Difference between open die forging and closed die forging

The method of deforming a piece of metal between various dies that does not fully enclose the material is open die forging. The metal is modified by a sequence of movements as the dies "hammer" or "stamp" material until the required shape is achieved. 

Let us have a deep insight into the difference between open and closed die forging.

Difference between open and closed die forging : 

• Open die forging is also known as free forging, meaning metal billets compressed under the external compressive force and deformed to desired dimensions in a freeway without forging dies while closed die forging is also known as impression die forging, is a process that heated by medium frequency induction heating furnace to high temperature and forced between upper and lower dies to get expected shapes like the drawing.
• Both forging processes are also different in the side of their processes. Moulding dies are firstly made for closed die forging, and then forged steel bars are placed on the dies and drop forged to desired shapes. In open-die forging, it involves enormous compressive force imposed by the continuous strike of a hammer to make the metal billets deformed. 
• Open die forging will require further rough machining due to its free forging and imprecise dimensions may be reached by second precision machining while closed die forging is more common in small parts for its high precision used to make forged fittings, forged flange and forged automotive parts. 
• The open die metal forged parts are more suitable for larger parts in a number of tons whereas for small parts closed die forging is preferred as high precision is obtained in closed die forging. 

Difference between hot rolling and cold rolling

One of the important processes in metal manufacturing is rolling, but there are two methods available for rolling one is hot rolling and another is cold rolling. It is a common misconception that these processes relate to a specification of metal or grade of metal instead, they refer to how metal is processed at the mill. Now in this article, you can check it out the hot rolling vs cold rolling and some key difference between them. 

What is hot rolling?

Hot rolling is the process in which rolling the steel at a high temperature which is higher than the recrystallization temperature of steel.

What is cold rolling?

Cold rolling is a similar process to hot rolling, the steel is subjected to further cooling process at room temperature in cold reduction mills after being rolled. 

Main difference :

The main difference between these two processes is the temperature in which they are performed. Hot rolling is under high temperature also called as above recrystallization and the cold rolling is under room temperature also called as below recrystallization. 

Some more difference between hot and cold rolling process is explaining below. 

• Hot rolling is the father of cold rolling which follows hot rolling. 
• Hot-rolled metal does not show work hardening effect whereas it shows in cold roller metal. 
• Co-efficient of friction between two rolls is higher in hot rolling it may even cause shearing of metal in contact with rolls and co-efficient of friction us lower in cold rolling. 
• Experiment measurement is difficult in hot rolling while it can be carried out easily in cold rolling.
• Heavy reduction area of a workpiece can be obtained in hot rolling whereas heavy reduction is not possible in cold rolling. 
• The radius of rolls is generally higher for hot rolling and it relatively smaller in cold rolling. 
• The very thin section is not obtained by a hot rolling process vice versa in the cold rolling process. 
• Hot rolling does not allow partial buckling of cross-section while cold rolling is allowed to have local buckling. 
• Mechanical properties are improved by beaking cast structure thus toughness increases in hot rolling and cold rolling increases the tensile strength and yield strength. 
• The hot-rolled surface is not good it has metal oxide on it while the cold-rolled surface is smooth and oxide-free. 

Positive caster Vs Negative caster

Positive caster is when the steering axis is in front of the verticle axis and negative caster is when the steering axis is behind the verticle axis. In this article, you have to clear your mind to check it out the difference between positive and negative caster, comparison and much more details about them.  

Difference : 

• Positive caster occurs when the axis of the steering wheel is ahead of the vertical axis and negative caster occurs when the axis of the steering wheel is behind the vertical axis.  
• A significant amount of positive caster provided that your vehicle has a well-fitted power steering system while negative caster symptoms make the steering wheel light and increasing the susceptibility of your vehicle, and make its path accurate without proper direction.
• Positive caster angles run between 3 - 5° on modern vehicles gives a good mix of highway stability and steering feel. Negative caster is opposite to positive caster. 

Summary : 

If you modify the caster settings on your vehicle, make sure that you keep the angular degrees of the casters completely symmetrical with one another. If you make the mistake of miscalculating the angles of the casters on various wheels of your vehicle, then you will find your car will start pulling more towards one side with respect to another side which doesn't have much of a caster angle. 

