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Bidirectional transducers are transducers in which the electrical quantity can be transformed into a non electrical quantity and vice versa.
Piezoelectric sensors are an example of bidirectional sensors. Force can be converted into an electrical signal. An electrical signal can also be converted into an physical movement or a force.

An inverse transducer is a transducer in which an electrical signal is converted into a non electrical quantity.
An example of an inverse transducer is a piezoelectric transducer in which an electrical signal can be converted into a movement or a vibration.

Mechanical car clutches are devices for engaging and disengaging two moving parts of a shaft and a driving mechanism. A clutch assembly consists of five major components:

1. The clutch flywheel
The clutch flywheel is connected to the engine crankshaft and it spins with the engine’s motions.

2. The clutch pressure plate
Bolted to the clutch flywheel is the clutch pressure plate. It has two jobs: to hold the clutch assembly together and to release tension, allowing assembly to rotate freely.

3. The clutch disc
Between the flywheel and the pressure plate is the clutch disc. The clutch disc has friction surfaces similar to a brake pad, allowing for smooth engagement and disengagement.

4. and 5. The throw-out clutch bearing and release system
These components work together and are key to the engaging and disengaging process.
The clutch helps the engine get disconnected from the wheels, thereby stopping it.

Ventilated discs or disc brakes are hollow discs with a plate on each side. The air enters the centre to cool these plates.  Today, almost all cars have ventilated disc brakes.

In motor racing, often, duct pipes are built to direct the cold air towards the discs. Disc brakes in motor racing almost get too hot and need a lot of cold air to cool down before the next corner.

Motor bikes usually have only one plate, so they don't need to be ventilated as they have free air on both side of the plate. A car is a lot heavier and to stop it, two plates are needed. Using one thick plate instead of two thin ones would require a lot of cooling down. Cars also don't have as much air
circulating around the brakes as motorbikes do. So the best solution is to have air circulating between the two plates.

There is a vacuum-powered pressure regulator at the end of the fuel rail which ensures that the fuel pressure in the rail stays constant. Fuel injectors are connected with rail, but their valves remain closed until the ECU sends injection signal.

Usually, the injectors contain two pins. One pin is connected to the ECU. The ECU sends a pulsing ground to the injector, closing circuit. This lets the injector's solenoid get charged. The magnet on the plunger is attracted, opening the valve. The high pressure in the rail  starts fuel injection at a high velocity when the valve opens.

When the plunger rises, it opens a valve and the injector sends fuel just upstream of the intake valve, or straight into the cylinder. The first system is called multiport fuel injection and the latter is called direct injection.

The ECU decides the amount of fuel to inject into the cylinders to make the mixture stoichiometric.

Dampers are convert parts of the kinetic energy of moving parts of a machine into thermal energy and thereby diminish the hard shocks or avoid too much oscillation amplitudes.

Dampers contain a pressure tube, a piston rod with a special piston system and the damping medium oil. The piston rod is submerged in the oil-filled pressure tube with its special seal and guiding system. This actually hermetically seals the inside compartment of the hydraulic damper from the atmosphere.

 The damping oil passes through the damping bores in the piston system via the movement of the piston rod. The damping forces thereby depend on the piston speed.

By closing the damping borings on both sides by valve washers, the damping forces are regulated in the direction of extension and compression. The damping force during compression decides the hardness of a shock absorber on retraction. The damping force on extension, on the other hand, regulates the extension speed.

Diesel is a liquid fuel used in diesel automobile engines. Diesel’s fuel ignition takes place, without spark, due to compression of the inlet air mixture and then injection of fuel.
 
Diesel engines have higher thermodynamic and therefore high fuel efficiencies. Diesel engines are usually run at part-load; as the air supply is not throttled as in a petrol engine, their efficiency is very high.

The most common type of diesel fuel is a particular fractional distillate of petroleum l, but alternatives, such as biodiesel, biomass to liquid (BTL) or gas to liquid (GTL) diesel, are also being developed and adopted increasingly.

Petroleum-derived diesel is usually referred to as petrodiesel. Ultra-low-sulfur diesel (ULSD) is a specific standard for diesel fuel that has substantially low sulfur contents.

The most common measure of diesel fuel quality is the cetane number. It is a measure of the delay of ignition of a diesel fuel.

