gas piston dimensioning

[Catartica]

Good evening,
I open this debate because I have found nothing concrete about it.
I need to size a piston that has the function of helping to open a hatch, to be more clear style luggage car.
I performed a dynamic analysis taking into account gravity and therefore the weight force of the object to be lifted, and I gave a driving force to the piston.
I expect to find a graph that has the performance of the resulting forces according to the opening angle: maximum opening, which cancels the balance of forces and is negative when the weight force becomes greater.
I also tried to drop the hatch, using as a result the reaction you have on the piston, but nothing to do. I don't understand what I'm wrong, but it seems like a pretty simple study.
I hope some of you have some valuable advice.
Thank you all in advance.

 

[meccanicamg]

if you do not place files or procedures....the seers cannot help you.

 

[egdo]

Bye.
Excuse me but I don't understand all this difficulty in dimensionaling a gas spring used for a hatch.
I'll leave you under an attached image.
you have to consider mainly 3 things: the weight of the hood, the distance from the center of gravity and the distance from the cylinder hinge (of course taken in parallel).

 

[Catartica]

Good morning.

Obviously my problem is not the dimensioning itself, but to make the analysis to create.
Thank you.