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A gear train or gear set is a machine element of a mechanical system formed by mounting two or more gears on a frame such that the teeth of the gears engage.. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, providing a smooth transmission of rotation from one gear to the next. [2]
Typical gear ratios on bicycles range from very low or light gearing around 20 gear inches (1.6 metres per revolution), via medium gearing around 70 gear inches (5.6 m), to very high or heavy gearing around 125 gear inches (10 m). As in a car, low gearing is for going up hills and high gearing is for going fast.
the number of possible gear ratios is 24 (=3×8, this is the number usually quoted in advertisements); the number of usable gear ratios is 22; the number of distinct gear ratios is typically 16 to 18. The combination of 3 chainrings and an 8-sprocket cogset does not result in 24 usable gear ratios.
Worm-and-gear sets are a simple and compact way to achieve a high torque, low speed gear ratio. For example, helical gears are normally limited to gear ratios of less than 10:1 while worm-and-gear sets vary from 10:1 to 500:1. [45] A disadvantage is the potential for considerable sliding action, leading to low efficiency. [46]
A hub gear, [1] internal-gear hub, [2] internally geared hub [3] or just gear hub [4] is a gear ratio changing system commonly used on bicycles that is implemented with planetary or epicyclic gears. The gears and lubricants are sealed within the shell of the hub gear, in contrast with derailleur gears where the gears and mechanism are exposed ...
The speed ratio for a pair of meshing gears can be computed from ratio of the radii of the pitch circles and the ratio of the number of teeth on each gear, its gear ratio. Two meshing gears transmit rotational motion. The velocity v of the point of contact on the pitch circles is the same on both gears, and is given by
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In the single-chain system, the chain runs from the top of a chainring attached to the cranks to the top of a sprocket attached to the rear wheel hub with a freewheel, as with most bicycle chain drives. The chain then, usually, wraps around the rear sprocket to an idler sprocket between the rear wheel and the cranks, then runs back to a second ...