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pulleys and torque
Last Post 18 Nov 2012 02:15 AM by pfeinstein. 5 Replies.
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tom92
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Posts:3

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05 Jun 2012 05:47 AM

    1.) The figure below shows a pulley winding a load of 100kg upwards, from rest. The load accelerates at 0.4ms-2, and the friction force between the rope and the pulley is equivalent to 20N.

    Determine;
    a.) The applied torque
    b.) The work done during one revolution of the pulley
    c.) The power dissipated







    2.) A centrifugal clutch has four shoes, each of which has a mass of 1.25kg. The shoes are held in to the centre of the clutch by springs with a stiffness of 8KNm-1. The internal diameter of the friction surface is 500mm and the radius of the centre of gravity of the shoes is 200mm. There is a gap of 18mm between the shoes and the inside of the drum when the clutch is static. The coefficient of friction is 0.22, Determine;
    a.) The rotational speed at which the clutch engages

    b.) The power transmitted at 1300rpm




    Nathaniel
    Basic Member
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    Posts:193

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    06 Jun 2012 08:49 AM
    Tom:

    The figures did not come through?

    Are these questions as part of an academic assignment? If so asking for more than general guidance violates the academic integrity of your school.

    Niel Leon
    engineering.com
    tom92
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    New Member
    Posts:3

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    06 Jun 2012 12:30 PM
    Hi neil,
    This is not part of an exam or assignement. They are work examples from a training pack, which will help us get through our end of year exam. But i am struggling with the two above examples. For some reason the image is not coming up, but if any one has an idea what to do, i can email it as i have typed it up from my example sheet. thanks
    Nathaniel
    Basic Member
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    Posts:193

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    08 Jun 2012 08:29 AM
    You need to go back to basics:

    1a. What is torque?

    It is force times the lever arm length

    1b. What is work

    This is force time distance traveled. For one revolution of pulley that distance = pi * diameter

    1c. Power is Energy / unit time. Total power = total work = Weight*distance + Friction*distance

    This should give you a start. Hints for question 2 later.


    Niel
    tom92
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    New Member
    Posts:3

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    18 Jun 2012 06:21 AM
    I have managed to do 1a & 1b and all of 2. but i am just stuck on 1c. Is it torque*angular velocity? My exam is on wednesday. so i am studying just about all aspects atm and stuck on this one. cheers
    pfeinstein
    New Member
    New Member
    Posts:16

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    18 Nov 2012 02:15 AM
    Tom: Have you read up on the basics of power dissipation? Here's a nifty tool: http://www.engineeringtoolbox.com/l...d_872.html

    _________________________________________________________________
    My interests include high alloy valves from The Alloy Valve Stockist, Barcelona, Spain at http://alloy-valves.com
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