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Overhead Travelling Crane

written by: kkaarthic • edited by: Lamar Stonecypher • updated: 3/29/2010

This article is about Overhead cranes. The article describes the basic principles of operation of the Overhead cranes and the design selection criteria for the various components of the overhead crane.

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    Necessity is the mother of all inventions. The need for mankind to handle and carry heavy loads led to the invention of Cranes. Through constant inventions and changes in the crane system, the current Over head crane systems are very effective and efficient method for material handling

    Here’s a picture to show how an over head crane system looks like

    Overhead crane Picture 

    The major components of the Overhead crane are:

    1. A traveling base with a traveling rail on either side. Imagine the railway tracks; it is quite similar to the same except for the distance.
    2. The End carriage on both sides which houses the wheel for the crane movement and also supports the top girder. It also houses a geared motor that provides the drive to the rollers enabling the crane to move longitudinally.
    3. The Top Girder provides the side movement of the hoist and trolley. The hoist and trolley assembly is mounted on the top girder
    4. The hoist and the trolley arrangement posses separate motor and gear assemblies for the chain hook. It also has a drive arrangement for the sideway movement on the top girder.

    The overhead crane systems normally consist of two types of travel to handle the materials. The two types of motion are

    1. Long Travel Motion
    2. Longitudinal Travel Motion

    The long travel motion denotes the travel of the crane in the longest direction. The movement provided by the end carriage is called as long travel. The traveling of the crane in the direction perpendicular to the Long travel is termed as Longitudinal Travel Motion. The movement provided by the hoist and trolley arrangement is termed as Longitudinal Travel Motion.

    Let us now look into the constructional and design aspects of two important components in the traveling crane system:

    Traveling rail: The traveling rail is one of the most important component. The section of the traveling rail is decided based on the amount of load to be carried. The various cross sections of the traveling rail are shown below.

    Sections of travelling rail 

    Some of the main design aspects that are considered during the selection of the traveling rail are

    1. They should have a very broad base and small height providing more stability and rigidity to the end carriage.
    2. They should posses comparatively a large moment of sectional inertia.

    A typical standard available for the special rail is given below for reference.

    Standard for special section 

    The hoist and trolley arrangement: This is another important component in the overhead crane. This is the component that carries the lifts the weight and provides longitudinal motion to the crane. A picture depicting the wheel arrangement in the hoist and trolley is shown below with respective mounting on the upper and lower flanges of the I- Beam.

    wheel running arrangement of hoist and trolley 

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