3 Four Stroke SI Engine Stroke 1: Fuel-air mixture introduced into cylinder through intake valve Stroke 2: Fuel-air mixture compressed Stroke 3: Combustion (~constant volume) occurs and product gases expand doing work Stroke 4: Product gases pushed out of the cylinder through the exhaust valve Compression Stroke Power Stroke Exhaust Stroke A I R Combustion Products Ignition Intake Stroke FUEL Fuel/Air Mixture
Crank shaft 90 o 180 o BC TC 0 o 270 o Spark plug for SI engine Fuel injector for CI engine Top Center (TC) Bottom Center (BC) Valves Clearance volume Cylinder wall Piston Stroke Cylinder Components
IVO - intake valve opens, IVC – intake valve closes EVO – exhaust valve opens, EVC – exhaust valve opens X b – burned gas mole fraction Four-Stroke SI Engine Exhaust gas residual
Two Stroke SI Engine Intake (“Scavenging”) Compression Ignition Exhaust Expansion Fuel-air-oil mixture Fuel-air-oil mixture compressed Crank shaft Check valve Exhaust port
EPO – exhaust port open EPC – exhaust port closed IPO – intake port open IPC – intake port closed Exhaust area Intake area Two-Stroke SI Engine scavenging
Cylinder Arrangement Single-cylinder engine gives one power stroke per crank revolution (2 stroke) or two revolutions (4 stroke). The torque pulses are widely spaced, and engine vibration and smoothness are significant problems. Used in small engine applications where engine size is more important Multi-cylinder engines spread out the displacement volume amongst multiple smaller cylinders. Increased frequency of power strokes produces smoother torque characteristics. Engine balance (inertia forces associated with accelerating and decelerating piston) better than single cylinder. Most common cylinder arrangements: - In-line 4-cylinder - In-line 6-cylinder - V-6 and V-8
Power Regulation (Throttling) An IC engine is basically an air engine, the more air you get into the cylinder, the more fuel you can burn, the more power you get out. The initial pressure in the cylinder is roughly equal to the pressure in the intake manifold. Pressure in the intake manifold is varied by opening and closing the throttle plate to change the pressure drop. Maximum air flow (and power) achieved at wide-open-throttle (WOT). Minimum air flow at idle P atm P int < P atm Intake manifold Fuel WOT Idle
Basic Carburetor Design Venturi Throttle Air Flow Mixture to manifold Fuel
Fuel Injection System Throttle Fuel tank Air intake manifold During start-up the components are cold so fuel evaporation is very slow, as a result additional fuel is added through a second injecting valve
Superchargers are compressors that are mechanically driven by the engine crankshaft and thus represent a parasitic load. Compressor P atm P int > P atm
Turbochargers couple a compressor with a turbine driven by the exhaust gas. The compressor pressure is proportional to the engine speed
The peak pressure in the exhaust system is only slightly greater than atmospheric – small P across turbine. In order to produce enough power to run compressor the turbine speed must be very fast (100k-200k rev/min). It takes time for the turbine to get up to speed so when the throttle is opened suddenly there is a delay in achieving peak power - Turbo lag. Waste gate valve controls the exhaust gas flow rate to the turbine. It is controlled by the intake manifold pressure INTAKE AIR EXHAUST FLOW
21 A centrifugal clutch is a clutch that uses centrifugal force to connect two concentric shafts, with the driving shaft nested inside the driven shaft.
22 Chassis The two-wheeler chassis consists of the frame, suspension, wheels and brakes. The chassis is what truly sets the overall style of the two-wheeler. Automotive chassis is the main carriage systems of a vehicle. The type determines the gearing configuration, flex and the type of modifications that can be accommodated. Frame: The frame serves as a skeleton upon which parts like gearbox and engine are mounted. It can be made of steel, aluminum or an alloy. It keeps the wheels in line to maintain the handling of the two- wheeler. Suspension: It is a collection of springs and shock absorbers. It can be of two types: front suspension and rear suspension. It insulates both the rider and the bulk of the machine from road shocks and also keeps the wheels in the closest possible contact with the ground and gives control of the vehicle to the rider. The front suspension helps to guide the front wheel, to steer, to spring, to dampen, and to provide support under braking.
23 Types of Frames: Motor cycles / Mopeds use three basic frame designs: 1.Cradle Frame, (2) Back Bone Frame, (3) Stamped Frame The cradle frame is one of the most enduring type and is shown in figure
24 Stamped underbone frame Details of shock absorber
25 Wheels: A wheel is a circular object which with an axle, allows low friction in motion by rolling. A wheel is made up of the rim and spokes or disc plate. Wheels should be aligned properly because it directly influences driving. Two-wheeler wheels are generally of aluminum or steel rims with spokes. Brakes: Generally, there are two independent brakes on a two- wheeler: one set on the front wheel and one on the rear, however, there are many models which have 'linked brakes' and apply both at the same time. The front brake is generally much more powerful than the rear brake. Brakes can either be drum or disc based. When the rider operates one of the brakes, a fluid element known as hydraulics is pressurized to provide the required forces to squeeze the brake pad material onto the rotor and slow down or stop the vehicle.