Difference between caster and camber

Definition of caster angle : 

The caster angle is the angular displacement of the steering axis from the vertical axis of a steered wheel in a car, motorcycle, bicycle measured in the longitudinal direction. In other words, it is the angle between the pivot line and vertical. 

Definition of camber angle : 

The camber angle is the angle made by the wheels of a vehicle, it is the angle between the vertical axis of the wheels used for steering and the vertical axis of the vehicle when measured from the front or rear. 

Camber angle is taken care of when designing the steering and suspension.

If the top of the wheel is farther out than the bottom, is called positive camber. If the bottom of the wheel is farther out than the top, is called the negative camber. 

This article is about the caster vs camber, what is caster angle, what is camber angle and the comparison between caster and camber.

Difference between the caster and camber : 

• Caster is the angle between the verticle line and kingpin centre line in the plane of the wheel when the view from the side is called the caster angle. Camber is the angle between the centre line of the tyre and the vertical line viewed from the front of the vehicle is known as the camber angle.
• Caster is the steering angle with respect to the wheel's centre and camber is the wheel's angle with respect to its centre. 

Explore more information: 

1. What is a caster?
2. What are toe-in and toe-out?
3. Difference between understeer and oversteer

How to adjust correct steering angle?

The perfect steering is achieved when all the four wheels are rolling perfectly under all running condition. While taking turns, the perfect rolling condition is satisfied if the axis of the front wheels when produced meet the rear wheel axis at one point. Then this point is called the instantaneous centre of the vehicle. 

It can observe that the inside wheel is required to turn through a greater angle than the outer wheel. The larger the steering angle, the smaller the circle of turning. However, a maximum to which we can go as the steering angle. 

It has been found that steering angle can have a maximum value of about 44 degrees. 

The extreme positions are called lock positions on either side. The diameter of the smallest circle which the outer front wheel of the car can traverse and get when the wheels are at their extreme positions is referred to as the turning circle.

Now let we discuss the formula for correct steering angle. 

Correct Steering Angle

Let the axis of the inner wheels makes a larger angle θ than the angle φ subtended by the axis of an outer wheel. 

Let a = wheel track
b =  wheelbase
c = distance between the pivots A and B of the front axle

From the triangle IBP 

cotθ = BP / IP 

From the triangle IAP

cotø = AP / IP = AB + BP / IP = AB / IP + BP / IP = c / b + cotθ

cotø - cotθ = c / b 

This is the fundamental equation for correct steering. 

Explore more information: 

1. What is a caster?
2. Difference between the caster and camber

What is Toe in and Toe out | Definition | Effect

Definition : 

Toe-in is the amount by which the front wheels are mounted closer together on the front than on the back when the vehicle is stationary and viewed from the top. The wheel can be set closer to the rear than to the front, in which case the difference of the distances between the front and rear wheels is called toe-out. 

Effect : 

In rear-wheel-drive vehicles, there is usually an inherent tendency for the wheels to toe-out due to purposeful deviation from centre point steering due to errors in the steering angles of the inner and outer bends of the wheels. 

There is usually an inherent tendency for the wheels to toe-out in rear-wheel drive vehicles just because of purposeful deviation from centre point steering due to errors in steering angles of the inner and outer wheels bends. In order to compensate for this tendency, a small amount of toe-in was initially provided in such vehicles so that the wheels move perfectly straight ahead under normal turning condition. However, the initial toe-out was provided in the case of some front-wheel-drive vehicles to counter the toe-in present therein. 

In rear-wheel-drive vehicles, due to errors in the steering angles of the inner and outer bends of the wheels, there is usually an inherent tendency for the wheels to toe out. 

In rear-wheel-drive vehicles, there is usually an inherent tendency for the wheels to toe out due to purposeful deviation from centre point steering due to errors in the steering angles of the inner and outer bends of the wheels. A small amount of toe-in was initially provided in such vehicles to compensate for this tendency so that the wheels move perfectly straight ahead under the normal turning conditions. 

Toe-in generally does not exceed 3 mm. 

