History Of Brakes And Principles Of Hydraulics Engineering Essay

History Of Brakes And Principles Of Hydraulics Engineering Essay Landing gears are one of the most important parts of the aircraft and play an important role because it can make the aircraft run through runways and lands the aircraft to safety with the aid of the braking system and other systems. The modern brake system has been refined for over 100 years and has become extremely dependable and efficient. The whole draft talks about the hydraulic brake system. Modern braking systems are complicated and understanding the operation of a braking system requires specialized skills and training. Brakes are the most important feature of any modern transportation these days. The principles of brakes in a landing gear of the aircraft gave us the idea that making a simple hydraulic break system would be our main project. The content is designed to show the insight of the principles of operation of the hydraulic break, components and its functions. The advantages and disadvantages against different types of brakes and other terminology. :History oF Brakes: All cars need a brake system; therefore it has been present in the automobile since its invention. However, the technology of the components and the design of the brake system have evolved throughout the years. In the early days of the automobile, drum brakes were the standard. Drum brakes offered several advantages over other types of brakes. One of these was that the drum could keep out water and dust, materials that could damage disc brakes which were out in the open. The other, more important advantage was that drum brakes required drivers to apply less pressure on the pedal as compared to disc brakes. This was especially important in the days before hydraulic and power brake systems, both of which decreased the amount of pedal pressure needed. The next major advancement in brake technology came in 1918 with the invention of four-wheel hydraulic brake systems by Malcolm Loughead. It is interesting to note that Loughead was a member of the Lockheed family, a company known better for producing airplanes. The hydraulic brake system replaced the mechanical brake system that was in use at this time. The mechanical system had numerous disadvantages. It made it difficult to brake all the wheels evenly, often causing a loss of control. In addition, it required drivers to exert tremendous amounts of force on the brake pedal to slow the car. The hydraulic brake system multiplied the force that was applied to the brake, lessening the amount of force needed to be applied to the brake pedal by the driver. This system was first used in the 1918 Duesenberg. Its advantages quickly caught on and by 1929, four wheel hydraulic braking systems were standard equipment on most higher priced cars. It took a few more years for the feature to becom e common on lower price cars. As the speed of automobiles and their weight increased, better braking systems were required. The main problem with drum brakes is that the heat is not efficiently disbursed. The heat that is produced inside the drum does not escape easily since the drum prevents wind from drawing it away. However, disc brakes were open to the passing wind. This allowed the heat to be carried away which increased the efficiency of the brake. It is interesting to note that disc brakes were first used in 1902. However, their use was limited up until the 1950s since their efficiency was not required and they required more pedal pressure to operate. The reason for the higher pedal pressure is that disc brakes have no self-servo effect or no self-energizing capacity that the drum brakes have. The self-servo effect is caused by the forward motion of the car. This forward motion helps pull the brake shoe into contact with the drum. This helped lower the required pedal pressure. Now that their efficiency was needed and the hydraulic brake system multiplied the force applied to the brake pedal, disc brakes seemed to be the better alternative. Chrysler was the first to widely introduce the disc brake in its cars in the early 1950s. The system did not have much success. It seemed that the brake pressure required of the driver was still a little to great for the system to gain widespread consumer acceptance and therefore it was dropped. It finally took the failing automaker Studebaker to reintroduce the system in 1964. This time it saw much more success and in a few years, disc brakes were common on most new cars. One of the reasons that disc brakes were a success with the Studebaker and not the Chrysler was due to the development of the power braking system. Power brakes became common in the 1950s, after Chrysler had developed and dropped its disc brake program. The system assisted the movement of the piston in the master cylinder which meant that the driver needed to apply less peddle pressure to get the same braking effectiveness. Therefore, since ease of braking was no longer an issue, the adoption of the more efficient disc brake became widespread. Another development in braking systems came with anti-lock or anti-skid braking. With conventional braking systems, when the brakes are applied with enough pressure, the wheels will lock up. This results in a loss of steering effectiveness which may cause a loss of control. With anti-lock braking, the wheels do not lock up, allowing the driver to continue steering. Anti-lock brakes are not a new technology. They had been