Fig. 218.
Fig. 219.
A similar result may be obtained by the construction shown in [Fig. 218], in which d and e are two discs fast upon their respective shafts, and c are discs of leather clamped in e. It is obvious that if d be the driver the speed of revolution of e will be diminished in proportion as it is moved nearer to the centre of d, and also that the direction of revolution of d remaining constant, that of e will be in one direction if on the side b of the centre of d, and in the other direction if it is on the side a of the centre of d, thus affording means of reversing the motion as well as of varying its speed. A similar arrangement is sometimes employed to enable the direction of rotation of the driver shaft to be reversed, or its motion to cease. Thus, in [Fig. 219], r is a driving rope driving the discs a, b, and c, d, e, f, g are discs of yellow pine clamped between the flanges h i; when these five discs are forced (by lifting shaft h), against the face of a motion occurs in one direction, while if forced against b the direction of motion of h is reversed.
Fig. 220.