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Vehicle_body_engineering.pdf

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VEHICLE_BODY_ENGINEERING
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VEHICLE BODY ENGINEERING AT1402 VEHICLE BODY ENGINEERING OBJECTIVE At the end of the course, the students will be able to have a sound knowledge for the design of the vehicles body to give maximum comfort for the passengers and exposed to the methods of stream lining the vehicles body to minimize drag. UNIT- I CAR BODY DETAILS Types: saloon, convertibles, limousine, estate car, racing and sports car. Visibility: regulations, driver’s visibility, tests for visibility, methods of improving visibility and space in cars. Safety: safety design, safety equipments for cars. Car body construction; design criteria, prototype making, initial tests, crash tests on full scale model, Dummies and Instrumentation UNIT-II VEHICLE AERODYNAMICS Objectives. Vehicle drag and types; various types of forces and moments, effects of forces and moments, side wind effects on forces and moments, Various body optimization techniques for minimum drag, wind tunnel testing: flow visualization techniques, scale model testing, component balance to measure forces and moments. UNIT- III BUS BODY DETAILS Types: mini bus, single decker, double-decker, two level and articulated bus. Bus body layout; floor height, engine location, entrance and exit location, seating dimensions. Constructional details: frame construction, double skin construction, types of metal sections used, Regulations, Conventional and integral type construction. UNIT-IV COMMERCIAL VEHICLE DETAILS Types of body; flat platform, drop side, fixed side, tipper body, tanker body, Light commercial vehicle body types. Dimensions of driver’s seat relation to controls. Drivers cab design. UNIT –V BODY MATERIALS, TRIM AND MECHANISMS Steel sheet, timber, plastic, GRP, properties of materials; Corrosion, anticorrosion methods. Selection of paint and painting process. Body trim items. Body mechanisms. TEXT BOOK 1. J.Powloski - “Vehicle Body Engineering” - Business Books Ltd, London -1989 REFERENCES 1. Giles.J.C. - “Body construction and design” - Liiffe Books Butterworth & Co. - 1971. 2. John Fenton - “Vehicle Body layout and analysis” - Mechanical Engg. Publication Ltd., London – 1982. 3. Braithwaite.J.B. - “Vehicle Body building and drawing” - Heinemann Educational Books Ltd., London – 1977. UNIT –I CAR BODY DETAILS ‘Carriage’ is the term for the vehicle jolting with 5miles/hour to the smooth comfort vehicle with a km/min. in the early version i.e. 1896-98 –Body is nothing but a convenient seat for the driver and a cover for the engine and other chassis. Initially horse carriage builder build the body to a steel framing/chassis. To reduce the weight and to get difference in shape, sheet metal panels replaced hardwood framing reinforced with ironwork. Around 1909-Vehicle speed 12miles/hr-design of body took place. In 1913 Henry Ford started mass production of cars-Ford “Model-T” with slogan “Car for everyone” This car took few man-hours to assemble engine but several man-hours for body manufacture. In the next model “Model-A” many wooden components are replaced. In 1930 Butt corporation of Philadelphia made all metal body, using sheet metal pressings-jointed by welding. In 1930 only Spot welding had been introduced. First style-Two seater open and equipped with sheets for covering the driver and passengers during inclement weather. Later a glass screen was erected in front of the driver. Four-seater style with collapsible hood and celluloid side screen-“all weather” body. Popular ‘saloon’ model-enclosed body, glass windscreen, wind-up windows and sheet metal roof. In 1950 integral construction was introduced in passenger car construction. Types of Car body 1. Saloon or Sedan i) Four door saloon ii) Two door saloon iii) Pillar less saloon iv) Hatch back v) Fast back vi) Notch back 2. Convertibles 3. Limousine 4. Estate car 5. Sports Coupe 6. Coupe 1. Saloon Saloon is a passenger car with two rows of seats and adequate passenger space in the rear compartment for passengers. The vehicle usually has a separate rearboot for luggage. - This is most popular passenger car - Passenger comfort such as easy Entery and Exit, Good A/C,heating,ventelation system and styling are the fetures of the model. - Drag co-efficient is about 0.35-0.5 - The features of Two door and Pillar less saloon are as same that of Four door saloon. - In Pillar less saloon, there not be center pillar and In case of Two door saloon, there is only Two doors are available. - Hatch back- Identified by a rear door including the back window that opens vertically to access a storage area not separated from the rest of the passenger compartment. May be 3 or 5-door and 2 to 5 seats. - Fast back- Fast back sedan is a two-box sedan, with continuous slope from the roof to the base of the Boot, but excludes the Hatback feature. - Notch back- Notchback sedan is a three-box sedan, where the passenger volume is clearly distinct from the trunk volume of the vehicle (when seen from the side). The roof is on one plane, generally parallel to the ground, the rear window at a sharp angle to the roof, and the trunk lid is also parallel to the ground. 