Technology and Engineering · Middle school

Hydraulic press

Pump the lever: the pressure on the small piston passes unchanged to the big one, and the force grows.

In the learning section below the figure, predict, try, complete the tasks and check yourself with short questions.

Fig. 1Hydraulic press

Drag the lever down, use “Pump the lever” or take the press apart

p 0 bar · 0.0 mm

Parts and inner workings

Separation0%

With the press apart, hover over a part, tap it or pick it from the list.

Pick an assembly to read what it does and what a real press uses.

Your own values

Small piston diameter

Large piston diameter

Force you apply to the small piston

Load on the large piston

Decimals are fine (e.g. 2.5 or 2,5); press Enter or leave the box. If a value is invalid, the figure does not change.

Fluid pressure

Pressure gauge

0 bar0 kPa

Weight of the load F₂981 N
Force you apply F₁150 N
Least force that lifts the load109 N
Oil’s push on the large piston F₁ · A₂ / A₁1,350 N
Force gain A₂ / A₁× 9
Hand force at the lever end30.0 N
Rise of the large piston0.0 / 60 mm

p = F₂ / A₂ = 981 N / 28.3 cm² = 3.47 bar

Work is conserved

Lever from the top to here

d₁ = 0.0 mmd₂ = 0 mm

With the force that balances the load

F₁ · d₁ = 0 J
F₂ · d₂ = 0 J

The large piston sits on its stop at the bottom, so the gauge reads 0. Pump the lever.

Lever

Learn

Progress is kept on this page only; no points are given.

1Predict
2Try
3Explain

If you shrink the small piston from 2 cm to 1 cm across, what happens to the least force that lifts the load?

Gold: hydraulic oil (dots in the line show the oil moving while you pump)Gold grip: the leverThe numbers come from the figure’s own model, using the values you enter; the article’s example uses pistons 2 cm and 6 cm across and a 100 kg load. One full push moves the small piston down 30 mm, and the lever ratio is 5. The fluid is taken as incompressible, with no friction or leaks; the weight of the piston and platen and the height difference between the pistons are ignored. The pressure p = F₂ / A₂ is the same everywhere, and the force that balances the load is F₁ = p · A₁. If you apply less, the lever will not move. What you gain in force you lose in distance: F₁ · d₁ = F₂ · d₂.Not to scale: the large piston is always drawn the same size, and the small one by the ratio of the two diameters.

How does a hydraulic press work? Pascal's principle and lifting a big load with a small forceRead the article

Hydraulic press

Parts and inner workings

Your own values

Fluid pressure

Work is conserved

Learn

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