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Engineering StudiesKiama HighBraking SystemsInvestigationGwilym PriceTeacher: Mr FergusonJune 2012AbstractThis report is being written about the undertaking of an investigation into braking systems. Section one gives a minor comparison on Drum and Disc brakes giving specific detail on both. Section two consists of an evaluation of Air powered brakes and there usage in trucks.Many different brands and types of braking systems were researched and observed via internet, telephone communications, field work at local trucking yards and email correspondence with employees at various brake and brake part manufacturers. A survey was undertaken involving members of Gates Haulage and the results of the survey showed popularity in braking system makers. Major conclusion into the investigation in section one was that disc brakes have now become a better solution over drum brakes. Major conclusion into the investigation in section two was that air pressure braking perform a more than satisfactory job for larger vehicles and are the best option for these vehicles at present times.AcknowledgmentsAcknowledgments must firstly go out the employees of Gates Haulage, who were very helpful in organising dates and allowing me access to their truck fleet and supplying more than adequate information about the various trucks at the yard. Acknowledgments must also be granted to an information employee of Bendix Braking Company, Ben was extremely helpful and enthusiastic in helping and supplying information, his last name was not given for safety reasons. The information consultant of Australian Brake Controls PTY LTD is worthy of a mention by supplying me with many websites and distributors of their products.My report would not have been possible without the help and cooperation of the above named people and I am very appreciative of their contributions.Table of ContentsPage No.Title Page………………………………………………………………...1Abstract…………………………………………………………………..2Acknowledgments……………………………………………………….3Table of Contents………………………………………………………..4Section 1. –Comparison of Drun and Disc Brakes…………………...5Introduction……………………………………………………………..5Main body……………………………………………………………...5How Drum brakes work………………………………………………...5Parts of Drum brake…………………………………………………….6How Disc brakes work…………………………………………………7Parts of Disc brake……………………………………………………..8Results and Discussion………………………………………………10Faults and Errors………………………………………………………13Conclusion…………………………………………………………….13Recommendations……………………………………………………..14Section2. –Air Brakes in Heavy Utility Vehicles…………………...15Introduction……………………………………………………………15Main Objectives (Aims)………………………………………………..16Main body…………………………………………………………….17How Air brakes work…………………………………………………17Components of Air brakes……………………………………………18Field Study……………………………………………………………23Heat Dissipation………………………………………………………25Conclusion…………………………………………………………...29References……………………………………………………………30Appendices…………………………………………………………..31Section: parison on Drum brakes and Disc BrakesIntroduction:In this section of the report examines the differences, advantages and disadvantages of both disc and drums brakes will be discussed. This will give the reader background knowledge on the mechanical side of braking systems when we enter the next section of the report which discusses truck and large vehicle braking systems.How Drum Brakes WorkDrum brakes consist of a backing plate, brake shoes, brake drum, wheel cylinder, return springs and an automatic or self-adjusting system.-31751036320The pedal for the brakes is applied, brake fluid is pumped through under pressure in the wheel cylinder, which pushes the pistons and brake shoes to apply friction to the spinning drum, slowing the car down or bringing it to stop. When the brake pedal is released the pressure is released inside the brake cylinder and the brake shoes are released from the edge of the drum and allowing the car to travel on. As the brake linings wear away (they are indicated as the black strips on the brake shoes) the more pressure and harder the brake pedal has to be forced down. The brake shoes and linings would need to travel more in order to slow the vehicle. Once the brake shoes reach a certain point a self-adjusting mechanism automatically reacts by adjusting the rest position of?the shoes so that they are closer to the drum. Parts of the Drum BrakeBrake ShoesBrakes shoes consist of a steel shoe with a friction lining added to the shoe. Eventually though the brake linings would need replacing as they get too thin and the steel brake shoe would start to rub against the drum causing damage. Backing PlateThe backing plate holds most of the parts of a drum brake together. It attaches to the rear axle and forms a solid surface for the wheel cylinder, brake shoes and most of the other parts. Brake DrumThe cast iron Brake Drum is the cover of the Drum Brake. It is attached to the wheel and on the inside edge is a machined surface where the pad is forced by the brake shoes causing friction and thus slows the vehicle down. Brake CylinderThe brake cylinder has two pistons inside it, one on each side. The pistons have a rubber seal and a shaft on it which connects to the brake shoe. When the brakes are applied the space in between the pistons fills up with pressure by hydraulics and forces the pistons apart pressing the brake shoes onto the drum.Return SpringsOnce the pressure is released