2 stroke engines in racing motorcycles

Although two stroke engines have long since been updated with four stroke racing bike engines, two stroke engines provide a lightweight and suitable solution for racing bikes, motocross and dirt bikes.
Earlier on, the two stroke engines in racing bikes were quite popular, but they have since then have been replaced with the four stroke version of the engine.

The two stroke engine was a much simpler design, therefore provided a low cost solution for racing teams.

The two stroke bike engine operates in two strokes, instead of the normal four stroke Otto cycle.
The stages in a two stroke engine are:

1. Power/exhaust stroke: This is the stroke that occurs right after the ignition of the charge, forcing the piston down. After sometime, the top of the piston goes over the exhaust port, with a large amount of the pressurized gases to escape. The downward movement of the piston continues to compress crankcase containing the air, fuel, oil mixture. The top of the piston having passed the transfer port, the charge that is compressed enters the cylinder with any exhaust being forced out.

2. Upon entering the cylinder, the air fuel mixture makes the piston move up, compressing the charge in the cylinder. This results in a vacuum being drawn in the crankcase, with drawing in more air, fuel and oil. The spark plug now ignites the compressed charge, and thereafter the cycle begins again.

The main variations of the two stroke engine types are found in the method of the fuel intake; this depends on the various different types of the cylinder arrangement.

The Reed valve type of configuration delivers power through a wider RPM range than the regular piston and port types, which is generally a suitable arrangement for dirt bikes, as a dirt bike course demands more power over the difficult jump sections.

A rotary inlet valve type of engine configuration has a thin disk attached to the crankshaft, which spins at the crankshaft speed. The fuel-air mixture is made to pass through the disk, with the disk having a section cut, opening if it passes the intake pipe, closing otherwise.

The advantage of the rotary valve arrangement is that it asymmetrically arranges the two stroke mechanism’s intake timing, not possible with piston port type of arrangements.

Cross flow engines are configured to house the transfer ports and exhaust ports on opposing sides, with on top of the piston being the deflector, directing the fresh intake charge on to the upper side of the cylinder.

The residual gas is pushed down the deflector’s other side, out of the exhaust port. The 235 hp 2.6 L V6 crossflow till date has some of the highest output, coming from a low weight engine.

For motocross bikes, such as the 125 SX, bought out in 2007, being ultra light is a key feature. The two stroke engines are competitive, and preferred by racers who do not want to indulge in complicated four stroke machinery.

This bike has a displacement of 124.8cc with bore and stroke 54/54.5, with a TVC power valve.
This 6 gear, premix fuel run two stroke has a front suspension of WP USD 48 mm, with a total weight being about 89.5 kg. Bikes such as this one have a multi-disc hydraulically operated clutch system, with an ignition through a Kokusan digital magneto CDI.

The basic advantage over such two stroke dirt bikes over their four stroke counterparts is that they provide a much more hassle free, yet powerful transmission solutions.

The 250 SX 2007 is a two stroke bike that is powerful enough to give the four stroke category bikes a run for their money. Added to this it is light, making it ideal for motocross racers.

The single cylinder, two stroke engine calls for easy maintenance, and the fantastic suspension, with PDS geometry means that it is a beast on the tough dirt circuit.

Common Rail Type Fuel Injection System

 

Electronic control common rail type fuel injection system drives an integrated fuel pump at an ultrahigh pressure to distribute fuel to each injector per cylinder through a common rail.

 

This enables optimum combustion to generate big horsepower, and reduce PM* (diesel plume) and fuel consumption.

Bosch will supply the complete common-rail injection system for the high-performance 12-cylinder engine introduced by Peugeot Sport for its latest racing car. The system comprises high-pressure pumps, a fuel rail shared by all cylinders (i.e. a common rail), piezo in-line injectors, and the central control unit which compiles and processes all relevant sensor data.

DISI Turbo or Direct Injection Spark Ignition Technology

DISI includes a whole new set of innovations for gasoline engines. To mention a few, direct injection (including cooling the air-gasoline mixture), a new combustion chamber geometry, variable timing technology, and nanotechnology for the catalyst. This all makes the engines consume 20 percent less while getting 15 to 20 percent better performance.

Further developments for its diesels: new direct injection technology (most European automakers are switching to piezoelectric injectors), making the engine lighter, DPF, and urea technology to reduce NOx emissions

Mazda’s DISI* engines balance sporty driving with outstanding environment performance. With the next generation engine in the series, we are aiming for a 15% ~ 20% improvement in dynamic performance and a 20% increase in fuel economy (compared with a Mazda 2.0L gasoline engine). Based on the direct injection system, we aim to reduce all energy losses (see figure on the right) and improve thermal efficiency through innovative engineering in a variety of technological areas. Among these technologies we are paying particular attention to direct injection, combustion control, variable valve system technology and catalyst technology. Also, among the various fuels on the market, we are studying the use of flex-fuel.

Variable Turbochargers Geometry (VTG)

Variable geometry turbochargers (VGTs) are a family of turbochargers, usually designed to allow the effective aspect ratio (sometimes called A/R Ratio) of the turbo to be altered as conditions change. This is done because optimum aspect ratio at low engine speeds is very different from that at high engine speeds. If the aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output. By altering the geometry of the turbine housing as the engine accelerates, the turbo’s aspect ratio can be maintained at its optimum. Because of this, VGTs have a minimal amount of lag, have a low boost threshold, and are very efficient at higher engine speeds. VGTs do not require a waste gate.

Most common designs
The two most common implementations include a ring of aerodynamically-shaped vanes in the turbine housing at the turbine inlet. Generally for light duty engines (passenger cars, race cars, and light commercial vehicles) the vanes rotate in unison to vary the gas swirl angle and the cross sectional area. Generally for heavy duty engines the vanes do not rotate, but instead the axial width of the inlet is selectively blocked by an axially sliding wall (either the vanes are selectively covered by a moving slotted shroud, or the vanes selectively move vs a stationary slotted shroud). Either way the area between the tips of the vanes changes, leading to a variable aspect ratio.