A toe-in wheel alignment can help to reduce oversteer problems and increase stability in front-wheel drives vehicles. 

A toe-out alignment can help to mitigate issues related to understeering and can improve the handling of a vehicle that has rear-wheel drive. 

Explore more information: 

1. What is a caster?

What is caster | Definition | Effect

Definition : 

The caster angle is called the angle between the kingpin centre line for the steering axis and the vertical in the wheel plane. 

If the centre line of the kingpin meets the ground at a point ahead of the verticle wheel centre line is called the positive caster and if it is behind the verticle wheel centre line is called the negative caster. 

Effect : 

The steering axis pulls the front tires, while the tire drag due to the weight of the vehicle is on the vertical line in the centre of the footprint. Since the positive caster steering axis would meet the ground ahead of the tire print centre, the later would always follow former, thus positive caster provides directional stability on the car wheels. 

A positive caster increases the effort required to turn the steering wheel. In the case of negative caster steering, it may be noted that it would be unstable. Example -There would be poor directional control, as in this case the centre of the tire print leads the steering axis. Extremely negative casters would cause shimmy and consequently cupped wear of the front tires. 

As the change of caster angle, the other angles of the steering geometry, the chamber, the inclination of the kingpin and the toe0in or toe-out are changed. Therefore, it is very important that this angle is adjusted first of all while doing the adjustment job. 

Approximately 3 degrees of castor gives good results. 

Explore more information:

1. Difference between caster and camber

Difference between understeer and oversteer

Understeer and oversteer both terms are both related to vehicle dynamics and especially wheel alignment. They are related to the sensitivity of an automobile to its steering. In this article, we can check out what is understeer and oversteer and the difference between them. 

What are Understeer and Oversteer?

When a car steers less than what the driver commands is called understeer and oversteer is the turning of the car more than what the driver commands. These actions depend on the changes in lateral acceleration and steering angle. 

Difference between understeer and oversteer : 

• Both of these are caused by the difference in slip angles for the front and rear wheels.

What is a slip angle?

It is basically the angle between the direction of the wheel heading or travel and the direction of the car heading or travel. 

• Understeer means lack of grip while oversteer means the front side of the vehicle has more grip than the backside. 
• When understeer happens, the driver will have little response from the steering wheel on the other side when oversteer happens, it makes the car spin when driving into a corner. 
• Understeer takes place when the vehicle's front wheels begin to plough straight despite turning the steering wheel and oversteer takes place as a result of the rear end of a car being fishtailed or sliding out. 
• Front-wheel drive cars are prone to understeer while rear-wheel cars are susceptible to oversteer. 
• Understeer most commonly happens due to early accelerating while turning in a corner so you can lift the weight distribution that takes the control off of the front tires and leads to the dangerous situation while oversteer is not something to be concerned about because it happens in everyday driving thus it could be dangerous if occurs in snowy, muddy or rainy conditions. 
• Applying more suspension or increasing the front wing can minimize the understeer and also tire pressure adjustment helps sometimes while you have to do the opposite to fix this problem you have to loosen the suspension or down-force to drop the grip. 

Explore more information:

1. Difference between caster and camber

Advantages and disadvantages of resistance welding

The resistance welding process is also a fusion welding process where both heat and pressure are applied to the joint but no filler metal or flux is added. The heat necessary for the melting of the joint is obtained by the heating effect of the electrical resistance of the joint and hence, the name is resistance welding. In this article, you can check out the advantages and disadvantages of resistance welding to understand more about it.

Advantages of resistance welding :

• It is a very economical process because there are no consumables used in this process so environment-friendly too. 
• The heating of the workpiece is confined to a very small part so less distortion.
• Very little skill is required to operate a resistance welding machine because easily automated. 
• By this process also weld dissimilar metal as well as metal plates of different thicknesses.
• Welding speed is very high.
• Weld up to 0.1 mm thin as well thick up to 20 mm metals. 
• High production rate thus suited for mass production. 
• This process does not require any filler metal, flux and shielding gas. 

Disadvantages of resistance welding :

• The resistance welding machine is highly expensive.
• Lower tensile and fatigue strength.
• It is limited only to lab joints.
• The limit of sheet metal thickness is less than 3 mm.
• Less efficient for high conductive materials. 
• High electric power is required. 