the return springs pull back on the on the brake shoes and returns them to their original position. The springs need to be checked constantly as they can wear easily and deform. If the springs are weak the brake shoes won’t return all the way and the linings will wear more easily and they would too need to be replaced.Self-Adjusting SystemThe self-adjusting system is needed so that when the linings wear down, the displacement between the linings and the brake drum is decreased back to the original measurement it was when the drum brake was equipped. The parts of the self-adjusting system need to be constantly checked and lubricated so when it is needed it will run smoothly. Otherwise the driver will find he/she would need to apply more pressure on the brake pedal.63817516510How Disc Brakes WorkDisc Brakes are made up of three main components these include the rotor, the brake pads and callipers 57150436880Hydraulic fluid applies pressure from the brake pedal to the piston on the calliper. The pressure builds up and forces the piston to push the brake pads on both sides on the calliper to clamp down on the disc rotor. The rotor is attached to the wheel of the car. Once the pressure on the brake pedal is released the hydraulic fluid backs down. The disc rotor has a slight uneven surface and as the speed of the car increases the disc turns and slightly pushes the piston back into its original position. Just like the drum brake the disc brake also uses brake pads. On the calliper there is a brake pad on each side to clamp down onto the disc and the brake pads are attached to a metal brake shoe. There are many different types of materials used for different brake pads and shoes but these will be explained later. Parts of the Disc BrakeCallipersThere are many different types of callipers but the two main popular choices are floating callipers and fixed callipers. Floating CallipersThese are easy to manufacture and service and are most popular due to this. They are used on most family cars due to their low cost. There are single piston floating callipers which the hydraulic fluid it forced from a pipe as above and pushes the piston against the rotor and tightens its hold. The above picture is only a single piston floating calliper found on most family cars. Floating callipers can come with two pistons but these are found on more luxury type cars as these give a more smoother and easy braking feel. 3048000-57150Fixed CallipersThese callipers are held in place so they cannot move and most consist of two callipers on each side of the rotor. Expensive racing type cars or salons tend to have four piston fixed callipers as these can apply more pressure to the brake pads and can resist more strain when needed for performance. These types of callipers are used on high performance vehicles due to the higher braking force they can create upon the vehicle. These callipers may be in a nice compact design but they are a lot heavier than floating callipers, but heat is easily dissipated with these callipers.Rotor27527252013585The rotor is generally made of Nodular Grey Cast Iron and consists of a highly machined surface where the brake pads come into contact with the disc. The rotor does wear down as well and needs to be replaced once the wear reaches a certain point. This is needed because the brakes would not be able to handle the heat and may slightly deform after the minimum wear point. Most modern rotors now consist of air holes or ventilated centres were air can easily get in and cool the rotor down. The solid rotor usually tended to overheat when needed for excessive performance. Although the heat is generally good for brakes as it increases the co efficient of friction on the surface. But too much heat can put too much wear onto the brake pads as the friction becomes too much.Brake pads/shoes2828925202565The brake pads come into contact with the disc rotor and this builds up friction and slows the rotor. The brake shoes and pads build up a lot of heat and can get very hot. There are a range of materials which are used to dissipate heat and cool the disc brakes down quickly and effectively. Brass fibres in the structure of the pads are an example. An indicator is also installed on the pads by the car manufacturer and is replaced when the vehicles pads are replaced. These are an indicator to the driver to notify them when the brakes have been worn down. Results and DiscussionOriginally there was a stage when all vehicles used cables from the brake pedal to the brakes on all wheels. These were a safety issue though as the cables eventually became unreliable due to stretching, wear and could eventually snap. The changeover to hydraulics was a huge innovation for vehicles of all types as they were so much more reliable than cables and made it easier for the driver to press down on the brake pedal. Power assisted hydraulics was another innovation and increased the safety of the vehicle as these were even easier to engage and the driver wouldn’t need to constantly pump fluid to the brakes.Most websites showed that disc brakes are better than drum brakes and only explained a little information on how.I was able to confirm that drum brakes don’t work well in wet weather and even the slightest amount of water can cause the drum surface to become slippery. It is obvious this was a serious safety issue and has caused many car accidents in the past 60 years. Drum