Antilock or Antiskid Device | Anti-lock Breaking System

Antilock or antiskid device

The vehicle will stop more quickly if the brakes are applied just hard enough to get maximum static friction between the tyres and road. If the brakes are applied harder than this then the wheels will lock, the tyres will skid or slide on the road and a lesser kinetic friction will result. Then braking the vehicle is much less effective.

To prevent skidding and thus provide maximum effective braking several devices have been proposed. Mostly skid control of the rear wheels only is provided. Some others provide control at all the four wheels. What is meant by “control” is this. As long as the wheels are rotating the antiskid device permits normal application of the brakes. But if the brakes are applied so tough that the wheels tend to stop turning and thus a skid starts to develop the device comes into operation and partly release the brakes so that the wheels continue to rotate. Still intermittent braking continues. But it is held to just below the point where a skid would start. The result is maximum braking effect.

Antilock brake system: The hydraulic unit is the central component of an ABS system. Each of the four wheels has a speed sensor, which measures the rotational speed of the wheel. This information is monitored by an Electronic Control Unit: which opens and closes the magnetic valves at the right time. If a wheel is about to lock under heavy braking, the system continues to reduce the hydraulic pressure on that wheel alone, till the threat of locking is past. Once the wheel is turning freely again, the hydraulic pressure is increased. This increase and release of pressure continues until the driver reduces the force on the brake pedal or until the tendency to lock is overcome. ABS is incorporated in some of the cars to prevent skidding and to rove braking.

Senstronic braking control (SBC) Senstronic Braking Control is basically a brake-by-wire system which eliminates the need for mechanical linkage between the brake pedal and brake master cylinder. SBS also work in conjunction with ABS to enhance braking.

It was developed by Mercedes in association with Robert Bosch GmbH. Among its most important performance features are the dynamic building up of brake pressure and the precise monitoring of driver and vehicle behavior using sensors. In an emergency situation, SBC increases brake line pressure and readies the brakes, so that they can grip instantly with full force when the brakes are applied.

Additionally, variable brake proportioning offers enhanced safety when braking on bends. SBC controls each wheel individually. When in corners, they apply varying degree of pressure on the inside and outside wheels of a car, and in the wet road condition. The SBC is found in Mercedes Benz E cars.

Published: By: Unknown - 03:06

Power Steering | Electronic Power Steering

Power steering

In heavy duty (dump) trucks and power tractors the effort applied by the driver is inadequate to turn the wheels. In this case a booster arrangement is incorporated in the steering system. The booster is set into operation when the steering wheel is turned. The booster then takes over and does most of the work for steering. This system called power steering uses compressed air, electrical mechanisms, and hydraulic pressure. Hydraulic pressure is used on a vast majority of power steering mechanism today.

When the steering wheel is turned, the worm turns the sector of the worm wheel and the arm. The arm turns the road wheel by means of the drag link. If the resistance offered to turn the wheels is too high and the effort applied by the driver to the steering wheel is too weak, then the worm, like a screw in a nut will be displaced axially together with the distributor slide valve. The axial movement of the distributor slide valve in the cylinder will admit oil into the booster cylinder through the pipe line. The piston in the booster cylinder will turn the road wheels via the gear rack, the toothed worm sector, arm and drag link. At the same time, the worm sector will act upon the work and will shift it together with the distribution slide valve to its initial position and stop the piston travel in the boost cylinder. When the steering wheel is turned in the other direction, the wheels will be turned appropriately in the same sequence.

The more the steering mechanism and wheels resist turning, the more the control valve is displaced. Hence, power assistance is always supplied in proportion to the effort needed to turn the wheels.

Electronic power steering

Electrically assisted power steering is used in some cars. The assistance can be applied directly by an electric stepper motor integrated with the steering column, or the steering mechanism, or it can be applied indirectly with hydraulic assistance pressurized by electric pump. EPS attached to the rack and pinion-steering-exists in Honda-City vehicles.

Electronic power steering Improves steering feel and power saving effectiveness and increases steering performance. It does so with control mechanisms that reduce steering effort. Nissan’s Blue Bird passenger car series use an electronically controlled three way power steering. This power steering is responsive to vehicle speed, providing maximum assistance as the speed rises. The driver can also select his or her own performance from three levels of assistance that make the steering effort heavy, normal or light.

