Extension speed
Theoretical cap-end speed.
Fluid mechanics · Hydraulics
Hydraulic cylinder extension and retraction speed
Speed equals volumetric flow divided by active area. Retraction is faster because annular area is smaller.
Created v1.0
By Thibaut Grzelak, Mechanical Analysis Engineer
02
Results
Retraction speed
Theoretical rod-end speed.
Piston area
Area used during extension.
Annular area
Area used during retraction.
Relation and numerical substitution
vsortie = Q/Ap ; vrentrée = Q/Aa—
Constant flow fully available at the cylinder. Incompressible fluid. Internal and external leakage ignored. d < D.
01Formulas and symbols
Formulas used
Ap
πD²/4Piston areaAa
π(D²−d²)/4Annular areav
Q/ALinear speed02Assumptions and limits
Scope of validity
- Constant flow fully available at the cylinder.
- Incompressible fluid.
- Internal and external leakage ignored.
- d < D.
03Validation example
Reference numerical case
- Q = 20 L/min, D = 50 mm and d = 25 mm.
- vextension = 169.765 mm/s; vretraction = 226.354 mm/s.
04References
Technical references
- Continuity relation Q = vA.
- Circular and annular areas.
Hydraulic preliminary sizing
Size a hydraulic cylinder: force, bore, flow and speed
Pressure and force determine required area. Area sets bore, then flow determines speed and stroke time.
Cap-end bore
Minimum bore depends on required force, available pressure and efficiency.
D = √[4F / (πPη)]Rod-end area
During retraction, the rod reduces active area.
Aa = π(D² − d²) / 4Complete calculation
The dedicated calculator connects force, bore, rod, stroke, time and flow.