Basic concept of Hydraulics?

Question

Can some please [simply] explain the basic concept of hydraulics, hydraulic brakes and pistons. Especially the last 2.. I'm a bit confused about what we've been learning in class..
Thanks!

Answer 1

Let's say you weigh 100 pounds and step onto a piston with an area of one square inch. You will move the piston down, and the gas or fluid behind it, until you increase the fluid pressure by 100 pounds per square inch (PSI). If it's a gas, you'll probably just compress the gas. If it's water or hydraulic fluid, you'll compress the fluid a very tiny bit and expand the container until the pressure is 100PSI.

If the hydraulic system is connected to another piston with an area of 200 square inches, your 100 pounds will apply a force on that piston of 2000 pounds, enough to lift a small car. But to move that piston up one inch, you'll need to push your piston down 200 inches to move the necessary volume of fluid.

Answer 2

If we want to talk about the very basics of hydraulics it has to be two concepts. 1] the principle of continuity in a hydraulic flow.rho*A*V=constant 2] Static head+potential head+dynamic head=constant[ this same as conservation of energy]. There are many other concepts besides these- namely pressure at in point in a fluid medium is same in all directions.[pascal's law]. Hydraulic fluid like oil or water in practically in compressible. This is the reason there is enormous capability to do useful work by using hydraulics. All you need to ensure is that the sealing is proper and there are no leaks. Second important issue is to ensure that the design pressure is never exceeded and the hoop tension and and longitudinal rupture is well within design limits. All these principles apply in design of pistons and hydraulic brtakes.

Answer 3

basically you cant compress a fluid, like you can with a gas. hydraulic brakes are basically just a hydraulic lever. when you step on your brakes, leverage multiplies the force applied to a piston which in turn forces the fluid pressure to rise and forcing the fluid through the brake lines to another piston which then applies the multiplied force to the brake pads which contact your rotors, causing friction and causing you to stop....whew. car brakes are also a good example of how much force can be generated with hydraulics. Imagine trying to force a car to stop by applying pressure to those brake pads with your hands. ouch, not going to work. But a much less amount of force applied by your foot routed through a hydraulic system generates more than enough force to stop your car. anyway, hope this helps a little...

Answer 4

Force multiplication depends on the ratio of surface area of the respective pistons. A big piston travelling a short distance pushes a small piston further. This creates a mechanical advantage that can be used in many ways.

That's about as simple as I can get. Is it enough?

Answer 5

Hydraulics is a topic of science and engineering subject dealing with the mechanical properties of liquids. Hydraulics is part of the more general discipline of fluid power.

Hydraulic pumps or pistons:
Hydraulic pumps supply fluid to the components in the system. Pressure in the system develops in reaction to the load. Hence, a pump rated for 5,000 psi is capable of maintaining flow against a load of 5,000 psi.

Pumps have a power density about ten times greater than an electric motor (by volume). They are powered by an electric motor or an engine, connected through gears, belts, or a flexible elastomeric coupling to reduce vibration.

Common types of hydraulic pumps for hydraulic machinery applications are;

Gear pump: cheap, durable, simple. Less efficient, because they are constant displacement, and mainly suitable for pressures below 200 bar (3000 psi).
Vane pump: cheap and simple, reliable (especially in g-rotor form). Good for higher-flow low-pressure output.
Axial piston pump: many designed with a variable displacement mechanism, to vary output flow for automatic control of pressure. There are various axial piston pump designs, including swashplate (sometimes referred to as a valveplate pump) and checkball (sometimes referred to as a wobble plate pump). The most common is the swashplate pump. A variable-angle swash plate causes the pistons to reciprocate.
Radial piston pump A pump that is normally used for very high pressure at small flows.
Piston pumps are more expensive than gear or vane pumps, but provide longer life operating at higher pressure, with difficult fluids and longer continuous duty cycles. Piston pumps make up one half of a hydrostatic transmission.