The pioneering lightweight construction technology, bundled with the expertise of and use of the development of innovations in the field of exhaust systems such as ANC (Active Noise Cancellation). Using the antisound principle, lightweight and compact exhaust systems can be produced.

Car designers are reducing vehicle weight, often by using less noise-dampening insulation in the car's interior. Using lighter materials inside, can however increases perceptible road noise inside the vehicle, which then penetrates the interior (and passenger ears).

Traditional NVH (Noise, Vibration, and Harshness) methods have difficulties in counteracting the above mentioned issues satisfactorily, and therefore these technologies also tend to add weight, which cancels out the fuel economy effect of using lighter materials.

Road Noise Cancellation (RNC) which detects and diminishes unwanted road noise, and thereby improves vehicle weight and handling without impacting interior noise levels is increasingly being used as antisound philosophy.

A silencer is a device for diminishing the loudness of noise created by the exhaust of an internal combustion engine.

Silencers are installed within the exhaust system of most engines. It is engineered as an acoustic sound-proofing tool made to reduce the loudness of the sound pressure orginited in the engine by the process known as acoustic quieting.

There are a series of passages and chambers lined with roving fibreglass insulation in the silencer system. There are also some resonating chambers harmonically tuned to create the effect of destructive interference wherein opposite and similar sound waves cancel each other out.

Some people remove or install an aftermarket silencer to increase power output or reduce fuel consumption, for recreational reasons such as motorsport and hypermiling and/or for personal sound preferences. In many countries, modification of a vehicle's silencer is usually highly regulated if not strictly prohibited.

Avgas or aviation gasoline is an aviation fuel. It is usually used in spark-ignited internal-combustion engines of aircrafts. Avgas is different from mogas (motor gasoline), which is the general gasoline used in automobiles and some light aircrafts.

Unlike mogas, which has platinum-content catalytic converters for pollution reduction, some types fo aviation gasoline still contain tetraethyllead (TEL) to prevent engine knocking (detonation).

The major petroleum component that is used in blending avgas is alkylate, a mixture of numerous iso-octanes. Some refineries also blend reformate in Avgas. All Avgas grades that meet CAN 2-3, 25-M82 have an average density of 6.01 lb/U.S. gal at 15 °C, or 0.721 kg/l.

Avgas has a lower and more uniform vapour pressure than automotive gasoline. That keeps Avgas in the liquid state even in reduced atmospheric pressure at high altitude, resulting in avoidance of vapour lock.

Avgas is now available in many grades with differing maximum TEL concentrations.

Brake linings is a layer of hard material affixed with the brake shoe or brake pad in order to increase friction against the drum or disc.

Brake linings are made of a relatively soft but wear-and-tear and heat-resistant material with a high coefficient of dynamic friction and also high coefficient of static friction. The linings are mounted to a solid metal structure using high-temperature adhesives or rivets. The complete assembly is then called a brake pad or brake shoe.

The dynamic friction coefficient "µ" for almost all of the brake pads is usually in the range of 0.35 to 0.42. In such a condition, a force of 1000 Newtons on the pad will give a resulting brake force close to 400 Newtons.

Some racing pads with a very high µ of 0.55 to 0.62 with excellent high-temperature properties are also available. These are high in iron content and they outperform other pads used with iron discs.

Aquaplaning, or hydroplaning, takes place when the water between the tyre and  road cannot be removed quickly enough. This layer of water on the tyres stays until the pressure of the water overtakes the pressure of the tyre on the road, which may result in the tyres losing contact with the road surface. As a result, the vehicle can start to skid or spin.

The presence water can let your vehicle lose contact with the road surface. A tyre running through water creates a wave ahead of it. The tyre tread hitting the water at the front of the contact patch suffers an increase of the water pressure. When the water pressure becomes greater than the average pressure of the tyre on the road surface the tyre vehicle may lose control.

Therefore the water covering the tyre must be removed quickly through tyre design to avoid aquaplaning.

Application of brake force on a vehicle wheel that is in normal contact with the pavement, results in the rubber of the tire beginning to stretch responding to friction heating and the force applied to the tire-pavement interface.

When brake force is applied, if the level of braking is increased to the levels of co-efficient of friction, mu, the wheel can no longer support the force being applied to the rubber, and hence the available stopping force begins to diminish.