Actuation
Often the vanes are controlled by a membrane actuator identical to that of a waste gate, however increasingly electric servo actuation is used. Hydraulic actuators have also been used in some applications.

Main suppliers

Several companies supply the rotating vane type of variable geometry turbocharger, including Garrett (Honeywell), Borg Warner and MHI (Mitsubishi Heavy Industries). The rotating vane design is mostly limited to small engines and/or to light duty applications (passenger cars, race cars and light commercial vehicles). The only supplier of the sliding vane type of variable geometry turbocharger is Cummins Turbo Technologies (Holset), who are effectively the sole supplier of variable geometry turbochargers for applications involving large engines and heavy duty use (i.e. trucks and off highway applications).

Other common uses
In trucks, VG turbochargers are also used to control the ratio of exhaust re-circulated back to the engine inlet (they can be controlled to selectively increase the exhaust manifold pressure exceeds the inlet manifold pressure, which promotes exhaust gas recirculation (EGR)). Although excessive engine back pressure is detrimental to overall fuel economy, ensuring a sufficient EGR rate even during transient events (e.g. gear changes) can be sufficient to reduce nitrogen oxide emissions down to that required by emissions legislation (e.g. Euro 5 for Europe and EPA 10 for the USA).

Another use for the sliding vane type of turbocharger is as downstream engine exhaust brake (non-decompression type), so that an extra exhaust throttle valve isn’t needed. Also the mechanism can be deliberately modified to reduce the turbine efficiency in a predefined position. This mode can be selected to sustain a raised exhaust temperature to promote "light-off" and "regeneration" of a diesel particulate filter (this involves heating the carbon particles stuck in the filter until they oxidize away in a semi-self sustaining reaction – rather like the self-cleaning process some ovens offer). Actuation of a VG turbocharger for EGR flow control or to implement braking or regeneration modes generally requires hydraulic or electric servo actuation.

Turbocharger

 

A turbocharger is actually a type of supercharger. Originally, the turbocharger was called a "turbo super charger." Obviously, the name was shortened out of convenience.

A turbocharger’s purpose is to compress the oxygen entering a car’s engine, increasing the amount of oxygen that enters and thereby increasing the power output. Unlike the belt-driven supercharger that is normally thought of when one hears the word "supercharger," the turbocharger is powered by the car’s own exhaust gases. In other words, a turbocharger takes a by-product of the engine that would otherwise be useless, and uses it to increase the car’s horsepower.

Cars without a turbocharger or supercharger are called normally aspirated. Normally aspirated cars draw air into the engine through an air filter; the air then passes through a meter, which monitors and regulates the amount of air that enters the system. The air is then delivered to the engine’s combustion chambers, along with a controlled amount of fuel from the carburetor or fuel injectors.

In a turbocharged engine, however, the air is compressed so that more oxygen will fit in the combustion chamber, dramatically increasing the burning power of the engine. The turbocharger is composed of two main parts: the compressor, which compresses the air in the intake; and the turbine, which draws the exhaust gases and uses them to power the compressor. Another commonly used term in relation to turbochargers is boost, which refers to the amount of pressure the air in the intake is subjected to; in other words, the more compressed the air is, the higher the boost.

Although the increase in power is advantageous to the car — and likely a source of enjoyment for the driver — a turbocharger has its drawbacks. First and foremost, a turbocharged engine must have a lower compression ratio than a normally aspirated engine. For this reason, one cannot simply put a turbocharger on an engine that was intended for normal aspiration without seriously undermining the life and performance of the engine. Also, a lower compression ratio means the engine will run less efficiently at low power.

Another major drawback of a turbocharger is the phenomenon known as turbo lag. Because the turbocharger runs on exhaust gases, the turbine requires a build-up of exhaust before it can power the compressor; this means that the engine must pick up speed before the turbocharger can kick in. Additionally, the inlet air grows hotter as it is compressed, reducing its density, and thereby its efficiency in the combustion chamber; a radiator-like device called an intercooler is often used to counter this effect in turbocharged engines.

Turbo lag

Turbo lag is the time required to change power output in response to a throttle change, noticed as a hesitation or slowed throttle response when accelerating from idle as compared to a naturally aspirated engine. This is due to the time needed for the exhaust system and turbocharger to generate the required boost. Inertia, friction, and compressor load are the primary contributors to turbo lag. Superchargers do not suffer this problem, because the turbine is eliminated due to the compressor being directly powered by the engine.
Turbocharger applications can be categorized into to those that require changes in output power (such as automotive) and those that do not (such as marine, aircraft, commercial automotive, industrial, engine-generators, and locomotives). While important to varying degrees, turbo lag is most problematic in applications that require rapid changes in power output. Engine designs reduce lag in a number of ways:

• Lowering the rotational inertia of the turbocharger by using lower radius parts and ceramic and other lighter materials
• Changing the turbine's aspect ratio
• Increasing upper-deck air pressure (compressor discharge) and improving wastegate response
• Reducing bearing frictional losses (e.g., using a foil bearing rather than a conventional oil bearing)
• Using variable-nozzle or twin-scroll turbochargers
• Decreasing the volume of the upper-deck piping
• Using multiple turbos sequentially or in parallel
• Using an Antilag system
• Using a turbo spool valve to increase exhaust gas flow speed to the (twin-scroll) turbine

