ME - Mechanical Engineering
Online resource for Mechanical Engineers

Welding joints
There are five types of welded joints for bringing two parts together for joining.
Five types of welded joints are butt joint, corner joint, lap joint, tee joint and edge joint.

Butt joint:

In Butt welded type, the parts lie in the same plane and are joined at their edges.

Corner joint:

The parts in a corner joint form a right angle and are joined at the center of the angle.

Lap joint:

Lap joint consists of two overlapping parts.

Tee joint:

In a tee joint, one joint is right angle to the other joint in the approximate shape of the letter "T".

Edge joint:

The parts in edge joint are parallel with at least one of their edges in common and the joint is made at the common edge(s).

butt joint, corner joint, lap joint, tee joint and edge joint

Different types of loads are compression, tension, torsion and bending.
Compression, tension, torsion and bending loads.


Compression loading is an effect in which the component reduces it size. During compression load there is reduction in volume and increase in density of a component.


Tension is the act of stretching rod, bar, spring, wire, cable etc. that is being pulled from the either ends.


Torsion is the act of twisting of an rod, wire, spring etc. about an axis due to applied couple (torque).


Bending is act of changing component from straight form into a curved or angular form.
A lathe machine is a mechanical device in which the work piece is rotated against a suitable cutting tool for producing cylindrical forms in the metal, wood or any other machinable material.
Lathe machine

Types of lathe machines:

  • Copy lathe machine
  • Automatic lathe machine
  • Turret lathe machine
  • Engine lathe machine
  • Bench lathe machine
  • Computer controlled lathe machine

Lathe machine parts:

Lathe machine parts
 image credits:

Operations that can be performed on lathe machine:

a) Straight turning
b) Taper turning
c) Profiling
d) Turning and external grooving
e) Facing
f) Face grooving
g) Cutting with a form tool
h) Boring and internal grooving
i) Drilling
j) Cutting off
k) Threading
l) Knurling
operations performed on lathe machine
image credits:
Foundry shop is the place where the metal casting is prepared by melting and pouring the molten metal into moulds. Some of the commonly used tools for moulding process in foundry shop are showel, trowel, riddle, rammer, draw spike, swab, vent wire and slick tool.


Showel tool
Showel tool is used for mixing and tempering moulding sand and for moving the sand pile to flask.


Trowel tool
Trowel tool is used to shape and smooth the surfaces of the mould and for doing small repairs. They are made of steel and are relatively long and narrow.


Riddle tool
Riddle tool is a screen or sieve used to remove small pieces of metal and foreign particles from the moulding sand.


Rammer tool
Rammer tool is used to compress the moulding sand. The hand rammer is made of tool and resembles like a handless mallet with one end flat and the other end blunt edge.

Draw spike:

Draw spike tool
Draw spike tool is used to remove the pattern from the mould  and also for rapping the pattern gently the loosen it from the sand to assure a clean draw.


Swab tool
Swab tool is made of flax or hemp and is used for applying water to the mould around the corners and edges of the patterns. This tool prevents the sand edges from crumbling, when the patern removed from the mould.

Vent wire:

Vent wire is a thin rod or wire carrying a pointed edge at one end and a wooden handle at the other end. Vent wire is used to make small holes called vents in the sand mould.

Slick tool:

Slicks tools are the spoon shaped trowels used for repairing or smoothening a mould surface.

Here are some of animations of the greatest mechanical principles and inventions, which shows greatness of human brain. Simple animation pictures are used to explain mechanisms of Boxer Engine, Geneva Drive, Radial Engine, Wankel Cycle.

1. Boxer Engine:

Boxer engine mechanism animation
A Boxer Engine is a flat engine IC engine with multiple pistons that move in a horizontal plane. The layout shown in animation has cylinders arranged in either side of a single crankshaft and it is sometimes known as horizontally opposed engine.

