HYDRAULICS

1. What is hydraulic technology?

In the hydraulic technology we transmit and control forces and velocities by transmitting and controlling pressure and flow. In nearly every kind of technology we use hydraulic drive and control techniques. A few examples are:

mechanical engineering car technology agriculture technology earthmoving and mining technology ship building technology offshore-technology aircraft and spacecraft technology

The Basic IdeaThe basic idea behind any hydraulic system is very simple: Force that is applied at one point is transmitted to another point using an incompressible fluid. The fluid is almost always an oil of some sort. The force is almost always multiplied in the

process. It is important that a hydraulic system contains no air bubbles,If there is an air bubble in the system, then the force applied to the first piston gets used compressing the air in the bubble rather than moving the second piston, which has a big effect on the efficiency of the system.

A simple hydraulic system consisting of :-1. Two pistons.2. Oil-filled pipe connectiong the two pistons.

The neat thing about hydraulic systems is that it is very easy to add force multiplication (or division) to the system. trading force for distance is very common in mechanical systems. In a hydraulic system, all you do is change the size of one piston and cylinder relative to the other.

log splitter

there is something called log splitter , it Is The simplest hydraulic device that you find in common use today . It contains all of the basic components of a hydraulic machine:

An engine, normally a small four-stroke gasoline engine, provides the power for the system. The engine is attached to a hydraulic oil pump.

The hydraulic oil pump creates a stream of high-pressure oil, which runs to a valve.

The valve lets the operator actuate the hydraulic cylinder to split a log.There is also a tank to hold the hydraulic oil that feeds the pump and usually a filter to keep the oil clean.

A. LogB. Hydraulic cylinderC. ValveD. PumpE. Engine

Basic Principles con’t By applying a downward force on the small piston, the

jack can be made to lift a heavy mass on the large piston. The liquid fills the entire volume between the two pistons,

and because it is incompressible, some liquid must moveinto the large piston chamber when the small piston ispushed downward.

1. Very high force despite small components (if pneumatics, bigger components are needed for high force, thus, incur high cost as well as wastage of compressed air)

2. Very slow and linear movements (if pneumatics, too slow will create jerking on the cylinder)

Advantages of using Hydraulics

3. Very exact positioning (stops exactly on a point). Compared to pneumatics, there’s a tolerance and if a load is given, it will move a little.

4. Start-up under heavy loads (Possible to start the motor & process a job with a load attached to it. This is because there is oil in the actuator though the pump is idling).

5. Simplicity, safety, economy6. In general, fluid power systems use fewer moving

parts than comparable mechanical or electrical systems. Thus, they are simpler to maintain and operate. This, in turn, maximizes safety, compactness and reliability

Disadvantages of using Hydraulics1. Slow movement of actuators (Pneumatics are faster)2. Messy (Leakage may occur and if not bothered, the

surrounding area could be messy. However, constant cleaning could avoid messy.)

3. Dangerous! i. It produces extreme pressure and if there’s a leakage,

oil will be forced out. Stopping the flow with bare hand would result in a punctuated wound.

ii. While in process, oil became hot and flammable (though not easily happened). Therefore, it is advisable to control the temperature by limiting it (turning off the machine if the limit is exceeded).

excavator

Fluids: Liquids and GasesLiquids – refer to both gases and liquids.- is a fluid that, for a given mass, will have a definite volume independent of the shape of its container.- A free surface is also formed in the case of a body of water, such as a lake.Gases – fluids that are readily compressible. In addition,

their volume will vary to fill the vessel containing them.

- the gas molecules always fill the entire vessel.

HYDRAULIC

Commercially available hydraulic retract systems have only been available for a fairly short period of time and are still a rarity at flying fields. However, they're likely to become increasingly popular due to the ever-growing number of larger models (particularly jets) with high wing loadings and consequent increased landing speeds / loads. Eurokit is currently the only manufacturer offering a wide range of hydraulic retracts to suit a variety of models, whilst some kit manufacturers offer tailor-made retracts to suit specific models.

A typical hydraulic system

In general, hydraulic retract units and operating valves appear very similar to those supplied with air up / air down units, the only real difference being the incorporation of seals that are compatible with the oil / fluid being used in the system. The air tank and fill valve are done away with, and in their place are an oil tank, electronic control unit (ECU), hydraulic pump and dedicated battery pack. Linking of the various items is carried out much like an air system, with two hydraulic lines running to each retract unit. Oil is introduced to the system by filling the tank, then running the pump to distribute it, bleeding any air from the lines. Once most of the air has been removed, the bit remaining tends to be forced back into the oil tank as the system is cycled.

The operating method is fairly simple in that the control valve and ECU are simultaneously activated via the retract channel, at which the pump forces fluid down the lines into the retract unit rams, operating the gear. Models with wing-mounted main undercarriage units are accommodated by the use of self-sealing, two-piece valves in the lines where the wing panels separate; when these valves are parted theres no oil loss, and air is not introduced into the system.

There are a number of advantages with hydraulic systems, including the ability to control very accurately the speed by either changing the input voltage to the

pump or by adjustment of the electronic control unit. Another positive is the extremely secure up /down lock (due to the incompressible nature of oil), and reduced leakage, given the much greater viscosity of oil over air. My relatively limited experience of hydraulic retracts suggests that they're generally more reliable than air systems, as long as they're correctly installed. Of course, you don't get all this accuracy and reliability for nothing, and hydraulic retracts tend to be more expensive, given the requirement for a high precision pump, ECU etc. They're also heavier due to the weight of oil carried and additional components

Hydraulic steering system: steering system that operates on water pressure.Pump: apparatus used to move a liquid.Reservoir: place where liquid is stored.Cylinder: type of roller that applies a uniform pressure.Feed pipe: feed pipe.Rudder: apparatus used to turn a boat.Piston: cylindrical part that moves up and down in a tube and transmits pressure generated by the fuel.Safety valve: steam engine valve that prevent explosion.Wheel: wheel used to regulate the output of the motor.