Boost threshold

The boost threshold of a turbo system is the lower bound of the region within which the compressor operates. Below a certain rate of flow, a compressor produces insignificant boost. This limits boost at a particular RPM, regardless of exhaust gas pressure. Newer turbocharger and engine developments have steadily reduced boost thresholds.
Electrical boosting ("E-boosting") is a new technology under development. It uses an electric motor to bring the turbo up to operating speed quicker than possible using available exhaust gases. An alternative to e-boosting is to completely separate the turbine and compressor into a turbine-generator and electric-compressor as in the hybrid turbocharger. This makes compressor speed independent of turbine speed. In 1981, a similar system that used a hydraulic drive system and overspeed clutch arrangement accelerated the turbocharger of the MV Canadian Pioneer (Doxford 76J4CR engine)^.
Turbochargers start producing boost only when a certain amount of kinetic energy is present in the exhaust gasses. Without adequate exhaust gas flow to spin the turbine blades, the turbo cannot produce the necessary force needed to compress the air going into the engine. The boost threshold is determined by the engine displacement, engine rpm, throttle opening, and the size of the turbo. The operating speed (rpm) at which there is enough exhaust gas momentum to compress the air going into the engine is called the "boost threshold rpm". Reducing the "boost threshold rpm" can improve throttle response.

Key components of a turbocharger

The turbocharger has three main components:

1. The turbine, which is almost always a radial inflow turbine
2. The compressor, which is almost always a centrifugal compressor
3. The center housing/hub rotating assembly

Many turbocharger installations use additional technologies, such as wastegates, intercooling and blow-off valves.

Supercharger

Engines combust (burn) fuel and use the energy of that combustion to do work. The more fuel that is combusted in any given time then the more energy is available to carry out the engines task. Fuel requires air (or the oxygen contained within air) to burn so if there isn’t enough air mixed with the fuel it will not burn. This also means that the amount of air entering an engine determines how much fuel can be burnt and consequently how much energy (or power) an engine can produce. Superchargers are essentially an air pump designed to cram extra air into an engine allowing it to combust more fuel than would otherwise be possible.

Mercedes pioneered automotive superchargers on their race cars during the 1920’s. These were simple reciprocating compressors attached to the engine by an electrically operated clutch. A switch activated by the accelerator pedal turned the pump on when extra power (full throttle) was required. A flurry of engineering endeavor ensued in order to reign in Mercedes advantage on the racetrack. Within a few short years most of the basic designs for modern superchargers had appeared.

During the 1930’s superchargers were largely the preserve of marine engines, aircraft and race vehicles but gradually found their way into commercial diesel engines by the 1950’s. It has been common for truck engines to be turbo supercharged (a.k.a. turbocharged) for decades but car engines originally had difficulty in effectively employing this technology.

Superchargers mostly fall into one of two categories, mechanically driven superchargers and turbo superchargers driven by exhaust gasses. A third category is starting to make an appearance and that is electrically powered superchargers.

Turbo superchargers (a.k.a. turbochargers or turbo’s) are relatively compact, lightweight and efficient but suffer from turbo lag and heat stress. By turbo lag we mean the amount of time it takes for the turbo’s rotor to speed up to full efficiency. Some of the earliest turbo charged vehicles took so long for the turbo to produce a usable amount of boost that they were all but useless. Modern turbo chargers are much better in this regard but turbo lag is still a problem. Heat is another bane of turbo chargers. Exhaust gasses are extremely hot and can cause so much heat to build up in the turbo that oil will burn and congeal within its galleries leading to a bearing failure. This is why many turbo chargers have a turbo timer. The timer will cause an engine to continue idling for a few minutes after it is switched off allowing excess heat to be dissipated.

Mechanically driven superchargers usually don’t suffer from turbo lag and can often produce more boost than an exhaust driven charger (turbo). On the negative side they are generally bulky, heavy, and have a cumbersome drive mechanism (usually belt drive). Furthermore most chargers of this type have to supply air at all engine speeds and loads making them difficult to match various engine conditions precisely.

As our supercharger is electrically driven we have devoted an entire article to the advantages and disadvantages of this type.

Heat exchangers (intercoolers) are frequently used in conjunction with superchargers. Compressing air increases its temperature thus making it less dense. By re-cooling the compressed volume of air before it enters, density is increased allowing even more air to be forced into the engine. Intercoolers are more important for turbo superchargers as there are two heating sources present, the act of compression and heat from exhaust gasses both increase air temperature.

Working of Fuel Cell Car

Fuel Cell Stacks

This is the heart of the hydrogen fuel cell car—the fuel cell stacks. Their maximum output is 86 kilowatts, or about 107 HP. Because hydrogen fuel cell stacks produce power without combustion, they can be up to twice as efficient as internal combustion engines. They also produce zero carbon dioxide and other pollutants. For more information on the stacks.

Fuel Cell Cooling System

This has several parts. Perched at an angle at the front of the vehicle is a large radiator for the fuel cell system, while two radiators for the motor and transmission lie ahead of the front wheels below the headlights. The car also has a cooling pump located near the fuel cell stacks to stabilize temperature within the stacks.

Ultra capacitor

This unit serves as a supplementary power source to the fuel cell stack. Like a large battery, the ultra capacitor recovers and stores energy generated during deceleration and braking. It uses this energy to provide a "power assist" during startup and acceleration.

Hydrogen Tanks

Space in a car is limited, yet hydrogen is the most dispersive element in the universe and normally requires lots of room. A challenge for manufacturers is how to compress the gas into tanks small enough to fit in a compact car and yet still provide enough fuel for hundreds of miles of driving between refueling. The two high-pressure hydrogen tanks in this vehicle can hold up to 3.75 kilograms of hydrogen compressed to roughly 5,000 PSI—enough to enable an EPA-rated 190 miles of driving before refueling, the manufacturer says.

Electric Motor

(General area only—motor not visible) The electric motor offers a maximum output of 80 kilowatts, enabling a top speed of about 93 miles per hour. The manufacturer says this vehicle can also start in subfreezing temperatures (down to about -4°F), a perennial problem in fuel cell prototypes. Being electric, the engine and the car as a whole are quiet, with none of the vibration or exhaust noise of a gas-powered automobile.