used in large aircraft since the 1950s and the British had used them in race cars in the 1960s. The first automaker to use this technology in its cars was Ford in 1969. It placed anti-lock brakes in the luxury Thunderbird and Continental Mark III. Today, anti-lock brakes are common on many new cars. : Basic Principles of Hydraulics: What is pressure? Pressure can be defined as the force per unit area and is expressed in Newtons per square millimeter (N/mm ²) or in bars and pounds per square inch (lbs/in ²) or p.s.i. in U.S. pressure. Formula: P = F / A Where: P = Pressure; F = Force; A = Area What is hydraulics? Liquids or fluids which are under pressure are usually used to transmit power through pipelines. The fluid power is converted into mechanical power by using rotary or linear actuators. What is Pascals Law? Pascals Law comprises a set of principles formulated in 1648 and states that pressure applied to a confined fluid at any point is transmitted undiminished throughout the fluid in all directions and acts upon every part f the confining vessel at right angles to its interior surfaces and equally upon equal areas. It defines the fundamental principle of power transmission by a hydraulic system. Figure 2: Pascals Law Pressure is created only when: The system is closed There is no air trapped in the system An attempt is made to compress the fluid Another important relationship in hydraulics is the area of the piston, the distance it moves, and the volume of fluid displaced. Formula: Volume =Area * Distance Fluid Compressibility: All liquids have a very high resistance to compression while air has a very low resistance to compression. Liquids used in hydraulic systems are also known as hydraulic fluids. Figure 3: Hydraulic fluid Bramahs Press: States that under a given load, the smaller the area it acts upon the greater the pressure produced and the greater the area under pressure, the greater the force available. Pressure = Load / Area Figure 4: Bramahs Press In an aircraft hydraulic system, Bramahs principle can be applied to the movement of different loads using actuators subject to one pressure. The figure above shows a large load and a small load being pushed by actuators having different piston areas. Bernoullis Principle : The relationship between the velocity and pressure exerted by a moving liquid is described by the Bernoullis principle: as the velocity of a fluid increases, the pressure exerted by that fluid decreases and as fluid decreases, pressure is increased. Figure 5: Bernoullis Principle Figure 6: Bernoullis principle also allows wings to produce lift Hydraulic Fluids: Hydraulic system fluid or liquids are used to transmit and to distribute the fluid to various units to be actuated. They are able to do this because they are almost compressible. If a number of passages exist in a system, pressure can be distributed to all of system by means of the liquid. Manufacturers of hydraulic devices usually specify the type of liquid best suited for use with their equipment, during working conditions, the service required, temperatures expected inside and outside the systems, pressures the liquid may withstand, the possibilities of corrosion, and other conditions. Figure 7: Types of hydraulic fluid Figure 8: Hydraulic Fluid (Aeroshell brand) Properties of Fluid: Fluids are incompressible They have a reasonable density with very little variation changes in temperature. Low rate of change of viscosity with temperature changes Large working range of temperature (-80 °C to +70 °C) Good Lubricating Properties It isnt harmful when in in contact (skin, hands) It doesnt foam Chemically stable with changes in temperature Good storage life Doesnt attack nor damage rubber. Fluid is preferably non-flammable Efficiency: Friction between the fluid and the walls of the pipes depends upon: The velocity of the fluid of the pipelines The bore, length and internal finish of the pipelines The number of bends in the pipelines and the radii of the bends The viscosity of the fluid What is Viscosity? It is one of the properties of hydraulic fluid. Viscosity is internal resistance to flow. Viscosity increases with a decrease in temperature. The knowledge of viscosity is needed for proper design of required temperatures for storage, pumping or injection of fluids. There are two related measures of fluid viscosity known as dynamic (or absolute) and kinematic viscosity. Types of Hydraulic Fluid: 1 Vegetable Based: (MIL-H-7644) is composed of a caster oil and alcohol. It is dyed blue. They are mostly used in older type aircraft. Natural rubber seal are used with vegetable base hydraulic fluid. This type is flammable. And the system may be cleaned with the use of alcohol. Figure 9: Vegetable based fluid 2 Mineral Base: (MIL-H-5606) it is processed from petroleum. It has an odour similar to penetrating oil and is dyed red. Synthetic rubber seals are used with petroleum base fluids. This type of fluid is flammable. They are used in common aircrafts and the precaution is damaging to rubber tyres. Figure 10: Mineral base fluid 3 Synthetic Base: (MIL-H-8446) This is one of the most commonly used fluid of this type. This fluid is of a clear purple colour or either dyed green. They are fire resistant. The seal material used is synthetic butyl Teflon and the precaution is of damaging to surface finishes. Figure 11: Synthetic base fluid These three types of fluids cannot be mixed nor any of them are compatible with each other.

