ME - Mechanical Engineering
Online resource for Mechanical Engineers

In this post We have written the top 15 most Popular automobile car manufacturing companies. We have given ranking to automobile companies by considering number of followers to company in social media. Social media that we have considered are google+, twitter and facebook. Calculation of number of followers is made on basis of calculating sum of total followers in facebook, google+ and twitter . Only the company's worldwide social accounts are considered (Regional social media accounts are not considered while making this analysis). If the company doesn't have worldwide account, USA accounts are considered for making analysis.

15. Volkswagen Group

Volkswagen is an German automobile manufacturer. Volkswagen group products are Automobiles, commercial vehicles, engines, motorcycles, turbomachinery. Vw stands 15th position in social media followers.

14. Mitsubishi

Mitsubishi is an autonomous Japanese multinational companies. Mitsubishi products are Mining, shipbuilding, telecom, financial services, insurance, electronics, automotive, construction, heavy industries, real estate, foods and beverages, chemicals, steel.etc. This company stands 14th position in social media followers with 2,299,000 fans as on 15th August.

13. Mazda

Mazda Motor Corporation is a Japanese automobile company. Mazda manufactures luxury vehicles, commercial vehicles, engines and motorcycles. It has 2720k fans with thirteenth position.

12. Toyota

Toyota is a Japanese Automotive Manufacturer. Toyota Motor Corporation manufactures luxury vehicles, commercial vehicles, engines and motorcycles. Toyota has 2771k fans on three social media.

11. Chrysler

Chrysler is an American Automobile Manufacturer owned by Italian company Fiat. Chrysler manufactures Commercial vehicles and Automotive parts. Chrysler and GM have nearly same number of followers in social media.

10. General Motors

General Motors is known as GM. It is an American Multinational corporation. General Motors manufactures are Automobile parts Commercial Vehicles. GM couldn't be successful in getting followers from facebook it stands 10th position with 2883k  fans.

9. Fiat

Fiat is the main Italian car manufacturer, founded in 1900. It owns the company Chrysler. Fiat products are Automobiles, commercial vehicles, auto parts, newspapers. Fiat company has 30 lakh followers in social media which makes it to stand in ninth position.

8. Honda

Honda Motor Company Ltd. is a Japanese company famously known as a manufacturer of automobiles, motorcycles and power equipment. Honda is the world largest two wheeler manufacture from the past 50 years. Honda has nearly 40 lakh fans.

7. Hyundai

Hyundai Group is a multinational chaebol headquartered in Seoul, South Korea. Honda was founded in 1947 as a construction. Hyundai products are Automobiles, Heavy industry, Finance and Insurance, Construction, Engineering, Retail, Aerospace, Defense and Steel. Hyundai has good number of fans in social media which sums up to 4,411,000 including facebook, google+, twitter.

6. Kia

Kia Motors Corporation is South Korea's second-largest automobile manufacturer. Kia's products are automobiles, Luxury cars and Commercial vehicles. It stands sixth in position in social media following with around 5 billion followers.

5. Ford Motor

Ford Motor company is an American multinational Automaker. Ford Motor Company Automobile products are Luxury Vehicles Commercial Vehicles Automotive parts. Ford stands fifth in social media fans with 4,988,000 followers.

4. Audi

Audi is a German automobile manufacturer that designs, engineers, produces, markets and distributes automobiles. Audi manufactures only luxury cars. It has clear leader on twitter with 810,000 fans, with overall 11,667,000 fans.

3. Nissan Group

Nissan Group products are Industrial machinery, telecommunications, power plants, information systems, electronics, automotive, materials, financial services, construction. It is third position with 13,791,000 followers.

2. Mercedes-Benz

Mercedes-Benz is a German automobile manufacturer, a multinational division of the German manufacturer Daimler AG. Mercedes-Benz is used for luxury automobiles, buses, coaches and trucks. Benz stands second in social network with 19,857,000 fans.

