The Modern Bicycle and Its Accessories

by Alex Schwalbach; Julius Wilcox

CONSTRUCTION AND STRAINS OF HUB AND SPOKES.

The pressure applied on the pedals of the bicycle causes a transverse strain on direct spokes which sometimes causes them to snap at the rim or hub; but spokes which are set at a tangent to the hub receives this strain directly, and in the tangent-spoke wheel, where the spoke is bent or hooked in order to pass through the side of the hub, it is necessary that the very best material and workmanship be used to prevent it from breaking at this point. The tangent-spoked wheel being almost absolutely rigid, is the best hill-climber, for there is no waste of power as in the direct-spoke wheel, the transverse strain on the spokes of which causes a certain amount of “give.” On the first safety bicycles built in this country 30 and 32 inch wheels were used. Afterward we settled down to the use of 28-inch wheels as a standard. There is now, however, a slight tendency to reversion toward using 30-inch wheels. The makers of the [Cleveland wheel] have announced that they will market a bicycle having 30-inch wheels. Probably the only reason for this step lies in the dropped crank-hanger fad; so that, by using larger wheels, they can still maintain the upper tube horizontal, and get the required drop of from three to four inches. Viewed in another aspect, however, it will be found a source of annoyance and expense to the makers and riders as necessitating an extra stock of spokes, rims and tires to fit the same, and where they are not to be had promptly delays will be sure to occur in repairing. The ruling size of wheel is not arbitrary, but has been arrived at as the best net adjustment of all the conditions, and any change to what has been thoroughly tested and abandoned is to be strongly disapproved, unless (which is not the case in this) substantial reasons can be shown.

COLUMBIA HUB.

Few people realize the torsional strain exerted on the rear hub when full power is applied to the pedals in climbing a steep hill where the momentum is not sufficient to carry the rider far and where the pull is more or less continuous on successive groups of spokes as the wheel revolves. In addition to this pull on the spokes is to be considered the weight of the rider, the greater proportion of which is sustained by the upper half of the rim and the corresponding spokes and not by the portion of the wheel nearest the ground as just explained. It will be understood that each group will be subjected for an infinitesimal space of time to a maximum pull as the chain passes over the sprockets, the strain being accentuated at each downward stroke of the pedals, so that a single spoke when at a very high tension as compared with its neighbor frequently snaps when directly in line with the chain at the proper instant of time. Originally all hubs were made of what is known as gun metal, the flanges of the hubs were very thick and tapered toward the centre of the hub. They were made in this manner to provide sufficient room for tapping and threading the hub flanges so that the direct spokes which were in use at that time could be directly threaded into the hub.

KEATING HUB.

The 1898 tubular and barrel hubs are, of course, the result of many processes. Some of them are turned whole from bar steel; others are stamped out of sheet metal; some of them are formed out of tubing, and a few of the cheaper makers use malleable iron or cast steel for this purpose. All of the spokes used are made of either a special drawn steel wire or a piano wire. They all possess great torsional or twisting strength, and the tensile strength or stretch is from 500 to 800 pounds. They average in gauge of thickness from 13 gauge, which is expressed by the figures .095, to 15 gauge, which is expressed by the figures .072. Front wheels have from twenty-four to thirty-six spokes and rear wheels from 28 to 40 spokes, and while it is true that all the makers now use a tangent spoke there are a great many variations in its use. The majority of them tie their spokes to each other where they cross. There are a great many of the makers who do not tie them at all, there being some difference of opinion as to the benefit to be derived from this treatment.

Those in favor of tying spokes say that tying two or more spokes together at the crossing some distance above the hub shortens the leverage from the rim and practically gives the wheel an additional hub; that they are also stiffer against side or lateral strain, and that the only good tangent spoke is one that is tied at the crossing with its mates. Those who are opposed to tying spokes say that tying them together makes them too rigid and inflexible, and that the process of wiring them and soldering them together has a tendency to crystallize the spokes at this point owing to the heat required to solder them. This part of the argument, however, has been met by not wiring and soldering the spokes at the crossing, but by pinching on them at this point a metal clamp such as is used on the Humber wheel. The opponents of tying the spokes assert that the very stiffness and rigidness which the wheel possesses when the spokes are tied has a tendency to also crystallize them at the hub flanges as well as cause them to break. It may, however, be here stated that the pneumatic tire acts as a buffer, and that the use of heavier rims and more spokes, which are prominent characteristic features of 1898 wheel construction, insures the whole wheel a greater factor of safety than heretofore known in construction, and therefore less liability to get out of true.

STERLING HUB.

The Raleigh cycle, an English production, and which came into prominence in this country because it was Arthur Zimmerman’s great mount, had wheels in which two-thirds of the spokes were direct from hub to rim, and the remaining third were crossed at a tangent. It was, however, a sort of a compromise between the direct and tangent spokes, and ultimately led the makers to use tangent spokes only.