brakes have become very unpopular over the past 10 years and it has been very difficult to find information about them today. Most searches always led me to how they work, or how to remove and replace them with disc brakes. Another result I was also able to confirm is that Drum brakes are excessively heavier than disc brakes and the use of them now in most racing cars where weight is an issue wouldn’t improve the racing capability of the vehicle. Although I was able to confirm Drum brakes are still very popular in trucks and buses where weight isn’t much of an issue. For cars though disc brakes are the cheaper and easier to maintain option and for a family car this has proved to be the more popular option. In terms of safety, an experiment which was carried out by Bendix Commercial Vehicle Systems LLC, a member of the Knorr-Bremse group they were able to confirm that the effectiveness and performance of disc brakes has now out manoeuvred drum brakes in trucks.This was carried out by The Society of Automotive Engineers, which was presented at the International Truck and Bus Meeting and Exhibition in Fort Worth Texas. The experiment they conducted was a test of two semi-trailer trucks both with the same weight and build. (Unfortunately not much information was given on the Truck Build.) One truck was equipped with a typical S-Cam brake setup, including 15" × 4" front brakes and 16.5" × 7" rear brakes. The other test truck had front and rear axle Bendix ADB225 air disc brakes with 17" rotors. From the data that was obtained the truck with the disc brakes had a stopping distance of 305 feet (93m) to 325 feet (99m). Whereas the Truck with the drum brakes equipped had a stopping distance of 450 feet (137m) to 518 feet (157m). These first results were undertaken when the brakes were cold. But it was found as the brakes heated up and expanded the hot drum brake equipped truck had stopping distance of 750 feet (228.6m). But the hot disc brake equipped truck only had a stopping distance of 320 feet (97.5m). These first brake tests were undertaken by both vehicles at 75mph (120kmh). The second brake tests were done at 60mph (96.5kmh) and the braking distance of the disc brake equipped truck had a stopping range of 185 to 210 feet (56.4m to 64m) in both cold and hot conditions of the brake. Whereas the drum brake equipped truck had a stopping range of 255 to 292 feet (77.8m to 89m) with cold brakes but when they were hot they stopped more than 425 feet (129.5m).Air holes in disc brakes are now used and this is very effective for dissipating heat. As heat builds up most in the callipers and rotor heat is required to escape otherwise the braking system will become faulty. That is the issue with drum brakes as heat builds up very easily inside the drum and is required to escape. This is a diagram indicating the effects on the brakes, just another comparison of drum brakes and disc brakes.Emergency brakes are another device of the braking mechanism. These are available in both braking systems and are and advantage to the users of the vehicles. These are for the use only when the cars brakes are faulty or the brake fluid has depleted. Most cases an emergency brake is only enabled when the vehicle is descending a hill or steep road this is the most likely case where a vehicle will require this brake. Below is a diagram of the energy dissipation and room that is required for drum and disc brakesMaterials used in brake pads have changed over the years and has been a vital innovation for the disc and drum brakes. Many materials have been tested and tried for the use on brakes. Original systems used cotton but that didn’t work due to the fact that it was very easy to set on fire. Other systems had tar this was too rough and was easy to wear through materials and also that tar was also easy to melt. So many rather odd materials have been tested and tried on braking systems to see the effectiveness. On some of the more relevant materials asbestos was probably one of the best materials ever used on braking systems but it was a real health hazard to car auto mechanics as asbestos is a very brittle and fibrous material and if broken up can be easily inhaled by the mechanic and cause lung issues later in life. Asbestos has been banned in many countries. Brass fibres in the brake pads help dissipate heat to prevent heating of the disc.Ceramics are now used on the top and expensive braking systems as these are very effective and heat can be easily dissipated on from the braking system.Errors and FaultsMy research discovered two tests that indicated that disc brakes did perform better than drum brakes.One test was carried out on trucks and the other on mechanical braking of machinery. I would have liked to compare a number of other vehicles such as high performance sports cars, small and medium sedans, 4 wheel drives and possibly motorcycles. Most websites and books only gave a short extract of information stating that disc brakes are better than drum brakes. There was another major issue as well, where the increased popularity of disc brakes over drum brakes have led to more innovations and improvements on the materials used. Therefore to find a proper test where the variables were the same was quite a challenge. The other issue was finding reliable sources as many websites are unreliable as they can be created by anyone in a number of minutes just to show their