Fig. 205.
[Fig. 205] represents Watt’s sun-and-planet motion for converting reciprocating into rotary motion; b d is the working beam of the engine, whose centre of motion is at d. The gear a is so connected to the connecting rod that it cannot rotate, and is kept in gear with the wheel c on the fly-wheel shaft by means of the link shown. The wheel a being prevented from rotation on its axis causes rotary motion to the wheel c, which makes two revolutions for one orbit of a.
Fig. 206.
An arrangement for the rapid increase of motion by means of gears is shown in [Fig. 206], in which a is a stationary gear, b is free to rotate upon its shaft, and being pivoted upon the shaft of a, at d, is capable of rotation around a while remaining in gear with c. Suppose now that the wheel a were absent, then if b were rotated around c with d as a centre of motion, c and its shaft e would make a revolution even though b would have no rotation upon its axis. But a will cause b to rotate upon its axis and thus communicate a second degree of motion to c, with the result that one revolution of b causes two rotations of c.