Advantages and disadvantages electrochemical machining

A method of removing metal by an electrochemical process is called electrochemical machining in short ECM. This process is usually used for mass production and working with extremely hard materials that are difficult to machine using other processes but its use is limited to electrically conductive materials. Let us have a deep insight into the advantages and disadvantages of electrochemical machining in this article. 

Advantages of Electrochemical Machining :

• The metal removal rate is quite high for high-strength-temperature-resistant (HSTR) materials as compared to the conventional process.
• Accurate machining.
• Residual stress is low.
• The surface finish is in the order of 0.2 to 0.8 microns.
• No direct contact between tool and workpiece.
• Negligible wear and tear of tool material.
• Environmental friendly.
• Possible to machine non-rigid and open workpieces.
• It can be a machine configuration that is beyond the capability of the conventional machining process.
• Extremely thin sheets of metal can be worked easily without distortion.
• A job with complex shapes can be machined easily and accurately.
• Several holes can be done at once during drilling.
• ECM is a time-saving machining process as compared to conventional machining.
• Deburring can be done in hard to access areas.
• Fragile and brittle materials can be machined easily by ECM without cracking or breaking.
• The metallic workpiece is not damaged due to thermal stresses.

Disadvantages of Electrochemical Machining :

• Power consumption is more.
• Initial tooling can be timely and costly.
• Non-conducting materials can not be machined.
• The process is costly because of expensive equipment.
• A continuous supply of electrolytes is necessary.
• Steady voltage should be maintained during the whole process.
• Corrosion and rust of the ECM machine can be a hazard.
• If hydrogen is liberated at the tool surface then it is possible to suffer from hydrogen-embitterment of the surface.
• There may be a possibility of damages because of sparks.
• Conventional machining produced more improved fatigue properties than ECM.

Advantages and disadvantages of internal expanding brake

An internal expanding brake consists of two shoes where the outer surface of the shoe is lined with some friction material to increase the coefficient of friction and prevent wearing away of the material. This type of brake is used in cars and light trucks. Let us have a deep insight into the advantages and disadvantages of internal expanding brake in this article. 

Advantages of internal expanding brake: 

• Requires little maintenance.
• It has a simple construction with a small number of parts.
• It is cheaper as compared with other types of brakes.
• It is more reliable due to the small number of parts.
• Offers protection against the entry of foreign particles.
• Produce a large braking torque with a small actuating force.

Disadvantages of internal expanding brake :

• Poor heat dissipating capacity.
• It becomes self-locking due to wear.

Advantages and disadvantages of Stirling engine

A Stirling engine is operated by cyclic compression and expansion of air or other gas at different temperatures and convert heat energy into mechanical work thus it is also called a heat engine. Let us have a deep insight into the advantages and disadvantages of the Stirling engine to know more about it. 

Advantages of Stirling engine :

• Stirling engines can run directly on any available heat source not produced by combustion so they can run heat from biological, geothermal, nuclear sources or solar.
• Most Stirling engine types have the cool side of the engine bearing and seals. They only need less lubricant and last longer than other types of engines that reciprocate.
• In some ways, the engine mechanisms are simpler than other types of engines that reciprocate.
• No valve is needed. 
• A Stirling engine uses a single-phase working fluid that keeps an internal pressure close to the pressure of design.
• Low operating pressure permits the use of lightweight cylinders in some cases.
• They can be constructed to run smoothly and without an air supply.
• In cold weather, they start easily and run more efficiently.
• They can extremely flexible.
• They can be used as CHP in winter and as a cooler in summer.
• Waste heat is easily harvested.
• Stirling engine is useful for duel-output heat and power systems.

Disadvantages of Stirling engine :

• Stirling engine requires heat exchangers for heat input and for heat output.
• For efficient operation, all thermodynamic cycles require large temperature differences.
• Dissipation of waste heat is especially complicated because coolant temperature is kept as low as possible to maximize thermal efficiency.
• A Stirling engine cannot start instantly and literally needs to warm up. It is true for all external combustion engines but for this warm-up time may be longer.