26 Gear Box: The motorcycle gear box contains a number of gears in different sizes. In the process of gear switching, different pairs of gearwheels lock together. A large and small wheel lock together in the lowest or slowest gear. Similar size wheels lock together in the highest or fastest gear. The motorcycle gear box is the component that makes the actual ratio between the engine and the driving wheels. It is also referred to as transmission gear. Types of Motorcyle Gear Box: In a general manner, the motorcycle gear box can be of three types, they are: Horizontally Split: It has a seam on the horizontal plane. Vertically Split: It has a seam on the vertical plane. Cassette Type: The gears are loaded in from one side.
27 Characteristics of Gear Box: The gears are constantly meshed with one another and they are always spinning. Uses of Gear Box: It controls gear and shaft alignment. It controls the engine RPM. It protects the gears and lubricants from water, dust and other environmental contaminants.
28 Functions of Two Wheeler Shock Absorbers: They absorb the shock from bumps on the road and helps to 1.make riding safe and smooth. 2.they allow the use of soft springs while controlling the rate of 3.suspension movement in response to bumps. 4.They also, along with hysteresis in the tire itself, damp the motion of the unsprung weight up and down on the springiness of the tire. 5.Shock Absorber system make the vehicle manageable. Materials used for making Shock absorbers: The most commonly used materials for making these absorbers are: Steel Aluminum Maintenance of Shock Absorbers: It should be checked regularly. Oils should be changed according to the recommended time.
30 Suspension system Introduction: A Motorcycle Suspension System consists of a spring coupled to a viscous damping element, a piston, in a cylinder filled with oil. The piston smooths out vibrations induced by the vehicle while moving as it moves through the oil. The flow of oil through the piston is regulated by an adjustable elastic deformable flap called a shim. Types of Motorcycle Suspension: Front Suspension: The predominant type of front suspension is the suspension fork. The bottom part of the fork is fitted over the tubes that connect the fork to the frame. When the vehicle hits a bump, the spring gets compressed and the piston forces fluid through the orifice. Rear Suspension: Most of the time the rear suspension are used as a shock absorber
32 Functions of Motorcycle Suspension: The main functions of the motorcycle suspensions are: To insulate both the rider and the bulk of the machine from road shocks. It makes a much safer and comfortable ride and is important for proper mechanical reliability and longevity. To keep the wheels in the closest possible contact with the ground and gives control of the vehicle to the rider. The front suspension helps to guides the front wheel, to steer, to spring, to dampen, and to provide support under braking. Materials used for making Suspensions: The materials most commonly used for making suspensions are: Steel Aluminum Maintenance of Suspensions: The suspensions should be checked for loose nuts and bolts and leaks. The swing arm bearings should be lubricated monthly.
36 Wheel parts: A wheel is a circular object which with an axle, allows low friction in motion by rolling. A wheel is made up of the rim and spokes or disc plate. The standard size of wheels for two-wheelers is 17 inch. Wheels should be aligned properly because it directly influences driving. Parts of a Wheel: There are two basic parts of a Wheel: Tire Wheel Rim Wheel Spoke or Compact Disc Tire is also an important part of a wheel. It works as a wheel only after it is installed on the rim and is inflated.
38 Wheel hub details Spoked wheel transmits driving torque and braking torque through different set of spokes. Split disc wheel
39 Materials used for making Motorcycle Wheel Parts: Wheel for two-wheelers are usually made of aluminum. Magnesium is also used for making wheels, but they are meant for race bikes because they are very strong and light. Even carbon fibers are also used for making wheels. Maintenance of Motorcycle Wheel Parts: Though a simple device, the wheel needs proper care and maintenance to keep it taut and free of damage and in perfect balance. Regular inspection for loose or damaged spokes is a must. They must be kept clean and free of rust. The wheel should be aligned properly otherwise it can wear the tires, reduce tire mileage and impair steering and cornering. Proper checking of the wheels to insure that they are in good condition is a must because cracked or bent wheel can lead to the loss of air and cause subsequent deflation of the tire.
40 Tyre A Rubber Tire is a device covering the circumference of a wheel. It is an essential part of most ground vehicles. The combination of air with rubber tire supports the vehicle and its contents.
41 Part of a tyre Figure: Simple tyre tread patterns Tyre wear: (1) Skid depth. (2) Side wall. (3) Wear indicator
42 Tyre road contact for different extent of tyre inflation: (a) Correct inflation. (b) Under inflation, tyre cries “ May side walls are heated due to bending. I need more air ”. (c) Over inflation. Tyre rotation
43 Parts of a Rubber Tire: The Bead: fits inside the rim of the wheel and is held in place by tire pressure. The Sidewall: protects the cord plies and has all the tire information printed on it. The Tread: provides strength and stability and is the interface that provides traction to the road surface. The Belt Plies and Body Plies: give the tire its stability and resistance to road damage. An inner liner: combats permeability (keeping the air in the tire). Sipes: are small slits in the tread that improve traction. Functions of Rubber Tires: Rubber Tire absorbs the shock of road roughness and can provide a smooth, safe ride. They protect the wheel from wear and tear. They provide a high-friction bond between the vehicle and the road to improve acceleration and handling. They also provide other functions such as traction for moving, stopping and steering as well as providing a cushion for the vehicle
45 Two wheelers www.iatss.or.jp/pdf/research/28/28-1-03.pdf www.ccsindia.org/ccsindia/policy/live/studies/wp00 65.pdf www.tvsmotor.in/pdf/analystmeet2005.pdf http://www.ustudy.in/node/2103 Case study to Two wheeler and three wheeler