A solenoid is a device which converts energy into linear motion. This energy may come from an electromagnetic field, a pneumatic (air-powered) chamber or a hydraulic (fluid-filled) cylinder. Solenoids are commonly found in electric bell assemblies, automotive starter systems, industrial air hammers and many other devices which rely on a sudden burst of power to move a specific part.
An even more powerful solenoid uses hydraulics as its source of power. The piston or pin is seated in a cylinder filled with a hydraulic fluid. As this hydraulic fluid fills the cylinder everything is pushed forward, including the piston or pin. As the piston travels towards a piece of metal or other target, the fluid buildup becomes very resistant to compression. The piston or pin will concentrate all of the cylinder's energy on whatever it encounters, even the heaviest titanium. When the solenoid has released all of its energy, the hydraulic fluid drains out of the chamber and the piston is drawn back to its original position. This action can take place in a matter of seconds. Hydraulic solenoids are so powerful that they are generally used only for the heaviest projects. Wave pools use hydraulic solenoids to release the giant stoppers at the bottom of their holding tanks. Aircraft manufacturers use hydraulic solenoids to bend titanium and other heavy metals.
http://www.wisegeek.com/what-is-a-soleno…
An even more powerful solenoid uses hydraulics as its source of power. The piston or pin is seated in a cylinder filled with a hydraulic fluid. As this hydraulic fluid fills the cylinder everything is pushed forward, including the piston or pin. As the piston travels towards a piece of metal or other target, the fluid buildup becomes very resistant to compression. The piston or pin will concentrate all of the cylinder's energy on whatever it encounters, even the heaviest titanium. When the solenoid has released all of its energy, the hydraulic fluid drains out of the chamber and the piston is drawn back to its original position. This action can take place in a matter of seconds. Hydraulic solenoids are so powerful that they are generally used only for the heaviest projects. Wave pools use hydraulic solenoids to release the giant stoppers at the bottom of their holding tanks. Aircraft manufacturers use hydraulic solenoids to bend titanium and other heavy metals.
http://www.wisegeek.com/what-is-a-soleno…