calculation of stresses of a pantograph lift

[Filippo Ottanelli]

Hello everyone, I am new on the forum! I am a mechanical engineering student at the third year.
because of the covid it is very difficult to have a consult with the professor and therefore I decided to ask for help to the forum, given the great availability of the members in other threads.
I am designing a pantograph lift, I have already read all the discussions already opened on the site but I did not find anyone with my own constructive solution (if not I apologize and link it to me).
I attach 2 photos to clarify better. our problem is the resolution of the binding reactions of the scissors at the centre of the structure, i.e. those where the piston acts (which is surrounded by the structure as in the figure).
Of course I do not want the resolution of the whole structure, but to know if there is a simplification of the problem to make that I am not applying.
because considering that the piston "downloads" on 4 hinges throughout the structure (c2, f, c4, g) too many unknowns come out for resolution.
Thank you all! !

 

[bip]

the load will not divide equally on a and b, plus raise the platform, and the two points approach, and the distribution of the load varies.

starts defining the cinematics: you can define all depending on the alpha angle, cylinder length, or platform height, at your choice.
to simplify the calculations a bit, I would do it according to the angle you indicated as "alpha" in your scheme.
be careful that the position of the point in relation to the vertical load changes in function of alpha.

Once you have defined the kinematics, draw the free body diagram of the various components, I suggest you start from above, so "take down" the loads.
everything will be parametric according to the alpha angle.

when you have completed free body diagrams, you have loads on the various components and cylinder according to alpha, calculate the structures for the alpha angle that maximizes effort (it will not be the same angle for all components). in this phase, paying great attention to not making mistakes in writing formulas, excel can be very useful to you, you can trace the maximum tensions according to the angle.
If the lengths of the various components are not yet defined, you can have a cell containing the length, so you can play a bit to vary the maximum height reached at the same angle, and you can also evaluate the best positioning for the cylinder moving the mechanism