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Have an any idea about hoist used in crane?

  1. Apr 17, 2010 #1
    i am working on a project of 450t eot crane project for final year.
    want detail on hoists and motor used for hoist.
    how i choose it?
     
  2. jcsd
  3. Apr 17, 2010 #2
    I have no experience with hoists but this is what my first thoughts are:

    Figure out the power you need. Decide how fast do you want the hoist to go up and how heavy a nominal load will be (450 tons?). Calculate the power needed to achieve this. Increase that number by a safety margin of 30%*. This is the minimal power rating that you need from a motor. Make a list of motors available for that rating.

    When you find some suitable motors, look at their speed-torque curves. Design a block and tackle so that the motor can run at it's normal operating speed while providing the necessary torque. Repeat that for a few more motors and decide what you think will work best.

    Here are some criteria that can help you decide: Which is cheapest? Does the motor require a complicated power source or starter? How much load, above your design specs, can the motor handle before it stalls? Efficiency rating.

    *It is a standard practice in engineering to use safety margins. You don't want a device to work on the razor's edge of failure or success.
     
  4. Apr 17, 2010 #3

    sophiecentaur

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    I agree. But a gearbox may be better than a block and tackle - there are more ratios available that way.
     
  5. Apr 17, 2010 #4
    Hoists almost always have a series wound field. I believe hoists are tested to at least 150% percent of rated load. (I was at a nuclear power plant outside of Pasco, WA where they were load testing a 200 ton crane using bags of concrete. They hauled in bags by the truckload for 2 1/2 days before they had 300 tons worth.)

    In my experience the larger cranes all use DC motors. Hoists typically have 3 or 5 speeds which are accomplished by switching in and out large resistor banks. High speed is almost always used for regular hoisting and the lower speeds mainly for setting things down or positioning.

    It would be good to actually see and inspect a large crane before you get too far along in your project.
     
  6. Apr 18, 2010 #5
    What's Eot??
     
  7. Apr 19, 2010 #6
    The crane motor may need a magnetic brake, so there is no creep (load slowly moving downward) when the crane hoist is turned off, or there is a power failure.

    Bob S
     
  8. Apr 19, 2010 #7
    http://wiki.answers.com/Q/What_is_an_EOT_Crane" [Broken]
     
    Last edited by a moderator: May 4, 2017
  9. Apr 19, 2010 #8
    Hoists have a drum with brake shoes for brakes. The brakes are released with the same current that powers the motor.
     
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