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Torque and power requirement for roller

  1. Aug 22, 2014 #1
    We have roller setup which is to be driven by a motor. The roller dia is 90 mm. A shaft which is connected to its end is 25 mm of dia. The roller weight is around 10 kg. On the periphery of the roller there are some 40 kgs of mass is acting. The roller rpm is 10. What is the torque required to run this roller and power required by motor. Thanks in advance
     
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  3. Aug 22, 2014 #2

    Baluncore

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    Once the system you describe is operating it will take little energy to keep it going.
    What is the purpose of the roller ? What does it do ?
    Where will the motor energy go when the system is operating ?
    Is there a belt ?
     
  4. Aug 22, 2014 #3
    The roller is used to drive another roller by surface contact. The driven roller is placed directly over the driver and it sits by means of gravity. The driven roller weight is 40 kg. The driving roller weight is 10 kg. The motor is to be directly connected at the driver,s roller end. No belt. Thanks for replying baluncore. If posible i need calculation steps
     
  5. Aug 22, 2014 #4

    Baluncore

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    Where does the energy go?
    You have still not identified why this is being done.
     
  6. Aug 22, 2014 #5
    Baluncore, its difficult application, hard to explain words. Can you help me with calculations?
     
    Last edited by a moderator: Sep 9, 2014
  7. Aug 22, 2014 #6

    Baluncore

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    Power is energy flow per second. That requires work to be done on something.
    You have not specified where the energy will go and so there can be no power calculation.
    What is between the rollers?
     
  8. Sep 9, 2014 #7

    berkeman

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    Why are you refusing to show any work on your part? Is this for schoolwork? We do not do your schoolwork for you here...
     
  9. Sep 9, 2014 #8

    billy_joule

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    P=Tω
    power = torque . angular velocity

    To calc power required (for a constant speed) you need to figure out/measure the opposing torque due to whatever loads are acting and know what speed the roller needs to run at.
     
  10. Sep 9, 2014 #9
    Let me rephrase my question

    Dimensions
    We’ve a roller of length 400mm & Dia of 90mm. At both ends of the roller a shaft is fitted. Shaft dia is 25 mm & length is 100mm each side. On the 25mm Dia shaft, two flanged bearings are fitted. The total roller & shaft weight is 6 kgs.

    Working Principle:

    Over the roller, a fabric in a roll form is loaded. The fabric roll sits over this roller by means of gravity. The roller has to drive the fabric roll on its circumference & feed the fabric end to another machine.

    Problem:

    1. What is the torque required to drive the roller at the shaft end.

    2. What HP of motor, we should select to drive the shaft, if the motor is directly connected (without any gear box) to the 25mm dia shaft
     
  11. Sep 9, 2014 #10

    berkeman

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    Thread is locked for Moderation. Please PM me with the answers to my questions.
     
    Last edited: Sep 10, 2014
  12. Sep 10, 2014 #11

    berkeman

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    Thread reopened for now.

    @saruvanan -- do you understand what billy_joule wrote in post #8? Can you post a picture of your setup or a similar one?
     
  13. Sep 10, 2014 #12
    @Billy_joule
    Power = torque. Angular velocity
    Torque = radius . Force
    Force = mass. Acceleration
    Acceleration= velocity/time
    Velocity= radius. Angular velocity
    Angular velocity = (rpm.2.pi )/ 60
    The roller needs to run @ 10 rpm.
    Using the above formulas i've calculated this.
    Hence angular velocity= 1.05 rad/secs
    Velocity = 0.045 x 1.05= 0.05 m/secs
    Acceleration= 0.05/3 = 0.02 m/sq.secs (0 to 10 rpm in 3 secs)
    Force = (20+6).0.02x 9.8= 4.0 N ( 20 kg fabric roll, 6 kg roller self weight )
    Now torque= 4.0 x 0.045 = 0.18 N.m

    This is the calculation i've done. Not sure its right. I cannot attach a picture of the setup. Perhaps a drawing i can attach
     
  14. Sep 10, 2014 #13
    attached a conceptual drawing

    This is a cinceptual design
     

    Attached Files:

  15. Sep 10, 2014 #14

    billy_joule

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    Bolded word mine.

    These calculations are all correct.

    It's a little strange that you specified the rpm and not the tangential velocity. I would've expected you to need the fabric to be fed at a certain rate as that is the entire purpose of the machine. 5 cm of fabric per second seems mighty slow to me, but then again you haven't told us the purpose of the machine... Why did you select 10 rpm? Why did you select 3 seconds? why not 6? That would half the motor cost/size/energy use..


    These are wrong.
    The weight of rolls acts through the center of rotation so the 'r' in the T=Fr equation is zero. That is to say they make no contribution to torque about the shaft.

    You need to calculate the moment of inertia ('I') of the rotating masses.
    http://en.wikipedia.org/wiki/Moment_of_inertia

    Then you can calculate the torque required for the acceleration:
    http://en.wikipedia.org/wiki/Angular_acceleration


    But what you are really need to know is the steady state operation- how much power you need to keep the motor turning at your target rpm. for that you need to know where energy is going (eg the opposing torques from friction etc); not a trivial task.

    EDIT: I now see your design. How does it compare with other similar machines?

    Many people have invested millions of dollars and man hours in designing machines just like that...Do you think you'll compete with those designs? Why do you want to reinvent the wheel? Why not get (or copy...) an off the shelf design with years of R&D already done for you?
     
  16. Sep 13, 2014 #15

    Dnomyar

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    Ummm - do they give these designs away for free ?
     
  17. Sep 13, 2014 #16

    Baluncore

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    Re; post #13.
    As the fabric unrolls at a set speed determined by the bottom roller, it rises up between two other pinch rollers.
    Fabric cannot be pushed uphill, so it must be pulled up by the two pinch rollers. All the work of moving the fabric must be done by the upper pinch rollers. The bottom "driving" roller is not driving and will therefore not require power.
     
  18. Sep 13, 2014 #17

    billy_joule

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    google image search "*machine you want to know about*" and look at the images.
    I bet every single image returned will have a better design than the OP's.

    You don't need the original engineering drawings to copy a simple design. a single photo or a 20 second explanation will do. This isn't cutting edge confidential technology. They have probably been made the same for 50 years!
     
  19. Sep 14, 2014 #18

    Dnomyar

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    Nope, not a one looking like the concept put forward - and Zero computations.
     
  20. Sep 14, 2014 #19

    billy_joule

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    Of course none look like the OP's, his idea won't work at all!

    Like Baluncore explained, fabric cannot be pushed off a roll.
    And generally you won't find calculations/computations with an image search.
     
  21. Sep 14, 2014 #20

    Dnomyar

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    "And generally you won't find calculations/computations with an image search."
    Duh - Really ? You didn't comment on the lack of suitable designs either, so you suggestion of Googling the solution wasn't so helpful.
    So, since there were no computations, perhaps you don't mind the OP trying to establish the calculations then ? Perhaps he is allowed to expand his understanding a bit ?


    "Like Baluncore explained, fabric cannot be pushed off a roll."
    Fabric 'can' be pushed off a roll. The easiest way would be to put two rollers under the fabric roll, and power them, making them rotate the fabric roll - the material will be pushed off the roll of fabric.
     
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