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Hydraulic Cylinder Force

Extend and retract force from pressure, bore, and rod diameter.

InputF_ext = P · πD²/4 F_ret = P · π(D² − d²)/4

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The engineering

A hydraulic cylinder is Pascal's principle with a paycheck: pressure times piston area, no gearbox required. The asymmetry is the number that bites — the rod steals annulus area on the retract side, so a cylinder pulls weaker than it pushes and, on the flip side, retracts *faster* for the same flow. Regeneration circuits and load-holding valves exist entirely because of that imbalance.

Watch the retract-side pressure intensification too: load a rod-side port against a blocked bore-side and the area ratio multiplies pressure beyond relief settings. And the rod in compression is a slender column — long-stroke cylinders are checked against Euler buckling (two cards up) before anyone trusts the force number here.

Where this math comes from

Blaise Pascal established around 1653 that pressure in a confined fluid pushes equally everywhere — and noted the disquieting corollary that a thin column of water could burst a barrel. Joseph Bramah, a locksmith of genius, weaponized the principle commercially with his 1795 hydraulic press patent; his workshop, incidentally, trained Henry Maudslay, whose leather cup seal made the press actually hold pressure.

William Armstrong industrialized hydraulics from the 1846 crane onward, building city-scale pressurized water networks to move cargo and open bridges. Oil replaced water in the twentieth century, pressures climbed from tens to hundreds of bar, and the excavator became the most visible descendant of Bramah's press.

  1. 1653Blaise PascalPressure transmits equally in a confined fluid.
  2. 1795Joseph BramahHydraulic press patented — force multiplication by area.
  3. 1846William ArmstrongHydraulic crane launches industrial fluid power.

See the full timeline of the math behind every calculator →

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