Advantages and disadvantages of abrasive jet machining

The principle of Abrasive jet machining involves the use of a high-speed stream of abrasive particles carried by a high-pressure gas or air on the work surface through a nozzle. The metal removal occurs due to erosion caused by the abrasive particles impacting the work surface at high speed. Let us have a deep insight into the advantages and disadvantages of abrasive jet machining in this article. 

Advantages of Abrasive Jet Machining :

• Abrasive jet machining is suitable for materials of any hardness and brittleness like ceramics, germanium, glass.
• Ability to cut fragile and heat-sensitive materials without damage as there is no heat generated by gas or air passage.
• Low capital cost.
• Holes of intricate shapes could be produced efficiently.
• It can be utilized for cutting, drilling, polishing, deburring, cleaning of the materials.

Disadvantages of Abrasive Jet Machining :

• The material removal rate is slow. 
• The precision of the machining is poor and the wear rate of the nozzle is high.
• Additional cleaning of the work surface may occur because the abrasive particles may remain embedded in the work surface.
• Abrasive particles cannot be reused.
• A dust collection chamber is a basic requirement to avoid causing health hazards from atmospheric pollution.

Steering axis inclination | Definition | Purpose | Effect

Definition of Steering axis or Kingpin inclination : 

The inclination of the kingpin from vertical is called the king inclination or steering axis inclination. 

Steering axis inclination causes both front wheels to gain positive camber because they steer away from the centre.

In modern cars where the kingpin has been replaced by the ball joints, this term has also been termed as steering axis inclination. It is defined as the inclination of the ball joint axis from the steering vertical axis. The steering axis is an imaginary line drawn through the lower and the upper steering pivot pins. 

Steering axis inclination is set by the dimensions of the upright and therefore no adjustable once it defined. 

Purpose of steering axis inclination :

To determine vehicle stability while moving on the straight road. 

Effect of steering axis inclination :

Kingpin inclination also called steering axis inclination helps the straight-ahead recovery, thus providing directional stability. When the vehicle takes a turn, the inclination of the kingpin causes the vehicle body to move up in relation to the wheels. So when the steering wheel is left after the turn is completed, the weight of the vehicle tends to return the wheels to the straight-ahead position. 

Amount of inclination is about 7 to 8 degrees. However, the exact amount is decided considering the wheel rack value. It is kept below 8 since too much inclination cause a lot rising of the front axle when steering. 

Wheel alignment explained | Factors | Steering geometry | Linkage

What is wheel alignment?

Wheel alignment is the positioning of the steered wheels to achieve the directional stability during straight-ahead position, perfect rolling condition on steering and recovery after completing the turn. 

Factors of wheel alignment : 

Wheel alignment is used in connection with the stability and control of the vehicle while in the situation of motion. It means that while moving straight ahead the wheels should be parallel. In the event when they are pointing inward, they are said to toe in whereas if they are pointing outward they are said to toe out. Both these situations are undesirable because in either case while rolling forward, each wheel will be simultaneously slipping laterally due to which a continuous cross-tread scrubbing would take place. 

For good handling, steering, and vehicle stability, it is also necessary that 

• There should no be any setback, which is said to be the distance between the placing of the front tyres. In other word set back is a condition in which one wheel on an axle is in front of or behind the other wheel in relation to the chassis frame. When a set back of less than 6 mm is considered normal tolerance by some manufacturers. 
• The thrust angle should be zero. Thrust angle is the angle made by the thrust line with the longitudinal centre line of the vehicle. If the thrust angle is not zero, the vehicle will dog track the steering wheel will not be centred. When the thrust angle is zero, rear wheels follow the front wheels properly. Obviously, for this condition, all the four wheels should be parallel to the frame. This is called tracking. 

