05-09-2012, 09:50 AM
Gear train
gear train.pdf (Size: 445.85 KB / Downloads: 46)
A gear train is formed by mounting gears on a frame
so 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, this provides a
smooth transmission of rotation from one gear to the
next.[1]
The transmission of rotation between contacting
toothed wheels can be traced back to the Antikythera
mechanism of Greece and the South Pointing Chariot
of China. Illustrations by the renaissance scientist
Georgius Agricola show gear trains with cylindrical
teeth. The implementation of the involute tooth yielded
a standard gear design that provides a constant speed
ratio.
Some important features of gears and gear trains are:
• The ratio of the pitch circles of mating gears defines
the speed ratio and the mechanical advantage of the
gear set.
• A planetary gear train provides high gear reduction
in a compact package.
• It is possible to design gear teeth for gears that are non-circular, yet still transmit torque smoothly.
• The speed ratios of chain and belt drives are computed in the same way as gear ratios. See bicycle gearing.
Mechanical advantage
Gear teeth are designed so that the number of teeth on a gear is
proportional to the radius of its pitch circle, and so that the
pitch circles of meshing gears roll on each other without
slipping. 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.
gear train.pdf (Size: 445.85 KB / Downloads: 46)
A gear train is formed by mounting gears on a frame
so 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, this provides a
smooth transmission of rotation from one gear to the
next.[1]
The transmission of rotation between contacting
toothed wheels can be traced back to the Antikythera
mechanism of Greece and the South Pointing Chariot
of China. Illustrations by the renaissance scientist
Georgius Agricola show gear trains with cylindrical
teeth. The implementation of the involute tooth yielded
a standard gear design that provides a constant speed
ratio.
Some important features of gears and gear trains are:
• The ratio of the pitch circles of mating gears defines
the speed ratio and the mechanical advantage of the
gear set.
• A planetary gear train provides high gear reduction
in a compact package.
• It is possible to design gear teeth for gears that are non-circular, yet still transmit torque smoothly.
• The speed ratios of chain and belt drives are computed in the same way as gear ratios. See bicycle gearing.
Mechanical advantage
Gear teeth are designed so that the number of teeth on a gear is
proportional to the radius of its pitch circle, and so that the
pitch circles of meshing gears roll on each other without
slipping. 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.