Pinned Hydraulic Cylinder Force

[PotashMechy]

Hi All,

I am trying to determine the force required of a cylinder to keep a plate pushed down, and to pull it up when needed. The cylinder is pinned at both ends. The plate is resting on a beam at one end, and is pinned at the other end to be able to pivot. The loads acting on the plate include its own weight, and considerable winds pushing up from beneath.

How would I solve for the required force of the cylinder? If my free body diagram of the plate is correct, I have more unknown forces than available equilibrium equations. Is there a simpler way to size a hydraulic cylinder?

Angle is 24.5 degrees,
Plate load is 1448 N
Wind load is 10,000N

Drawing of the problem is attached.

 

[BrianE22]

Is Fy,a considered an unknown? I would think you would specify that as the "desired closing force". Then you have 3 equations and 3 unknowns.

 

[TheTick]

Since the plate is pinned (i.e. hinged), solve for the net torque on the plate. Then you can solve for the force F_y,a to hold the plate down, and then the resultant force on the actuator.

As for opening force, also start with the torque on the plate due to gravity. Opening torque will lessen as the center of gravity moves toward the hinge axis. Resultant force on the actuator will also vary as position and angle change.

I used to do a lot of similar problems, but with torsion springs. Usually best to graph torque and/or force vs open angle.