For effective steering under all conditions and at all loads, it is very important to consider and understand the factors which influence the stability and control of the vehicle. The factors are following below : 

• Factors pertaining to wheels 
• Steering geometry
• Steering linkage
• Suspension system 

Factors pertaining to wheels : 

• Balance of wheels 
• Inflation of tyres 
• Brake adjustment 

Steering geometry : 

• Camber 
• Caster 
• Toe-in 
• Toe-out

Steering linkage :

• Kingpin inclination ( Steering axis inclination )
• Combined angle and scrub radius 
• Over-steer 
• Under-steer 

Requirement of good steering system

For smooth and appropriate operation and performance of the steering system vehicle should fulfil the requirement given below : 

• The steering system should be very accurate and easy to handle. 
• The effort required to The spear should be minimal and must be not tiresome to the driver. 
• The steering the mechanism should also provide directional stability implies that the vehicle should have a tendency to return to its straight-ahead position after turning.
• To provide pure rolling motion to the wheel. 
• It should be designed in such a manner that shocks of the road are not transmitted to the driver. 

Principle of steering system

The steering system used along with suspension system allow driver to safely and easily control the direction of vehicle while driving. Now you can check the some functions of steering system. 

Primary function of steering system is to achieve accurate angular motion of the front wheels to negotiate a turn. This can be done through linkage and steering gear which convert the rotary motion of the steering wheel into angular motion of the front road wheels. 

Secondary function of steering system are following below : 

• To provide directional stability when the vehicle running on the straight road. 
• To provide perfect steering condition. For example perfect rolling motion of the road wheels at all times. 
• To provide facilitate straight ahead recovery after completing a turn. 
• To minimize tyre wear.

Advantages and disadvantages of carburetor

Carburetion is the process of formation of a combustible air-fuel mixture by mixing the proper amount of fuel with air before admission to the engine cylinder. The device with does this job is called a carburettor. Let us have a deep insight into the pros and cons of the carburettor in this article. 

Advantages of carburettor :

• Carburettor parts are not as expensive as that of fuel injectors, especially EFI, which would give you large savings.
• With the use of carburettor, you get more air and fuel mixture.
• In terms of the road test, carburettors have more power and precision.
• Carburettors are not restricted by the amount of gas pumped from the fuel tank, which means that cylinders can pull more fuel through the carburettor, leading to a denser mixture in the chamber and higher power.

Disadvantages of carburettor :

• The mixture provided by a carburettor is so weak at very low speed that it will not ignite properly and some arrangement in the carburettor is required for its enrichment under such conditions.
• The working of the carburettor is affected by changes in atmospheric pressure. 
• It provides the right mixture at only one engine speed and load, therefore only suitable for engines running at a steady increase or decrease in speed.
• More fuels are consumed since carburettors are heavier than fuel injectors.
• More air emissions than fuel injectors.
• Maintenance costs of the carburettor are higher than with fuel injection system.

Advantages and disadvantages of gaseous fuel

Gaseous fuels are hydrocarbons, hydrogen and carbon monoxide mixtures present in a gaseous state that form the basis of potential heat energy or light energy that can be easily disseminated through pipes from source to place of consumption. Let us have a deep insight into the pros and cons of gaseous fuel in this article. 

Advantages of Gaseous fuels :

• They can be conveyed easily through a pipeline to the actual place of need that is the main reason for eliminating the manual labour cost in transportation.
• They can be lighted at moment's notice.
• They have high heat content and hence, help us in having high temperatures.
• They can be pre-heated by the heat of hot waste gases, thereby affording the economy in heat.
• Their combustion can readily be controlled for changes in demand like oxidizing or reducing atmosphere, length of flame etc.
• They burn without any smoke.
• They are ashless so there is no labour involved in ash handling.
• They are clean in use.
• They do not require any special burners.
• They can be produced by using even the poorest quantity of coal.
• They burn without heat loss, due to convection currents.
• They burn in slight excess of air supply.
• They are free from solid and liquid impurities.
• Complete combustion without pollution is possible due to the uniform mixing of air and fuel.
• They have high calorific value as well.
• They can also be used in internal combustion engine fuels.

Disadvantages of Gaseous fuels :

• Very large storage tank needed for them.
• They are highly inflammable, so chances of fire hazards are high in their use.
• They are more costly as compared with solid and liquid fuels.

