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Nut-Busting Torque?

  1. Feb 3, 2015 #1
    I need to lift 300 pounds with a lever arm 3 ft long. So, I need 900 ft-lbs. A electric impact has 1100 ft-lb of nut-busting torque. Will this electric impact work? What does nut-busting mean?
     
  2. jcsd
  3. Feb 3, 2015 #2
    The longer the lever arm the less force needed. (move the earth with a long enough lever)
    Not sure how this is laid out, using a fulcrum and its location etc.

    To lift 300 lb load with a 3 ft lever arm would take 100 lb of force.
    A 300 ft lever would take 1 lb of force
    Ever put a "cheater bar" on a wrench?

    How is this laid out?
     
  4. Feb 3, 2015 #3

    berkeman

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    You could also use a system of pulleys or gears to give you a mechanical advantage...
     
  5. Feb 5, 2015 #4

    jim hardy

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    "Nut busting" is a marketing term not a scientific one,. It is a double entendre.
    The straight man marketer's meaning is the tool will break loose a nut that's rusted in place, or is so tight and located such that you simply can't get a tight enough grip on the whole assembly to keep it from turning when you apply torque. Example of latter is the nut on an automobile alternator pulley.... the whole shaft just spins.
    The wise guy marketer's second meaning involves a pun, search on 'scrotal hernia' .

    The impact wrench applies torque in short impulses so that the inertia of the assembly keeps it from rotating, rather like striking the end of a regular wrench with a hammer.
    So - that 1100 ft-lb number is not the constant torque you'll need for lifting.
    Nobody could hold a hand tool producing that much constant torque.

    How far and how fast do you need to lift that 300 lbs?
    image_22163.jpg
    around twenty five bucks
     
    Last edited: Feb 5, 2015
  6. Feb 5, 2015 #5

    Baluncore

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    An impact wrench produces a torque impulse like a hammer does in a straight line. The impact is for a very short period of time. Each impact is capable of breaking the friction between the nut and the thread. Once started the nut spins off rapidly with very little force or impact being required. “Nut busting” is an advertising term that describes the force available to start the nut moving. An impact wrench can turn backwards in the time between impacts, so it won't work to turn a long lever arm.
     
  7. Feb 13, 2015 #6
    Please see attached layout. IMG_2008.JPG
     
  8. Feb 13, 2015 #7

    Baluncore

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    How are you going to hold the impact driver once the load starts to rise. There will be 900 ft.lbs on the handle continuously.
    Maybe you need to use a gearbox mounted on a solid base, a boat winch or a chain block. Some small lifting arms for vehicles use a hydraulic ram.
    How often will you need to lift it? Why?
     
  9. Feb 17, 2015 #8
    I drew a more detailed sketch of device.
     

    Attached Files:

  10. Feb 17, 2015 #9

    Baluncore

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    Unfortunately your design will probably not work for a number of reasons.

    (A). The torque / time characteristics of a cordless impact driver will not provide a sustained torque of 3 ft * 300 lbs = 900 ft.lbs.
    (B). The impact driver mounting will be torn off the table by the continuous 900 ft.lbs, with or without the added impact.
    (C). The device overhangs the edge of the table, the table will probably overturn.

    There are many different solutions available. Choice of the best method will depend on why you really need to do this?
     
  11. Feb 17, 2015 #10
    Nice thanks for the input. Would a electric impact cordlessdriver lift 260 lbs with a 3 ft lever arm? The maximum torque of the electric impact cordless driver is 780 ft lbs.
     
  12. Feb 17, 2015 #11

    Baluncore

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    No.
     
  13. Feb 17, 2015 #12

    jim hardy

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    That seems to me like asking a woodpecker to push over a tree.
    You need an elephant.
     
  14. Feb 18, 2015 #13
    Lets see if I can do the math.
    Electric impact driver with 780 ft-lbs torque and 1/4" lever but give a force of 39,000 lbs? Am I correct?
    My problem is I need to lift 260 lbs with a 3 ft lever arm. So, I need a torque of 780 ft-lbs.

    Kevin
     
  15. Feb 18, 2015 #14
    What am I missing?
     
  16. Feb 18, 2015 #15

    jim hardy

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    That to overcome gravity you need constant torque not just brief pulses of it.
     
  17. Feb 18, 2015 #16
    ok it does not give a constant torque. Thanks for the info. This is a great forum.
     
  18. Feb 18, 2015 #17

    jim hardy

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    You'd do well to try out an impact wrench. It'll give you an intuitive feel for "impulse", and you'll see why i picked the 'woodpecker' analogy.
    http://en.wikipedia.org/wiki/Impulse_(physics)
    Thanks for the kind words. We all come here to learn.
     
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