opinions. The more complex reports had quite a lot of work in them and tended to be more reliable, however, most of the information tended to be irrelevant but still had some research in drum brakes compared to disc brakes. ConclusionsAs discussed before innovations in brakes have increased dramatically in disc brakes recently more than drum brakes, even though both brakes were developed around the same time in the early 1900’s. Drum brakes did become the popular product as disc brakes weren’t as effective due to the limited technology of the time. The main issue with the disc brakes at first was heat. Friction on metals causes a tremendous amount of heat which can cause deformation of materials and wear. Swell and growth is also caused by this even though this can be useful and increase braking performance as was found on disc brakes. Too much swelling and growth can do damage to the material especially the more brittle the material, but this can also damage and affect other devices in the brake, for example self-adjusting systems. RecommendationsDrum brakes were found to be not as effective as disc brakes. Drum brakes are very heavy in weight and would not suit in a racing light weight car today where every little bit of weight is considered to increase its performance. Even in a family car today disc brakes are used on all four wheels not only for safety but for cost and maintenance as well. Disc braking systems have become extensively popular and are the most ideal choice for all people in terms of safety and performance. New materials are constantly being made and can be of huge use for disc brake pads. These innovations are constantly increasing the performance and safety measures in all vehicle types. Air compressed brakes are a new type of innovation now used in trucks to replace brake fluid and hydraulics as the liquids have to travel quite a distance throughout the truck and can be hard to pump very fast and effectively. Air compressors are now a popular safety measure installed on most trucks and can be even more effective than hydraulics.Section 2.Air brakes in Heavy utility vehicles55245036195IntroductionOver the past forty years there has been a huge change in technology in vehicles and braking systems which have dramatically improved the functioning of motor cars. As demand for better, lighter and more effective brakes are needed and rapid change in technology has been required. As we are now able to transport large quantities of goods from the development in our engines, the braking power also needed to equal the power of the engine moving the truck, train, bus or semi-trailer. Air pressure brakes are perfect for this.Air brakes are used mainly in commercial vehicles such as trucks, buses, trailers, and semi-trailers. George Westinghouse first created air brakes for the railway service. On March 5th 1872 he patented a safer version of his previous air brake system. Westinghouse made numerous alterations to improve his air pressured brake invention, which led to various forms of the automatic brake and the subsequent use on heavier road vehicles. These braking systems consist of service brakes, parking brakes, a control pedal, an engine-driven air compressor and a compressed air storage tank. For the parking brake, a disc or drum brake arrangement is used which is designed to be held in its applied position by the use of spring pressure. Air pressure must be produced to release these "spring brake" parking brakes.Main Objectives (Aim)The aims are to discuss and show research into air compression brakes and why they are an effective brake for large vehicles. I have done an analysis into this brake type and how they work and researched the popularity and why they are best suited for large utility vehicles. It would have been great to undertake an experiment but for obvious reasons I personally cannot conduct an experiment myself testing different types of vehicles and how their brakes work. So I have gone to secondary resources on the internet and books to find out information on these brakes and their effectiveness in a range of different aspects on different types of vehicles. A meeting with a local hauling company was undertaken and information was received about the various trucks they were using. The details of the meeting are explain later on in the report. Analysis:How Air brakes workThe compressor pumps the air into the wet reservoir, a safety valve is in place to prevent over pressurization. A governor then controls the pressure that is inside the reservoir all the way to the bottom of the foot valve. When the driver pushes down upon the foot valve treadle the air pressure flows to all of the front and rear braking chambers. The brake chamber’s push rods then move the slack adjusters by having the air flow into it. The slack adjusters when moved rotate the S-cams which then force the brake shoes against the drums. This causes friction and the vehicle slows down when the driver releases the pressure on the foot valve the air in the brake chambers is exhausted and the brakes are released.Air is everywhere, we cannot run out of it unless under extreme circumstances which vehicles are unlikely to find themselves in. Trains, buses and tractor-trailers use air-brake systems so there is no reliance on the hydraulic fluid which is commonly used in car braking systems, which can run out in the event of a leak. All of these