1. BMW Group

BMW (Bayerische Motoren Werke AG) is a German automobile company. BMW products are luxury vehicles, motorcycles and bicycles.
It stands first position in the social media with 23,276,000 followers.

Below table shows the social media fans count to top 15 automobile manufacturing companies.

There is no positive correlation between increase in sales and increase in social media fans.
All these data were collected on August 15th, 2014.
A temperature scale is established by assigning numerical values to certain reproducible states. It is customary to use the fixed points ice point and steam point.
Ice point is the equilibrium temperature of ice with air-saturated water at a pressure of 101.325 kPa which assigned a value of 0 degree centigrade.
Steam point is the equilibrium temperature of pure water with its own vapor at 101.325 kPa which is assigned a value of 100 deg C.
The temperature scale with the above fixed points is called Celsius scale.

Relationship between different temperature scales
temperature conversion from one scale to another scale
LPF = Lower Fixed Point,
UPF = Upper Fixed Point.
F = Fahrenhiet scale,
C = Centigrade scale,
K = Kelvin scale
R = Reaumer’s scale,
ρ = Our defined scale,
temperature conversion formulae
Below I have given the program for converting temperature from one scale to another scale. Write the value of any one scale and then press 'Calculate' then you will get corresponding values in the remaining scales.

Temperature Scale Converter

Fahrenheit Scale(F): 
Celsius Scale (C): 
Reaumer Scale (R): 
Kelvin Scale (K): 

Welding, Soldering and Brazing are the process used for joining separate pieces of metal. Each type of joining process has its own significance. Type of joining process to be used depends on many factors. In this article I have written the three major differences the welding, soldering and brazing joints.

Welding joints are strongest joints used to bear the load. Strength of the welded portion of joint is usually more than the strength of base metal.

Soldering joints are weakest joints out of three. Not meant to bear the load. Use to make electrical contacts generally.

Brazing are weaker than welding joints but stronger than soldering joints. This can be used to bear the load up to some extent.

2 Temperature required is 3800 degree Centigrade in Welding joints.

Temperature requirement is up to 450 degree Centigrade in Soldering joints.

Temperature may go to 600 degree Centigrade in Brazing joints.

3 Work piece to be joined need to be heated till their melting point. Heating of the work pieces is not required Work pieces are heated but below their melting point.
The Wien's Displacement Law states that a black body having a wavelength (λmax) carrying the maximum energy is inversely proportional to the absolute temperature (T).

λmax * T = b

Where, λmax  =  Wavelength of maximum intensity in meters,
T  =  Temperature of the black body in kelvins,
b  = Wien's displacement constant  =  2.898 × 10^(-3) meter.kelvins

weins Displacement law graph of power density vs wavelength
Image Credits : Hyperphysics

Wien's Displacement law equation is useful for the find the temperatures of hot radiant bodies such as stars and used for a finding of the temperature of any radiant object which is far above that of its surroundings.

The LMTD is a logarithmic average of the temperature difference between the hot and cold fluid streams at each end of the heat exchanger. The larger the value of LMTD, the higher heat is transferred.
The rate of heat transfer can be expressed as q = U*A*ΔTm
Where ∆Tm is the log mean temperature difference given as
log mean temperature difference

Parallel Flow Heat Exchanger
Parallel Flow Heat Exchanger LMTD

Counter Flow Heat Exchanger
Counter Flow Heat Exchanger LMTD

Assumptions made in LMTD method are

  • The Internal Energy (U) is constant throughout the Heat Energy
  • Cp and m are constant.
  • The Heat Exchanger is perfectly insulated
  • The Cross Section of stream is uniform
  • No conduction of heat along the tubes of Heat Exchanger
  • The Kinetic Energy and Potential Energy changes are negligible
  • The flow conditions are steady
Gas Laws explain the behavior of an ideal gas in terms of Temperature, Pressure, Volume. The following are some of the important gas laws are
  • Boyle’s Law
  • Charles Law
  • Gay-Lussac’s Law
  • Avogadro’s law
  • Universal Gas Law

