suspended. by shackles from their hinder extremities, and fastened to the body at its centre. To meet I the deficiencies of the springs in common use, Mr. Adams contrived one on the prin ciple of the bow, which will yield in any direction, and may be made capable of adjust ment, by means of screws, to a light or heavy load.