Hydraulic brake
The hydraulic brake is an arrangement of braking mechanism which uses hydraulic fluid, typically some type of light-viscosity silicone oil, to transfer pressure from the controlling unit, which is usually near the operator of the vehicle, to the actual brake mechanism, which is usually at or near the wheel of the vehicle.

The most common arrangement of hydraulic brake, found on most automobiles, consists of a brake pedal, a master cylinder, hydraulic lines, a "slave cylinder", and the braking unit.

When the brake pedal is depressed, leverage multiplies the force applied from the pedal to a piston in the master cylinder.

As force is applied to this piston, pressure in the hydraulic system rises, forcing fluid through the lines to the slave cylinders.

The two most common arrangements of slave cylinder are a pair of opposed pistons which are forced apart by the fluid pressure, (drum brakes) and a single piston which is forced out of its housing (disc brakes.)

The pistons then apply pressure to the braking mechanism, whether shoes inside a drum, or pads which compress on a disc.

Answer 6

Hydraulics Is a topic of science and engineering subject dealing with the mechanical properties of liquids. Hydraulics is part of the more general discipline of fluid power. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. Hydraulic topics range through most science and engineering disciplines, and cover concepts such as pipe flow, dam design, fluid control circuitry, pumps, turbines, hydropower, computational fluid dynamics, flow measurement, river channel behavior and erosion. The word "hydraulics" originates from the Greek word ὑδραυλικός (hydraulikos) which in turn originates from ὕδραυλος meaning water organ which in turn comes from ὕδρω (water) and αὐλός (pipe). how they work The principles of hydraulics have been present in automotive design since the first brake system distributed pressure to each wheel by means of compressing fluid rather than pulling cables or mechanical linkages. Hydraulic systems were further used in similar ways such as operating clutch mechanisms, and in new ways such as hydraulically dampened shock absorbers, power assisted steering, and automatic transmissions. The master hydraulic system was kept at a constant pressure, fed by a pump that was powered by the engine itself by means of a belt (the way a conventional power steering unit is powered). Hydraulic pressure was distributed to the various subsystems as needed, and would always return to a common reservoir. Pressure to a fluid transmits in all directions. PRINCIPLES OF HYDRAULIC PRESSURE A Frenchman named Pascal discovered that a pressure applied to any part of a confined fluid transmits to every other part with no loss. The pressure acts with equal force on all equal areas of the confining walls and perpendicular to the walls. Remember when you are talking about the hydraulic machine, you are talking about the way a liquid acts in a closed system of pipes and cylinders. The action of a liquid under such conditions is somewhat different from its behavior in open containers or in lakes, rivers, or oceans. You also should keep in mind that you cannot compress most liquids into a smaller space. Liquids don’t “give” the way air does when you apply pressure, nor do liquids expand when you remove pressure. Punch a hole in a tube of toothpaste. If you push down at any point on the tube, the toothpaste comes out of the hole. Your force has transmitted from one place to another through the toothpaste, which is a thick, liquid fluid. If you were to press on the tube at one point, the toothpaste would come out of all four holes. You have illustrated a basic principle of hydraulic machines. That is, a force applied on a liquid transmits equally in every direction to all parts of the container. We use this principle in the operation of four-wheel hydraulic automobile brakes. You push down on the brake pedal and force the piston in the master cylinder against the fluid in that cylinder. This push sets up a pressure on the fluid as your finger did on the toothpaste in the tube. The pressure on the fluid in the master cylinder transmits through the lines to the brake cylinders in each wheel. This fluid under pressure Hydraulic brakes.Liquid transmits force. pushes against the pistons in each of the brake cylinders and forces the brake shoes out against the drums. MECHANICAL ADVANTAGES OF HYDRAULIC PRESSURE Another aspect to understand about hydraulic machines is the relationship between the force you apply and the result you get. The U-shaped tube has a cross-sectional area of 1 square inch. In each arm is a piston that fits snugly, but can move up and down. If you place a 1-pound weight on one piston, the other one will push out the top of its arm immediately.