Buckling strength of the piston rods

The danger of the piston rods buckling during long strokes and an additional unfavorable cylinder mounting determine the cylinder sizes and their limits.

The calculations are usually carried out according to Euler since the piston rods are to be seen as slender rods.

The following applies:

Fk = 3,14² * E * I


FK = Force at which the piston rod buckles in [N]
E =

Modulus of elasticity (Steel 210000 N/mm2)

in [N/mm2]
I =

Moment of inertia (for circle cross-section)

in [mm4]
LK = Free buckling length in [mm4]

The following diagram shows the four so-called Eulerian load cases. The permissible stroke lengths of every hydraulic cylinder series are listed in the appendix.