Scissor Lift Help (Analysis)

This might help....

http://www.engineersedge.com/mechanics_machines/scissor-lift.htm

Tnx for the reply SolarEagle, I was looking for something a little more indept analysis, similar to the documentation in the link below, which was written by H.M Spackman:

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA225220

Sometimes FEA is faster for analyzing more complex load case such as these compared to hand calc methods as shown in that doc. We've done a few scissor lift type mechanisms before. The scissor concept is relatively simple and takes very little time to model the basics of the arms, hydraulic cylinders,etc then derived your loads. The advantage to doing it this way is your values are updated automatically as you make design changes thus allowing you to fine tune the design. You couldn't do that with hand calcs unless you have some type of Excel based table but thats really time consuming to setup up.

Truck mounted lift table as an example.

Food for thought.

Hi TerraMan, what software did you use for the FEA analysis, was it a dynamic simulation software which allowed you to define load through out the scissor movement.

The only way I can see using FEA is to use a computational program (such as matlab or excel etc.) which will calculate all the load at the pins throughout the scissor movement, then use that data to input your load conditions into an FEA Model software. So I am unsure what you mean when you say:

"The advantage to doing it this way is your values are updated automatically as you make design changes thus allowing you to fine tune the design"

Unless you use a specialized software?

We use Catia and you can apply reaction sensors to joints which give you the loads at those points. The load comes from gravity load of the assembly plus platform capacity. We simply position the platform at it's lowest poistion, apply reaction sensor to the joints, apply load to the platform, and hit "compute". Results within a few seconds. We then positioned the platform at it's highest point and hit compute again. We don't get into dynamic analysis because Catia is cumbersome for that. For a simply mechanism like this it's not necessary. I know that Solidworks does a nice job with dynamic analysis for small assemblies but I haven't used it. There's a demo of it on the "Let's Go Design" website if your interested. Search "Ultimate Cad Chair" on the site.

Give me an example of your scissor lift dimensions (arm length, width, thk, and pivot c to c) and I can show you what I mean. It only takes a few minutes.