Pick the bore and rod, set the pressure, flow and stroke. Get push and pull force, extend and retract speed and time, the oil returning from each port, pump power and the rod buckling limit.
Bore · ISO 3320
bore mm
Rod
rod mm
bar
L/min
mm
Circuit
Mounting (for rod buckling)
kN
Shows the pressure this cylinder needs, and the smallest standard bore that does it at your pressure.
Extending: oil in at the cap end
How it is calculated
D is the bore, d the rod, p the pressure, Q the pump flow. A₁ is the full piston area (cap end), A₂ the annulus (rod end). Forces are theoretical; real cylinders lose about 5–10% to seal friction.
Areas A₁ = π·D²/4, A₂ = π·(D² − d²)/4, area ratio φ = A₁/A₂
Force F = p · A (N = bar · 0.1 · mm²)
Speed v = Q / A (extend Q/A₁, retract Q/A₂)
Return flow extending: Q·A₂/A₁ leaves the rod end; retracting: Q·A₁/A₂ leaves the cap end
Regenerative extend speed Q/A_rod, force p·A_rod
Pump power P = p · Q / (600 · η) (kW, bar, L/min, η ≈ 0.85)
Rod buckling F_k = π² · E · I / (K·L)², I = π·d⁴/64, E = 210 GPa, safe load = F_k / 3.5
Bores and rods follow the ISO 3320 preferred series. The buckling length L is taken as stroke + 1.5 × bore for the fully extended cylinder, times the mounting factor K (2 fixed–free, 1 pinned–pinned, 0.7 fixed–pinned, 0.5 fixed–fixed). Check the maker's buckling chart for the final design. Keep oil speed in pipes under about 5 m/s on pressure lines and 3 m/s on return lines.