types of transportation are weighed down by heavy passenger or goods loads, so safety is of critical importance. A speeding heavy combination vehicle that relied on hydraulic press rebuild or liquid brake would turn into a deadly block of steel in there happened to be a leak within its braking system. There are 3 major steps in the air brakes process:Charging: The system must always undergo pressurisation of air before any of the brakes are released from lock. At rest, the brakes remain engaged. Once the system reaches its optimal operating pressure, the brakes are freed and ready to use. Applying: As the brakes are applied, the pressure of the air inside the brake chamber decreases. As the amount of air decreases, the valve opens and begins to allow air back into the reservoir tanks. This all happens while the brakes move from the disengagement position to the applied position.Releasing: The reserve of the applying stage happens. Once the brakes are disengaged and the air is compressed back through the valve from the reservoir tanks and back into the brake chamber, the increased pressure releases the brakes.717550109220Components Of Air BrakesA basic air brake system with the ability of bringing a vehicle to rest has six main components:Compressor - to pump air with a governor to control it.2. Reservoir or tank - to store the compressed air.3. Foot valve - to control a regulated flow of compressed air from the reservoir when it is required for optimal braking.4. Brake chambers and slack adjusters - to transfer the force created by the pressurised air to mechanical linkages.5. Brake linings and drums or rotors - to create the friction required to slow down and gradually stop the wheels.6. Safety valve – protects the reservoir from becoming over pressor3238501261745All of the compressed air used in braking systems comes from the compressor. A compressor is designed to push air from itself into a reservoir which results in the creation of pressurized air. Compressed air is used to transmit force throughout an air brake system. The compressor is powered by the main engine of the vehicle, either by a combination of pulleys and belts or gears and shafts. If a vehicle has a compressor which is driven by a belt and pulley system it should be inspected regularly for cracks and tension lines, the compressor should also undergo regular inspection for broken bracket and bolts. All compressors are coupled with a governor. This controls the minimum and maximum air pressure in the brake system; this is done by regulating when the compressor pumps air. This process is commonly known as the “loading” or “unloading” phase. Most compressors use two cylinders which look similar to the pistons found in engines.ReservoirsReservoirs or tanks hold compressed air which can be distributed at any time. The number of reservoirs and their size are very dependent on the number of brake chambers a vehicle has and the configuration of the parking brakes. Air brake vehicles are equipped with more than one reservoir. The more reservoirs means the greater volume of main reservoir air the system can hold at once. The reservoir right after the compressor is referred to as either the supply or wet reservoir. The ones following are called the primary and secondary reservoirs and are occasionally referred to as the dry reservoirs. Air becomes very hot when it undergoes compression. The air cools once in the reservoir, forming condensation, this process mainly happens in the reservoir preceding the compressor, this is how it become known as the wet reservoir.1515745772795Drain valves are equipped with all reservoirs so that if moisture or sludge builds up it can be drained and not affect the braking system. Some reservoirs have multi compartments to maximise space and have a more even flow of air when required.Foot ValveThe foot-operated valve is how the driver of the vehicle can apply air to operate the brakes. The air pressure that is applies depends on how far the treadle of the foot valve is depressed. However the maximum application will never exceed the pressure that is inside the reservoir. Releasing the foot valve reverses the process. The valve automatically maintains the application of air pressure without the operator having to constantly readjust the applied force of his force on the treadle. Unlike hydraulic powered brake systems the air treadles are spring loaded which produces a different “feel” for the operator.1416050311150 Brake Chambers and Slack AdjustersThe brake chamber is a cylindrical container which is divided into two equal sections by a flexible diaphragm. When air pressure is pushing against the diaphragm it causes movement away the direction of pressure. This forces the push rod out and against the slack adjuster. The force that is exerted by this motion depends on the scale of air pressure and the size of the diaphragm. Air is allowed to escape when a leak is present in the diaphragm, this critically affects the working capability of the brake chamber. If entirely ruptured the brakes cease to work. The brake chambers located at the front of the vehicle are usually smaller as opposed to the rear ones as the front axles carry less weight. Brake chambers normally are securely mounted upon the axle, close to the wheel that is equipped for braking. An inlet port is used for air pressure to feed through. The air is forced up against the diaphragm and