Boyle’s Law:

Boyle’s law states that the volume of a given mass of gas (V) is inversely proportional to its absolute pressure (P), provided the temperature of the gas (T) remains constant.
Boyle’s law formula
boyles law equation

Charles Law:

According to Charles law, the volume of a given mass of gas (V) is directly proportional to its absolute temperature (T), when its pressure remains constant.
Charles law formula
Charles law equation

Gay-Lussac’s Law:

Gay-Lussac's Law is also know as Amontons’ law. It states that if the volume of a given mass of a gas (V) is kept constant, then the pressure of the gas (P) is directly proportional to its absolute temperature (T).
Gay-Lussac's Law Formula

gay lussacs law equation

Avogadro’s Law:

Avogadro's law states that equal volumes of different perfect gases, at the same temperature (T) and pressure (P), contain equal number of molecules (n).
Avogadro’s law equation
avogadros law formula

Universal Gas Law:

Combined Gas law is derived from the three gas laws Boyles law, Charles law and Gay-Lussacs law.
Universal Gas Law Formula
universal gas law equation
free body diagram of body sliding in friction
The sliding of a solid body in contact with another solid body is always opposed by  force of friction. Friction acts in the direction opposite to that of relative motion and it is tangential to the surface of two bodies at the point of contact.
Friction is a necessary in every machine because it involves wearing of machine component and consumes energy that transfers into heat. In come cases friction is desirable in case for functioning of a machine, such as belt drives, friction clutches.

The Five Laws of Friction:

  1. When a body is moving, the friction is directly proportional to normal force and frictional force direction is perpendicular to the normal force.
  2. Friction doesn't depend on the area of contact so long as there is an area of contact.
  3. The coefficient of static friction is slightly higher the value than the coefficient of kinetic friction.
  4. Kinetic friction is independent of velocity of the body.
  5. Friction depends upon the type of the surfaces in contact.
A manometer is a device used for measure the pressure of a fluid by balancing it with against a column of a liquid. Five different types of manometers are shown with pictures below.

U-Tube Manometer :

It consist a U – shaped bend whose one end is attached to the gauge point ‘A’ and other end is open to the atmosphere. It can measure both positive and negative (suction) pressures. It contains liquid of specific gravity greater than that of a liquid of which the pressure is to be measured.
U-Tube Manometer
where 'γ' is Specific weight, 'P' is Pressure at A.
Pressure at A is P = γ2h2 – γ1h1

Differential Manometer :

A U-Tube manometric liquid heavier than the liquid for which the pressure difference is to be measured and is not immiscible with it.

Differential Manometer
Pressure difference between A and B is given by equation
PA – PB = γ2h2 – γ3h3 – γ1h1

Inverted U-Tube Manometer :

Inverted U-Tube manometer consists of an inverted U - Tube containing a light liquid. This is used to measure the differences of low pressures between two points where where better accuracy is required. It generally consists of an air cock at top of manometric fluid type.
Inverted U-Tube Manometer
Pressure difference can be calculated from equation
P1 - ρ1*g*H1 – ρm*g(H2 – H1) = P2 – ρ2*gH2

Micro Manometer :

Micro Manometer is is the modified form of a simple manometer whose one limb is made of larger cross sectional area. It measures very small pressure differences with high precision.
Micro Manometer
Let 'a' = area of the tube,
A = area of the reservoir,
h3 = Falling liquid level reservoir,
h2 = Rise of the liquid in the tube,
By conversation of mass we get A*h3 = a*h2
Equating pressure heads at datum we get 
P1 = (ρm ρ1)*gh3 + ρm*gh2 - ρ1*gh1

Inclined Manometer :

Inclined manometer is used for the measurement of small pressures and is to measure more accurately than the vertical tube type manometer. Due to inclination the distance moved by the fluid in manometer is more.
Inclined Manometer
Pressure difference between A and B is give by equation
Governor is a device used to maintain the speed of an engine within specified limits when the engine works in varying of different loads.
Based on the source of controlling force, the governors can be classified into two types. They are centrifugal governors and inertia governors.

