Bicycle cranks can vary in length to accommodate different sized riders and different types of cycling. Crank length is measured from the center of the pedal spindle to the center of the bottom bracket spindle or axle. The larger bicycle component manufacturers typically offer crank lengths for adult riders from 165 mm to 180 mm long in 2.5 mm increments, with 170 mm cranks being the most common size. A few small specialty manufacturers make bicycle cranks in a number of sizes smaller than 165 mm and longer than 180 mm. Some manufacturers also make bicycle cranks that can be adjusted to different lengths. While logic would suggest that, all other things being equal, riders with shorter legs should use proportionally shorter cranks and those with longer legs should use proportionally longer cranks, this is not universally accepted. However, very few scientific studies have definitively examined the effect of crank length on sustained cycling performance and the studies' results have been mixed. Bicycle crank length has not been easy to study scientifically for a number reasons, chief among them is that cyclists are able to physiologically adapt to different crank lengths. Cyclists are typically more efficient pedalling cranks with which they have had an adaptation period. Several different formulas exist to calculate appropriate crank length for various riders. In addition to the rider's size, another factor affecting the selection of crank length is the rider's cycling specialty and the type of cycling event. Historically, bicycle riders have typically chosen proportionally shorter cranks for higher cadence cycling such as criterium and track racing, while riders have chosen proportionally longer cranks for lower cadence cycling such as time trial racing and mountain biking. However, the evolution of very low rider torso positions to reduce aerodynamic drag for time trial racing and triathlon cycling can also affect crank selection for such events. Some have suggested that proportionally shorter cranks may have a slight advantage for a rider with a very low torso position and an actute hip angle, especially as the rider pedals near the top-dead-center position of the pedal stroke.
Saturday 31 August 2013
Thursday 22 August 2013
Flywheel
A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia and thus resist changes in rotational speed. The amount of energy stored in a flywheel is proportional to the square of its rotational speed. Energy is transferred to a flywheel by applying torque to it, thereby increasing its rotational speed, and hence its stored energy. Conversely, a flywheel releases stored energy by applying torque to a mechanical load, thereby decreasing its rotational speed.
Common uses of a flywheel include:
- Providing continuous energy when the energy source is discontinuous. For example, flywheels are used in reciprocating engines because the energy source, torque from the engine, is intermittent.
- Delivering energy at rates beyond the ability of a continuous energy source. This is achieved by collecting energy in the flywheel over time and then releasing the energy quickly, at rates that exceed the abilities of the energy source.
- Controlling the orientation of a mechanical system. In such applications, the angular momentum of a flywheel is purposely transferred to a load when energy is transferred to or from the flywheel.
Flywheels are typically made of steel and rotate on conventional bearings; these are generally limited to a revolution rate of a few thousand RPM.Some modern flywheels are made of carbon fiber materials and employ magnetic bearings, enabling them to revolve at speeds up to 60,000 RPM.
wagon r STINGRAY
Maruti Suzuki India Ltd, the country's largest passenger car manufacturer, never fails to amaze us. The last time we wrote about them it was about Maruti Ertiga CNG that help Indian car-owners beat rising fuel prices and the Maruti Suzuki app for car serving. This time around, the automobile industry is getting a new entrant. With the upcoming launch of Maruti Suzuki Wagon R Stingray hatchback rumored to be around end of August this year or during the festive season as sales for passenger cars normally see a substantial increase at that time, there's much excitement among the folks who love unveiling of cars.
We all are aware of the fact that Maruti Suzuki's Wagon R has been popular on the Indian roads and it still sells on an average 13000 units per month. So, the all new Wagon R Stingray is among a lot of speculations about the features that it is going to sport. There was also news about the hatchback being spotted in a photography session and a demo version of the new car was seen at a Maruti Suzuki dealership. What took to everyone's attention was the huge Experience Stingray logo on a new chrome strip. The overall sporty look and feel of the Suzuki Wagon R Stingray has a bold front fascia that makes it look more masculine
Much is being written about the new Wagon R and its features - such as it features a bonnet with a large dam, slim headlamps, revised fog lamp clusters and a slim chrome grille. Running on four grey-finish alloy wheels, new rear spoiler and sleek tail lamps, the car has a kind of aggressive look that's just out there. Coming to the interiors, we are reading about black upholstery, high quality floor mats, an advanced audio system, electronically adjustable optical rear view mirrors, projector headlights, Anti-lock Braking System (ABS) and airbags.
