Design a 1000Kg Hydraulic Scissors Lift

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Discussion Overview

The discussion revolves around the design and fabrication of a hydraulically operated scissors lift with specific load and height requirements. Participants are exploring various aspects of the design, including actuator positioning, structural integrity, and force analysis, while addressing issues encountered in previous attempts to build the lift.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses a need for assistance in redesigning a scissors lift that failed to operate as intended, specifying load and height requirements.
  • Another participant suggests that understanding the reasons for the initial failure could be beneficial for future designs.
  • Concerns are raised about the positioning of the actuator, with one participant noting that previous positions led to bending of the arms during trials.
  • A participant with a mechanical engineering background shares their experience and context for the lift's intended use in a warehouse setting, seeking advice on optimal actuator placement and structural calculations.
  • One participant proposes that the axial force on the hydraulic cylinder may be significantly higher than the load, suggesting design modifications to distribute the load more effectively.
  • There is a discussion about the effectiveness of pulling versus pushing forces from the hydraulic cylinder, with some arguing that pushing is generally more effective.
  • A recommendation is made to conduct a force analysis of the mechanism to ensure that all components can handle the required loads with appropriate safety factors.
  • One participant suggests that increasing the closed height of the lift might improve functionality and proposes testing with fewer stages.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding actuator positioning and structural design, with no consensus reached on the best approach or solution to the issues faced in the initial design.

Contextual Notes

Participants highlight the complexity of stress distribution near load application points and the need for careful consideration of design parameters, but specific assumptions and calculations remain unresolved.

Vaibhav Mestri
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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
 
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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.
 
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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.
 
Vaibhav Mestri said:
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

Vaibhav Mestri said:
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.

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?
 
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?
 
I am attaching here pdf file for your reference. It shows how I made it & where it failed.
 

Attachments

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.
 
If I make cylinder to pull the arm upward than pushing it from down like it is now will make difference?
 
Vaibhav Mestri said:
If I make cylinder to pull the arm upward than pushing it from down like it is now will make difference?

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.
 
  • #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.
 
  • #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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