Operation at the peak of the mu-slip offers the highest braking efficiency. Research suggests that a skid develops that may lock the wheel and blow the tire if unchecked.

Modern anti-skid brake control systems measure the speed of the wheel to find slip and developing a correction signal. The control unit finds out where the tire is operating on the mu-slip curve and sends a correction signal to the antiskid valve to reduce applied brake pressure. This helps the vehicle to avoid skidding.

Anti rust treatment or Rustproofing is the prevention or delaying of rusting of iron and steel objects, or the permanent protection against corrosion.

 Typically the protection is done by a process of surface finishing or treatment. Depending on mechanical wear or environmental conditions, the degradation is not permanent, unless the process is periodically repeated. The term is used frequently in the automobile industry.

In the factory, automobiles are protected with unique chemical formulations, which typically are phosphate conversion coatings. Some firms first galvanize a part or all of the automobile’s body before the primer coat of paint is applied.

If a car has a chassis, it and its attachments must also be anti-rust treated. Paint is the final part of the anti-rust treatment of barrier between the body shell and the atmosphere.

Aftermarket kits are also available that apply rustproofing compounds both to external surfaces and inside enclosed sections, for example sills/rocker panels etc.

An antique car is generally an automobile that is an antique or a vintage vehicle. Narrower definitions fluctuate depending on the age of a car.

 In the United States, generally, antique cars are of over 25 years of age, this being the definition used by the Antique Automobile Club of America. However, the legal definitions of antique vehicle registration vary far more widely.

The antique cars are those which were produced in the Veteran era, the Brass era, and the Vintage era, which are spread from the beginning of the automobile up to the 1930s. Later cars that have been produced after 1930 are often described as classic cars.

In original or originally restored condition antique cars are considered to be very valuable. These vehicles are usually either protected and stored or exhibited in car shows but they are seldom driven.
Some people also consider such collectibles to be a form of investment.

Alloy wheels are made from an alloy of aluminium or magnesium. Alloys are mixtures of metal and other elements which generally provide more strength over pure metals.

Alloys of aluminium or magnesium are lighter but provide the same strength. They also provide better heat conduction, and often are better in appearance over steel wheels.

 Although steel is an alloy of iron and carbon, the term "alloy wheel" refers usually to  wheels made from nonferrous alloys.

Lighter wheels better the handling by reducing unsprung mass which allows suspension to follow the terrain more closely and thus improve grip. However all alloy wheels are not lighter than their steel equivalents. Reduction of weight can also help to reduce fuel consumption.

Better heat conduction helps in dissipating the generated heat from the brakes, which improves braking performance in more demanding driving conditions. This improved performance of brakes reduces the chance of compromised brake performance or even failure due to overheating.

A fuel cell automobile (FCA) or fuel cell electric automobile (FCEA) is an automobile which uses a fuel cell to power its on-board electric motor. Fuel cells in automobiles create electricity to provide power to an electric motor, generally using oxygen from the air and compressed hydrogen.

A fuel cell automobile that is fuelled with hydrogen exhausts only water and heat, but no tailpipe pollutants. Therefore it is considered a zero-emissions vehicle as well. Depending on the method, however, producing the required hydrogen used in the automobile creates pollutants.

Fuel cells are used in various kinds of vehicles including forklifts, especially in indoor applications where their clean emissions are important to air quality, and in space applications. Fuel cell technology has attracted a lot of attention and research spending in recent years.

Honda FCX Clarity, Hyundai Tucson Fuel Cell and Toyota Mirai are some examples of FCA.

Wheel alignment refers to the adjustment of a vehicle's suspension that connects a vehicle to its wheels. It is not just an adjustment of the tires or wheels. The key to good alignment is in adjusting the angles of the tires that decides how the tires make contact with the road.

In a nutshell, wheel alignment means adjusting the angles of the wheels so that they make a perpendicular angle to the ground and stays parallel to each other. The purpose is getting maximum tire life and a vehicle that has straight and true tracks when driving along a straight and level road.

If your vehicle tracks like an arrow, the wheels likely are properly aligned. Even so, it is good to check alignment when you have your tires aligned.

Wheel alignment should be done when the tyres are replaced.  

Alcohols have been used as a fuel. The preliminary four aliphatic alcohols (methanol, ethanol, propanol, and butanol) are of interest as fuels because they can be synthesized chemically or biologically.