The Maruti Suzuki Wagon R Stingray specifications may resemble mostly with the current Wagon R running on the roads. Therefore, we might see three-cylinder K Series 1-litre petrol engine that will be mated to a 5-speed manual gearbox. Though there's no official word about the price or the availability of this new car, according to reports, the hatchback's price in India could be around Rs. 4.10 lakh. So are the recently launched nissan micra and micra-active 2013 as well as hyundai grand i10 the competitors to the Wagon R Stingray? We will find out in due time. Let us know your views about the upcoming hatchback in the Indian car market through comments below.
Update: The car is going to feature tilt-adjustable steering wheel and electrically adjustable rear view mirrors. The KB 10B 1-litre engine produces 68PS of power and 90Nm of torque. Top-spec Vxi (O) gets driver-side airbag and ABS. A fuel economy figure of 20.51 kmpl for the Wagon R Stingray is being claimed.
We all are aware of the fact that Maruti Suzuki's Wagon R has been popular on the Indian roads and it still sells on an average 13000 units per month. So, the all new Wagon R Stingray is among a lot of speculations about the features that it is going to sport. There was also news about the hatchback being spotted in a photography session and a demo version of the new car was seen at a Maruti Suzuki dealership. What took to everyone's attention was the huge Experience Stingray logo on a new chrome strip. The overall sporty look and feel of the Suzuki Wagon R Stingray has a bold front fascia that makes it look more masculine
Much is being written about the new Wagon R and its features - such as it features a bonnet with a large dam, slim headlamps, revised fog lamp clusters and a slim chrome grille. Running on four grey-finish alloy wheels, new rear spoiler and sleek tail lamps, the car has a kind of aggressive look that's just out there. Coming to the interiors, we are reading about black upholstery, high quality floor mats, an advanced audio system, electronically adjustable optical rear view mirrors, projector headlights, Anti-lock Braking System (ABS) and airbags.
The Maruti Suzuki Wagon R Stingray specifications may resemble mostly with the current Wagon R running on the roads. Therefore, we might see three-cylinder K Series 1-litre petrol engine that will be mated to a 5-speed manual gearbox. Though there's no official word about the price or the availability of this new car, according to reports, the hatchback's price in India could be around Rs. 4.10 lakh. So are the recently launched nissan micra and micra-active 2013 as well as hyundai grand i10 the competitors to the Wagon R Stingray? We will find out in due time. Let us know your views about the upcoming hatchback in the Indian car market through comments below.
Update: The car is going to feature tilt-adjustable steering wheel and electrically adjustable rear view mirrors. The KB 10B 1-litre engine produces 68PS of power and 90Nm of torque. Top-spec Vxi (O) gets driver-side airbag and ABS. A fuel economy figure of 20.51 kmpl for the Wagon R Stingray is being claimed.
Tuesday 20 August 2013
Audi Q3 2.0 TDI Quattro base
Engine and Transmission
Fuel Economy
Performance
Brakes Steering Suspension and Tyres
Exterior Dimensions
Interior Dimensions
Westinghouse Air Brake Company
The Westinghouse Air Brake Company was established by George Westinghouse in 1869. The Air Brake plant was moved to wilmerding pennsylvaniain1889. Wilmerding is a small town about 14 miles outside of Pittsburgh which, at the time, was only inhabited by about 5,000 people. socialism was strong in Wilmerding and it was a peaceful non-violent farming borough. It was thought to be “The Ideal Town” for the company because of its location right along the pennsylvania railroad and its mainly blue collar inhabitants. The Air Brake Company employed 3,000 citizens from the surrounding Pittsburgh area, but its work force was composed almost entirely of individuals from Wilmerding.
This stretch of lightly populated farmland known as Wilmerding developed completely around this new and industrially important company and was finally put on the map. A little under one third of its population was somehow related and more often than not one would end up raising their children in the same home that they were raised in. After the company's development business thrived. Many of the passengers that were departing or coming into Wilmerding stopped to shop at these stores along the narrow sidewalk before heading home. One could get anything from hair cuts to comic books, groceries to lumber; Wilmerding was where you would find it.