Explore more information:

1. Advantages and Disadvantages of Fossil fuels
2. Advantages and Disadvantages of the Fuel injection system
3. Advantages and Disadvantages of Liquid fuel
4. Advantages and Disadvantages of Solid fuel
5. Advantages and Disadvantages of LPG fuel

Drum brakes vs Disc brakes | Difference

A brake is a mechanical device that slows down a motion by absorbing energy from a moving system. Braking is done due to the friction between two surfaces. The heat generated during braking is the major problem nowadays so different brakes are used where this heating problem is resolved. 

Brakes are mainly classified into three main categories mechanical brake, hydraulic brake, pneumatic and electric brake. 

Nearly the same idea as the disk and drum brake the difference is its working. They both fall under the mechanical brake. Here, you can check it out the difference between disc and drum brake. 

What is a disc brakes?

The disk brake has a metal plate in the shape of a disk and a calliper that is attached to the wheel and the disk is rotated with the car wheel. The calliper is used on the pads for exerting power. The friction lining of the calliper comes into touch with a tiny part of the disk. The reaming part of the disk enables the surroundings to dissipate the heat. Two pads are used on either side of the disk and both pads are connected to the friction lining. Calliper is connected to the non-rotating part and on both pads it exerts force. When the brake paddle is pushed, the pads are pushed against the rotating disk as well, the friction between the disk and the pads will retard the speed of a car and prevent the disk.

What is a drum brakes?

The drum brake is a small drum that rotates with the wheel and has inside a pair of shoes known as brake shoes. When the brake paddle is pressed, the brake shoes are forced against the side of the drum walls and the brake is applied by means of friction.

Drum Brakes vs Disc Brakes | Difference between the drum and disc brakes : 

• In the case of disc brakes friction surfaces are directly exposed to the cooling air, whereas in the drum brakes, the friction occurs on the internal surfaces, from which heat can be dissipated only after it has passed by conduction through the drum. 
• The friction pad in the case of disc brakes is flat as compared to curved friction linings in the case of drum brakes means that there is uniform wear of friction pads. Adding that the friction pad material is not subjected to any bending, thereby increasing the range of materials from which to choose the suitable one. Generally, we use asbestos fibre with metal oxide fillers bonded with organic compounds as the material for friction pads. 
• Unlike the standard drum brake, the design of the disc brake is such that there is no loss of efficiency due to expansion. As the system becomes hot, expansion of the drum of the internally expanding shoe type of brake tends to move the friction surfaces apart, causing a loss of effective pedal travel. On the other hand, disc expansion merely changes the relative positions on the friction surfaces slightly without tensing to increase the clearance. 
• Disc brake weighs less than their conventional drum-type counterpart, so a saving of approximately 20 to 30 % is possible. 
• The disc brake has comparatively better anti-fade characteristics as compared with drum brakes. 
• Drum brakes are simple in design as compared to disc brakes. There are very small numbers of parts to wear or do not function properly. 
• When required, replacing the friction pads is very easy compared to the type of drum where the brake lining must be either riveted or attached to the brake shoes with adhesives.
• Changes in brake factor for a unit change in friction coefficient is much less in the use of disc brakes than it is for two leading shoes or the simple, leading or trailing shoe brakes. 
• Compared to conventional drum-type brakes, the total frictional area of pads in disk brakes is very less. The approximate ratio of 1:4 means that disc brakes have greater pressure intensity than drum brakes. 
• Drum brakes are purely mechanically operated whereas disc brakes are mechanically operated but also be linked with ABS system and some other advanced technology. 
• Drum brake has less torque transmitting capacity and disc brake has high torque transmitting capacity in a small volume. 
• Disc brakes are as easy to control and have a fast response time as compared to drum brakes. 
• The drum brake may be self-locking while the disc brake lever.
• Drum brake maintenance is cheaper than disk brake maintenance.

The above point implies that frequent relining would be necessary, due to an increased rate of wear. So that there are compensating factors are the following below :

1. Pads can be made considerably thicker, for a given initial cost, so that more wear can take place before replacement is necessary. 
2. New wear-resistant friction materials that are more suitable for disk brakes than for drum brakes have been developed.

Summary : 

The only factor limiting the more extensive use of disc brakes is their initial cost. However, with further improvement in design and savings due to increased production. It is hoped that ultimately this type may replace the drum type brakes altogether at least for medium to heavy vehicles.