2. Convertibles A convertible is a type of automobile in which the roof can retract and fold away, converting it from an enclosed to an open-air vehicle. 3. Limousine - limousine is a luxury sedan or saloon car, especially one with a lengthened wheelbase. The chassis of a limousine may have been extended by the manufacturer or by an independent coach builder. It is usually provided with a partition between the passenger compartment and driver compeartment. - It is provided with components and equipments of high quality and better finish. -Cusion seats, A/C, cooling glass etc are the features of this model. 4. Eastate car -The luggage compartment is countinuation of the passenger of the passenger compartment without partition between them. -Thus more luggage space and longer wheel base are the speciality of this model. -The other names are “Universal”, “Kombi”, “ Station wagen”, “Campaing van”, “Break van”. -Convertible limousine has provited with windup window and foldind roof. 5. Sports Coupe -It is a two seater with fixed roof. -Better Aerodynamic shape to better acceleration. -Light weight combined with rigidity. -Drag Co-efficient is 0.2-0.3 6. Coupe -Similar to sports coupe but with two small seats at back. Visibility Good allround visibility is now one of the main requirements of body design.This is clearely depends on the size of the window openings and their position relative to the occupents. Forward visibilty can be improved by bringing the front seats of the passenger car closer to the front windscreen. On the other hand the problem of entry is increased, since the distance between the seat and the pillar is decreased. Ease entery is possible by suitably shaping doors( as shown by dotted line) at the expence of a more complecated structure. In military vehicles the downward visibility is improtant and the driver must be positioned as high as possible in relation to the lower edge of the windscreen. There are no strict regulations regarding visibility. It is assumed that the upward angle of the vertical visibility should be such as to enable the driver to see the trafic lights etc and this must be taken into consideration at the design stage. Rearward visibility has assumed considerable importance in modern trafic conditions and the increase in glass area required to maintain a given rear view veartical angle with a ‘Fast Back’ window is shown in fig. Visibility can be divided into two aspects 1. Ability to see 2. Ability to be seen Safety Safety equipments for cars: 1. Bumber design: The bumber should be designed to absorb more energy. 2. Ignition switch should be connected with door lock that ignition can be switched , only when all four doors are perfectely locked. 3. Airbag and Safety bags have to be used. 4. Herlomatic flash or Horn. 5. Collapsible steering. 6. Heat toughened glass. Car body Construction -Four door saloon considered as a hollow tube with holes cut in the sides. Front and rear bulkheads complete the box form provide torsional stability.Roof stable structure- curved shape-prevents misalignment. -Floor-complete panel from front to rear. Fitted with integral straightening ribs to prevent buckling. -With sill, Wheel arch, cross member and heelboard- strongest part of the body. Prototype Car prototype can be considered to be the test model of a new car design that is intended to be produced in mass quantity. There is no company that goes out and starts mass production of a new car, without first creating a prototype of it. A car prototype can also be referred as a test car. These car prototypes are developed to demonstrate the new qualities of their product to clients. By subjecting these car prototypes to numerous tests, the car designer gets to see the strengths, weaknesses, mistakes and limitations in a new car project. Then, by gathering this information, the car designer proceeds to rework the design through the car prototype until the car reaches the objectives of the designer. Sometimes, the participating cars in a race are also called prototypes. The reason for this is that these cars are not mass-produced. These car prototypes are specialized machines that are supposed to showcase new innovations and designs that the car manufacturer carries. These car prototypes are the models for future mass-produced cars the manufacturer will be creating, based on the results of the tests on the car