Working conditions at the Westinghouse Air Brake Company (WA&B) were more than proficient and the company had many new developments in effect for its employees. In 1869 it was one of the first companies to institute a 9-hour work day and a 55-hour work week. WA&B also got the reputation for being the first industry in America to adopt half holidays on Saturday afternoons. A series of welfare options were also instituted to better the working and living conditions of its employees.
The Air Brake plant was obviously very prosperous and was nothing far from a gift for this small town. By 1905 over 2,000,000 freight, passenger, mail, baggage, and express cars and 89,000 locomotives were equipped with the Westinghouse Air Brakes. But just as in all big businesses, it had its ups and downs. There was one general complaint among the Wilmerding business men. It was that only about half of the workers could find work during the non-busy season. This made sense since these men and women depended entirely on the company. When the economy struggled and profits in the company declined, workers then had to alter their standard of living. Wilmerding’s prosperity and misfortune all depended on the success of the Air Brake Company and when the company was failing the citizens just had to try and adjust to its losses.
During this time, in the early 1900s, the Westinghouse Company built houses on a tract of land that it had purchased, in turn, it then sold those homes to its workers at a very inexpensive price. The company also offered educational and cultural activities, usually run through the local Y.M.C.A, to obtain better workers. WA&B catered to those who were not exactly fit in its working conditions. To insure a certain income to employees who might have been unfit for work because of illness or injury, an ordered sum would be paid to the beneficiary. Any employee under 50 was eligible for membership after a physical examination. The members contributed according to the class which they belonged, with their class being determined by the amount of money they made per month. Their contribution ranged from fifty cents to $1.50, which in turn in case of disability would receive benefits for thirty-nine consecutive weeks. According to Wilmerding News during this time, about 76% of WA&B’s employees held a membership with the company.
The Westinghouse Air Brake company was still producing products up until around the year 2000, under several different managers over the years. The company had become significantly less important with the shedding of Pittsburgh’s industrial past, but continued manufacturing its products.
The company has two 21st century successors, which are independent of each other. One, which continues to design and manufacture railway air brakes in Wilmerding, Pennsylvania, merged with locomotive manufacturer MotivePower Industries, to form wabtac. The other, now known as WABCO Holdings Inc, designs and manufactures control systems for commercial road vehicles, including air brakes, and is headquartered in brussels Belgium. was floated in a 2007 initial public offering by A S, WABCO's owners for 30 years.
Advantages of air brake
Air brakes are used as an alternative to hydraulic brakes which are used on lighter vehicles such as automobiles. Hydraulic brakes use a fluid to transfer pressure from the brake pedal to the brake shoe to stop the vehicle. Air brakes have several advantages for large multitrailer vehicles:
- The supply of air is unlimited, so the brake system can never run out of its operating fluid, as hydraulic brakes can. Minor leaks do not result in brake failures.
- Air line couplings are easier to attach and detach than hydraulic lines; there is no danger of letting air into hydraulic fluid. So air brake circuits of trailers can be attached and removed easily by operators with little training.
- Air not only serves as a fluid for transmission of force, but also stores potential energy. So it can serve to control the force applied. Air brake systems include an air tank that stores sufficient energy to stop the vehicle if the compressor fails.
- Air brakes are effective even with considerable leakage, so an air brake system can be designed with sufficient "fail-safe" capacity to stop the vehicle safely even when leaking.
pneumatic starting motor
Some gas turbine engines and diesel engines, particularly on trucks, use a pneumatic self-starter. In ground vehicles the system consists of a geared turbine, an air compressor and a pressure tank. Compressed air released from the tank is used to spin the turbine, and through a set of reduction gears, engages the ring gear on the flywheel, much like an electric starter. The engine, once running, drives the compressor to recharge the tank.
Aircraft with large gas turbine engines are typically started using a large volume of low-pressure compressed air, supplied from a very small engine referred to as an auxiliary power unit, located elsewhere in the aircraft. Alternately, aircraft gas turbine engines can be rapidly started using a mobile ground-based pneumatic starting engine, referred to as a start cart or air start cart.
