A mechanical bearing
is a component used between two parts that allows rotational or liner
movement, reducing friction and enhancing performance to save energy.
Both metal and plastic bearings can be found everywhere, from refrigerators to computers to the 100 or so bearings found in your car. The concept behind them
is a simple one: things roll better than they slide. Without bearings,
the wheels in your car would rattle, the transmission gear teeth
wouldn’t be able to mesh, and the car wouldn't run smoothly. They are
composed of a smooth inner and outer metal surface for metal balls to
roll against. The balls or rollers help “bear” the load and the device
functions more efficiently.
There are many
different types of bearings, each used for specific purposes and
designed to carry specific types of loads, radial or thrust. Here, we’ll
look at the 6 most popular types: plain bearings, rolling element
bearings, jewel bearings, fluid bearings, magnetic bearings, and flexure
bearings.
Plain bearings are the
simplest type of bearing and are composed of just the bearing surface
with no rolling elements. They have a high load-carrying capacity, are
generally the least expensive and, depending on the materials, have much
longer lives than other types.
Rolling element
bearings place balls or rollers between two rings - or “races” - that
allows motion with little rolling resistance and sliding. These bearings
include ball bearings and roller bearings.
Ball bearings are the most common type of rolling element bearing.
These bearings can handle both radial and thrust loads but are usually
used where the load is relatively small. Because of its structure, there
is not a lot of contact with the balls on the inner and outer races.
If the bearing is overloaded the balls would deform and ruin the
bearing. Roller bearings are able to handle a much heavier, radial load,
like conveyor belts, because they don’t use balls. Instead, they have
cylinders allowing more contact between the races, spreading the load
out over a larger area. However this type of bearing is not designed to
handle much thrust loading.
Jewel bearings are
plain bearings with a metal spindle that turns in a jewel-lined pivot
hole. They carry loads by rolling the axle slightly off-center and are
usually used in mechanical watches or clocks. This is due to their low
and predictable friction that improves watch accuracy.
Fluid bearings support
their load using a thin layer of gas or liquid and can be classified
into two types: fluid-dynamic bearings and hydrostatic bearings.
Fluid-dynamic bearings use rotation to form the liquid into a
lubricating wedge against the inner surface. In hydrostatic bearings,
the fluids - usually oil, water, or air - rely on an external pump.
Fluid bearings are used
in high load, high speed or high precision applications that ordinary
ball bearings either couldn’t handle or would suffer from increased
vibration and noise.
Magnetic bearings
support moving parts without physical contact, instead relying on
magnetic fields to carry the loads. They require continuous power input
to keep the load stable, thus requiring a back-up bearing in the case of
power or control system failure.
Magnetic bearings have
very low and predictable friction and the ability to run without
lubrication or in a vacuum. They are increasingly used in industrial
machines like turbines, motors, and generators.
A typical flexure
bearing is one part joining two others, like a hinge, in which motion is
supported by a load element that bends. These bearings require repeated
bending, so material selection is key.
Some materials fail after repeated bending, even at low loads, but with
the right materials and bearing design the flexure bearing can have an
indefinite life. Another notable characteristic of this bearing is its
resistance to fatigue. Many other bearings that rely on balls or rollers
can fatigue as the rolling elements flatten against each other.
Here you have it!
Did we miss a type of bearing that you prefer? Have more questions
about specific kinds of bearings? Let us know in the comments section
below.