A Crypto or epicyclic gear is arranged as shown in fig. 14, and consists of two gear wheels, a small one a, with external teeth, and a large one b arranged on the outside of it with internal teeth, whilst in the space between the two one or more pinions or smaller gear wheels, c, c, just large enough to fill the space and cut with teeth to correspond with those on the two gear wheels, are placed, these pinions being mounted on pins carried by a ring or disc d, which may or may not be supported by arms, e, e, e, e, from a centre as shown. We thus have three members, the outside gear wheel, the inside gear wheel, and the pinions, and the whole makes a most accommodating arrangement; for
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Fig. 14
if the inner wheel a be held fast and the ring d, carrying the pinions, revolved, the outer wheel b is caused to revolve at a faster rate than the ring, whilst if the outer wheel is held the inner wheel will also be driven at a faster speed, but in different ratios. On the other hand, if either the outer or inner wheel be held and the other driven, the ring or disc d, carrying the pinions, will be caused to revolve at two several lower rates of rotation; whilst if, in its turn, the pinion-ring is held and either of the wheels driven, the other wheel will be rotated at a different rate of speed, but in the opposite direction, and so a reversing action obtained, and by locking any two members
