Hydraulics work because pressurized liquid goes from one chamber to another and causes the rods or pistons in the system to move. The most basic hydraulic system is a hydraulic cylinder, which can be found in everything from your car to the crane building a high rise. 

Hydraulic Cylinder

These tools are basically just a tube that has a rod inside of it, along with pressurized hydraulic fluid. The rod divides the cylinder into two parts. There is also usually a pump connected to one end of the tube, opposite the end where the rod comes out when activated. There may also be a series of valves and seals that go along with the cylinder and pump, depending on where the cylinder is being used and what its job is. 

How It Works

The way that a hydraulic cylinder works is that when the pump pushes fluid into the cylinder, the rod goes up. In some places, like your car, the pump is a manual pump, working when the door gets opened, and it is usually contained in the cylinder itself. In order uses, like in a bulldozer, the cylinder may be attached to a pump that is attached to a large reservoir of hydraulic fluid and a control switch. When the switch is activated, the pump pushes the fluid into the cylinder, activating the rod and causing the rod to move whatever piece of equipment that it is attached to. For example, activating a particular cylinder may make the blade on the bulldozer angle one way, but when the rod retracts, the blade angles back to its original state. As the rod retracts, the fluid is pushed out of the cylinder and back into the reservoir. As part of a larger system, one hydraulic cylinder may be used to activate one or more cylinders. This is especially true in a large or complex system. In a large system, it may be difficult for everything to work correctly without a boost, so a series of cylinders may be the perfect option. 

Hydraulics have been around for a long time because they are a very simple tool to use, and one that can be used to make more complex systems that can power all kinds of things. Hydraulic cylinders can be found in everything from the simple cylinder in your car's trunk, the hydraulic press that you enjoy watching videos of, and in heavy construction equipment. No matter the size or use, they all work in the same way.