# I want to know all of the maths concerning this scissor mechanism!

#### Maglatron

Jul 12, 2023
1,640
I would like info on this mechanism, thanks guys

#### Maglatron

Jul 12, 2023
1,640
any info or sites or knowledge you might have that can point me in the right direction will be warmly welcomed, thanks

#### bertus

Moderator
Nov 8, 2019
3,381
Hello,

This is what the wiki tells:

Bertus

#### Maglatron

Jul 12, 2023
1,640
thank you Mr bertus! the wiki has nothing math wise and also the explaination goes on the say that "Extension is achieved by applying pressure to the outside of a set of supports located at one end of the mechanism, elongating the crossing pattern" I want to apply the force in the middle upwards where the yellow slider is in this picture with the cam I need formulas for the Mechanical Advantage, the ratios for how high the yellow slider and the full extention of the top of the scissors to the number of stages in the scissor, and the forces involved, I think this problem is probably best suited to the physics guys over at physicsforums but they don't want me on there for some reason! but thanks again for the help!!

Moderator
Nov 8, 2019
3,381
Hello,

Does this help?

Bertus

#### Maglatron

Jul 12, 2023
1,640
that was very nice but I don't think it helps or at least I don't know how to apply it to what I want, look at this where the force is applied on these images the one I need is centre vertical!! thanks

#### Maglatron

Jul 12, 2023
1,640
here's another, I want the same witchout the curving as it moves

#### Maglatron

Jul 12, 2023
1,640
I will sign up to the site though because they have some PDF files that I'm interested in thank you

#### Maglatron

Jul 12, 2023
1,640
so I drew a diagram

#### Attachments

• scissor yes.png
13 KB · Views: 2

#### Delta Prime

Jul 29, 2020
2,115
Be careful!

Error in Scissors Lift Equations??

7.12.2012 Update:

Ok…. finally Engineers Edge has corrected their equations. So I have modified this post to take out the obsolete references.

#### Maglatron

Jul 12, 2023
1,640
thanks mate caught that myself! anyone recommend a book with mechanisms in??

#### Maglatron

Jul 12, 2023
1,640
so breaking it down
1) the cam, shaped like a snail shell, need in depth info on how force and displacement (energy) is consumed during a rotation of (2pi rad)
2) how to design the scissor bar lengths and how many stages do I need, in my diagram that I privided, there are two stages above where the force is applied

#### Attachments

• scissor yes.png
13 KB · Views: 2
Last edited:

#### Maglatron

Jul 12, 2023
1,640
from memory Mr Alec_t was very good with mechanical stuff are you around Mr Alec_t??

#### Delta Prime

Jul 29, 2020
2,115
how to design the scissor bar lengths and how many stages do I need
You have to be agile in your approach.
Apologies if you have already visited this site.

#### Alec_t

Jul 7, 2015
3,644
are you around Mr Alec_t?
I'm around, but other members here are giving you good info already and my maths is a bit rusty.
What is the purpose of this mechanism?

#### davenn

Moderator
Sep 5, 2009
14,296
What is the purpose of this mechanism?

Scissor lift, as per the earlier posts, surely you have seen one in a warehouse etc ?

Last edited:

#### Alec_t

Jul 7, 2015
3,644
I'm fmiliar with the scissor lift and mechanism Dave, but curious as to the TS's intended use of it.

#### Maglatron

Jul 12, 2023
1,640
I want to use the scissor mechanism in conjunction with the mechanism (that I posted in another thread) to lift the weight of 275grams a hieght of 1.26m and drive the cam with the motion of the wheel!my thinking is that if the wieght is lifted quickly it won't have the time to slow the wheel (too much) it's impulse; whereby if a thing is moving, then it provides a really high force at impact to slow it down, the faster it's slowed the higher the force on impact, so taking advantage of the high force as a product of the change velocity and inertia and the time it took, thanks in other words, it takes a really high force to change the momentum quickly especially if the unit of momentum is high and me thinks this high force short time will be enough to lift the wieght up if the scissor and cam are designed correctly, not looking for you to work it our for me I just want the equations and formulas to work it out myself I've just bought 3 books on the matter of mechanisms and the math to go along with it so might not need the help if the stuff I need is in the books!!

Last edited:

#### Delta Prime

Jul 29, 2020
2,115
Yeah Dave! Focus pick on me..

#### Maglatron

Jul 12, 2023
1,640
what on earth is a huckleberry?

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