Air Pump

(General area only—air pump not visible) Run by a high-voltage electric motor, this pump supplies air at the appropriate pressure and flow rate to the fuel cell stacks. The air, in turn, mixes with the stored hydrogen to create electricity.

Humidifier

The humidifier monitors and maintains the level of humidity that the fuel cell stack needs to achieve peak operating efficiency. It does this by recovering some of the water from the electrochemical reaction that occurs within the fuel cell stack and recycling it for use in humidification.

Power Control Unit

(General area only—power control unit not visible) This controls the vehicle’s electrical systems, including the air and cooling pumps as well as output from the fuel cell stacks, electric motor, and ultra capacitor.

Cabin

With the fuel cell stacks hidden beneath the floor and the hydrogen tanks and the ultra capacitor beneath and behind the rear seats, respectively, the four-passenger cabin is isolated from all hydrogen and high-voltage lines. Hydrogen gas is colorless and odorless, and it burns almost invisibly. In case of a leak, therefore, the manufacturer has placed hydrogen sensors throughout the vehicle to provide warning and automatic gas shut-off. Also, in the event of a collision, the electrical source power line shuts down.

Hydrogen Filler Mouth

(Not visible—located on other side of vehicle) Drivers would fill the car with hydrogen just as they do with gasoline, through an opening on the side of the vehicle. The main difference is that a fuel cell car must be grounded before fueling to rid the car of hazardous static electricity. For this reason, this model has two side-by-side openings, with the latch to open the hydrogen filler mouth located inside the opening for the grounding wire. The manufacturer says filling up this model’s two tanks at a hydrogen filling station would take about three minutes.

Note

The limited-production vehicle seen in this feature is a Honda 2005 FCX, which is typical of the kinds of hydrogen fuel cell automobiles that some major automakers are now researching and developing. With such vehicles at present costing about $1 million apiece, none is currently for sale, though hundreds of fuel cell cars are now undergoing tests on the world’s roads.

Kinetic Energy Recovery System (KERS) in F1

The introduction of Kinetic Energy Recovery Systems (KERS) is one of the most significant technical introductions for the Formula One Race. Formula One have always lived with an environmentally unfriendly image and have lost its relevance to road vehicle technology. This eventually led to the introduction of KERS.

KERS is an energy saving device fitted to the engines to convert some of the waste energy produced during braking into more useful form of energy. The system stores the energy produced under braking in a reservoir and then releases the stored energy under acceleration. The key purpose of the introduction was to significantly improve lap time and help overtaking. KERS is not introduced to improve fuel efficiency or reduce weight of the engine. It is mainly introduced to improve racing performance.

KERS is the brainchild of FIA president Max Mosley. It is a concrete initiative taken by F1 to display eco-friendliness and road relevance of the modern F1 cars. It is a hybrid device that is set to revolutionize the Formula One with environmentally friendly, road relevant, cutting edge technology.

Components of KERS

The three main components of the KERS are as follows:

• An electric motor positioned between the fuel tank and the engine is connected directly to the engine crankshaft to produce additional power.
• High voltage lithium-ion batteries used to store and deliver quick energy.
• A KERS control box monitors the working of the electric motor when charging and releasing energy.

A – Electric motor

B – Electronic Control Unit

C – Battery Pack

Working Principle of KERS

Kinetic Energy Recovery Systems or KERS works on the basic principle of physics that states, “Energy cannot be created or destroyed, but it can be endlessly converted.”

When a car is being driven it has kinetic energy and the same energy is converted into heat energy on braking. It is the rotational force of the car that comes to stop in case of braking and at that time some portion of the energy is also wasted. With the introduction of KERS system the same unused energy is stored in the car and when the driver presses the accelerator the stored energy again gets converted to kinetic energy. According to the F1 regulations, the KERS system gives an extra 85 bhp to the F1 cars in less than seven seconds.

This systems take waste energy from the car’s braking process, store it and then reuse it to temporarily boost engine power. This and the following diagram show the typical placement of the main components at the base of the fuel tank, and illustrate the system’s basic functionality – a charging phase and a boost phase. In the charging phase,

kinetic energy from the rear brakes (1)

is captured by an electric alternator/motor (2),

controlled by a central processing unit (CPU) (3),

which then charges the batteries (4).

 

In the boost phase, the electric alternator/motor gives the stored energy back to the engine in a continuous stream when the driver presses a boost button on the steering wheel. This energy equates to around 80 horsepower and may be used for up to 6.6 seconds per lap. The location of the main KERS components at the base of the fuel tank reduces fuel capacity (typically 90-100kg in 2008 ) by around 15kg, enough to influence race strategy, particularly at circuits where it was previously possible to run just one stop. The system also requires additional radiators to cool the batteries. Mechanical KERS, as opposed to the electrical KERS illustrated here, work on the same principle, but use a flywheel to store and re-use the waste energy.

Types of KERS

There are basically two types of KERS system:

Electronic KERS

Electronic KERS supplied by Italian firm Magneti Marelli is a common system used in F1 by Red Bull, Toro Rosso, Ferrari, Renault, and Toyota.

The key challenge faced by this type of KERS system is that the lithium ion battery gets hot and therefore an additional ducting is required in the car. BMW has used super-capacitors instead of batteries to keep the system cool.
With this system when brake is applied to the car a small portion of the rotational force or the kinetic energy is captured by the electric motor mounted at one end of the engine crankshaft. The key function of the electric motor is to charge the batteries under barking and releasing the same energy on acceleration. This electric motor then converts the kinetic energy into electrical energy that is further stored in the high voltage batteries. When the driver presses the accelerator electric energy stored in the batteries is used to drive the car.