Coffee Industry in the UK Essay -- Business Marketing Essays

Coffee Industry in the UK The coffee industry has grown rapidly since the 1990s; before Starbucks emerged, people were used to drinking low quality coffee from tins. Starbucks introduced fresh coffee made from top quality beans that have excellent taste and drinks such as the caffe latte and cappuccino, which have helped to fuel the development of the coffee market into a multi million pound industry. The size of UK branded coffee chains have quadrupled from 1999 to 2004, with a current market turnover of over  £1 billion. 2 Market Forecasts The coffee market is forecast for continued growth and expansion, without threat of saturation in the near future. In 2004 the coffee market was estimated at having around 2,299 outlet units and it 2006 it is predicted that the number of units will have increased to an estimated 2,965, with the growth of the branded coffee sector predicted to increase by 11% between 2004 and 2006. Indeed, branded chain outlets have accounted for most of the coffee market growth according to forecasts by industry analysts Allegra Strategies. Allegra claims that although there are more independents than branded coffee chains, in 2005 and 2006 it is expected that more branded than independent chains will be opening. Indeed, some independents. such as Bewley’s in London, have had to close down. 3 Macro - environment analysis of the market Social The coffee market must adapt to a change in consumer attitudes or else it may be threatened by health and lifestyle issues. In 2003 the hot drinks market declined by an estimated 2.3%. Consumers, especially young people, are becoming more health conscious which makes coffee a less attractive choice; the increasing number of alternatives available such as health and energy drinks are becoming competitors in the coffee industry. Research carried out by Mintel shows that there is an increased diversification of tea, with a trend towards premium and herbal teas. The coffee industry are responded to this change in attitude by provision of de-caf drinks, options such as soy milk, and alternative drinks such as freshly squeezed fruit juices, chai lattes and herbal teas. People are now working harder than ever before but have more leisure time; they now use coffee shops to socialise. Allegra research claims that dwelling time in coffee shops has increased; 44.9% of consumers stay... ...au then tic cost a coffee e www.dandad.org/inspiration/ creativityworks/pdf/authentic.pdf UK coffee shop market statistics 14 Mar 2005, Caterer & Hotelkeeper magazine, http://www.caterer-online.com/archive/articledetail.asp?articleID=57531 Nestle Caterer & Hotelkeeper magazine, http://www.caterer-online.com/archive/articledetail.asp?articleID=50580 Branded coffee bars are squeezing independents http://www.thehospitalitysite.com.au/article/44/OcO2db44.asp 2005 Allegra Strategies Ltd. No.1 Northumberland Av, Trafalgar Square. London, http://www.allegra.co.uk/project-cafe5-keyfindings.html Oxfam to open coffee shops BB News May 2004 Http://news.bbc.co.uk/1/hi/magazine/3708585.stm Starbuck’s success - More than just coffee ICFAI University Press http://www.icfaipress.org/304/AN-Starbuckway_72.asp The Coffee Market ‘A Background Study’ Oxfam International Commodity Research http://www.maketradefair.com/en/assets/english/BackgroundStudyCoffeeMarket.pdf . The State of Sustainable Coffee Executive Summary http://www.ico.org/libser/executive%20summary.pdf . Whitbread Briefing Book 2005 Volume 1 http://www.whitbread.co.uk/docs/Briefing_Book_2005_voll.pdf

Why plastic bags should be banned

They use up natural resources–â€Å"Every time we use a new plastic bag they go and get more petroleum from the Middle East and bring it over in tankers,†. â€Å"We are extracting and destroying the Earth to use a plastic bag for 10 minutes.†. They harm wildlife and marine life-plastic bags are now in all places in our environment, and animals, on land and water, are getting choked, strangled and killed by them. They create litter-Aside from polluting beaches and waterways, plastic bags for example in China plastic bags are blowing around streets of China, they are so common they've earned the name â€Å"white pollution.† It is not environmentally friendly and may cause harm to children and water life all around the world. It should also be banned for a list of reasons such as it is unfriendly to the environment and may be harmful to children and water life all around the world and also it takes years for plastic bags to break down and we're not even able to recycle them. No, because plastic doesn't break as easily as glass and is water-proof. They take a long time to biodegrade-Most plastic bags used either end up as litter or in landfills. Plastic bags pose a suffocation hazard to people, particularly children, and pets. Plastic bags are made out of non-biodegradable substances. They are durable they do not rot. Making plastic bags can lead to exhaustion of oil, because to make a lot of plastic bags, we need a lot of oil. If we reduce oil we could save much more oil. Plastic bags even kill a lot of marine animals. Plastic bags gets blown into the ocean and floats around like a jelly-fish. A lot of sea-creatures choke and die for mistaking them as their food.

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