Having now described the several parts of an ordinary carriage wheel, excepting the axletree, and box, we refer the reader for information on those points to their initial letter (also to the articles Carriage and Railway,) in this work; and proceed to the description of some modern improvements.
The purposes to which iron, whether cast or malleable, may be usefully applied, are daily becoming more numerous; its great durability, and the facility with which it may now (by the aid of our varied and powerful machinery,) be wrought to any desired form, point it out as peculiarly adapted for the wheels of carriages. Accordingly, various attempts have been made at different times to construct wheels wholly of this material, but certain difficulties have opposed their general introduction; and their use may be said to have been confined to rail-roads, until the invention of Mr. Theodore Jones, who took out a patent for an "iron suspension-wheel," about eight years ago, and a large manufactory of them has been established at Vauxhall, from whence are constantly sent out considerable numbers, attached to the carts and waggons of the metropolis, as our London readers will testify, upon recognizing their representation in the above engravings, of which Fig.1 is an elevation, and Fig.2 a perspective view of a cart or light waggon-wheel, the principle of their construction not differing according to
their application, but only in the proportions of their parts. Fig. 3 represents a nave, shown on a larger scale, with the front shield or cap removed to show the construction. It contains eight feathers or divisions, dividing it into eight compartments. Fig. 4 is a section of the nave, with the front and back shields in their places.
At a is a strong rim of cast or wrought iron, with a rib on the inside to give additional strength. Sixteen conical holes are made through the rim at equal distances; b b b are wrought iron rods, with conical heads c c c fitting into the holes of the rim, and have screws cut at their other ends. These rods, through the holes in the rims, and corresponding holes in the nave, where the screwed ends are secured by nuts, are plainly shown in the sections. The shields are then placed over the nave, and by the pressure of their flat surfaces against the sides of the nuts, they are prevented from becoming unscrewed. A hoop or iron tire is fixed on the outer circumference which is to be replaced when it becomes worn by use.
The description we have thus given is derived from the specification of the patentee; but since the enrolment of that document, the experience of the inventor, derived from great practice, has enabled him to introduce many subordinate improvements, amongst which we may mention, the making the rim, with the projecting rib underneath, of one single solid piece of wrought iron, obviating the use of any cast iron, and dispensing entirely with the necessity of any tire ring. This is a very important improvement, as it was discovered that the battering which the tire rings received against the stone pavement, had the effect of expanding them, and consequently of causing them to separate or become loose upon the iron periphery underneath; and when the latter was of cast-iron, fractures were sometimes made by the concussions of the road. Now, as there is only one ring, and that of wrought iron, the expansion that it may undergo by severe battering, has only a tendency to inorease the tension of the rods, and the stability of the whole.
It will be observed in the drawings that the wheels are not conical, nor dished as usual, but cylindrical; which, in the opinion generally of those who have been enabled to examine the subject, unprejudiced, causes them to move with les3 resistance on their peripheries, or run lighter, as the phrase is; and they will, from the same cause, prove less destructive to the road. This latter property may be considered as established, as an act of parliament empowers the trustees of the roads to reduce the tolls on the cylindrical wheels, to two thirds of the sum paid for conical wheels of similar width. The reason of these patent wheels being called suspension wheels, is that the nave may be considered as constantly suspended by the rods above it to an inflexible arch; instead of, as in the common wooden wheels, resting with its load upon the particular spoke that may happen to be underneath it; and thus it is argued the cohesive strength of the metal is made available, which is undoubtedly the most advantageous mode of employing malleable iron, (it having been proved by repeated experiments, that a rod of wrought iron, an inch in diameter, is capable of sustaining a pull of twenty-seven tons weight;) and the weight of the load upon the axles being thus suspended to the upper side of the wheel, the lower rods have to sustain but a small portion of the pressure, and are not liable to be broken by sudden concussions or jolts.
From the superior tenacity of the metal over wood, the mass of material is so considerably reduced, as to render a suspension wheel not heavier than a wooden one, which is applicable to the same kind of carriage or strain; and from the circumstance of this diminution of material they have a more elegant and light appearance, require less draught, whilst they unquestionably possess increased strength and durability.
However excellent may be the workmanship, or however firmly an ordinary wooden wheel may be put together in the first instance, the wooden felloes that form the periphery, being constantly exposed to the effects of wet and dry, are continually expanding and contracting; consequently thejoint or connexions between the ends of the spokes and the felloes, and the former, either become loose, or split the felloes; when this takes place, the several parts of the wheel yield by little and little to the strain of the load, or the effects of concussions, and the whole wheel becomes dislocated. As a remedy to this defect, Mr. Wm. Howard, the ironmaster of Rotherhithe, has recently proposed some new arrangements of a precisely opposite character to Mr. Jones's; which we proceed to describe.