Pascal law

[ap5234]

Hi,

im currently working on a system where 2 cylinders (same plunger area) are acting in isolation.

Case 1: i understand that if F1 > F2 and A1 = A2 than you will have a resulting force of F1-F2 = Fr on A2 and vice versa.

But Case 2 : if i got a beam support by cylinder at both ends and im loading the beamn at different position. Again A1 = A2. How do you think the system will react ? (see picture)

Assume the beam well connected on the 2 plungers.

Thank you!

regards

AP

 

[PNachtwey]

Case 1, F2 will go down until it covers the port and the oil at the end compress to equalize forces.
Case 2, Depends on the torque. piston 2 will go down until the some of torques is 0. The guides need to supply a resistive force that will oppose F2 and aid F1. This will be a binding situation.

Are you trying to make an auto leveling press that can handle offset loads?
The sum of forces on the pistons must be equal to the set point force. To keep the platten level the sum of torques is 0. The piston on the left is actually pulling or applying a negative force.

https://youtu.be/G3uM1NjVIgo

Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

http://forum.deltamotion.com/

 

[ap5234]

it's for a lifting application. Im trying to find what will be the delta between the 2 top pistons at loading. during loading the valve is shut off, so the 2 cylinders are isolate together. So the only thing will reduce the delta is the resistance of the beam in bending. I want to know the moment at both ends too.

And cause of the 2 guide connection, Both angle of deflection will be zero at ends.

sorry for my bad english ..

Thank you for your help Peter

AP

 

[hydtools]

Draw a free body diagram of the beam rigidly attached to the pistons. Solve for forces and moments. Pressure could be assumed to be the same all through the fluid space if velocties are relatively low. A static condition.

As Peter noted, at some differencial in ram movement one or both will bind.
Ted

 

[TimSchrader2]

Hello. For case 2 the only way to balance the forces is to change the area of the plunger areas. Because, as Noted above the press in fluid must be same in both, if connected. So each side must support 43/2 + dead wieght.

Or use a valve between the two, if you can.

Another way to look at this is to assume the 43 lbs is on the centerline, so each side takes the 43/2. Then the moment is 43lbs x the dist from centerline. Pretty much the same as the F1-F2=FR, just getting there a different way. So the plunger seals and beam will need to handle that moment. Or forces caused by that moment.

 

[chicopee]

If the beam is not welded to the top of each cylinder head there will not be any end moment on the beam. One end of the beam will rest on the top of the cylinder head and the other end will be contacting the cylinder edge.