push rod. A clevis and pin connect the push rod to the crank arm which is referred to as the “slack adjuster”. The pushing motion of the push rod is then converted from the chamber to a twisting motion of the brake camshaft. When the air is completely expelled, the return spring which is inside the brake chamber returns the push rod and diaphragm back to its original position which is known as the “release position”. As the name clearly states, the slack adjuster is used to adjust the “slack” between the push and the brake shoes. This slack happens as the brake linings become subject to wear, if the slack adjusters are not functioning within its limitations the effectiveness of the brakes decreases and the brakes lag time increases.307530523114093345223520Safety ValveThe safety valve is put in place to protect the reservoirs from over pressurising and rupturing if there is a malfunction in the governor, where did not stop the compressor in the unloading stage. There is a spring loaded ball inside the valve which allows air to be exhausted from the reservoir into the atmosphere. The pressure setting in the valve is determined by the force of the spring. Safety valves are normally set at 150psi. If this pressure is reached then the pressure would force the ball off its position which allows the air escape through the exhaust port in the spring cage. Once the pressure is significantly reduced back down to approximately 135psi, the spring will then force the ball back into position and once again sealing off the reservoir pressure. Some safety valves are built in with a manual release feature. Field Study6286501102995On the 6th June 2012 I went down to Gates Haulage which is a local hauling company in Gerringong. They have a fleet of 30 trucks and use Truck manufactures such as Western Star, Eagle, Sterrlings, Ken worth and Freightliner which are all reliable Truck distributers. While at the Truck yard I decided to specialise on a Western star Truck, the model 4864FX 201 inch wheel base. The 4864FX is one of the most popular trucks in the Western Star catalogue. This particular model features a set of Cummins InteBrake compression brakes as the front to wheels. The rear brakes are Bendix ADB22X Air Disc rear brakes. The Compressor is a Cummins 18.7 CFM single cylinder compressor with internal safety valve, the Reservoir and brake chambers and also Bendix stainless steel.The brake pads are made from ceramic metallic material and have a friction rating of GG (GG being the highest rating possible) and have not needed to be replaced at all. The truck’s driver named Haddon claims it to have the best braking ability out of the whole fleet.I undertook further investigation on the 8th June 2012 and took photos of the reservoirs and brake chambers. These photos are displayed on the next page. 2901950102757-38100101600A Bendix reservoirA Bendix reservoir leading to a Bendix brake chamber.On completion of taking photos I took a survey on a few aspects of brakes. I chose three of the most common braking brands found in the Trucks at Gates Haulage and assessed them on 3 categories: efficiency on the road, ease to change and time the brake lasted. I asked 6 of the professional drivers who also are the maintenance managers for the trucks and have changed brakes and brake pads of multiple trucks at the yard. I asked them to rate each brand out of 10 for each category and then I took the average. The results are displayed in a table below. Brand↓ Category →Efficiency on roadEase to changeTime brake lastedBendix889Cummins978Jacobs768From the results above I concluded that the best brake company was Bendix. Although these results are unofficial and are not backed up with any proof or fact and is purely based on opinions of the drivers, it gave me an idea of what brand was popular.I would have liked to have conducted my own experiments on the brakes but that was clearly not possible. Heat DissipationHeat has been a problem in all types of braking systems for centuries now. The more friction the more heat is created and too much heat results in loss of effectiveness in the brakes. The engine converts the energy of heat into the energy of motion (Kinetic Energy), when the brakes are applied they do the complete opposite and turn the kinetic energy back into heat energy. Heat is produced from the friction between the brake drums and the brake linings this reduces the mechanical energy of the revolving brake drums and the wheels. The brake drums are made from metal and absorb the heat which is produced in the braking produced, this heat dissipates into the atmosphere. Thickness of the metal ultimately decides how much heat the brake drums can absorb. I looked into many different techniques that could be used to prevent or lessen the affects that heat can have on the braking system, and found a variety of different solutions and styles of beating the heating.14128751109640Cross drilling: Cross drilling is a technique which involves putting small holes into the disc plate. This allows the heat to pass through easier. As I couldn’t conduct an experiment myself I went to the internet and looked at secondary sources and experiments. I found that this technique does work well but through tests showed that the disc plates were much more vulnerable to cracks and tension lines.Air Cooling: Air cooling involves the use of a high powered air jet blowing cool air onto the disc