On larger diesel generators found in large shore installations and especially on ships, a pneumatic starting gear is used. The air motor is normally powered by compressed air at pressures of 10–30 BAR. The AIR motor is made up of a center drum about the size of a soup can with four or more slots cut into it to allow for the vanes to be placed radially on the drum to form chambers around the drum. The drum is offset inside a round casing so that the inlet air for starting is admitted at the area where the drum and vanes form a small chamber compared to the others. The compressed air can only expand by rotating the drum, which allows the small chamber to become larger and puts another one of the cambers in the air inlet. The air motor spins much too fast to be used directly on the flywheel of the engine; instead a large gearing reduction, such as a planetary gear, is used to lower the output speed. A Bendix gear is used to engage the flywheel.
Large Diesel generators and almost all Diesel engines used as the prime mover of ships use compressed air acting directly on the cylinder head. This is not ideal for smaller Diesels, as it provides too much cooling on starting. Also, the cylinder head needs to have enough space to support an extra valve for the air start system. The air start system is conceptually very similar to a distributer a car. There is an air distributor that is geared to the camshaft of the Diesel engine; on the top of the air distributor is a single lobe similar to what is found on a camshaft. Arranged radially around this lobe are roller tip followers for every cylinder. When the lobe of the air distributor hits one of the followers it will send an air signal that acts upon the back of the air start valve located in the cylinder head, causing it to open. Compressed air is provided from a large reservoir that feeds into a header located along the engine. As soon as the air start valve is opened, the compressed air is admitted and the engine will begin turning. It can be used on 2-cycle and 4-cycle engines and on reversing engines. On large 2-stroke engines less than one revolution of the crankshaft is needed for starting.
Since large trucks typically use air brakes, the system does double duty, supplying compressed air to the brake system. Pneumatic starters have the advantages of delivering high torque, mechanical simplicity and reliability. They eliminate the need for oversized, heavy storage batteries inprime mover electrical systems.
Power brakes
The vacuum booster or vacuum servo is used in most modern hydraulic brake systems which contain four wheels. The vacuum booster is attached between the master cylinder and the brake pedal and multiplies the braking force applied by the driver. These units consist of a hollow housing with a movable rubber diaphragm across the center, creating two chambers. When attached to the low-pressure portion of the throttle body or intake manifold of the engine, the pressure in both chambers of the unit is lowered. The equilibrium created by the low pressure in both chambers keeps the diaphragm from moving until the brake pedal is depressed. A return spring keeps the diaphragm in the starting position until the brake pedal is applied. When the brake pedal is applied, the movement opens an air valve which lets in atmospheric pressure air to one chamber of the booster. Since the pressure becomes higher in one chamber, the diaphragm moves toward the lower pressure chamber with a force created by the area of the diaphragm and the differential pressure. This force, in addition to the driver's foot force, pushes on the master cylinder piston. A relatively small diameter booster unit is required; for a very conservative 50% manifold vacuum, an assisting force of about 1500 N (200n) is produced by a 20 cm diaphragm with an area of 0.03 square meters. The diaphragm will stop moving when the forces on both sides of the chamber reach equilibrium. This can be caused by either the air valve closing (due to the pedal apply stopping) or if "run out" is reached. Run out occurs when the pressure in one chamber reaches atmospheric pressure and no additional force can be generated by the now stagnant differential pressure. After the run out point is reached, only the driver's foot force can be used to further apply the master cylinder piston.
The fluid pressure from the master cylinder travels through a pair of steel brake tubes to a pressure differential valve, sometimes referred to as a "brake failure valve", which performs two functions: it equalizes pressure between the two systems, and it provides a warning if one system loses pressure. The pressure differential valve has two chambers (to which the hydraulic lines attach) with a piston between them. When the pressure in either line is balanced, the piston does not move. If the pressure on one side is lost, the pressure from the other side moves the piston. When the piston makes contact with a simple electrical probe in the center of the unit, a circuit is completed, and the operator is warned of a failure in the brake system.
From the pressure differential valve, brake tubing carries the pressure to the brake units at the wheels. Since the wheels do not maintain a fixed relation to the automobile, it is necessary to use hydraulic brake hose from the end of the steel line at the vehicle frame to the caliper at the wheel. Allowing steel brake tubing to flex invites metal fatigue and, ultimately, brake failure. A common upgrade is to replace the standard rubber hoses with a set which are externally reinforced with braided stainless-steel wires; these have negligible expansion under pressure and can give a firmer feel to the brake pedal with less pedal travel for a given braking effort.
