[6] Since the subject of a patent.
CHAPTER XV.
THE SIDE-SLIP OF THE SAFETY.
The question of side-slip is not entirely new; it was first mooted in connection with the Safety of the Kangaroo type, which had a driver of from thirty-six to forty inches in front of a rear wheel of eighteen or twenty inches, as will be noticed in the cut of this machine given hereinafter. Now, to come to the specific features supposed to account for the side-slip, note that, in order to make room for the sprocket-wheels, the cranks had to be unusually wide apart and, by the necessary construction of the machine, also very low down; in other words, the machine had a very wide tread, swinging very close to the ground. The slip of this wheel was something fearful to behold, and its cause was supposed to be fully explained by the peculiarities of construction just noted, in accordance with a theory which, though religiously believed in at the time, has of late been somewhat shaken, and which we now proceed to develop.
In order to compare the different machines in respect to this theory, suppose we take, first, the Ordinary with a fifty-inch wheel and cranks, say, eight inches apart, or four inches from the centre of the wheel to either crank. Now, if the pedal b ([Fig. 1]) is four inches long, the distance from the centre of the pedal to the centre of the axle of the drive-wheel is six inches, and the diameter of the wheel fifty inches; then, when the crank is extended horizontally out in front, this being the position when it is supposed to be subjected to the greatest strain, we have the following conditions (see [Fig. 2]):
Fig. 1.
Fig. 2.
Side-slip diagrams.