DIFFERENT TYPES OF LAYOUT IN AUTOMOBILES

1.)Front engine front wheel drive 

Front-wheel drive is the most common form of engine/transmission layout used in modern passenger cars, where the engine drives the
front wheels only.In this layout a front mounted engine-clutch-gear box unit drives a beam type rear axle suspended on leaf sprints through a propeller shaft with two universal joints.  Most front wheel drive vehicles today feature transverse engine mounting, though many in prior decades were positioned longitudinally instead.

Advantages:-

•  Balanced weight distribution between the front and the rear wheels.
• Easy front wheel steering.
• Behind the rear seats, large luggage space is available.
•  Accessibility to various components like engine, gearbox and rear axle is better in  comparison to other layouts. The control linkages-accelerator, choke, clutch and gearbox are short and simple.
• Full benefits of the natural air stream created by vehicle’s movement is taken by the forward radiator resulting in reduced power losses from a large fan.
• Small length of the propeller shaft permits the angularity of the universal joints to be small and easily provided by simple types.

2.)Rear engine rear wheel drive

Rear-engine, Rear-wheel-drive layout places both the engine and drive wheels at the rear of the vehicle.It is shown in figure below

Advantages:-

• Better road adhesion preferably on steep hills and while accelerating with increased weight on the driving wheels.
• Generally a proportional part of weight of the car is transferred to the front wheels while braking. Therefore, due to the firm road surface contact maintained by rear engined car results in assistance to stopping of the vehicle.
• In this arrangement, front wheels are only for steering purposes.
• The necessaity of the propeller shaft is altogether eliminated due to the combination of engine, gear box and final drive. This also requires only one common oil sump.
• Good visibility and stream lining is provided by proper design of vehicle front.

3.)All wheel drive

An AWD vehicle (short for All-wheel drive vehicle) is one with a powertrain capable of providing power to all its wheels, whether full-time or on-demand.It appears in everything from supercars with out-of-this-world performance like the Audi R8 to family crossovers and SUVs like the Volvo XC90.

Advantages:-

• As compared to rear wheel driven car, there is a faster and safer travelling due to good road holding on curves.
• Gives sportier handling and traction to a broader range of cars.
• A lower flat floor lines is provided due to dispensing with the propeller shaft resulting in lowering of centre of gravity.
• The engine, clutch, gear box and final drive are combined similar to the rear engine car. This provides a more comfortable drive due to final drive spring. 
• Good road adhesion is obtained due to a large part of the vehicle’s weight being carried on the driving wheels under normal conditions.

ALL ABOUT GEARS

Gears are toothed wheels which are used to transmit force to other gears or toothed parts by meshing with minimal slip.
When two gears are meshed together, the smaller gear is called a pinion. The gear transmitting force is referred to as a drive gear, and the receiving gear is called the driven gear.

When pinion is the driver, it results in step down drive in which the output speed decreases and the torque increases. On the other hand, when the gear is the driver, it results in step up drive in which the output speed increases and the torque decreases.

Law of gearing:-

The angular velocity ratio of all gears of a meshed gear system must remain constant also the common normal at the point of contact must pass through the pitch point.

Screw thread terminology

Powder metallurgy

Powder metallurgy:-

Powder metallurgy is the process of blending fine powdered materials, pressing them into a desired shape or form (compacting), and then heating the compressed material in a controlled atmosphere to bond the material (sintering). The powder metallurgy process generally consists of four basic steps: powder manufacture, powder blending, compacting, and sintering. Compacting is generally performed at room temperature, and the elevated-temperature process of sintering is usually conducted at atmospheric pressure. Optional secondary processing often follows to obtain special properties or enhanced precision. The use of powder metal technology bypasses the need to manufacture the resulting products by metal removal processes, thereby reducing costs.

Powder metallurgy is also used in "3D printing" of metals.