Electro-Mechanical KERS

The Electro-Mechanical KERS is invented by Ian Foley. The system is completely based on a carbon flywheel in a vacuum that is linked through a CVT transmission to the differential. With this a huge storage reservoir is able to store the mechanical energy and the system holds the advantage of being independent of the gearbox. The braking energy is used to turn the flywheel and when more energy is required the wheels of the car are coupled up to the spinning flywheel. This gives a boost in power and improves racing performance.

Limitations of KERS

Though KERS is one of the most significant introductions for Formula One it has some limitations when it comes to performance and efficiency. Following are some of the primary limitations of the KERS:

• Only one KERS can be equipped to the existing engine of a car.
• 60 kw is the maximum input and output power of the KERS system.
• The maximum energy released from the KERS in one lap should not exceed 400 kg.
• The energy recovery system is functional only when the car is moving.
• Energy released from the KERS must remain under complete control of the driver.
• The recovery system must be controlled by the same electronic control unit that is used for controlling the engine, transmission, clutch, and differential.
• Continuously variable transmission systems are not permitted for use with the KERS.
• The energy recovery system must connect at one point in the rear wheel drive train.
• If in case the KERS is connected between the differential and the wheel the torque applied to each wheel must be same.
• KERS can only work in cars that are equipped with only one braking system.

Chasis Frame

Chassis is a French term and was initially used to denote the frame parts or Basic Structure of the vehicle. It is the back bone of the vehicle. A vehicle with out body is called Chassis. The components of the vehicle like Power plant, Transmission System, Axles, Wheels and Tyres, Suspension, Controlling Systems like Braking, Steering etc., and also electrical system parts are mounted on the Chassis frame. It is the main mounting for all the components including the body. So it is also called as Carrying Unit.

The following main components of the Chassis are:

• Frame: it is made up of long two members called side members riveted together with the help of number of cross members.
• Engine or Power plant: It provides the source of power
• Clutch: It connects and disconnects the power from the engine fly wheel to the transmission system.
• Gear Box
• U Joint
• Propeller Shaft
• Differential

FUNCTIONS OF THE CHASSIS FRAME:

1. To carry load of the passengers or goods carried in the body.
2. To support the load of the body, engine, gear box etc.,
3. To withstand the forces caused due to the sudden braking or acceleration
4. To withstand the stresses caused due to the bad road condition.
5. To withstand centrifugal force while cornering

VARIOUS LOADS ACTING ON THE FRAME:
1. Short duration Load – While crossing a broken patch.
2. Momentary duration Load – While taking a curve.
3. Impact Loads – Due to the collision of the vehicle.
4. Inertia Load – While applying brakes.
5. Static Loads – Loads due to chassis parts.
6. Over Loads – Beyond Design capacity.

Gorilla Glass Touch Screen

Touch screen technology in fast few years has grown drastically in various applications, in order to overcome the difficulties faced by the touch screen; a new frontier technology has to take its part to revitalize the use of touch screen. In this counterpart gorilla glass has thrown a flash light focus on touch screen technology. Gorilla Glass has taken an apt plays in touchscreen technology. This scratch repellent glass is used to form touchscreen panel for portable gadgets like ATM machines, android mobile phones, tablets, personal computers and MP3 Players. It’s designed to protect display screens from scratches, sticky oils, fractures, etc,.

Characteristics of Gorilla Glass:

• Scratch resistance
• Slimness / Thinner
• Stronger
• Improved Touch Sensitivity

Comparatively perfect fit for today’s abundance touch-screen handsets.

 

Difference between ‘Scratch- Proof ‘ and ‘Scratch Resistant’ glass:

A Scratch- screen proof is impermeable resistant to scratches. This kind of technology is not on the market however – any glass may break if it is placed under enough stress. Gorilla Glass is NOT a scratch-proof.

A Scratch- screen resistant is much stronger than most screens. It is less probable to smash/crack if dropped, and less probably to scratch if scratched. Extreme force, sharp objects, and continual exposure to abrasive oils may leave scratches.

History of Gorilla Glass:

The Gorilla Glass is the trade name of “Corning”, an United States of America Glass maker. They form the toughened glass (Alkali – Alumino Silicate Sheet) for the portable electronic gadgets. This idea generated in the 60s period as a project name, “Project Muscle”. The glass invented was called as “Chemcor” glass, which are ultra strong and light weight. The product is developed for windshield glass for cars, But the product is very costly so they are not succeeding on that time.

In the period of 2005, they again started researching with the project name of “Gorilla Glass”. In this period touch screen cell phones are popular, and the product needs a resilient, scratch resistant cell phone cover glass. At that time, the company take the idea from Chemcor glass and they start building the Gorilla glass.

After completing the research, first production starts at the period of 2007 and they got the first order in the period of 2008. At that period nearly 200 million users (about 20% of Devices) uses the gorilla glass for their cell phones. 

 

In 2012, the second generation of gorilla glass they built and launched, achieved a goal of one billion devices.

In 2013, the Third generation Gorilla Glass they launched, which are three times more resistant and stronger; 40% scratches which occur will not be visible to naked eye.

