Calculation of Scissors Lift

  • Thread starter nabilishes
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  • #1
nabilishes
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Homework Statement


I need help in calculating the forces that act upon the arms of a scissors lift. Attached is the force diagramm and some calculations i made earlier. The calculation was made based on each arm

It would be nice if any of you could have a look and check whether the calculation are correct or perhaps i missed something out.

Thankss


Homework Equations





The Attempt at a Solution


solutions are in the attached picture
 

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Answers and Replies

  • #2
nvn
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nabilishes: It seems you are assuming Fa, Fb, Fc, and Fd are axial forces in members 1 and 2, which is incorrect. You would need to quit making that assumption, and rewrite your solution. Also, you did not give the dimensions of each arm segment. Also, you can solve for M in terms of F and alpha.
 
Last edited:
  • #3
nabilishes
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For M and F, i already know how to solve that. If i'm not wrong
M=(F+(Warm/2)) / tan alpha

Say L= 0.5 m

i need to calculate the stress acting upon the pivot and the moving points C and A.
C and A is bolted to a slot, where when the mechanical actuator or hydraulic cylinder acts upon C, the scissors lift will the object. Attached is a picture of the slot

So how do i get the force acting on both points?
 

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  • #4
nvn
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nabilishes: OK, do what is mentioned in the first two sentences of post 2. And also use your expression for M in post 3, which is correct. However, I prefer to define, W = self weight of each arm, in which case, M = (F + W)/tan(alpha). Show your work, and someone might check your math.
 
  • #5
nabilishes
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I made some additional reading at stumbled upon the principle of virtual work and came to a conclusion that there sum of the work done by the pivot is zero since both forces have the same magnitude but opposite in sign.

Thanks for the help.
 

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