prototype. Tests: -Initial tests -Crash test Dummies and Instrumentation Crash test dummies are full-scale anthropomorphic test devices (ATD) that simulate the dimensions, weight proportions and articulation of the human body, and are usually instrumented to record data about the dynamic behavior of the ATD in simulated vehicle impacts. Non-contact optical speed & distance measurement systems EEP-2, EEP-3, Micro EEP-10 and DAS 1A Pass by noise measurement system Ex. M/s Bruel & Kjaer, Denmark. Gyro platform for pitch, roll and yaw measurement Measurement of steering wheel Ex. M/s Datron Messtechnik, Germany. Steering torque / angle measurement system Dynamic simulation software – ADAMS Correlation software ‘n code’ Ride quality meter Fuel flow meters (positive displacement type) High speed multi-channel data acquisition systems Draw bar pull measuring Equipment 8 – Channel thermal array recorder UNIT- I I VEHICLE AERODYNAMICS This study concerns about the airflow around the vehicle body. At a speed of about 70 km/hr aerodynamic drag exceeds to 50% of total resistance to motion and above 100 km/hr it is the most important factor. Aerodynamic Drag Form drag - 57% Lift drag - 8% Surface drag -10% Interference drag -15% Cooling and ventilation drag - 10% Aerodynamic forces and moments Forces 1. Lift force 2. Side force or cross wind force 3. Drag force Moments 1. Rolling moment 2. pitching moment 3. Yawing moment Optimization Technique 1. Modification of Fore body 2. Modification of windshield 3. Modification of Roof 4. Modification of vehicle rear end Wind tunnel and Flow visualization test It is the most useful tool to study the aerodynamic aspects of the vehicle. The various forces and moments can be evaluated for the vehicle by using scale models. The instrument used to measure the forces and moments is called a component balance. Flow pattern can be obtained by using smoke method, Tuft or Oil coating methods. Advantages of wind tunnel test 1. Wind velocity and wind angle can be easily and accurately measured. 2. Flow pattern study can also be made accurately. 3. Forces and moments can be measured simultaneously. 4. Testing time and cost is less. UNIT- I I I BUS BODY DETAILS Types of Bus body 1. Classic or Normal control bus 2. Single deck bus 3. Split level 4. Double Decker 5. Two level single Decker 6. Articulated bus 1. Classic or Normal control bus This type of bus has the engine in front of the passenger carrying compartment. This design which has almost universal at one time has practically disappear and is mainly of historical interest. 2. Single Ducker The single deck bus is almost universal today as this layout eliminates all the disadvantages of above type. 3. Split level It is intermediate solution between single and double ducker. It having More seats than single ducker and more stability than Double Ducker. 4. Double Decker These vehicles have more number of seats for a given overall length but Stability is not so high compared to single ducker. 5. Two level single Decker It is used for luxury coaches. This layout provides good forward visibility for all passengers. good luggage space and easy installation of an under floor or rear engine. 6. Articulated bus Bodies for very large coaches or in particular city buses are often made in two parts because of axial load limitations Classification of bus by Passenger capacity 1. Micro bus 2. Small coaches for long distance 3. Small buses for towns 4. Medium coaches for long distance 5. Medium buses for towns 6. Large coaches for long distances 7. Large buses for towns 8. Very large buses for towns Body design aspects 1. Floor height Shaping of the frame allows the body to be lowered. The floor should be placed as low down as possible so that the distance of center of gravity from the road surface is as small as possible. 2. Power plant location 1. Engine behind the front axle 2. Engine above front axle 3. Engine in front of front axle 4. Engine at rear 5. Engine at under floor 3. Location of Entrance and Exit Construction details Frame construction 1. Chassis preparation 2. Side and front framing 3. Roof framing and rear end 4. Truss panel riveted 5. General inspection 6. Flooring and interior lining 7. Roof panels 8. Panelling and moulding 9. Final finishing Double skin construction All metal bodies or composite bodies are adopted for bus body construction. In composite body construction wood is used considerably in between metal member and outside panels. Double skin construction is also being adopted. Normally inner skin will take part in load carrying and outer skin will be fixed in such a way that it can be replaced easily. Types of metal sections used 1. Curved section 2. Channel section 3. Angle section 4. Zed section 5. Corner pillar section 6. Drip rail section
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