Thursday 15 August 2013
Power valve of carburetor
For open throttle operation a richer mixture will produce more power, prevent pre-ignition detonation, and keep the engine cooler. This is usually addressed with a spring-loaded "power valve", which is held shut by engine vacuum. As the throttle opens up, the vacuum decreases and the spring opens the valve to let more fuel into the main circuit. On two stroke engines the operation of the power valve is the reverse of normal — it is normally "on" and at a set rpm it is turned "off". It is activated at high rpm to extend the engine's rev range, capitalizing on a two-stroke's tendency to rev higher momentarily when the mixture is lean.
Alternative to employing a power valve, the carburetor may utilize a metering rod or step-up rod system to enrich the fuel mixture under high-demand conditions. Such systems were originated by Carter Carburetor in the 1950s for the primary two venturis of their four barrel carburetors, and step-up rods were widely used on most 1-, 2-, and 4-barrel Carter carburetors through the end of production in the 1980s. The step-up rods are tapered at the bottom end, which extends into the main metering jets. The tops of the rods are connected to a vacuum piston and/or a mechanical linkage which lifts the rods out of the main jets when the throttle is opened (mechanical linkage) and/or when manifold vacuum drops (vacuum piston). When the step-up rod is lowered into the main jet, it restricts the fuel flow. When the step-up rod is raised out of the jet, more fuel can flow through it. In this manner, the amount of fuel delivered is tailored to the transient demands of the engine. Some 4-barrel carburetors use metering rods only on the primary two venturis, but some use them on both primary and secondary circuits, as in the Rochester Quadrajet.
Principles of carburater
The carburetor works on Bernoulli's principle: the faster air moves, the lower its static pressure and the higher its dynamic pressure. The (accelerator) linkage does not directly control the flow of liquid fuel. Instead, it actuates carburetor mechanisms which meter the flow of air being pulled into the engine. The speed of this flow, and therefore its pressure, determines the amount of fuel drawn into the airstream.
When carburetors are used in aircraft with piston engines, special designs and features are needed to prevent fuel starvation during inverted flight. Later engines used an early form of fuel injection known as a pressure carburetor.
Most production carbureted engines have a single carburetor and a matching intake manifold that divides and transports the air fuel mixture to the intake valesi, though some engines (like motorcycle engines) use multiple carburetors on split heads. Multiple carburetor engines were also common enhancements for modifying engines in the USA from the 1950s to mid-1960s, as well as during the following decade of high-performance muscle cars fueling different chambers of the engine's .intake manifold
Older engines used updraft carburetors, where the air enters from below the carburetor and exits through the top. This had the advantage of never flooding the engine as any liquid fuel droplets would fall out of the carburetor instead of into the intake manifold; it also lent itself to use of an oil bath air cleaner where a pool of oil below a mesh element below the carburetor is sucked up into the mesh and the air is drawn through the oil-covered mesh; this was an effective system in a time when paper air filters did not exist.
Beginning in the late 1930s, downdraft carburetors were the most popular type for automotive use in the united states. In Europe, the sidedraft carburetors replaced downdraft as free space in the engine bay decreased and the use of the su-type carburetor (and similar units from other manufacturers) increased. Some small propeller-driven aircraft engines still use the updraft carburetor design.
outboard moter carburetors are typically sidedraft, because they must be stacked one on top of the other in order to feed the cylinders in a vertically oriented cylinder block.
Tuesday 13 August 2013
Brake caliper
The brake caliper is the assembly which houses the brake pads and pistons. The pistons are usually made of aluminium or chrome-plated steel.
Calipers are of two types, floating or fixed. A fixed caliper does not move relative to the disc and is thus less tolerant of disc imperfections. It uses one or more single or pairs of opposing pistons to clamp from each side of the disc, and is more complex and expensive than a floating caliper.
