A gear is a component
within a transmission
device that transmits
rotational force to another
gear or device. A gear is
different from a pulley in
that a gear is a round wheel
that has linkages ("teeth" or
"cogs") that mesh with other
gear teeth, allowing force to
be fully transferred without
A rack and pinion gear system composed of two gears.
The normal round gear is called “pinion” gear and
straight or flat gear is called “Rack” gear.
Rack and Pinion
Rack and Pinion
A rack and pinion is a type
of linear actuator that
comprises a pair of gears
which convert rotational
motion into linear motion.
The circular pinion
engages teeth on a linear
"gear" bar which is called
Rotational motion applied to the pinion will cause
the rack to move to the side, up to the limit of its
For example, in a rack railway, the rotation of a
pinion mounted on a locomotive or a railcar
engages a rack between the rails and pulls a train
along a steep slope.
The rack and pinion is also used to convert between
rotary and linear motion. The rack is the flat, toothed
part, and the pinion is the gear. Rack and pinion can
convert from rotary to linear of from linear to rotary
Rack and Pinions are commonly used in the
steering system of cars to convert the rotary
motion of the steering wheel to the side to side
motion in the wheels.
The steering ratio is defined by the ratio of
pinion revolutions(steering wheelrevolutions)
to rack travel. Suitable toothing of the rack
allows the ratio to be made variable over the
travel. This lowers the actuating force or
reduces the travel for steering corrections.
Rack and pinion steering is quickly becoming
the most common type of steering on
cars, small trucks. It is actually a pretty simple
mechanism. A rack-and-pinion gear set is
enclosed in a metal tube, with each end of the
rack sticking out from the tube. A rod, called a
tie rod, connects to each end of the rack.
The pinion gear is attached to the steering
shaft. When you turn the steering wheel, the
gear spins, moving the rack.
The rack-and-pinion gear set does two things:
It converts the rotational motion of the steering wheel
into the linear motion needed to turn the wheels.
It provides a gear reduction, making it easier to turn
On most cars, it takes three to four complete
revolutions of the steering wheel to make the wheels
turn from lock to lock (from far left to far right).
The primary components of the rack and pinion
steering system are:
Inner ball joint or socket
A chain is a series of connected links which are typically
made of metal. A chain may consist of two or more links.
Chains are usually made in one of two styles, according to
their intended use:
Those designed for lifting, such as when used with a hoist;
for pulling; or for securing, such as with a bicycle
lock, have links that are torus shaped, which make the
chain flexible in two dimensions (The fixed third dimension
being a chain's length.)
Those designed for transferring power in machines have
links designed to mesh with the teeth of the sprockets of
the machine, and are flexible in only one dimension. They
are known as roller chains, though there are also non-roller
chains such as block chain.