Currently Used Gorilla Glass products:

Phones

• Iphone
• HTC
• LG
• Motorolla
• Nokia
• Samsung

Tablets

• Samsung
• Blackberry
• Lenovo

Laptops

• Dell
• Sony
• Lenovo

TV’s

• Sony

Cameras

• Leica

BENEFITS:
• Glass designed for a high degree of chemical strengthening
- High compressive stress
- Deep compression layer
• High retained strength after use
• High resistance to scratch damage
• Superior surface quality
APPLICATIONS:
• Ideal protective covering for displays in
- Smart phones
- Laptop / Portable Computers and tablet computer screens
- Mobile devices
• Touchscreen devices
• Optical components
• High strength glass articles

Job Interview Questions

1. A hollow shaft of same cross-section area as solid shaft transmits

A. Same torque

B. Less torque

C. More torque

D. Unpredictable

Answer:

B. Less torque

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2. In a cantilever beam, maximum deflection occurs at where

A. Bending moment is zero

B. Bending moment is maximum

C. Shear force is zero

D. Slope is zero

Answer:

A. Bending moment is zero

---

3. In a rectangular beam, when width, depth and length are doubled, the bending stress will be

A. Shall remain unchanged

B. Shall be doubled

C. Shall become ¼ th

D. Shall be halved

Answer:

C. Shall become ¼ th

---

4. In an I –section beam, the bending moment is resisted mainly by

A. Flanges only

B. Web only

C. Both by flanges and web

D. None of the above

Answer:

B. Web only

---

5. In internal combustion (I.C.) engines, combustion of fuel takes place in

A. Outside the cylinder

B. Inside the cylinder

C. Not in the cylinder

D. None of the above

Answer:

B. Inside the cylinder

---

6. Power available at the shaft of an I.C engine is known is

A. Brake horse power

B. Indicated horse power

C. Net indicated horse power

D. Pumping power

Answer:

A. Brake horse power

---

7. In internal combustion engine piston the maximum temperature occurs at

A. Ring section

B. Gungeon pin

C. Bottom centre

D. Top centre

Answer:

A. Ring section

---

8. A two-stroke engine is generally preferred to a four-stroke engine because

A. It offers low fuel consumption

B. It gives lesser shocks and vibrations

C. It can be easily started

D. It has smaller size for the same output.

Answer:

D. It has smaller size for the same output.

---

9. During idling process, a petrol engine requires

A. Lean mixture

B. Rich mixture

C. Variable mixture

D. None of above

Answer:

A. Lean mixture

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10. Cavitation in a pipe will begin when

A. Pressure at any location reaches pressure equal to the saturated vapour pressure of liquid

B. Pressure becomes more than critical pressure

C. Flow is increased

D. Pressure is increased

Answer:

A. Pressure at any location reaches pressure equal to the saturated vapour pressure of liquid

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11. Capillary action of liquid is due to the

A. Viscosity of liquid

B. Cohesion of liquid particles

C. Surface tension

D. Adhesion of liquid particles on the surface

Answer:

B. Cohesion of liquid particles

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12. In one ton refrigeration machine, the term “one ton” implies

A. One ton refrigerant is used

B. One ton water can be converted into ice

C. One ton ice when melts from and at 0^oC in 24 hours, the refrigerating effects is equivalent to 3000 kcal/hour

D. None of the above

Answer:

C. One ton ice when melts from and at 0^oC in 24 hours, the refrigerating effects is equivalent to 3000 kcal/hour

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13. In a refrigeration cycle, the moisture content is to be removed before it enters into which system

A. Cold side of system

B. Evaporator

C. compressor

D. condenser

Answer:

B. Evaporator

(1) Pitot tube is used for measurement of
(a) Pressure
(b) Temperature
(c) Discharge
(d) Velocity
Ans.: (d) Velocity

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(2) Slow plastic deformation of material under constant stress is
(a) Creep
(b) Fatigue
(c) Endurance
(d) Elastic deformation
Ans.: (a) Creep

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(3) Mass balancing is done to
(a) Avoid flutter
(b) Increase bending stress
(c) Reduce drag
(d) Distributing mass on control surface
Ans.: (a) Avoid flutter

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(4) Short columns are preferred over long columns from
(a) Strength consideration
(b) Buckling consideration
(c) Weight consideration
(d) None of the above
Ans.: (b) Buckling consideration

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(5) Centre of pressure of an aerofoil with an increase of angle of attack will
(a) Move forward
(b) Move backward
(c) Not move
(d) None of the above
Ans.: (a) Move forward

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(6) Thermal efficiency of a gas turbine plant as compared to diesel engine plant
(a) Higher
(b) Lower
(c) Same
(d) May be higher or lower
Ans.: (a) Higher

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(7) A closed cycle gas turbine works on
(a) Carnot cycle
(b) Rankine cycle
(c) Joule cycle
(d) Atkinson cycle
Ans.: (c) Joule cycle

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(8) A bolt of uniform strength can be developed by
(a) Keeping the core dia of threads equal to the dia of unthreaded portion of bolt
(b) Keeping the core dia of threads smaller than the dia of unthreaded portion of bolt
(c) Keeping the nominal dia of threads equal to the dia of unthreaded portion of bolt
(d) None of the above
Ans.: (a) Keeping the core dia of threads equal to the dia of unthreaded portion of bolt

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(9) Stress concentration factor is defined as ratio of
(a) Max stress to endurance limit
(b) Nominal stress to endurance limit
(c) Max stress to nominal stress
(d) Nominal stress to max stress
Ans.: (c) Max stress to nominal stress

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(10) Principle effect of humidity is
(a) Corrosion
(b) Leaking from sealed enclosures
(c) Permanent set of packing and gaskets
(d) Differential contraction of metal parts
Ans.: (a) Corrosion

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(11) Backlash is
(a) Sum of the clearance of two gears
(b) Mutual play between two gears
(c) Amount by which the width of a tooth space exceeds the thickness of the engaging tooth on pitch circle
(d) Any of the above
Ans.: (c) Amount by which the width of a tooth space exceeds the thickness of the engaging tooth on pitch circle

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(12) Teflon is used for bearings because of
(a) Low co-efficient of friction
(b) Better heat dissipation
(c) Smaller space constraint
(d) All of the above
Ans.: (a) Low co-efficient of friction

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(13) When two elastic bodies collide with each other
(a) Two bodies will momentarily come to rest after collision
(b) The two bodies tend to compress & deform at the surface of contact
(c) Two bodies begins to retain their original shape
(d) All of the above
Ans.: (d) All of the above