A floating caliper (also called a "sliding caliper") moves with respect to the disc, along a line parallel to the axis of rotation of the disc; a piston on one side of the disc pushes the inner brake pad until it makes contact with the braking surface, then pulls the caliper body with the outer brake pad so pressure is applied to both sides of the disc. Floating caliper (single piston) designs are subject to sticking failure, caused by dirt or corrosion entering at least one mounting mechanism and stopping its normal movement. This can lead to the caliper's pad's rubbing on the disc when the brake is not engaged or engaging it at an angle. Sticking can result from infrequent vehicle use, failure of a seal or rubber protection boot allowing debris entry, dry-out of the grease in the mounting mechanism and subsequent moisture incursion leading to corrosion, or some combination of these factors. Consequences may include reduced fuel efficiency, extreme heating of the disc or excessive wear on the affected pad. A sticking front caliper may also cause steering vibration.
disc brake
A disc brake is a wheel brake which slows rotation of the wheel by the friction caused by pushing brake pades against a brake disc with a set of calipers. The brake disc (or rotor in American English) is usually made of cast iron, but may in some cases be made of composites such as reinforced carbon-carbon or ceramic matrix composite. This is connected to the wheel and/or the axle. To stop the wheel, friction material in the form of brake pads, mounted on a device called a brake caliper, is forced mechanically, hydraulicaly, pnumatrically or elecromagnatically against both sides of the disc. friction causes the disc and attached wheel to slow or stop. Brakes convert motion to heat, and if the brakes get too hot, they become less effective, a phenomenon known as brake fade
Disc-style brakes development and use began in England in the 1890s. The first caliper-type automobile disc brake was patented by frederice william in his birmingham, UK factory in 1902 and used successfully on Lanchester cars. Compared to drum brakes, disc brakes offer better stopping performance, because the disc is more readily cooled. As a consequence discs are less prone to brake fade; and disc brakes recover more quickly from immersion (wet brakes are less effective). Most drum brake designs have at least one leading shoe, which gives a servo-effect. By contrast, a disc brake has no self-servo effect and its braking force is always proportional to the pressure placed on the brake pad by the braking system via any brake servo, braking pedal or lever, this tends to give the driver better "feel" to avoid impending lockup. Drums are also prone to "bell mouthing", and trap worn lining material within the assembly, both causes of various braking problems.
Tuesday 6 August 2013
Double wishbone suspension
The double-wishbone suspension can also be referred to as "double A-arms," though the arms themselves can be A-shaped, L-shaped, or even a single bar linkage. A single wishbone or a-arm can also be used in various other suspension types, such as macpherson strut and chaman strut. The upper arm is usually shorter to induce negative camber as the suspension jounces (rises), and often this arrangement is titled an "SLA" or short long arms suspension. When the vehicle is in a turn, body roll results in positive camber gain on the lightly loaded inside wheel, while the heavily loaded outer wheel gains negative camber.
Between the outboard end of the arms is a knuckle with a spindle, hub, or upright which carries the wheel bearing and wheel.
To resist fore-aft loads such as acceleration and braking, the arms require two bushings or ball joints at the body.
At the knuckle end, single ball joints are typically used, in which case the steering loads have to be taken via a steering arm, and the wishbones look A- or L-shaped. An L-shaped arm is generally preferred on passenger vehicles because it allows a better compromise of handling and comfort to be tuned in. The bushing inline with the wheel can be kept relatively stiff to effectively handle cornering loads while the off-line joint can be softer to allow the wheel to recess under fore-aft impact loads. For a rear suspension, a pair of joints can be used at both ends of the arm, making them more H-shaped in plan view. Alternatively, a fixed-length driveshaft can perform the function of a wishbone as long as the shape of the other wishbone provides control of the upright. This arrangement has been successfully used in the jagure IRS. In elevation view, the suspension is a 4-bar link, and it is easy to work out the camber gain and other parameters for a given set of bushing or ball-joint locations. The various bushings or ball joints do not have to be on horizontal axes, parallel to the vehicle centre line. If they are set at an angle, then antidive and antisquat geometry can be dialed in.
In many racing cars, the springs and dampers are relocated inside the bodywork. The suspension uses a bellcrank to transfer the forces at the knuckle end of the suspension to the internal spring and damper. This is then known as a "push rod" if bump travel "pushes" on the rod (and subsequently the rod must be joined to the bottom of the upright and angled upward). As the wheel rises, the push rod compresses the internal spring via a pivot or pivoting system. The opposite arrangement, a "pull rod," will pull on the rod during bump travel, and the rod must be attached to the top of the upright, angled downward. Locating the spring and damber inboard increases the total mass of the suspension, but reduces the unspring mass, and also allows the designer to make the suspension more aerodynamic.
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