A five-port directional valve alternately supplies the cap and rod chambers of a double-acting cylinder. You watch the spool, chamber pressures, exhaust flow and the unequal extension and retraction force caused by the rod area.
• A cylinder barrel and piston cutaway, a piston rod and guided carriage, a 5/2 directional spool valve, an air receiver and pressure regulator, and exhaust silencers and chamber hoses. • Controls for supply gauge pressure (1-6 bar), cylinder bore (25-63 mm), constant load opposing extension (0-700 N), pressure response time (0.05-0.5 s) and valve command (automatic, hold extend, hold retract). • Readouts of rod position, cap and rod chamber gauge pressure, net force and the ideal full-pressure extension and retraction forces. • Experiments: unequal piston areas, a load that prevents extension, and slow pressure response.
Acap = πD²/4 and Arod = Acap − π(0.016)²/4. Net pressure force is Fp = pcap Acap − prod Arod − load, with each chamber pressure approaching supply or zero at time constant τ. The 5 kg moving mass follows m dv/dt = Fp − 400v with the stroke clamped to 0-0.2 m; the automatic valve alternates every 3 s.
This is a lumped teaching model with first-order chamber pressure response, ideal supply, viscous damping and inelastic end stops. It has no mass-flow or compressibility, seal stiction, cushion design or air-consumption prediction. Force figures are illustrative, not actuator selection approval.
The rod reduces the effective piston area: the rod-side area excludes the rod cross section.
No. The numerical model uses first-order chamber pressure dynamics rather than an air-consumption calculation.
Pressure force cannot overcome the opposing load, so the rod remains at the retracted stop.
In automatic mode the valve alternates extend and retract every 3 s; the hold extend and hold retract commands keep the spool in one position.