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(14) Antifriction bearings are
(a) Thick lubricated bearing
(b) Thin lubricated bearing
(c) Ball & roller bearing
(d) Plastic bearing
Ans.: (c) Ball & roller bearing

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(15) What is Hertzian stress?
(a) Tensile stress on inner surface of cylinder
(b) Bending stress on two contact surface
(c) Contact stress on two contact surfaces
(d) Shear stress on two contact surfaces
Ans.: (c) Contact stress on two contact surfaces

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(16) Mohr’s circle can be used to determine following stress on inclined surface
(a) Principal stresses
(b) Normal stresses
(c) Maximum shear stresses
(d) All of the above
Ans.: (a) Principal stresses

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(17) What size of material required for making rolled threads?
(a) Pitch diameter
(b) Root diameter
(c) Major diameter
(d) None
Ans.: (a) Pitch diameter
1. Normalizing operation is carried out in
a) Water
b) Oil
c) Air
d) Furnace

Ans.: c) Air

2. The main purpose of heat treatment of steels is to change the
a) Chemical composition
b) Mechanical properties
c) Surface finish
d) Physical properties

Ans.: b) Mechanical properties

3. Which of the following is a non-destructive test
a) Impact test
b) Charpy test
c) Cupping test
d) Radiography test

Ans.: d) Radiography test

4. Polymerization is associated with
a) Stainless steel
b) Cast iron
c) Thermoplastic
d) Duralumin

Ans.: c) Thermoplastic

5. The material of pattern in the investment casting is
a) Resin
b) Sand
c) Wax
d) Wood

Ans.: c) Wax

6. Shell moulding process requires
a) Wooden pattern
b) Plastic pattern
c) Sand pattern
d) Metal pattern

Ans.: d) Metal pattern

7. Liquid nitrogen containers can be made from
a) Ferritic stainless steel
b) HSLA steel
c) Titanium
d) Austenitic stainless steel

Ans.: d) Austenitic stainless steel


8. Stretching of rolled rings is done to
a) To meet dimensional requirement
b) To relieve stresses
c) To introduce stresses
d) To improve finish

Ans.: b) To relieve stresses

9. During manufacturing of spring, the coiling pitch is assumed to be larger than specified pitch by
a) 5-8%
b) 10-12%
c) 2-5%
d) none

Ans.: a) 5-8%

10. Metric thread have included angle:
a) 60°
b) 55°
c) 30°
d) None

Ans.: a) 60°

11. Which part of the cutting tool is prone to crater wear
a) Flank
b) Face
c) Shank
d) Base

Ans.: b) Face

12. The crater wear of a cutting tool is due to
a) Chemical action of the coolant
b) Excessive heat generated during cutting operation
c) Rubbing of tool against the work piece
d) Abrasive action of the chip

Ans.: d) Abrasive action of the chip

13. Crater wear is predominant in
a) Carbon tool steels
b) Tungsten carbide tools
c) High speed steel tools
d) Ceramic tools

Ans.: b) Tungsten carbide tools

14. Identify the single point cutting tool
a) Milling cutter
b) Hacksaw blade
c) Grinding wheel
d) Cutting tool used in a slotting machine

Ans.: d) Cutting tool used in a slotting machine

15. The angle between the tool face and the plane parallel to the base of the cutting tool is called
a) Lip angle
b) Cutting angle
c) Rack angle
d) Shear angle

Ans.: c) Rack angle

16. In metal cutting operation, the cutting angle is defined as the angle
a) between the flank and the horizontal machined surface
b) between the shear plane and the direction of tool travel
c) between the face of tool and the line tangent to the machined surface at the cutting point
d) between the tool face and the ground end surface of flank

Ans.: c) between the face of tool and the line tangent to the machined surface at the cutting point

17. The angle between the face and the flank of the single point cutting tool is known as
a) Rack angle
b) Clearance angle
c) Lip angle
d) Point angle

Ans.: b) Clearance angle

18. Cutting tool may be provided with large positive rack angle to
a) Have a better heat dissipation
b) Avoid rubbing with the finished surface
c) Increase the strength of cutting edge
d) Reduce the magnitude of cutting forces

Ans.: d) Reduce the magnitude of cutting forces

19. Single point thread cutting tool should ideally have
a) Zero rack angle
b) Positive rack
c) Negative rack
d) Normal rack

Ans.: a) Zero rack angle

20. With an increase in nose radius of single point cutting tools
a) Tool life increases
b) Excessive heat is generated
c) Surface finish deteriorates
d) Cutting speeds have to be kept small

Ans.: a) Tool life increases

21. Tool signature
a) Is a pictorial view of the tool
b) Outlines the orthographic projection of the tool
c) Represents complete specification of the tool
d) Is a numerical method of tool identification
e) Indicate life of tool

Ans.: d) Is a numerical method of tool identification

22. The cutting speed of a tool refers to
a) Revolution made by the tool in a specified time
b) Revolutions turned by the job in a specified time
c) Distance travelled by the tool in one revolution of the job
d) Rate at which cutting edge of the tool passes over the surface of work piece

Ans.: d) Rate at which cutting edge of the tool passes over the surface of work piece


23. Which is not the primary function of coolant in a metal cutting operation
a) To cool the tool and work piece and conduct the heat generated
b) To improve the cutting action
c) To help in giving bright shining surface to the job
d) To reduce the friction at the cutting point

Ans.: a) To cool the tool and work piece and conduct the heat generated


24. Choose the coolant that would be most appropriate for light cuts on aluminum alloys
a) Kerosene
b) Mineral oil
c) Soluble oil or emulsions
d) Straight fatty oil

Ans.: a) Kerosene


25. Tool life may be measured by the
a) Total time the tool has been in contact with the job
b) Quantity of material removed between the total sharpening
c) Number of work pieces machined between tool sharpening
d) Time for the flank wear to reach a certain dimension
e) Any one of the above