Octane Rating: Alcohol is, on the average, about 16 points higher on the research octane scale than premium gasoline.

Heat value:  There's oxygen in the alcohol's structure which means that this fuel will naturally be "leaner".  This is one reason why we must add more fuel when burning alcohol by increasing the size of the jets

Volatility :  Very volatile fuel is potentially dangerous. Alcohol, has a higher flash point than gasoline, making it a much safer automotive fuel.

Exhaust Emissions: The emission produced by a vehicle running on alcohol are far lesser than a vehicle on any other fuel.

A car burglar alarm is a security alarm. It is an electronic device used to discourage theft of the vehicle itself, its contents, or both.
Car alarms emit high-volume sounds, such as a siren, klaxon, previously recorded verbal warning, the vehicle's horn, or a combination thereof when there is any security threat or when conditions for triggering an alarm are met.
The alarm may also flash some of the vehicle's lights, and some of these alarms also notify the car's owner via a paging system. There is also an option to interrupt and stop various electrical circuits so that the car cannot be started.
Car alarms can be divided into two categories: OEM that is built in factory and Aftermarket that are installed later on.
Keyless remote car burglar alarms are generally based on strong cryptography authentication methods, including Radio receiver, Immobilizer, Motion detector and Wireless USB.

Hydraulic brakes follow a simple principle: forces applied at one point are transferred to other points by means of an incompressible fluid. In brakes we call this brake fluid.

The initial force applied is multiplied in the process by means of increasing the area of application. Therefore, the multiplication is derived by increasing the sizes of the pistons at either end.

 In braking systems, the piston at the end of application of force, driving the fluid is smaller than the pistons at the brake pads. Therefore the force is multiplied many times, helping to brake easily and more efficiently.

Another important characteristic of hydraulics is that the pipes having the fluid can be of any size, length or shape which allows the lines to be fed almost anywhere. They can also be split to let the master cylinder to operate two or more slave cylinders in case of a need.

An air brake or, a compressed air brake system, is a friction brake for vehicles in which pressing compressed air on a piston is used to apply the force to the brake pad needed to stop the vehicle.

Air brakes are generally used in large heavy vehicles, especially those having multiple compartments which must be linked into the brake system, such as trucks, buses, trailers and the railroad trains.

The system is made up of service brakes, parking brakes, a control pedal, and an air storage tank. For the parking brake, a disc or drum brake system designed to be held in the 'applied' position by spring pressure is placed.

Air pressure releases these "spring brake" parking brakes. For the service brakes to be applied, the brake pedal has to be pushed, so that the air creates pressure (approx 6.89-8.27 bar) to engage the brake chamber. This stops the movement of wheels.

During an accident, airbags inflate very quickly. Airbags are the key components in automotive safety systems, and, they soften the impact of collisions by keeping passengers from hitting the steering wheel, dashboard, front glass, and other parts of the automobile.

Airbags are made of stretchable fabrics or other materials that are tightly packed in various locations throughout your vehicle. Airbags are at the front of the dashboard in most cars, and many vehicles also have airbags on sides as well.

These bags are compressed and kept in tiny areas. During an accident, the airbags fill up with air very quickly to offer cushioning system for the people in the car so that they do not collide with car parts in the event of a crash.

The success of the airbag system depends on the crash sensors. There is also an inflator that offers an explosion of nitrogen gas, filling up the airbag during a crash.

A headlamp aimer is a means to check both the orientation and intensity of a vehicle headlamp. It is used to ensure that the headlamp meets a minimum standard for the country of use of the vehicle.

A headlight aimer comprises of a fully adjustable single optical collimated light lens assembly. This assembly is rail mounted and designed to prevent any distortion of the optical lens supporting structure during general use.

The optical lens is designed to accurately focus all types of vehicle headlamp. It is completely adjustable in the vertical plane; achieved by mounting it to a vertical column. The measurement travel of the optical lens used in the aimer is between the heights of 500mm and 1500mm, allowing the testing of all types of vehicles.

Finally, a mirror or laser at the top of the lens mounting column allows the headlight aimer to be aligned with the longitudinal axis of the presented vehicle.

Automatic guided vehicle systems are robots or unmanned machines used to safely transport all kinds of products without human intervention within production, logistic, warehouse and distribution environments.