Published: By: Unknown - 03:04

Choking Device | Functions of Choking Device

Choking device

Starting an engine in cold weather is somewhat difficult. Choking device makes engine starting easier. The choke valve is butterfly valve, similar to the throttle valve. This valve is situated between the air intake and the venture.

At the time of starting, the choke valve is turned to close almost the inlet passage. This is called choking. Then, during suction stroke, a greater depression is created in the inlet passage and is felt on the fuel jet which is situated at the throat of the venture. This causes more fuel to be ejected by the fuel jet. Choking restricts airflow and provides an over supply of fuel. It should be remembered that only the lighter fractions of the supplied fuel evaporate at lower temperatures and form a combustible mixture in the cylinder.

During initial cranking of the engine, the choke valve is almost completely closed. Once the engine fires consistently, the choke valve is opened slightly to keep the engine running. As the engine warms up to its normal temperature, the choke valve is opened gradually to its full extent. At all other times of engine operation, the choke valve is kept wide open. Thus the inlet passage is unrestricted.

The choke valve may be operated either manually or automatically. Manual choke operation is usually effected by a flexible cable connected to a knob in the dash board/instrument panel. Automatic choking is accomplished by a thermostatic element. The tension of the thermostat spring keeps the choke valve in a nearly closed position. As soon as the engine begins to operate, the exhaust gases heat the thermostat casing. This decreases in the tension of the spring and causes the choke valve to open to wide open position.

During choking, only the lighter fractions of the supplied fuel evaporate and form the combustible mixture in the cylinder. The unvapourized heavier fractions of the fuel mxi with lubricating oil film on the cylinder wall. The contaminated lubricating oil may run down into the crankcase as the piston rings scrape the oil. Thus, the crankcase oil gets diluted. This lowers the lubricating characteristics of the oil and may cause greater wear of the engine parts. It is evident, that during choking, fuel is wasted. Hence, choking should be done only when the engine fails to start and should be limited to the minimum period necessary to realize starting.

Unloader or dechoker If, for any reason during starting period, the engine is flooded, it becomes necessary to clear the excessive gasoline out of the intake manifold. This is accomplished by an arrangement of the throttle lever and chokes lingage. In one arrangement depressing the accelerator pedal to the floorboard forces the choke to open sufficiently to allow the engine to clean out the intake manifold. This device is called unloader or dechoker.

Published: By: Unknown - 03:04

Application of Laser in Mechanical Engineering | Laser Heat Treatment Process | Laser Metal Cutting and Joining Process

   

 Process involving heating and cooling under the controlled conditions of a material to obtain certain desirable properties is known as heat treatment.

1. Laser surface alloying

       The different types of heat treatment process using laser are shown in the picture. In the process of annealing there is no zone affected by the heat and melting takes place only in the level of picometer thickness.

        In hardening process there is a zone in the form of hemisphere which is affected by the heat. In this surface alloying method there is a coating of alloying or cladding materials deposited on the substrate surface.

        A controlled amount of melting of work piece surface to the desired thickness using laser beam with the addition of powdered alloying elements in equal interval of time is called as laser surface alloying.

2. Laser cladding

           A very thin layer of work piece melts when the beam of laser is applied on the surface. This thin layer of metal mixes with the cladding alloy and forms a metallurgical bonding in between the cladding and subtracts by freezes.

ADVANTAGES

1. Using laser radiation and doing heat treatment is very fast.

2. Comparing to other heat treatment process, lasers are able to do heat treatment in a particular spot where other process are inaccessible.

3. LASER WELDING

          Welding is a process of joining or combining two or more metal pieces into a single unit.

        If we consider welding of two metal plates, the metal plates will be held in contact at their edges and the laser beam will be allowed to move along the line of contact of the two plates.

       The laser beam will heat the edges of the two plates to their melting point and it will join them together.

ADVANTAGES

1. Impurities will not be present between the joints, because it is a contact- less process.

2. Because of rapid cooling the heat affected zone is relatively small.

3. Laser welding can be done without any difficulties even in small places.

4. This welding is usually done in very high rates.

5. Even different types of metals can be welded.

6. The work piece will not get distorted, so the total amount of input is very small when compared to other welding processes.

4. LASER CUTTING

       Laser cutting means evaporation or vaporization of the material at a point by focusing the laser beam.

