Engineers and Mechanics Encyclopedia 1839: Railways: William Chapman

It is perhaps impossible entirely to prevent the sinking of certain parts of a railroad, so as to cause by such inequality of level the carriages travelling upon it occasionally to bear upon only three wheels, rendering them thereby liable to severe strains, and sometimes to breakage, as well as flying off the rails.

At page 477, we have described Mr. Stevenson's axletrees designed to remedy this evil, and we have now to notice a patent granted to William Chapman, of Newcastle-upon-Tyne, for a similar object, and dated the 14th of August, 1827.

The improvements for this purpose are performed by detaching the axles from the bottom of the waggon, and connecting them together at the same distance from each other as before, by two bars of wood or iron of that length, fixed on the turned parts near the wheels which bars have cavities at each end, opening downwards, properly fitted for the revolution of the axles, and extending below them a sufficient distance to admit of the introduction of a greasing apparatus, that will presently be described these bars may be made elastic, so as to have the effect of springs, if this be preferred.

The waggon is supported above these bars by a gudgeon or axle that passes across the middle of its bottom underneath, and rests on the middles of the two bars. This gudgeon is fastened to the side pieces of the frame-work of the waggon's bottom by staples at each end, while it is secured to the bars by sockets or joints, that admit of motion in a vertical, but preclude it in a horizontal direction; and, at the same time, vertical bolts descend from the waggon's bottom frame, below their sustaining bars, near ends, and outside them, so as to enclose and secure them better from lateral motion, in passing round curvatures in the rails, admitting them at the same time to move up and down with facility. To strengthen the lower frame of the waggon, and give more support to its extremities, upright bars are fixed directly over the central gudgeon at each of its sides, from the tops of which diagonal rods descend obliquely in opposite directions to the terminations of the side pieces of the frame.

By this arrangement of parts all resistance to the vertical motion of the wheels is removed, by the flexibility of the joints of this secondary frame beneath the waggon, so that the load will be supported equally by each of the wheels when not exceeding the usual number of four, in any inequality of the level of the rails that is not beyond all bounds; though should six or more wheels be employed with one waggon, a more complicated frame-work would be necessary to produce the same equality of support.

The greasing apparatus before mentioned, that is directed to be placed beneath the revolving parts of the axles, consists of a horizontal balance, lever-jointed at its centre of motion to the middle of one of the descending sides of the axle beds at the ends of the sustaining bars, the outward arm of which lever has a sliding weight attached to it, the shifting of which farther from or nearer to the centre, regulates the degree of pressure with which the other arm is forced up against the under part of the axle; above this latter arm a piece of metal is placed, that is excavated at its upper surface on as to fit the lower part of the axle, and has projecting parts at its ends that slide up and down in grooves at the sides of the lower part of the axle, and has projecting parts at its ends that slide up and down in grooves at the side of the lower parts of the axle bends, which retain it in its place while being pressed upwards by the means mentioned; and a double piece of woollen cloth, or other substance proper for holding grease or oil, and well saturated with either, being placed between this last mentioned piece of metal, and the lower side of the axle, the pressure caused by the weight on the opposite arm of the lever will make it closely apply to the axle, so as to keep the latter constantly well greased, independent of any minute care of the attendants.

A spring may also be used similarly to the weight mentioned, for pressing the hollow metal piece towards the axle in the latter apparatus; that which the patentee recommends for this purpose, is a flat thin lamina of steel, placed horizontally through apertures in the lower parts of the axle beds in the sustaining bars, so as to press against the bottom of the hollow metal piece with a force, that is regulated by a screw, which passes upwards against one of its ends through a hole underneath the apertures in which this latter is inserted.

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