Ans.: e) Any one of the above

26. The tool life is influenced maximum by
a) Cutting speed
b) Tool material and geometry
c) Cutting fluid
d) Surface conditions of the workpiece
e) Skill of the operator

Ans.: a) Cutting speed

1. Draft on pattern means
b) Allowance for machining
c) Locating pad
d) Compensate for stripping
e) Compensation for shrinkage



Ans.: d) Compensate for stripping


2. Slag inclusion in the casting is a
a) Surface defects
b) Internal defect
c) Crack
d) Notch



Ans.: a) Surface defects

3. Fettling is an operation performed
a) Before casting
b) After casting
c) During casting
d) After heat treatment



Ans.: b) After casting
 
4. Sprue in casting refers to
a) Gate
b) Runner
c) Riser
d) Vertical passage



Ans.: d) Vertical passage

5. Severe quenching can cause
a) Blow holes
b) Warping
c) Inclusions
d) Non of them

Ans.: b) Warping

6. Casting defects caused by the molten metal is
a) Blow holes
b) Swell
c) Scab
d) All of the above

Ans.: d) All of the above

7. Forming operation which does not involve rotation of work piece is
a) Spinning
b) Thread rolling
c) Ring rolling
d) Upsetting

Ans.: d) Upsetting

8. In hot working process
a) Poor surface finish is produced
b) Scale formed
c) Close tolerance is difficult to maintain
d) All of the above

Ans.: d) All of the above

9. Swaging is an operation of
a) Extrusion
b) Forging
c) Casting
d) Rolling

Ans.: b) Forging

10. Age hardening is related with
a) Stainless steel
b) Duralumin
c) Gun metal
d) Cast iron

Ans.: b) Duralumin

11. Foundry crucible is made of
a) Stainless steel
b) Mild steel
c) Lead
d) Graphite

Ans.: d) Graphite


12. A 1000 tonne press implies that
a) The weight of press is 1000 tonne
b) The press can handle works weighing up to 1000 tonne
c) It can exert pressure up to 1000 tonne
d) Its turn over in a day is 1000 tonne

Ans.: c) It can exert pressure up to 1000 tonne

13. The transistor is made of
a) Silver
b) Germanium
c) Copper
d) Cast iron

Ans.: b) Germanium

14. Pre heating is essential in welding of
a) High speed steel
b) German steel
c) Stainless steel
d) Cast iron

Ans.: a) High speed steel

15. Spring back phenomenon occurs in
a) Forging
b) Hot penning
c) Spinning
d) Bending

Ans.: d) Bending

16. Wire is made by
a) Drawing
b) Forging
c) Rolling
d) Casting

Ans.: a) Drawing

17. Greater forging capacity is achieved with
a) Mechanical press
b) Power hammer
c) Hydraulic press
d) Non of them

Ans.: c) Hydraulic press

18. Turbine rotor is made by
a) Rolling
b) Sand casting
c) Forging
d) Extrusion

Ans.: b) Sand casting

19. Which of the following welding process uses consumable electrodes
a) TIG
b) MIG
c) Thermit
d) Laser

Ans.: b) MIG

20. The phenomenon of weld decay occurs in
a) Cast iron
b) Brass
c) Bronze
d) Stainless steel

Ans.: d) Stainless steel

21. The crystal structure of alpha iron
a) BCC
b) FCC
c) HCP
d) Cubic

Ans.: a) BCC

22. The hardest known material is
a) Ceramic
b) High speed steel
c) Cemented carbide
d) Diamond

Ans.: d) Diamond

23. Which of the following is the most ductile material
a) Lead
b) Copper
c) Mild steel
d) Vanadium

Ans.: a) Lead

24. Brinell hardness tester uses a hardened steel ball of size
a) 1 mm
b) 5 mm
c) 10 mm
d) 15 mm

Ans.: c) 10 mm

25. Trimming process is associated with
a) Polishing of metals
b) Machining
c) Electroplating
d) Forging

Ans.: d) Forging

Throttling Process

Throttling is a process in which the flow of fluid is restricted by closing the valve partially. Now imagine their are students in a class room and as the bell rungs they started moving out. Now if the door is opened partially then their will be clusters form by the students. Similarly in flow of fluid their is restriction to flow. now as students form clusters they pushing other students and in the same way fluid particles start rubbing with other molecules and as a result friction is their and as we all know friction is one of the biggest reason for any process to make it irreversible.

Hence it is clear that Throttling is irreversible.

EXAMPLES OF THROTTLING PROCESS
1. Flow through a partially opened valve as in IC engines
2. Flow through a very small opening e.g orifice.
3. Flow through a porous plug.

Characteristics of Throttling
1. No Work Transfer
Explanation:
As we know their is work transfer in turbines due to very large pressure difference. but in the case of throttling their is very low pressure differences so the work we get is very small and this work is lost in overcoming friction. so here we generally neglect the work transfer.

2. No Heat Transfer
Explanation:
Lets see it with a example... imagine you open the freeze and took out your water bottle and just within the fraction of seconds you put back that bottle, now what is the temperature difference between the two states of the water bottle, it is approx. zero. It means heat transfer needs some time , now what happened in throttling is that device length is very small and the fluid is always pushed ahead due to the bulk coming and due this their is not much time for the heat transfer. As we are considering the steady flow and bulk is not accumulated in the device so heat transfer is also neglected.

3. Irreversible Process

4. Isenthalpic Process
Explanation:
The word ISENTHALPIC means same Enthalpy.
look we apply steady flow energy equation:

now neglecting potential energy changes and
heat transfer(q) and work transfer (w) are zero as the characteristics of throttling..

equation becomes:

now what we generally seen that practically velocities values (c1 and c2 ) are very very small as compared to enthalpies values so c1 and c2 can be neglected and finally

hence the process is Isenthalpic.