AutoMotive News

Future Developments in Automotive Transmission Systems: 1.  The CVT will gradually replace the conventional automatic transmission due to its high fuel efficiency and smooth gear shift. 2.  The technology of semi-automatic transmission systems will also be improved to perform smooth gear shift and extend the cars' lifetime, without losing fast acceleration and fuel efficiency. 3.  The torque converter with fluid coupling may be improved, or may no longer be used for cars in the future due to its low-efficiency power transfer. 4.     5. Shift-by-wire totally eliminates mechanical lever shifting, keeping both of the driver's hands on the wheel.  The clutch is used only for starting and stopping. Once the vehicle is in motion, Auto-Shift operates like an automatic transmission, with the efficiency of a manual transmission. 6. Adaptive transmission control:   ATC has also been invented by using the computer to recognize and memorize different drivers' styl...

Continuously Variable Transmissions (CVT)                CVT is an “infinite speed” transmission that can change step-less through an infinite number of effective gear ratios between maximum and minimum values. Unlike traditional automatic transmissions, continuously variable transmissions don't have a gearbox with a set number of gears, which means they don't have interlocking toothed wheels. The word gear in CVT refers to a ratio of engine shaft speed to driveshaft speed. Moreover, CVTs change this ratio without using a set of planetary gears. Different types of CVTs : 1.     Pulley-based CVTs 2.     Toroidal CVTs 3.     Hydrostatic CVTs                The most common CVT design uses a segmented metal V-belt running between two pulleys. Each pulley consists of a pair of cones that can be moved clos...

Semi-Automatic Transmission        The two most common semi-automatic transmissions are- 1.     Dual-clutch Transmission 2.     Sequential Transmission Dual Clutch Transmission:                A dual-clutch transmission, commonly abbreviated to DCT uses two clutches but has no clutch pedal. Sophisticated electronics and hydraulics control the clutches, just as they do in a standard automatic transmission. In a DCT, however, the clutches operate independently. One clutch controls the odd gears (first, third, fifth, and reverse), while the other controls the even gears (second and fourth) as shown in the figure. Using this arrangement, gears can be changed without interrupting the power flow from the engine to the transmission.                  A two-part transmission shaft is at the heart of a DCT. Unlike a conventional manual gearbox,...

Comparison between Manual & Automatic Transmission:                Both automatic transmission and manual transmission accomplish exactly the same thing, but they do it in a totally different way. Advantages of manual transmission over automatic transmission: 1. It is easier to build a strong manual transmission than an automatic one. This is because a manual system has one clutch to operate, whereas an automatic system has a number of clutch packs that function in harmony with each other. 2. Manual transmissions normally do not require active cooling, because not much power is dissipated as heat through the transmission. 3. Manual gearshifts are more fuel-efficient as compared to their automatic counterpart. Torque converter used to engage and disengage automatic gears may lose power and reduce acceleration as well as fuel economy. 4. Manual transmissions generally require less maintenance than automatic transmissions. An automatic ...

Automatic Transmission                The concept of an automatic transmission is new in India. An automatic transmission is a motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears.  In this transmission system, the gears are never physically moved and are always engaged to the same gears. Automatic transmissions contain mechanical systems, hydraulic systems, electrical systems, and computer controls, all working together in perfect harmony manually. Main Components of an Automatic Transmission: 1.        Planetary Gear Sets             2.        Clutches and Bands 3.        Torque Converter 4.        Valve Body 1 .  Planetary Gear Sets  ...

Manual Transmission                The first transmission invented was the manual transmission system. A manual transmission, also known as a manual gearbox or standard transmission (informally, a "manual", "stick shift", "straight shift", or "straight drive") is a type of transmission used in motor vehicle applications. It generally uses a driver-operated clutch, typically operated by a pedal or lever, for regulating torque transfer from the internal combustion engine to the transmission, and a gear-shift, either operated by hand (as in a car) or by foot (as on a motorcycle).                 In a manual transmission, the driver needs to disengage the clutch to disconnect the power from the engine first, select the target gear, and engage the clutch again to perform the gear change. Components of Manual Transmission The diagram below shows a very simple two-speed transmission in neutral: ...

