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    Discussion in 'Calculations' started by Ste_Mulv, Jul 10, 2013.

    1. Ste_Mulv

      Ste_Mulv Member

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      Hi all,

      I am not very good at this stuff at all and could do with help.
      Here is a sketch of what I am looking to do.

      http://stevenmulvenna.com/wp-content/uploads/2013/07/photo-1.jpg

      The weight of the load is 25kg and the load is to be lifted up and down, and the load will be passed to another wheel assembly either above or below. I am looking to size the wheels, chain, drive motor and springs, however just the motor size (or motors if anyone recommends that dual motors will be better) will do for now.

      Can any one recommend how I can calculate the forces needed and then use this to size and specify a motor(s).
      Any other general comments of the design are more than welcome too, as I am going to use guess work to size the wheels and sprockets.

      Thanks for reading!

      Steve
       
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    3. stevo1900

      stevo1900 Member

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      This is a big job to work out all those parts. I'm having trouble visualizing exactly what's going on but I might be able to give you a starting point.

      You want to know the work that the motor is doing. So firstly you'll need to know the forces working against it. Start with 25Kg x 9.81 = 245.25N. Is that 25Kg the total mass of the hole assembly when loaded?

      On a basic level you can calculate the torque produced by that force on a certain size sprocket and then try to match that to a motor. If there are no motors close then change the size of the sprocket.

      Not understanding exactly what's going on makes it hard to suggest much else. Hopefully this will spur some replies from our other members.

      Steve.
       
      Last edited: Jul 16, 2013
    4. mecano

      mecano New Member

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      I do not see sense in rollers on the right. Suffice upper drive shaft. Everyone else should do quieting material.
       
    5. Ste_Mulv

      Ste_Mulv Member

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      Hi Steve,

      Thanks for coming back, that is a helpful start.
      The wheels will be powered to push the load up and down (imagine a strip of iron 2m long and 50x4mm as the load).
      The wheels will sprung to keep the load from slipping.

      The 25kg is just the load's mass. Thus the torque rating on the sprocket will be based only on this 25kg. I need now to select a sprocket and wheel to power it up and down. Thus is if the sprocket 10cm diameter, the torque will be 24.525Nm.

      My main problem is I have never looked at the products available on the market to actually select a sprocket, thus I am not even certain where to start looking. I need to consider wheel spec and chain spec too...

      Also I need to account for accelerating the load up to the speed and decelerating the load back to stationary, how can I account for this too?

      Best regards,

      Ste
       
    6. vidgolob

      vidgolob Active Member

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      I dont think you need extra calculations for that. Just use the maximum force that will be present in all your calculation and use a solid safety factor.
       
    7. stevo1900

      stevo1900 Member

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      Steve ,

      Sorry for the late reply; I've been snowed under by work over the last week. Hopefully I'll get some time at the end of the week if you still need help.

      Steve B.
       
    8. fishon91

      fishon91 Member

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      Others on here may have better places, but McMaster-Carr, grainger or motion industries is a good place to start looking for sprockets, chains, etc..
      I'm also confused on your design. You made a second post in another section about this project. You are making this to move product vertically? Or horizontally? Or both?
      You are gonna need tensioners between the sprockets
       
    9. joninstjohn

      joninstjohn Member

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      Steve,

      The motor needs to be sized based on power, allowing for inertia and inefficiencies within the system. How fast do you want the payload to go?

      Cheers

      Jon
       
    10. joninstjohn

      joninstjohn Member

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      Hi Steve,

      I have a motor sizing calculation. It's for a cross travel drive on a crane crab but might be of use to you.

      It's in mathcad format but can pdf if required.

      Cheers

      Jon
       
    11. mechaboy

      mechaboy Active Member

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      at first you need to draw a free body diagram and assume a static condition.you have five drive rollers so each one must carry more than 50 N force.by assuming a diameter for rollers like 0.2 m and so 0.1 m radius the torque that each sprocket needs to make is 500 N/m and by assuming a diameter for sprockets you can find chains force and then by assuming motors sprocket diameter you will find motors torque and you can choose the motor.
      after that you need to make rollers like brakes.for that you need estimate friction coefficient between roller and beam.then assume static condition and find normal force on the surface that its equal to spring's force and choose springs.
      a suitable safity factor is needed.
      i hope that it is usefuall and clear but if you have any question you can ask:D
       

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