2. Geneva Drive:

Geneva drive mechanism animation
The Geneva drive is a gear mechanism that translates a continuous rotation into an intermittent rotatory motion. The rotating drive wheel has a pin that reaches into a slot of the driven wheel in regular intervals advancing driven wheel by one step. The drive wheel has a raised circular blocking disc that locks the driven the driven wheel in position between steps.

3. Radial Engine:

Radial Engine Mechanism animation

Radial Engine is a reciprocating type IC engine configuration in which the cylinders moves outward and then inwards in regular intervals from a central crankshaft. It looks like a stylised star when viewed from the front. The radial engine configuration was very common used in aircraft engines before turbine engines became in use.

4. Wankel Cycle:

Wankel Cycle mechanism animation
The Wankel engine is a type of IC engine using an eccentric point rotatory design to convert pressure into rotatory motion. Use of Wankel engine delivers advantages they are simplicity, smoothness, compactness, high RPM and a high power to weight ratio. Wankel Cycle engine is commonly referred to as a rotatory engine. 

The application of First Law of Thermodynamics process led to the establishment of a new property named internal energy (U), the application of the second law to a process leads to the establishment of another new property names as entropy (S).
Entropy is defined as follows
Change in entropy for an reversible and irreversible cycle by second law of thermodynamics

For a reversible thermodynamic process between two states, from state 1 to state 2 in an open system, the change in entropy is given by

It is found by applying Clausius inequality that for for an irreversible process from state 1 to state 2, the change in entropy is given by

Below tables shows list of 112 Mechanical Inventions arranged in the order of invented year with inventor(s) name and inventor country they belong to.

Mechanical Inventions

If you want us to include any more Mechanical Inventions comment below.
The First Law of Thermodynamics states that energy is neither created nor destroyed, thus the total energy of the universe is a constant. However, energy can certainly be transferred from one form to another form.

The 1st Law of thermodynamics is mathematically stated as follows:
§dQ = §dW

During a thermodynamic cycle, a cyclic process the systems undergoes, the cyclic integral of heat added is equal to integral of work done. the first law equation can also be written in the form,
§(dQ – dW) = 0

Equation dU = dQ - dW is corollary for first law of thermodynamics. It shows that there exists a property internal energy (U) of the system, such that a change in its value is equal to the difference in heat entering and work leaving the system.
Sign convention for heat and work in  first law of thermodynamics is represented in picture below.
Another property named enthalpy (H) can also be defined now as a combination of properties U, p and V.
H = U + pV

For a reversible process, since dW = pdV, the first law of thermodynamics can also be written as
dQ = dU + pdV
properties of fluid
Understanding the properties of fluids is essential to analyse their behavior in working conditions.
In this post I have written the fluid properties namely mass density, specific weight, specific volume, specific gravity, viscosity, vapor pressure, compressibility and surface tension.

Mass Density:

Mass Density (ρ) is the property of a fluid is the mass per unit volume.

Specific Weight:

Specific Weight (w) of a fluid is the weight per unit volume.

Specific Volume:

Specific Volume (v) of a fluid is the volume of the fluid per unit mass.

Specific Gravity or Relative Density:

Specific Gravity (s) of a fluid is the ratio of the mass density of a fluid to the mass density of a standard fluid.


Viscosity is property by virtue of which it offers resistance to the movement of one layer of fluid over the adjacent layer.

Vapor Pressure:

When a liquid is confined in a closed vessel, the ejected vapor molecules accumulated in the space between free liquid pressure and top of the vessel exert a partial pressure on the liquid surface. This pressure in liquid is known as vapor pressure.


The normal compressive stress of any fluid element at rest is known as hydro static pressure which arises as a result of innumerable molecular collisions in the entire fluid. The degree of compressibility of a substance is characterized by bulk modulus of elasticity (K).

Surface Tension:

Surface is a measure of fluid tendency to take a spherical shape, caused by mutual attraction of the liquid molecules.
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
Gas laws : Boyles, Charles and Gay-Lussacs 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