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Scissors lift design

  1. Feb 24, 2015 #1
    Hello guys

    I want to fabricate hydraulically operated scissors lift.
    I preformed calculations & fabricated same but unfortunately it didn't work.
    Can anybody help me out to design it again.
    Required specifications are
    Maximum load: 1000Kg
    Open height: 1500mm
    Closed height: less than 375 mm

    Thanks in advance
     
  2. jcsd
  3. Feb 24, 2015 #2

    Bystander

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    If you give us the details of what didn't work, it will probably be more useful to you in the future to learn what kept it from working.
     
  4. Feb 24, 2015 #3
    Actully I am concerned about actuator position. I tried couple of positions for actuator but didn't work.
    All the time in trial run arms bent.
    Also I am not sure whether my calculations for arms & rest of the structure were correct. Can anybody help out
    with complete design from beginning.
     
  5. Feb 24, 2015 #4

    berkeman

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    Welcome to the PF.

    What is your design background? Do you have a degree in ME, or some other degree? What kinds of things have you designed and built in the past?

    What will this lift be used for? Can you provide some context?
     
  6. Feb 24, 2015 #5
    I have done BE Mechanical from University of Mumbai India. I have worked as design engineer in couple of companies,
    Now I run my own workshop to manufacture & repair hydraulic cylinders. I have experience in designing hydraulic actuators.
    This is kind of new project I am working on. This scissors lift is to be used for moving goods from on place to other in warehouse.
    I saw many images & video on internet for actuator position in scissors lift, I found it to be placed in many different positions.
    What is the best position to place it. Do I need to start calculations assuming cross section of arm & check it for bending?
     
  7. Feb 24, 2015 #6
    I am attaching here pdf file for your reference. It shows how I made it & where it failed.
     

    Attached Files:

  8. Feb 25, 2015 #7

    Baluncore

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    I suspect that, where n is the number of stages, the axial force on the hydraulic cylinder will be about 2n times the load being lifted. The cross bar where the rod end attaches needs to have a better designed profile so as to distribute that high load, (1000kg * 2 * 3 = 6000kg), to the sides of the scissors.

    Your picture shows pins being used across the machine. Torque tubes should be used to join the two sides of the machine.

    You might consider using two cylinders in parallel, one on each side of the machine.
     
  9. Feb 25, 2015 #8
    If I make cylinder to pull the arm upward than pushing it from down like it is now will make difference?
     
  10. Feb 25, 2015 #9

    Baluncore

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    It would not be better. Cylinders work better when they push.

    The problem is that the cylinder force is applied at approximately 90° to a diagonal member. That member must be strong enough to transfer that force. The member that bears the force could be reinforced to handle the load.
     
  11. Feb 26, 2015 #10
    You should do a force analysis of the entire , mechanism in a variety of positions. Then, based on the calculated forces, design the members to take the required forces, with a generous safety factor.

    Bear in mind also that near any point of load application, such as a connection pin, cylinder attachment, etc. the stress distribution will be much more complicated than that predicted by a simple stress analysis.
     
  12. Mar 1, 2015 #11
    You may have better luck if you can increase the closed height. Try it with just to stages and see if you can get the height.
     
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