What is hydraulics?

Hydraulics is a mechanical system that functions through the application of liquid pressure. In hydraulic systems, mechanical movement is generated by pressurized liquid, often through hydraulic cylinders that move pistons. This technology is a part of mechatronics, a field that integrates mechanical, electronic, and software engineering to design and create various products and processes.

Who invented hydraulics?

It’s challenging to identify a single inventor of hydraulics, but the technology has been in use since the 1st century. Blaise Pascal, a French physicist, mathematician, inventor, philosopher, and theologian, made significant contributions to hydrostatics and hydrodynamics. He is credited with inventing the first hydraulic press, which utilized hydraulic pressure to amplify force. Pascal also formulated Pascal’s law, which describes how fluid at rest in a confined space experiences pressure changes uniformly throughout the fluid and the container’s walls.

How do hydraulic systems work?

Modern Car Lift For Sale hydraulic systems consist of components such as actuators, hoses, and hydraulic cylinders that use water pressure, often aided by gravity, to create mechanical movement. These systems can amplify force by employing a smaller cylinder to push a larger piston in a bigger cylinder, often with multiple pistons in use. Hydraulic pumps pressurize liquids (commonly hydraulic oils) to move pistons through cylinders, and control valves manage the flow rate of the oil.

What are the applications of hydraulic systems?

Car Lift For Sale Hydraulic systems are widely used across various industries. In the automotive sector, they are integral to braking systems and power steering. They are also crucial in construction equipment, manufacturing machinery, and aircraft. Many everyday interactions with hydraulics-based systems occur without conscious realization.

Examples of hydraulic machinery include:

– Log Splitters: These single-piston hydraulic machines use pressurized liquid to drive a wedge that splits wood and then returns to its original position.

– Backhoes: Large industrial equipment like backhoes use multiple hydraulic cylinders for various functions, including operating the bucket, dipper arm, and extendable boom. These setups are often controlled electronically.

– Bucket Trucks: Also known as cherry pickers, bucket trucks use hydraulics to elevate and lower the bucket for work at high altitudes. The hydraulic system may also rotate the bucket.

Hydraulics vs. Pneumatic Systems

Car Lift For Sale Hydraulics and pneumatics are similar in that both use pressurized fluids to generate power, but hydraulics utilize liquids, while pneumatics use gases. Hydraulics can handle higher pressures (up to 10,000 psi) compared to pneumatics (about 100 psi), due to the incompressibility of liquids. This results in more efficient power transfer. Hydraulic fluids can also lubricate, cool, and transmit power, whereas pneumatics require separate oil lubrication, which can be messy. Car Lift For Sale Pneumatics offer simpler design and control and are generally safer with a lower risk of fire, as the compressibility of gas can absorb shock and protect the mechanism.

What Is Flow Rate?

In the U.S., flow rate is typically measured in gallons per minute (GPM). In a fixed displacement pump system, the flow rate is directly linked to the pump’s speed. A higher flow rate means the cylinder or motor will move more quickly.

For fixed displacement Car Lift For Sale hydraulic motors, a specific volume of oil is needed to make the shaft complete one revolution. This volume is known as the motor’s displacement, often measured in cubic inches (CID) or cubic centimeters (CC). For instance, if you provide a motor with 100 times its CID per minute, it will turn at 100 RPM. Increasing the flow rate will speed up the motor, while decreasing it will slow the motor down.

To convert flow measurements, use equations based on different units. To convert this to gallons, divide by 231 (cubic inches per gallon): 3,000 / 231 ≈ 12.99 gallons per minute (rounded to 13 GPM). Smaller motors will run faster, while larger motors will run slower given the same flow rate.

Flow Implications

The flow rate through tubes and hoses impacts performance. As oil flows through these conduits, it experiences friction, which creates resistance. To overcome this friction, pressure must be generated. For instance, in a 100-foot hose, the pressure at the downstream end will be lower than at the upstream end due to this resistance, known as back pressure.

Back pressure results in a loss of energy, which is converted into heat. Consider a 13 GPM flow rate for the motor example. Hose diameter affects oil velocity and pressure drop. 

For the example above, a 5/8” hose is suitable for working lines, while a ¾” hose is ideal for return lines. The suction line should be at least 1-¼” to prevent cavitation. If a 5/8” hose is unavailable, a ¾” or ½” hose can work, though the latter may result in higher pressure drop and increased fuel or electricity costs. A larger hose can help save pump pressure, but using a smaller hose like ¼” can lead to significant pressure drops and potential system failure.

Working With Cylinders

The extension speed is related to the piston area the oil acts upon. For a 3” bore cylinder, the area is 7.07 square inches.

For example, with a 1 GPM pump, the IPM can be calculated by first determining the volume required to displace the cylinder’s cap end. If the stroke is 12 inches, the volume needed is 7.07 cu/in × 12 inches = 84.84 cubic inches. Converting 1 GPM to cubic inches per second: (1 GPM / 231) / 60 ≈ 3.85 cu inches per second. 

The bore size affects extension speed: larger bores extend slower, while smaller bores extend faster at the same flow rate. Cylinders come in various types, including single acting, double acting, telescopic, single rod, and double rod, with different formulas applied to each.

About Hydraulic Pumps

Car Lift For Sale Hydraulic pumps generate flow, not pressure. Pressure arises from resistance to oil flow. For instance, a hydraulic cylinder not connected to a load will extend and retract with low pressure. The pressure measured at the pump is needed to overcome friction and back pressure.

Car Lift For Sale Hydraulic components must be protected from excessive pressure. A relief valve typically manages this by allowing oil to return to the tank if pressure exceeds the maximum setting, preventing damage or failure.