A crane is a tower or derrick that is equipped with
cables and pulleys that are used to lift and lower
material. They are commonly used in the construction
industry and in the manufacturing of heavy equipment.
Cranes for construction are normally temporary
structures, either fixed to the ground or mounted
on a purpose built vehicle.
They can either be controlled from an operator in
a cab that travels along with the crane, by a push
button pendant control station, or by radio type
controls. The crane operator is ultimately responsible
for the safety of the crews and the crane.
Cranes of the Middle Ages were used to build the
cathedrals of Europe. The crane was fixed on top
of a wall as it was being constructed and was
powered by men that ran inside of two large wheels
on each side. Cranes were also used in medieval ports
and in shipyards.
The most basic type of crane consists of a steel
truss or telescopic boom mounted on a mobile platform,
which could be a rail, wheeled, or even on a cat
truck. The boom is hinged at the bottom and can
be either raised or lowered by cables or hydraulic
This type of crane offers a boom that consists of
a number of tubes fitted one inside of the other.
A hydraulic mechanism extends or retracts the
tubes to increase or decrease the length of the
The tower crane is a modern form of a balance
crane. When fixed to the ground, tower cranes
will often give the best combination of height and
lifting capacity and are also used when constructing
Truck mounted crane
Cranes mounted on a rubber tire truck will provide
great mobility. Outriggers that extend vertically
A gift from www.dotcomhunter.com
or horizontally are used to level and stabilize
the crane during hoisting.
Rough terrain crane
A crane that is mounted on an undercarriage with
four rubber tires, designed for operations off
road. The outriggers extend vertically