Formula Finding - Scissors Lift Actuator. 1

[Joshmead923]

My name is Josh, I work in the theatre industry and have an interest in automation. I recently set myself the task of creating a scissor lift from scratch. However, having never touched Mechanical Engineering I fear I’m well and truly out of my depth!

I’m struggling to find the correct formulas for working out the force needed to active the scissor lift at different points, e.g the bottom middle or top. I’m hoping you could point me in the correct direction, please.

I have found the formula:
F=(W+WA/2) / Tan (A)
Where as:
W = Weight of load
WA = Weight of arm
A= Angles of arms to the ground

However I do not understand where the force calculated should be applied on the scissor lift arm?

Additionally, I have found the formula:
The sum of the movement of A = FA X (L/2 x Cos Alpha) - ( F x (L X Cos Alpha)
Where as:
FA = Force on actuator
L= length of leaver
Alpha = angle of leaver.

I believe this formula gives me the force on an actuator vertical to a leaver, unfortunately I don’t know how to change this so the actuator doesn’t have to be vertical.

I found a few papers online but, alas, as a novice I don’t understand them.

I would greatly appreciate any help in finding the correct formulas.

I’m enjoying learning about this new subject and would love to know what books or reference material you would recommend for future projects.

I appreciate you taking the time to read this email, any guidance would be greatly appreciated.

 

[SWComposites]

you are way out of your depth. there is a lot of engineering that goes into such a device, and there are a lot of safety regulations to consider and comply with. just buy a scissor lift.

 

[IRstuff]

I fear I’m well and truly out of my depth!

Really? It takes an experience mechanical engineer to design a scissor-lift and you think that your only problem is that you can't find the correct design force equations?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[3DDave]

When a non-engineer suggests they want a shortcut to build a device that can easily main or kill the user we aren't being any more negative than if someone says "I want to learn about snakes, is a coral snake a good first choice?" and the reply is "Please, don't."

The problem for us is having seen non-engineers make things like this and we don't want to increase unnecessary suffering.

OTOH,

There are likely hundreds of YouTube videos of do-it-yourself scissor lift makers.

If it's the math you are after - start here:

https://oli.cmu.edu/courses/engineering-statics-open-free/

You don't need to sign in. I just tried it and except for the "Pick all the images with a car in them" anti-robot (bigots) I was right at the course material. If you like You Tube:

https://www.youtube.com/results?search_query=statics+engineering

 

[dvd]

One way to analyze a lift is by looking at the work to lift the load an incremental distance versus the actuator force over whatever stroke distance is required to produce the corresponding lift distance, as dictated by geometry. There will be inefficiencies that need to be considered, also.