Figs. 167, 168, 169. Parallel motion methods
[Fig. 168]. Oscillating engine. The cylinder has trunnions at the middle of its length, working in fixed bearings, and the piston rod is connected directly with the crank, and no guides are used.
[Fig. 169]. Inverted oscillating or pendulum engine. The cylinder has trunnions at its upper end, and swings like a pendulum. The crank shaft is below, and the piston rod connected directly with crank.
[Fig. 170]. Section of disc-engine. Disc-piston, seen edgewise, has a motion substantially like a coin when it first falls after being spun in the air. The cylinder heads are cones. The piston rod is made with a ball to which the disc is attached, said ball working in concentric seats in cylinder-heads, and the left-hand end is attached to the crank arm or fly-wheel on end of shaft at left. Steam is admitted alternately on either side of piston.
[Fig. 171]. The gyroscope, or rotascope, an instrument illustrating the tendency of rotating bodies to preserve their plane of rotation. The spindle of the metallic disc C is fitted to return easily in bearings in the ring A. If the disc is set in rapid rotary motion on its axis, and the pintle F at one side of the ring A is placed on the bearing in the top of the pillar G, the disc and ring seem indifferent to gravity, and instead of dropping begin to revolve about the vertical axis.
[Fig. 172]. Bohnenberger's machine, illustrating the same tendency of rotating bodies. This consists of 3 rings, A, A´, A2, placed one within the other, and connected by pivots at right angles to each other. The smallest ring, A2, contains the bearings for the axis of a heavy ball B. The ball being set in rapid rotation, its axis will continue in the same direction, no matter how the position of the rings may be altered; and the ring A2, which supports it, will resist a considerable pressure tending to displace it.