AGVs are used to consistently and predictably transport material to places that may be serviced by fork lift trucks, conveyors, or manual cart transport. They are generally used in warehouses where high volumes of repetitive movements of material is required, but only little or no human decision making skill is applicable to perform the movement. They are very useful in serving processes where there is no change is contact and use of barriers - such as conveyors - are undesirable in AGVs.

Application of the AGV has broadened during the late 20th century. AGVs often follow markers or wires in the floor, or use own vision, or magnets, or lasers for navigation within a limited range of transportation.

A catalytic converter is a part of automobiles that uses a catalyst to convert three harmful compounds in the exhaust into harmless compounds.

The three harmful compounds are:

Hydrocarbons (unburned gasoline)
Carbon monoxide ( created due to combustion of gasoline)
Nitrogen oxides (created when nitrogen in the air combines with oxygen)

Carbon monoxide is a dangerous poison for any air-breathing animal. Nitrogen oxides create smog and acid rain, and hydrocarbons create smog.

In a catalytic converter, the catalyst, either platinum and palladium, is coated onto a ceramic honeycomb or ceramic beads that are placed in a muffler-like package on the exhaust pipe. The catalyst converts carbon monoxide into carbon dioxide, hydrocarbons into carbon dioxide and water, and nitrogen oxides back into nitrogen and oxygen.

A diesel particulate filter (or DPF) is a device created to remove the diesel particulate matter or soot from the exhaust gas of a diesel engine.

As with any filter they have to be regularly cleaned to maintain performance. This cleaning process is called 'regeneration' in which the collected soot is burnt off at high temperatures.

Passive regeneration occurs automatically on fast A-road runs when the exhaust temperature is high. However, many cars don't get this sort of use and hence vehicle manufacturers design an 'active' regeneration processor.

When the soot loading in the filter approaches about 45%, the vehicle's ECU will initiate post combustion fuel injection to increase the exhaust temperature to optimum levels and trigger active regeneration.

A regeneration cycle takes place when driving a journey for 10 minutes or so at speeds greater than 40mph.

Charge-Air Cooler is an air-to-air or air-to-liquid heat exchange device used to improve the volumetric efficiency of internal combustion engines by increasing intake air-charge density through isochoric cooling. A fall in air intake temperature offers a denser intake charge to the engine and offers more air and fuel to be combusted per engine cycle, which increases the performance of the engine.

In the past, turbochargers were run in stages. The first stage compressor fed the inlet of the second stage compressor which, in turn, would further compress the air before it enters the engine. Extremely high pressure is developed in such arrangements and a charge-air cooler is placed between the first and second stage compressors. That cooler is called the "Intercooler".

Another charge-air cooler is often positioned after the second stage, which is the final compressor stage, and that is called the "aftercooler". An aftercooler is a type of cooler whose outlet fed the engine.

There is a process called incineration or combustion which is actually rapid oxidation that can be used to convert VOCs and other gaseous hydrocarbon pollutants to carbon dioxide and water. Incineration is ideally accomplished in a special incinerator called an afterburner.

An afterburner is generally made of a steel shell lined with refractory materials such as firebrick. The refractory lining saves the steel shell and acts as a thermal insulator. When enough time and high enough temperatures are used, gaseous organic pollutants get completely oxidized, with an incineration efficiency approaching near 100 %.

To get complete combustion of the VOCs and other hydrcarbons, the afterburner must offer the proper amount of turbulence and burning time, and it must also maintain high enough temperature.

Afterburners are generally used to control odours, destroy toxic compounds, or reduce the amount of photochemically reactive substances released into the air.

The air-fuel ratio is the ratio of weight of air to that of gasoline mixed by the carburettor for ideal combustion by the engine. This ratio of paramount importance because there are limits to how rich (with more fuel) or how lean (with less fuel) it may become, and still stay fully combustible for an efficient firing and better engine performance.

The engine can operate with an air fuel ratio that ranges from 8:1 to 18.5:1 i.e. from 8 kg of air/kg of fuel to 18.5 kg of air/kg of fuel.

Stoichiometric Air-Fuel Ratio

It is the ideal ratio at which all of the fuels blend with all available oxygen in the air and be completely burned. An air fuel ratio of about 14.7:1 i.e. 14.7 kg of air/kg of gasoline produce this ratio, but the exact ratio can vary somewhat.

