MEE 121 - ferdousalam.weebly.com

MEE 121 INTRODUCTION TO MECHANICAL

ENGINEERING

Prepared by- Md Ferdous Alam, Lecturer, MEE, SUST

Hello Class

Radiator

Radiator is the application of the heat

exchanger which is the part of the engine

cooling system.

Purpose of a radiator

Remove excessive heat produced by the engine

during combustion and by friction.

1500-2000 Degree Celsius temps. could

seriously damage engine parts.

Types of Cooling Systems

Air cooling system

Liquid cooling system

Air cooling system

Its design of air-cooled engine is simple.

It is lighter in weight than water-cooled engines

due to the absence of water jackets, radiator,

circulating pump and the weight of the cooling

water.

It is cheaper to manufacture.

It needs less care and maintenance.

No risk of damage from frost, such as cracking

of cylinder jackets or radiator water tubes.

This system of cooling is particularly

advantageous where there are extreme climatic

conditions in the arctic or where there is

scarcity of water as in deserts.

Some older cars, motorcycle and very few modern

cars, are air-cooled.

Instead of circulating fluid through the engine, the

engine block is covered in aluminum fins that

conduct the heat away from the cylinder.

A powerful fan forces air over these fins, which

cools the engine by transferring the heat to the air.

Liquid cooling system

Uniform cooling

Volumetric efficiency is this type of engine is higher

This system requires more maintenance

Compact design of engine is possible

Some important components

Clutch

The clutch allows the driver to engage or disengage the engine and manual transmission.

Shaft vs axle

Constant-velocity joints (AKA homokinetic or CV joints) allow a drive shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction.

A constant velocity joint is a coupling that connects two rotating shafts, an input shaft and an output shaft, at an angle. A constant velocity joint, by design, ensures that both the input and output shaft rotate at the same speed, regardless of the angle of the joint.

They are mainly used in front wheel drive vehicles,

CV Joint

Universal Joint (UJ)

A universal joint (universal coupling or Hooke's joint) is a joint or coupling in a rigid rod that allows the rod to "bend" in any direction, and is commonly used in shafts that transmit rotary motion.

It consists of a pair of hinges located close together, oriented at 90° to each other, connected by a cross shaft. The universal joint is not a constant-velocity joint.

At each end of the shaft there is a universal joint

(UJ), which allows the rear axle to move up and

down in relation to the gearbox without bending or

snapping the shaft.

Differential

A differential is a gear train with three shafts that has the property that the angular velocity of one shaft is the average of the angular velocities of the others, or a fixed multiple of that average.

The differential allows the outer drive wheel to rotate faster than the inner drive wheel during a turn.

This is necessary when the vehicle turns, making the wheel that is traveling around the outside of the turning curve roll farther and faster than the other

The average of the rotational speed of the two driving wheels equals the input rotational speed of the drive shaft.

An increase in the speed of one wheel is balanced by a decrease in the speed of the other.

FWD

A transmission system that provides power to the front wheels of a motor vehicle.

Hence, Front wheel drive (FWD)

This arrangement is extremely popular in modern vehicles:

Smaller drivetrain: Instead of the engine, transmission, and differential running from the front to the back of a vehicle, a front-wheel drive vehicle has the entire drivetrain in the front.

Less weight: Because of the compact drivetrain, front-wheel drive vehicles weigh less than the equivalent rear-wheel or all-wheel drive vehicle.

More traction than rear-wheel drive: With most of the vehicle’s weight near or above the drive wheels, front-wheel drive vehicles tend to have more traction than rear-wheel drive vehicles. This is especially helpful when the road is slippery or wet.

Most fuel efficient type of drivetrain: Due to the light weight and more efficient use of power, front-wheel drive vehicles get more miles out of every gallon compared to the equivalent all-wheel drive or rear-wheel drive vehicle.

Ford Focus ST

RWD

RWD means that the power from the engine is delivered to the rear wheels and the rear wheels push the car forward.

The front wheels do not receive any power and are free to manoeuvre the vehicle.

Due to the weight of a RWD vehicle being more evenly spread than a FWD vehicle, creates a better balance of weight.

The disadvantage of a RWD vehicle are that they do not perform well in poor weather conditions such as rain or snow because they are more prone to loss of traction on slick roads.

Ford Mustang

All wheel drive

AWD Power is delivered to any 2 of the four wheels at any time. The biggest advantage of an AWD vehicle is that it provides the best traction in all kinds of conditions. The cons of an AWD vehicle are that it is heavier which hurts acceleration and uses more fuel. AWD is also the most expensive drivetrain option but will provide the most traction resulting in a safer ride.

4WD

4WD means the power from the engine is delivered to all 4 wheels all of the time 4X4 is engaged and has an option to operate in a RWD format to conserve fuel.

The biggest advantage of a 4WD vehicle is that it provides the versatility and power to take on any terrain or weather condition.

The con of a 4WD vehicle is that it operates in RWD format most of the time and has less traction then a AWD vehicle.

Why high performance cars are RWD?

High performance cars have a higher torque at the wheels. If a high torque is at the wheels of a FWD, the car tends to pull hard to the right or the left and the driver could lose control.

One basic thing!

Practically, torque is a better measurement of how quickly your car will accelerate, while horsepower (relative to weight) is a better measure of your car's top speed

Fun question!

What do you think?

Which one does Batman use as batmobile?

4WD

AWD

Fun question!

What do you think?

Which one does Batman use as batmobile?

4WD

AWD

Thank you