       The laser cutting setup is shown in the figure. The exothermal reaction between the metal and the gas provides the required energy for cutting. Gas jet helps in removing the vaporized materials.

       The cut metal’s adjacent edges are also cooled with the help of gas jet. Hence, the gas blow reduces the requirement of laser power, it also increases the depth and speed of cutting and a high quality cut will be provided.

ADVANTAGES

1. Laser cutting can be done at room temperature and pressure without preheating and vacuum condition.

2. The microstructure of surrounding layers are not affected since heat affected zone is very small.

3. High cutting speed can be obtained.

Published: By: Unknown - 03:02

What Are CAD Drawings | 2D Design | 3D Design |Modeling | Drafting | By CAD Software’s like Pro-e, AutoCAD, Solidworks, CATIA, Unigraphics etc

Computer-aided design (CAD) is a process that allows computer users to design a variety of products and geometric shapes on-screen, rather than building them by hand. Using CAD software, one can create and modify an object to determine how it will appear and function after it is built. CAD drawings often include a computer-generated image of the design, as well as its dimensions, processes, and materials. CAD drawings may be either two dimensional (2D) or three-dimensional (3D). When an object is drawn in 3D using CAD, the process is often referred to as rendering or modeling, while 2D design is often called “drafting.”

CAD drawings are used in a large number number of industrial and manufacturing applications. This technology is widely utilized in art and graphic design, and gives these artists a greater level of design flexibility than that of other mediums. CAD drawings are also used in automotive and aerospace design, as well as in the development of industrial products and equipment. Many special effects used in films and television rely on computer animation generated with CAD software. Finally, CAD drawings are a critical component of the construction and engineering trades.

Before the invention of CAD, products and building plans were drawn by hand. This was a laborious and time-intensive process that required a high number of draftsmen, as well as frequent revisions. With the introduction of CAD software, engineers and designers were able to quickly and easily generate and modify drawings. Design firms could hire fewer staff, and both design and product development cycles were greatly reduced. CAD software also allowed engineers and designers to generate their own drawings, rather than to attempt to explain them to a draftsman, resulting in more accurate design.

Though CAD drawings have been in use since the 1960s, it wasn’t until the late 1980s and early 1990s that CAD software became a cost-effective option for many industries. Early versions of the software relied on 2D vector design, while modern CAD drawings include 3D modeling capabilities. Today’s modeling software allows designers to not only draw an object, but to rotate it on an axis, and to see through the object’s walls from the inside. This modeling capability is particularly useful in construction and engineering, allowing designers to virtually “walk-through” a structure and explore different angles.

Most CAD software is designed only for Windows or Linux operating systems. Complex CAD drawings may require advanced graphics cards and high levels of random access memory (RAM), but simpler drawings can be done on almost any basic computer. CAD software is operated using a traditional mouse, though some professional designers may supplement this operation using a digital pen or drawing tablet.

Published: By: Unknown - 02:59

Artificial Photosynthesis | Artificial Photosynthesis To Create Clean Fuel | Artificial Photosynthesis Solar To Fuel | Artificial Photosynthesis Process

Artificial photosynthesis is one of the newer ways researchers are exploring to capture the energy of sunlight reaching earth.

    

Photosynthesis:

Photosynthesis is the conversion of sunlight, carbon dioxide, and water into usable fuel and it is typically discussed in relation to plants where the fuel is carbohydrates, proteins, and fats. Using only 3 percent of the sunlight that reaches the planet, plants collectively perform massive energy conversions, converting just over 1,100 billion tons of CO2 into food sources for animals every year.

Photovoltaic Technology:

This harnessing of the sun represents a virtually untapped potential for generating energy for human use at a time when efforts to commercialize photovoltaic–cell technology are underway. Using a semiconductor–based system, photovoltaic technology converts sunlight to electricity, but in an expensive and somewhat inefficient manner with notable shortcomings related to energy storage and the dynamics of weather and available sunlight.

Artificial Photosynthesis:

Two things occur as plants convert sunlight into energy:

• Sunlight is harvested using chlorophyll and a collection of proteins and enzymes, and
• Water molecules are split into hydrogen, electrons, and oxygen.

These electrons and oxygen then turn the CO2 into carbohydrates, after which oxygen is expelled.