or drum (depending on what brake is being used). Through my online research into this particular technique I found that air cooling gives a major improvement on minimalizing the heat but was a more expensive technique and took up extra room and weight.Brake Linings250°C is the temperature where most brake linings operate at their best, the temperature should never exceed 425°C and once over passed dramatic loss in efficiency starts to occur. Brake linings have been altered and changed over the last century using a variety of materials. Asbestos was first used by Herbert Frood in 1902, asbestos was discovered to be a fantastic insulator and served as the brake lining’s material for many years. Asbestos was then banned when it became apparent that when the material’s fibres were broken and inhaled it had deadly consequences and results in the health condition of Mesothelioma. -1016003810Although Asbestos brake linings have been banned in many countries all across the world, I was able to locate a brake linings manufacturing company which still made some products from asbestos. This company is called Qunli Friction Linings. These asbestos linings are listed for a wide variety of products and are classified as reliable and safe. I have included the website address and the specifications of its asbestos brake linings in the appendices.I was able to find a test on disc brakes heat dissipation on the internet which seemed to have detail in depth and plenty of information. This test was undertaken by Maxcess which is a mechanical components company. They tested air pressure disc brakes made by a company called Tidland. Firstly I did some background reading into Tidland and found that they were considered as an extremely reliable company and made 1st class brakes. They are a single rotor disc brake, they are high output brakes featuring a unique design for dissipating heat to a high degree which in turn results with a higher quality performance and a long lasting pad life. Standard models are capable of handling torque between a range of 1,430 lb-in to 23,700 lb- in.The brakes that were tested were all Tidland models from 200-1-1 to 200-3-9 (9 different brakes). Each brake was tested on with two different braking pads, one with a coefficient of friction of 0.38 and the other with a coefficient of friction of 0.12. The brakes were tested at 75 psi. The results have been displayed in a table and I have placed them on the next page for the reader’s convenience.312420050800-3810012700This table below shows the results from the Tidland/Maxcess experiment involving heat dissipation in air disc brakes. ConclusionAs discussed in the above information the air brake is powerful yet lightweight braking system. Making this brakes system ideal for larger vehicles for its safety capacity, the power the system provides and the weight of the system. I believe that air pressure brakes systems are the most appropriate for heavy utility vehicles at the present time for the just given reasons, but I am sure that with the way technology is moving it won’t be long until we see a new system on the market doing greater things. As technology is advancing so fast it’s hard to conclude what is the best option as by the time the report on it is finished a new design is being created and developed. Much of my information came from secondary sources and I was disappointed with how little firsthand information I could conclude myself. An experiment would have been fantastic, where testing the stopping speeds of different trucks and brakes at different speeds, but this was just not possible and these sorts of investigations and experiments are undergone by professionals who dedicate their life to developing and testing these systems. Most of these tests are also created on software which is extremely expensive and the experiments are funded by large companies. In saying this I was able to collect a wide range of information from many different sources, I was happily impressed with the amount of information on braking systems and I thoroughly enjoyed creating this report.ReferencesThe employees of Gates Haulage. Contact Number: The Brake Handbook by Fred Puhn.(road_vehicle) of the Western Star 4864FXEngine- Detroit Diesel DD15 EGR 14.8 Litre 475,500, 505, 530 & 560hp.ABS- Wabco Antilock Braking System (ABS).Tyres & Wheels -Front tyres: Continental HSR2 295/80R22.5” 16 ply.Rear tyres: Continental HDR1 11R22.5 16 ply.Front rims: Motor Wheel 22.5” x 8.25” steelRear rims: Vehicle comes standard without rims: Hayes Lemmerz 22.5” x 8.25” steel Tyre option includes Michelin. Steel & aluminium disc wheels available.A great deal more information can be found at this website: includes a great deal of information on all of the trucks made under this name; I was able to find a great deal of information to aid my field study.Qunli Friction lining asbestos padding featuresWorking Condition:Maximum Continuous Temperature:150℃, Maximum Intermittent Temperature:200℃Maximum Pressure:1.0mpaAvailable Sizes:Supplied in roll form, cut and shaped liningsNormal Roll Lengths: 10 metres (33ft) or on requestThickness:5.0mm (0.2inch) to 30mm (1.2inch)Width:up to 500mm (20inch)Wear PerformanceTemperature Friction Coefficient Wear Rate (cm3/N·m)100°C/212°F 0.40—0.65 0.7×10-7 150°C/302°F 0.35—0.65 0.9×10-7200°C/392°F 0.30—0.60 1.1×10-7 ................
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