4 Wheel Drive (4WD)

4WD:

4wd Amblem

Whats is it??

Its a mechanism in which all the 4 wheels of an vehicle simultaneously receive torque from the engine. The best system will send exactly the right amount of torque to each wheel, which is the maximum torque that won't cause that tire to slip.  This provides a stable control over the vehicle and provides better traction over the toughest of terrains. Normally the vehicles have 2WD in which the engine power is transferred to any of the front or rear set of wheels. This feature is mostly available in SUV's or Other high end cars as it is not much necessary feature to have for normal city driving. 

How it works??  

4wd works with the help of differential present on the front and the rear drive shaft of the vehicle. A car has two differentials, one located between the two front wheels and one between the two rear wheels. They send the torque from the driveshaft or transmission to the drive wheels. They also allow the left and right wheels to spin at different speeds when you go around a turn.

The differential

A differential

A differential is able to split the rotations delivered by the drive shaft either equally or proportional to left and right as needed.
The differential is a mechanical device that reacts to resistance. The inside tire, by following a smaller circle in a turn, puts up resistance. The differential reacts to this resistance and allows it to rotate less. At the same time the outside tire is forced to rotate faster by the same rate the inside wheel rotates less.
When you go around a turn, the inside wheels follow a different path than the outside wheels, and the front wheels follow a different path than the rear wheels, so each of the wheels is spinning at a different speed. The differentials enable the speed difference between the inside and outside wheels. These differentials have a unique gearset: As soon as it senses a decrease in torque to one wheel (which occurs when a tire is about to slip), the gearset transfers torque to the other wheel.

4wd Shift Button

The vehicle has a switch to turn the 4WD ON or OFF.

When the 4WD mode is turned on the engine starts supplying torque to the all the 4 wheels with the help of transfer case present in the 4WD assembly. The sole purpose of this transfer case is to create connection between the rear differential and the engine. When the 4wd mode is turned off the connection in the transfer case is open and when the mode is changed the connection is closed  and the vehicle is in 4wd Mode. 

Watch the video to understand the functioning:

Alloy Wheels : The Beautification

Alloy Wheels:

Range of different types of alloy wheels

Alloy wheels are automobile (car, motorcycle and truck) wheels which are made from an alloy of aluminium or magnesium. They are typically lighter for the same strength and provide better heat conduction and improved cosmetic appearance than "normal" wheels. The earliest light alloy wheels made were made of magnesium alloys.Although the cost of making an alloy wheel is higher than the cost involved in steel wheel manufacturing but the benefits mentioned below creates demand in the market.

An Alloy Wheel in a Truck

Benefits of alloy wheels:

• They are lighter so they decrease the overall weight of the vehicle and thus improve efficiency and acceleration of the car .
• In addition to lighter weight, the alloys wheels have more strength as compared to their steel counterparts. This means that the chances of any deformation in the wheel structure is less in case of harsh roads.
• The most appealing feature of using alloy wheel is the style factor that it adds on to the car. Most of the people switch to alloy wheels just because to improve the cosmetic appearance of their vehicle.

Custom Alloy Wheels in Maruti Suzuki Swift

How they are made:

• Forging 

Forging can be done by a one or multi-step process forging from various magnesium alloys, most commonly AZ80, ZK60 (MA14 in Russia). Wheels produced by this method are usually of higher toughness and ductility than aluminum wheels, although the costs are much higher.

• High pressure die casting (HPDC) 

This process uses a die arranged in a large machine that has high closing force to clamp the die closed. The molten magnesium is poured into a filler tube called a shot sleeve. A piston pushes the metal into the die with high speed and pressure, the magnesium solidifies and the die is opened and the wheel is released. Wheels produced by this method can offer reductions in price and improvements in corrosion resistance but they are less ductile and of lower strength due to the nature of HPDC.

• Low pressure casting (LPDC)

This process usually employs a steel die, it is arranged above the crucible filled with molten magnesium. Most commonly the crucible is sealed against the die and pressurized air/cover gas mix is used to force the molten metal up a straw like filler tube into the die. When processed using best practice methods LPDC wheels can offer improvements in ductility over HPDC magnesium wheels and any cast aluminum wheels, they remain less ductile than forged magnesium.

• Gravity casting (permanent mold and sand casting)

Gravity cast magnesium wheels have been in production since the early 1920s. This method offers wheels with good ductility, and relative properties above what can be made with aluminum casting. Tooling costs for gravity cast wheels are among the cheapest of any process. This has allowed small batch production, flexibility in design and short development time.

Mercedes Benz A-Class

Mercedes Benz A-Class:

This post of mine is the latest edition of Mercedes Benz A-Class, which is boasting very new and innovative features in addition to the previous ones by Mercedes   Shown below is a a commercial for Mercedes Benz A-Class have a look and explore the convenience and luxury with power..

A-Class : 

Mercedes Benz A-Class

The car is available in both petrol and diesel variants with an option to choose between a 6-speed manual transmission or the 7-Speed automatic transmission. The car is a part of the exclusive Hatchback segment of the Mercedes giant collection. The A-Class is also available in sports variant where the engine has few tweaks and the interiors are made much sportier. Now lets have a look at the features that it has :

Features:

• Attention Assist : The sensors present detects the driver's behavior and alert him to stay focussed on the road.
• Parking Assist: To auto park the car in toughest conditions.
• Collision Prevention Assist: The sensors present prevent a collision to happen and stop the car prior to the vehicle ahead.
• Adaptive Brake Assist: Assist the driver when to apply brake if there is a obstruction nearby.
• Distronic Plus: This features allows the car to maintain a certain distance with the car ahead in cruise control mode. 
• Intelligent Light System: It detects the outside lighting and switch the lights on or off according to the outer atmospheric lighting.