Centrifugal Governors :

In centrifugal governors, multiple masses know as governor balls, are responsible to revolve about the axis of a shaft, which is driven through suitable gearing from the engine crankshaft. Each ball is acted upon by a force which acts in the radially inward direction and is provided by dead weight, a spring or a combination of two. This force is commonly called as the controlling force and it will increase as the distance of the ball from the axis of rotation increases. The inward or outward movement of the ball is transmitted by the governor mechanism to the valve which controls the amount of energy supplied to the engine.

Centrifugal governor
Image Source :

Inertia Governor :

In inertia governors, the balls are arranged in manner that the inertia forces caused by angular acceleration or retardation of the governor shaft tend to change their position. The obvious advantage of inertia governor lies in its rapid response to the effect of a change of load. This advantage is small, however by the practical difficulty of arranging for the complete balance of the revolving parts of the governor. For this reason Centrifugal governors are preferred over the inertia governors.
In statics, Lami's theorem is an equation that relates the magnitudes of three coplanar, concurrent and non-collinear forces, that keeps a body in static equilibrium.
Lami’s theorem states that if three forces acting at a point are in equilibrium, each force is proportional to the sine of the angle between the other two forces.
Consider three forces A, B, C acting on a particle or rigid body making angles α, β and γ with each other.

Lami's Theorem

According to Lami’s theorem , the particle shall be in equilibrium if
Lami's Theorem condition
The angle between the force vectors is taken when all the three vectors are emerging from the particle.

A belt is a looped strip of flexible material used to mechanically link two or more rotating shafts. A belt drive offers smooth transmission of power between shafts at considerable distance. Belt drives are used as source of motion to transfer to efficiently transmit power or to track relative movement.

Image source :

Types of Belt Drives:

In a two pulley system, depending upon direction the belt drives the pulley, the belt drives are divided into two types. They are open belt drive and crossed belt drive. The two types of belt drives are discussed below in brief.

Open belt drives :

open belt drive
An open belt drive is used to rotate the driven pulley in the same direction of driving pulley.  In motion of belt drive, power transmission results makes one side of pulley more tightened compared to the other side.  In horizontal drives, tightened side is always kept in the lower side of two pulleys because the sag of the upper side slightly increases the angle of folding of the belt on the two pulleys.

Crossed belt drive
Crossed belt drives :

A crossed belt drive is used to rotate driven pulley in the opposite direction of driving pulley. Higher the value of wrap enables more power can be transmitted than an open belt drive. However, bending and wear of the belt are important concerns.

Advantages of belt drives :

  • Belt drives are simple are economical.
  • They don't require Parallel shafts.
  • Belts drives are provided with overload and jam protection.
  • Noise and vibration are damped out. Machinery life is increased because load fluctuations are shock-absorbed.
  • They are lubrication-free. They require less maintenance cost.
  • Belt drives are highly efficient in use (up to 98%, usually 95%).
  • They are very economical, when distance between shafts is very large.

Disadvantages of belt drives :

  • In Belt drives, angular velocity ratio is not necessarily constant or equal to the ratio of pulley diameters, because of slipping and stretching.
  • Heat buildup occurs. Speed is limited to usually 35 meters per second. Power transmission is limited to 370 kilowatts.
  • Operating temperatures are usually restricted to –35 to 85°C.
  • Some adjustment of center distance or use of an idler pulley is necessary for wearing and stretching of belt drive compensation. 

Newton's three laws of motion

Newton’s First Law of Motion :

Newton’s first law of motion states that every object will remain at rest or in uniform  motion in a straight line unless compelled to its state by the action of an external force.
The first law of motion is normally taken as the definition of inertia. If there is no net force acting on an object then object will remain a constant velocity. If an external force is applied, the velocity of body will change because of force.

