How Hydrolic Motors Work

Basic Hydraulics

The basic concept of hydraulics is the use of incompressible fluids in mechanical, industrial or heavy equipment applications. All hydraulic motors use hydraulic liquids as the main source of power. A basic hydraulic motor will have a pair of pistons distanced apart by tubing that houses hydraulic fluid. When a piston moves, the next piston will also move as a result of the incompressible hydraulic fluid. The hydraulic fluid transfers the pressure from the first piston, plus the built up pressure in the fluid to the next piston. The result is more force/ power with less start up power. In essence, the pressurized hydraulic fluid turns the motor.

Mechanical Replacement

Gears and levers are replaced with pressurized fluids in a hydraulic motor system to literally multiply the amount of start up force. This is accomplished by implementing hydraulic fluid cylinders between pumps and motors. In the case of using cylinders for hydraulic power, the start up force is the smaller piston, with the next piston being a number of times larger in surface area than that of the first piston. The force accrued from the second piston is greater due to its larger surface area (divide the smaller surface area into the larger surface area. The resulting number is how many units the bigger cylinder will move each time fluid is pumped). A 10-pound down force on the first piston, for example, will produce an upward force that is X number of times more powerful on the second piston. The smaller piston is able to move the second piston only because the fluid between the two cylinders is hydraulic (oils or other fluids that will not compress under pressure). In essence, it is the fluid that does the real work in any hydraulic system. Because the fluid doesn't compress, the amount of work accomplished is more than the start up work.

Motors

Hydraulic motors are run by rotary pumps. The motor will always have more rotary power (torque) than the rotary pump. In contrast, the shaft on the rotary pump is significantly faster than the motor shaft speed. The effect is the multiplication of the start up force by the displacement between the pump shaft and the motor shaft. Motors can also be the start up force in a hydraulic system. The motor is connected to a directional valve. The pump is connected to the valve as well. The valve is fixed to a hydraulic fluid tank. The hydraulic fluid in the tank supplies the necessary pressure build up in the system to run hydraulic machinery.