Specifications:

Mercedes Benz A-Class : Specification Diesel Variants

Mercedes Benz A-Class : Specification Petrol Variants

Exteriors:

Mercedes Benz A-Class : Back

Mercedes Benz A-Class : Side

Interirors:

Mercedes Benz A-Class : Dashboard

Mercedes Benz A-Class : Interior

This is it about the Mercedes Benz A-Class..Hope you liked the post..for more such post visit auto-gyaan.

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Electronic Brake Force Distribution

Electronic Brake Force Distribution:

Electronic Brake Force Distribution

EBD is based on the principle that the weight being supported by the wheels of your car isn't evenly distributed. Some wheels carry a heavier load than others and will require more brake force in order to bring the car to a stop without it going out of control. Furthermore, the amount of weight being supported by a wheel shifts during the braking process, so the amount of force necessary at each wheel can change rapidly. An EBD system can not only detect how much weight is being supported by each wheel, but change the amount of braking power sent to each wheel on an instant-by-instant basis.

It's important for driving safety to maintain the friction between the tire and the road, yet there are a number of conditions under which this friction can be lost. One is acceleration on icy roads, as mentioned above, but friction can also be lost if you brake too hard. The forward momentum of the car can keep it moving at a speed significantly greater than the speed at which the tires are spinning. This is called wheel lock and it's a common cause of driving accidents. Once it happens, the tires no longer grip the pavement and the car continues to travel in the direction it was heading when the skid started.

The key to avoiding a skid is the slip ratio, the difference between the speed at which the car is moving and the speed at which the tire is rotating. Antilock braking systems (ABS) can sense the slip ratio of the individual tires and modulate the brake force applied to each tire so that the slip ratio remains within a safe range, thereby avoiding a skid.

With EBD, a computer called an electronic control unit (ECU) determines the slip ratio of each of the tires individually. If the ECU notices that the rear wheels are in danger of slipping, it applies less force to them while maintaining (or, if necessary, increasing) the force applied to the front wheels. EBD is also useful when the car is braking while driving around a corner. While turning, the outer wheels of the car rotate more quickly than the inside wheels. If too much brake force is applied to the inner wheels they can lock, causing the car to oversteer and go out of control. EBD can sense the slippage of the inner wheels and reduce the brake force on those wheels without reducing the force on the outer wheels.

EBD system needs two pieces of information: the speed at which the wheel is rotating and the speed of the car. If the speed at which the wheel is rotating is slower than the speed at which the car is moving, then the wheel is slipping and a skid can result. A sensor is placed at each wheel to determine wheel speed. There is no specific sensor to measure the forward motion of the car. Instead, the speed measurements from all four wheels are averaged to create an estimate of the vehicle's overall speed.

Brake force modulators: Brake force is applied to the wheels hydraulically, with brake fluid pumped into brake lines in such a way as to pneumatically activate the brake cylinders. The EBD system can modulate the amount of brake fluid going to each wheel through electrically actuated valves.

Electronic Control Unit (ECU): The ECU is a small computer embedded in the antilock braking system. It receives input from the speed sensors, calculates the slip ratio of the wheels, and uses the brake force modulators to apply an appropriate amount of force to keep the slip ratio of each wheel within a reasonable range.

Benefits of EBD:

Imagine that you're driving on an icy surface or a road slick with rainwater. Under these conditions it's really easy for your car to go into a skid. And although EBD cannot detect road conditions directly, it can deduce them from the slip ratio of the wheels and compensate accordingly. If conditions are different for each wheel -- for instance, if one wheel is on a patch of ice and the other is not -- this can be detected through the slip ratio. Although there's no magic solution to the problem of stopping a car under bad road conditions, EBD can make emergency braking under these conditions as safe as possible.

Watch the video to understand the working:

Parking Assist

Parking Assist:

An automated parking system that requires the driver to do nothing more than just sit back and watch the car steer itself into the best suited parking position

Park Assist System though a recent phenomenon in India, is expected to soon become a standard feature in most upper segment compact sedans and SUV’s. The systems is basically aided by three critical components, which are the ultrasonic sensors, a rear view camera and an Intelligent Parking System that ultimately gauges and decides the angle of steering and movement to put your car in the right slot.

Parking Sensors
The first step in achieving the Park Assist function, automobiles using this function come with ultrasonic sensors that are fitted in the front, side and (sometimes) the rear of the vehicle. These ultrasonic sensors gauge the exact length and breadth of a parking slot as you drive past a parking zone, and informs you when you have passed a suitable parking space that is wide and long enough to fit the dimensions of your car.

Backup Camera

Once the car has found a suitable parking slot, all the driver is required is move forward and then bring the vehicle to a standstill. He then has to switch to reverse gear, and just let go of the steering wheel. The system will then take over the wheel and begin to self maneuver the car using its rear view camera to adjust the track overlay, which you can observe on the screen fitted on your cars entertainment console area.

Intelligent Park Assist System

A combination of the cars sensors and the back up camera allows the onboard computer to adjust the angle of traction and speed depending on the proximity of nearby vehicles, so as to maneuver your vehicle perfectly in order to make it fit into the limited parking space available. One the car has been brought into position, the Intelligent Park Assist System will inform the driver that the parking operation has been executed successfully, and that you are free to take over control or kill the engine and simply walk out.

Watch the video and see how it works!!

KnowTheAuto : The Automobile Blog :)

A-Z of AutoMobiles

KnowTheAuto : The AutoMobile Blog

The blog is all about the various technologies, types and functionality of the Automobiles. In auto-gyaan you will find interesting topics about the automobiles and much likely u'll be gaining some knowledge from this blog about the topics that maybe you were not aware of before.

       

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