Newton’s Second law of Motion :

Newton’s Second law of motion states that if the resultant force acting on a particle is not zero, the particle will have acceleration proportional to the magnitude of the resultant and in the direction of this resultant force.  This law explains how velocity of an object changes when it is subjected to an external force. The law defines force to be equal to change in momentum (mass times velocity) per unit time.
For an object  with constant mass m, Newton’s second law of motion states that the force 'F' is the product of an object’s mass 'm' and its acceleration 'a'.
F = m.a
For an externally applied force, the acceleration depends on mass of the object and a change in velocity will generate a force. The above equation works in both ways.

Newton’s Third Law of Motion :

Newton’s third law of motion states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object 'A' exerts a force on object 'B', then object 'B' also exerts an equal force on object 'A'.
The third law of motion can be used to explain the generation of lift by a wing and the production of thrust by a jet engine.

Heat exchanger is a process equipment designed for the effective transfer of heat energy between two fluids. For the heat transfer to occur two fluids must be at different temperatures and they must come thermal contact. Heat exchange involve convection in each fluid and conduction through the separating wall. Heat can flow only from hotter to cooler fluids, as per the second law of thermodynamics.

Fin type heat exchanger

Heat exchangers can be classified into four types, according to

1. Nature of heat exchange process:

  • Direct contact heat exchanger: this is done by complete physical mixing of heat and mass transfer. Examples are water cooling towers and jet condensers in steam power plants.
  • Regenerator: here hot and cold fluids flows alternately when hot fluid passes, the heat is transferred to the solid matrix and then stopped the flow of hot fluid, next cold fluid is passed on the matrix which takes heat from solid matrix. Examples are Open hearth and blast furnaces.
  • Recuperator: the cold fluid flows simultaneously on either side of a separating wall. Examples are super heaters, condensers, economizers and air pre-heaters in steam power plants, automobile radiators.

2. Relative direction of motion of fluids:

According to flow of fluids, the Heat Exchangers are classified into three categories:

2.1 Parallel flow heat exchangers:

In parallel flow heat exchangers, both the tube side fluid and the shell side fluid flow in same direction. In this case, the two fluids enter the heat exchanger from the same end with a large temperature difference.

2.2 Counter flow heat exchangers:

In counter flow heat exchangers, the two fluids flow in opposite directions. Each of the fluids enter the heat exchanger from opposite ends. Because the cooler fluid exists the counter flow heat exchanger at the end where the hot fluid enters the heat exchanger, the cooler fluid will approach the inlet temperature of the hot fluid.

2.3 Cross flow heat exchangers:

In cross flow heat exchangers, one fluid flows through tubes and second fluid passes around the tubes perpendicularly.

3. Mechanical Design of Heat Exchanger Surface:

  1. Concentric tubes
  2. Shell and tube
  3. Multiple shell and tube passes

4. Physical state of heat exchanging:

  1. Condenser
  2. Evaporator

The following are the important dimensions and geometries concerned with toothed gear:

Pitch Circle :

Pitch circle is the apparent circle that two gears can be taken like smooth cylinders rolling without friction.

Addendum Circle :

Addendum circle is the outer most profile circle of a gear. Addendum is the radial distance between the pitch circle and the addendum circle.

Dedendum Circle :

Dedendum circle is the inner most profile circle. Dedendum is the radial distance between the pitch circle and the dedendum circle.

Clearance :

Clearance is the radial distance from top of the tooth to the bottom of the tooth space in the mating gear.

Gear Terminology

Backlash :

Backlash is the tangential space between teeth of mating gears at pitch circles.

Full Depth :

Full depth is sum of the addendum and the dedendum.

Face Width :

Face width is length of tooth parallel to axes.

Diametral Pitch :

Diametral pitch (p) is the number of teeth per unit volume.
p =  (Number of Teeth) / (Diameter of Pitch circle)

Module :

Module (m) is the inverse of diametral pitch.

m = 1/p

Circular Pitch :

Circular pitch is the space in pitch circle used by each teeth.

