A hydraulic device used in the real world is the hydraulic crane. A hydraulic crane uses a incompressible fluid (usually oil) to lift an object. Most cranes will use a two gear pump to increase the pressure and lift the object. When pressure is applied, one piston is pushed down. This will push the other piston back up. A hydraulic crane will typically have three pumps, the main pump, the counterweight pump and the steering pump. The main pump is the pump that actually raises and lowers the arm of the crane. The counterweight pump is used to keep the crane from actually tipping over. The steering pump actually powers the outriggers as well as steering the crane. The outriggers are the supports that are used to keep the crane balanced. All these pumps are controlled by foot pedals and joysticks located in the driver’s cab.

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