Aerodynamic Drag is the force that opposes an automobile’s motion through the air. Drag is created in the direction of the moving air when the air pressure encounters a solid object. Drag is generally undesirable because power is required to overcome it.

To quantify the amount of drag on an automobile, we use a value called the drag coefficient (cd). This number depends on the shape of the automobile , its speed and surface roughness, the density of the air and the nature of the air flow (laminar (smooth) or turbulent).

Forces that influence drag include the air pressure against the automobile, the amount of friction along the sides of the automobile’s body and the relatively negative pressure, or suction, on behind the automobile.


Fuel additives are compounds used to enhance the quality and efficiency of the fuels. Sometimes, the additive is injected into the gasoline itself; at other times, the fuel additive is added from outside. The aim of fuel additives is to improve or maintain the optimum performance of the engines.

Fuel additives may boost the octane level of the gasoline. This helps the engine derive more power from the same amount of gas. This offers the ability to travel longer with the same amount of fuel.  
Engine maintenance is another task of fuel additives. With these types of additives, the focus is on preventing the gathering of sludge and other unwanted deposits in different areas of the engine. 

Because of lesser buildup of sludge in the lines and in the various moving parts on the motor, the engine life is effectively prolonged.
Types of additives range wide and include metal deactivators, oxygenates, corrosion inhibitors and antioxidants.

For a true rolling of a four wheeled vehicle moving on a curved track, the straight lines drawn through all the wheel axes must intersect at the instantaneous centre.

The Ackermann steering uses the two front steered wheels pivoted at the finishing points of an axle-beam. There is an original Ackermann linkage which usually has parallel set track-rod-arms ensuring that both steered wheels swivel equally. Consequently, the projection lines do not meet at one point.
In case both of the front wheels are allowed follow their own natural paths, they would ultimately
converge and come across each other. As the vehicle will have to move along one mean path, so both of the wheel tracks would conflict which may cause tyre slip and tread scrub.

Therefore a modified linkage is used at inclined track-rod arms so that the inner wheel swivels about the king-pin a little bit more than the outer wheel.

Acceptance testing is basically done by the user or customer to establish confidence in the system. In case of automobiles, the vehicle is checked whether it meets certain standards in terms of safety and performance etc.

The types of acceptance testing applied to automobiles are:
The User Acceptance test: is done to test the functionality to validate the fitness-for-use of the system by the user. User acceptance test is done by the users and application managers.

The Operational Acceptance test: is also known as Production acceptance test. It validates whether the system meets the standards for operational reasons. In most of the organization the operational acceptance test is performed by the administrators before the vehicle is released for sale. 

Compliance acceptance testing: is done because the governmental, legal or safety regulations must be adhered to.
Various other testing including safety and mobility may also be done as acceptance testing from time to time for automobiles.

For an automobile to get smooth acceleration, advancement in the timing and an increase in fuel flow are required. There is a vacuum distributor in automobile carburettor that senses when you open the throttle and then it provides the extra advance timing. The accelerator pump provides the extra fuel needed for acceleration.

The accelerator pump is usually connected by to the accelerator; when momentary acceleration is required, the pump squirts fuel directly into the carburettor for increasing the amount of fuel-to-air concentration.

Most carburettors contain a small bent brass pipe pointing straight down it-- it is called the delivery tube. When the throttle arm is pulled firmly, a squirt of fuel flows into the carburettor right from the delivery tube.


This increased fuel increases the power of the engine and the automobile gets an instant acceleration. The accelerator pump must be adjusted suitably for optimum performance, and it is wrong to believe that the more fuel the pump injects, the better it is for the vehicle.

An automobile air conditioner has the following:

Compressor: This is the heart of your a/c system. The compressor intakes the refrigerant (the gas) and pressurizes it so that it cools the air. An engine belt runs it.

Condenser: The condenser is like a miniature. The condenser has its own electric cooling fan, too. The hot, compressed air passes through the condenser and gets cooler.

Evaporator: The evaporator does just the opposite task as the condenser. When the cooler liquid passes through its tubes, air is forced through and gets really cold. When it warms, the refrigerant starts turning back into a gas.

Thermal Expansion Valve: To save from excess cooling, the a/c system has a valve that controls the flow of super-cool refrigerant to the evaporator. 


Drier or Accumulator:  The compressor compresses the gas form of your refrigerant. However, some liquid could make it back that far. The drier catches this liquid before it can damage the compressor. 