Gear Ratio :

Gear ratio is numbers of teeth of larger gear to smaller gear.

Pressure Line :

Pressure line is the common normal at the point of contact of mating gears along which the driving tooth exerts force on the driven tooth.

Pressure Angle :

Pressure angle is the angle between the pressure line and common tangent to pitch circles. It is also called angle of obliquity. high pressure angle requires wider base and stronger teeth.

Pitch Angle :

Pitch angle is the angle captured by a tooth.
Pitch angle = 360/T

Contact Ratio :

Contact ratio is angle of angle of action and pitch angle.

Path of Approach :

Path of approach is the distance along the pressure line traveled by the contact point from the point of engagement to the pitch point.

Path of Recess :

Path of recess is the distance traveled along the pressure line by the contact point from the pitch point to the path of disengagement.

Path of Contact :

Patch of contact is the sum of path of approach and path of recess.

Arc of Approach :

Arc of approach is the distance traveled by a point on either pitch circle of the two wheels from the point of engagement to the pitch.

Arc of Recess :

Arc of recess is the distance traveled by a point on either pitch circle of the two wheels from the point to the point of disengagement.

Arc of Contact :

Arc of contact is the distance traveled by a point on either pitch circle of the two wheels during the period of contact of a pair of teeth.

Angle of Action :

Angle of action is the angle turned by a gear during arc of contact.

Gears can be classified according to relative positions of their shaft axes into three types. They are:
1. Gears for Parallel shafts
2. Gears for Intersecting Shafts
3. Gears for Skew Shafts

Different types of Gears.
Different types of gears

1. Gears for Parallel Shafts:

The motion between parallel shafts is same as to the rolling of two cylinders. Gears under this category are the following:

1.1 Spur Gears:

Straight Spur gears are the simplest form of gears having teeth parallel to the gear axis. The contact of two teeth takes place over the entire width along a line parallel to the axes of rotation. As gear rotate , the line of contact goes on shifting parallel to the shaft.

Spur Gears

1.2 Helical Gears:

In helical gear teeth are part of helix instead of straight across the gear parallel to the axis. The mating gears will have same helix angle but in opposite direction for proper mating. As the gear rotates, the contact shifts along the line of contact in in volute helicoid across the teeth.

Helical Gears

1.3 Herringbone Gears:

Herringbone gears are also known as Double Helical Gears. Herringbone gears are made of two helical gears with opposite helix angles, which can be up to 45 degrees.

Herringbone gears

1.4 Rack and Pinion:

In these gears the spur rack can be considered to be spur gear of infinite pitch radius with its axis of rotation placed at infinity parallel to that of pinion. The pinion rotates while the rack translates.

Rack and Pininon

2. Gears for Intersecting Shafts:

The motion between two intersecting shafts is equivalent to the rolling of two cones. The gears used for intersecting shafts are called bevel gears. Gears under this category are following: 

2.1 Straight Bevel Gears:

Straight bevel gears are provided with straight teeth, radial to the point of intersection of the shaft axes and vary in cross section through the length inside generator of the cone. Straight Bevel Gears can be seen as modified version of straight spur gears in which teeth are made in conical direction instead of parallel to axis.

Straight Bevel Gears

2.2 Spiral Bevel Gears:

Bevel gears are made with their teeth are inclined at an angle to face of the bevel. Spiral gears are also known as helical bevels.

Spiral Bevel Gears

3. Gears for Skew Shafts:

The following gears are used to join two non-parallel and non-intersecting shafts.

3.1 Hypoid Gears:

The Hypoid Gears are made of the frusta of hyperboloids of revolution. Two matching hypoid gears are made by revolving the same line of contact, these gears are not interchangeable.

Hypoid Gears

3.2 Worm Gears:

The Worm Gears are used to connect skewed shafts, but not necessarily at right angles. Teeth on worm gear are cut continuously like the threads on a screw. The gear meshing with the worm gear is known as worm wheel and combination is known as worm and worm wheel.

Worm Gears