Owing to the effects of expansion and contraction, and the violent shocks and strains to which the fastenings of a railway are subjected, the task of perfecting these parts of the mechanism has until recently been found one of difficult accomplishment. With the view of remedying the defects then existing, Mr. Robert Stephenson obtained letters patent in 1833 for certain modes of providing "firm and secure bearings at the bottoms of the notches in the chairs for the rails to rest upon, these bearings being capable of self-adjustment, in order that they may adapt themselves correctly to the under parts of the rails; and the making of adequate provisions for fastening the iron rails securely downwards, upon such self-adjusting bearings, as well as for confining the rails laterally within the notches in the chairs, but in such manner that the self-adjusting bearings will not be subject to be deranged, nor the fastenings to be loosened, by the effect of any such slight tilting or inclination of the chairs in the direction of the length of the rails, as may result from the partial or unequal subsidence of the ground beneath the stone blocks or wood sleepers upon which the chairs are fastened, nor by the effects of any such slight elongations or contractions in the length of the rails as they are usually liable to from ordinary changes of temperature."
Mr. Stephenson's mode of effecting this, is by the application of a self-adjusting segmental bearing piece, into a suitably formed concavity made below the level of the bottom of the notch of each chair; the flat or chord side of the segmental piece being uppermost, and forming the bearing surface at the bottom of the notch in the chair. Upon that flat bearing surface, the under side of the rail is to rest, so that the bearing surface will always accommodate itself to the under side of the rail, and form an even contact therewith; in consequence of the circular side of the segmental piece adapting itself to the required position, by turning in its concave cell. Having thus explained the general arrangement of the parts, it will not be requisite to enter into the minutiae introduced into the specification, as sufficient knowledge will be obtained by the insertion of the following illustrated figures, and description of them: bottom or base of the chair, which is to be bedded upon the block or sleeper, and fastened thereto by spikes driven through the holes a a. - B B are the cheeks of the notch in the chair, that notch being the parallel space which is left between the cheeks for the reception of the rails C c D d, which may join together with a half lap joint, as shown in perspective at Fig. 1, and in the plan Fig, 4, the overlapping parts c d being of the same size, or nearly of the same size, as the other parts of the rails, and those parts are included within the
Fig. 1 is a perspective view, and Fig. 2 a lateral elevation; Fig. 3 a transverse section, and Fig. 4 a horizontal plan of a chair, for supporting and uniting the extremities of the lengths of iron rails for edge-railways. A A is the flat
notch of the chair. The bottom of this notch is deeper than is necessary for receiving the rails, and is depressed into a concavity of a suitable form, for receiving the segmental bearing-piece which is shown on the next page, at 4 4 4, in plan, elevation, and perspective: the under edges of the rails rest upon the uppermost flat surface of this bearing-piece. The small figures 5 and 6 are cylindrical pins, which are fitted into cylindrical sockets, through each of the cheeks or sides BB; and 8 and 9 are tapering or wedge-like keys, which are inserted through suitable mortices in the cheeks and across the pins 5 and 6, for the purpose of forcing forward those pins, so that their pointed extremities may press obliquely upon the lower parts of the grooved recesses in the rails, with a bearing-down action, to confine the rails downwards upon the bearing-piece, and laterally in the chair. The cylindrical pins are shown detached, in order to explain the manner in which the pointed extremity applies into the grooved recess in the rails, so as to exert a bearing-down action thereon.
Fig. 5 represents perspective views, and Fig. 6 a transverse section of a chair for supporting the iron rails at intermediate distances between the extremities or junctions of their several lengths; it has only one cylindrical pin 5, fitted through one of its cheeks B, the opposite cheek K being aflat vertical surface, against which the flat side of the rail is pressed and held firm, by the keying up of the cylindrical pin 5, so as to confine the rail laterally at the same time that the oblique action of the point of the cylindrical pin 5, in the grooved recess of the rail, may produce a bearing-down action, which confines the rail down upon the segmental bearing-piece. The chairs are made of cast iron; the sockets for the cylindrical pins, the mortices for the wedge-like keys, and the cells for the segmental bearing-pieces, being formed in the casting, as well as the holes for the holding-down spikes; the wedge-like cross keys, the cylindrical pins, and the segmental bearing-pieces, are made of wrought iron.