Types of Transmission System 1.       Manual Transmission 2.       Automatic Transmission 3.       Semi-automatic Transmission:- a)        Dual-clutch Transmission b)        Sequential Transmission 4.       Continuously Variable Transmission

Transmission system Introduction                       Need For a Transmission                The need for a transmission in an automobile is a consequence of the characteristics of the internal combustion engine. Engines typically operate over a range of 600 to about 7000 revolutions per minute (though this varies, and is typically less for diesel engines), while the car's wheels rotate between 0 rpm and around 1800 rpm.               

Comparison between MacPherson Double Wishbone Suspension Systems                Two of the most popular suspensions systems for passenger cars today are the double-wishbone suspension system and the MacPherson strut suspension system. While it is more usual to see the double-wishbone system at the rear end of the car, MacPherson’s solution normally finds its place at the front end of the car. Both types of suspensions have their own sets of benefits and limitations, thus let us look at both the advantages and disadvantages of both systems, starting with the simpler of the two, the MacPherson struts.   MacPherson Struts:                The struts are designed with more simplicity, and thus takes up less space horizontally. As a result, passengers get more compartment place in the car. They also display low un-sprung weight, an advantage that reduces the overall weight of the vehicle as well as ...

Components of Suspension System 1.      Control Arm:  A movable lever that fastens the steering knuckle to the frame of the vehicle. 2.      Control Arm Bushing:  This is a sleeve that allows the control arm to move up and down on the frame. 3.      Strut Rod:  Prevents the control arm from swinging forward and backward. 4.      Ball Joints:  A joint that allows the control arm and steering knuckle to move up and down and sideways as well 5.      Shock absorbers or Struts:   prevents the suspension from bounce after spring compression and extension 6.      Stabilizer Bar:  Limits body roll of the vehicle during cornering 7.      Spring:  Supports the weight of the vehicle Common Problems of the Suspension System Shocks and Struts:       Ball joints:   ...

Suspension System Introduction                The suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to the car's road-holding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps, and vibrations, etc.                 These goals are generally at odds, so the tuning of suspensions involves finding the right compromise. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible because all the forces acting on the vehicle do so through the contact patches of the tires. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. Principle of Suspension System 1.   ...

Mechanical Advantage                Gear teeth are designed so that the number of teeth on a gear is proportional to the radius of its pitch circle, and so that the pitch circles of meshing gears roll on each other without slipping. The speed ratio for a pair of meshing gears can be computed from the ratio of the radii of the pitch circles and the ratio of the number of teeth on each gear.                Two meshing gears transmit rotational motion.                The velocity v of the point of contact on the pitch circles is the same on both gears and is given by v=r A w A   =r B W B                Where input gear A has radius r A  and meshes with output gear B of radius r B , therefore, w A  /   w B =   r B /   r A =   N B /   N A    ...

Gear Train                A gear train is formed by mounting  gears  on a frame so that the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping; this provides smooth transmission of rotation from one gear to the next. •      A gear train is two or more gear working together by meshing their teeth and turning each other in a system to generate power and speed •        It reduces speed and increases torque                              •       Electric motors are used with the gear systems to reduce the speed and increase the torque   Types of the gear train Simple gear train Compound gear train Epicyclic gear train Reverted gear train Simple Ge...

Gear Ratio             The gear ratio of a  gear train  is the ratio of the angular velocity of the input gear to the angular velocity of the output gear, also known as the speed ratio of the gear train. The gear ratio can be computed directly from the numbers of teeth of the various gears that engage to form the gear train.                In simple words, the gear ratio defines the relationship between multiple gears.   Gear Ratio= Output gear # teeth / Input gear # teeth                  For example, if our motor is attached to gear with 60 teeth and this gear is then attached to a gear with 20 teeth that drives a wheel, our gear ratio is 60:20, or more accurately 3:1                If you do not want to count a gear's teeth (or if they do not exist), gear ratios can also be determined by...

The terminology of Spur Gear   ●       Pitch surface : The surface of the imaginary rolling cylinder (cone, etc.) that the toothed gear may be considered to replace. ●       Pitch circle : A right section of the pitch surface. ●       Addendum circle : A circle bounding the ends of the teeth, in the right section of the gear. ●       Root (or dedendum) circle : The circle bounding the spaces between the teeth, in the right section of the gear. ●       Addendum : The radial distance between the pitch circle and the addendum circle. ●       Dedendum : The radial distance between the pitch circle and the root circle. ●       Clearance : The difference between the dedendum of one gear and the addendum of the mating gear. ●  ...