Rather than release only oxygen at the end of this reaction, an artificial process designed to produce energy for human use will need to release liquid hydrogen or methanol, which will in turn be used as liquid fuel or channeled into a fuel cell. The processes of producing hydrogen and capturing sunlight are not a problem. The challenge lies in developing a catalyst to split the water molecules and get the electrons that start the chemical process  to produce the hydrogen.

There are a number of promising catalysts available, that, once perfected, could have a profound impact on how we address the energy supply challenge:

• Manganese directly mimics the biology found in plants.
• Titanium Dioxide is used in dye-sensitized cell.
• Cobalt Oxide is very abundant, stable and efficient as a catalyst

Artificial Photosynthesis Operation:

Under the fuel through artificial photosynthesis scenario, nano tubes embedded within a membrane would act like green leaves, using incident solar radiation (H³) to split water molecules (H2O), freeing up electrons and oxygen (O2) that then react with carbon dioxide (CO2) to produce a fuel, shown here as methanol (CH3OH). The result is a renewable green energy source that also helps scrub the atmosphere of excessive carbon dioxide from the burning of fossil fuels.

History:

Plants use organic compounds that need to be continuously renewed. Researchers are looking for inorganic compounds that catalyze the needed reactions and are both efficient and widely available.

The research has been significantly boosted by the application of nano technology. It’s a good example of the step wise progress in the scientific world.

Studies earlier in the decade showed that crystals iridium efficiently drove the reduction of CO2, but iridium is extremely rare so technology that required its use would be expensive and could never be used on a large scale.

Cobalt crystals were tried. They worked, and cobalt is widely available, but the original formulations weren’t at all efficient.

Things changed with the introduction of nano technology.

The main point is that this unique approach increasing appears to be feasible. It has the advantage of harnessing solar energy in a form that can be stored and used with greater efficiency than batteries and it is at least carbon neutral.

Published: By: Unknown - 02:58

Artificial Leaf Solar Power | Artificial Leaf Produce Electricity

Photosynthesis:

Photosynthesis is the process by which plants, some bacteria, and some protists use the energy from sunlight to produce sugar, which cellular respiration converts into ATP, the “fuel” used by all living things. The conversion of unusable sunlight energy into usable chemical energy, is associated with the actions of the green pigment chlorophyll.

They release molecular oxygen and remove CO₂ (Carbon Dioxide) from the air.

ATP: Adenosine Tri-Phosphate (ATP)  Here the energy is stored in living systems; it consists of a Nucleotide (with Ribose sugar) with Three Phosphate groups.

Why is photosynthesis important:

Nearly all living things depend on the energy produced from photosynthesis for their nourishment. Animals need the plants for food as well as oxygen. Only green plants are able to change light energy into chemical energy stored in food, thus they are vital to life on Earth.

Solar cells:

Conventional solar cells are also called as Photo Voltaic Cells. These cells are made out of semiconducting material, usually silicon. When light hits the cells, they absorb energy though photons. This absorbed energy knocks out electrons in the silicon, allowing them to flow. By adding different impurities to the silicon such as phosphorus or boron, an electric field can be established. This electric field acts as a diode, because it only allows electrons to flow in one direction. Consequently, the end result is a current of electrons, better known to us as electricity.

Drawbacks of Solar cells:

They can only achieve efficiencies around 10% and they are expensive to manufacture. The first drawback, inefficiency, is almost unavoidable with silicon cells. This is because the incoming photons, or light, must have the right energy, called the band gap energy, to knock out an electron. If the photon has less energy than the band gap energy then it will pass through. If it has more energy than the band gap, then that extra energy will be wasted as heat.

Artificial Leaf:

Mixing of Photosynthesis + Conventional Solar Cells + Hydrogen Fuel Cell

This Leaf device combines a commercially available solar cell (Silicon) with a pair of inexpensive catalysts made of Cobalt and Nickel that split water into Oxygen and Hydrogen. The hydrogen can be stored and used as an energy source. (For example to power a fuel cell).

The collection and storage of the sun’s energy as hydrogen fuel is a key step in overcoming one of the limitations of solar power — it generates energy when the sun is shining, but it needs to be stored somewhere to be useful at night and in cloudy weather. Batteries are one place to store the energy, but it is limited. Storing solar energy as hydrogen fuel could be an answer for producing the electricity continuously.

Using this approach, a solar panel roughly one square meter bathed in water could produce enough hydrogen to supply electricity for a house.

Published: By: Unknown - 02:56