# Double scissor lift

1. Dec 29, 2012

### hisham Aliyan

Hello everybody ,
i'm new here .. so i hope that you help me in this problem ..
i have to make an analysis for a double scissor lift , it has to lift 4000 kg , for a length of 2 meter ,,
i have to calculate fatigues ,buckling ,deflection , welding ,screws and the material selected !! so any body can help !!

2. Dec 29, 2012

### 256bits

There is a scissor lift freight elevator I go by at times and when operating it just seems fascinating.

Since you have 2 members as a unit ( 8 members altogether i guess ) that straighten out as the lift rises,you would want the members to be more than 1 meter each in length, otherwise the thing would topple over when fully extended. So you could start by picking a particlular member length and with the use of FBD, check the forces on members at specific heights of the lift, and stabiliy at maximum height with a 4000 kg load.

If that is OK, then you have to pick a material, cross-section and size of member, calculate stresses and deflections, etc. I not acceptable then you may have to do several iterations in choosing lengths, cross-section, and size of member.

The iteration thing no doubt threw you off, as there is not one single simple equation to plug in some numbers and voila - out pops the answer.
have fun!!