A bumper is a kind of structure attached in the front and rear of an automobile to absorb impact in a minor collision, ideally minimizing repair costs. Bunpers are standard equipments that are commonly used in vehicles nowadays.

Bumpers also have two major safety functions: diminishing height mismatches between vehicles, and safeguarding pedestrians from major injury.

The bumper structure on modern automobiles usually have a plastic cover over a reinforcement bar made up of steel, aluminum, fiberglass composite, or plastic.

Bumpers save other vehicle components by dissipating the impact of kinetic energy generated in a collision. This energy is a function of vehicle mass and velocity squared. In formula form, it is given by  which suggests that a vehicle protecting the components at 5 km/ hr must be four times stronger than the bumper that protects at a 2.5 km/hr.

A shock absorber or shock damper is a mechanical or hydraulic device designed to absorb and decrease the impact of a shock impulses. Shock absorbers convert the kinetic energy of the shock to some other form of energy to dissipate it. A shock absorber is a type of dashpot.

Most used in vehicles, shock absorbers reduce the effect jerks, resulting in improved ride quality and vehicle handling.

There are two major types of shock absorbers: Twin tube and Mono tube.
Twin tube: Also called a "two-tube" shock absorber, this device has two nested cylindrical tubes, the inner, "working tube" and an outer "reserve tube". Twin tube shock absorbers can be basic, gas charged, position sensitive, acceleration sensitive or coilovers.


Mono tube: the mono-tube shock absorber is a gas-pressurized shock absorber that also comes in a coilover format. It is made up of only one tube, the pressure tube, however, it has two pistons.

Sandpaper or Glasspaper are a type of coated abrasive that consists of sheets of paper or cloth with abrasive material affixed to one face. Nowadays, sand or glass is not used. 

Sandpaper is produced in different sizes and is used to remove unwanted material from surfaces, either to make them smoother (in painting and wood finishing), to remove a layer of material (e.g. old paint), or to make surface rougher (in gluing). 

Types
Backing:  Backing for sandpaper can have clothes (cotton, polyester, and rayon), PET film, and "fibre", or rubber apart from the paper.

Material: Garnet, emery, aluminium oxide, silicon carbide, alumina-zirconia, Chromium(III) oxide, ceramic aluminium oxide can also be used in sandpapers.

Bonds: Different adhesives, such as Hide glue, are used to bond the abrasive to the paper. Waterproof sandpapers use resin bond and a waterproof backing.

Open coat sandpapers have particles that are separated from each other and it is more flexible.

Abrasive Disc is a disc of abrasive material that rotates in a tool such as a sander. Abrasive discs are used usually for use in stock removal, blending, finishing and polishing applications. 

Abrasive discs use the combination of several minerals, resin systems and backings for better functionality. This combination results in a wide range of products to meet various requirements for use on most wood, metal, composite, gel coat, painted substrates or hard‑to‑grind materials.

The discs are generally manufactured using a composite material with coarse-particle aggregate pressed and attached together using a cementing matrix to give it a solid, circular shape. Depending on the intended usage of the disc, various forms and cross sections are available. 

Abrasive Discs may also be built using a solid steel or aluminium disc with particles bonded to the surface. Most abrasive discs are artificial composites of artificial aggregates, but initially natural composite stones (millstones) were also used.

An Abrasive Cleaner is a type of mechanical cleaner that physically removes dirt, stains and tarnish the surface.  They are made up of particles or physical abraders and use friction to remove the dirt stains etc. Physical abraders include sandpaper, steel wool, scrubbing pads, etc.  Abrasiveness usually depends or coerciveness of the used material.

Depending on the harshness, there are three types of Abrasive Cleaners.
Mild Abrasives such as fine plastic mesh pads, soft brass wool, nylon coated sponges, rotten-stone and whiting are often used to clean pots and pans, interiors of ovens, and drip pans.

Examples of Moderate Abrasive Cleaners are fine pumice and fine steel wool. Steel wool has grades from 0000-super fine, 000-extra fine, 00-very fine, 0-fine, 1-medium, 2-medium coarse and 3-0 coarse.

Strong Abrasives are the strongest among abrasives. Examples include medium and coarse steel wool, metallic mesh cloths and balls, metallic brushes, coarse pumice, and sand/silica etc.