Gear Materials ( Gear Manufacturing)

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Material to manufacture a gear is selected as per the strength needed. the material that can sustain a wear and noise etc. Based on the requirement, the metal or nonmetal material can be choosen for gear manufacturing.

Metals like Steel, cast iron, bronze and a non metal like wood, compressed paper, synthetic resins etc can be choosen as the material for gear manufacturing. Non metallic gear material is preferred when there is a need to reduce the noise in the gear operation.

Gear material properties
To select an appropriate material for gear, it should have following properties
1. Good machinability
2. High tensile Strength to bear the load and prevent failure
3. Coefficient of friction should be low.
4. High endurance to wear dynamic loads.

Factors to select gear material
There are many factors on the basis of which a gear material should be selected.
Strength, durability, machinability, endurance, cost are some factors under which a material can be selected.

Gear Terminology ( Terms Used In Gear )

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The following are the terms used in Gears. During the design and calculation of the gears these terms are considered.
Gear Terminology

Pitch Circle

Pitch Circle Is an imaginary circle where two gears will meet as two cylinders with Zero friction.

Pitch circle diameter

It is an important parameter because pitch Circle diameter is used to define the size of the gears. It is simply the diameter of the Pitch Circle.

Pitch point

The point where to Pitch Circle meets is referred as pitch point.

Pitch surface

The surface at the pitch point of the Rolling cylinder replaced by meshing gears.

Pressure angle or obliquity

Angle between the common normal to the point of contact of two gears and the common tangent in the Pitch Circle. It is also called obliquity.
The standard obliquity are 14½° and 20°.


The radial distance of a tooth from the Pitch Circle to the top of the tooth is called addendum


The radial distance of a tooth from the Pitch Circle to bottom of the tooth is called dedendum.

Addendum circle

The circle from the top of the tooth which is corecentric to the Pitch Circle

Dedendum circle

A circle from the bottom of the tooth which is Cocentric to the Pitch Circle.

Circular pitch

In the pitch circle distance between two identical points of two consecutive teeth or distance between a point in a tooth and some point on the nearby gear is called circular pitch

Diametral pitch

The ratio between number of teeth and pitch circle diameter


The ratio between pitch circle diameter and number of teeth. It is inverse of diametral pitch


The radial Distance from the top of the tooth to the bottom of the tooth in a mating gear is called clearance.

Full depth

Distance between addendum circle and dedendum circle or the sum of addendum and dedendum is called full depth.

Working depth

Distance between addendum Circle to the clearance circle is called working depth.

Tooth thickness

The thickness of tooth along the Pitch Circle is called tooth thickness.

Tooth Space

The space between two consecutive teeth along the Pitch Circle is called tooth space.


The difference of toothpaste and tooth thickness is called backless, or in a meeting gear the space between two teeth is called backlash.

Face of tooth

The surface of tooth above the Pitch Circle called face of tooth.

Flank of teeth

The surface below the Pitch Circle is called flank.


The top surface of a gear is called topland.

Face width

Width of the tooth parallel to the gear rotation axis is called face width.

Gear profile

A Curve formed by the face and the flank of the tooth

Fillet radius

In The root of a gear teeth a fillet is provided. And the radius That connect the root circle and profile of the tooth is called fillet radius.

Path of contact

It is path of point of contact of two mating gears from beginning to the end of the gear meshing.

Arc of contact

In the mating gear the path of a point on the pitch circle is called arc of contact.

Arc of approach

It is a path of a point on pitch Circle of mating gear from the point of engagement to the pitch.

Arc of recess

Path of point on Pitch Circle of two mating gears from the point of disengagement.

Mechanical Governor (Device), Working Principle, Types and Function of Governer

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A mechanical governor is a device used to control the speed of machine such as vehicle engine. It governs the speed of engine. It is used in small engine to large engine. It also used in car engines.

 It makes the engine to run at the speed you want it to run. even with varying loads controlling speed of engine. In the modern vehicle there is always a need of  varying the load. This device helps to control the speed with varying loads and make compliance with requirements.
fig mechanical governer ( image source )

When there is increase in load, it causes the speed of engine to decrease and when there is decrease in load, it causes the speed of engine to increase. Increase in load needs more fuel to maintain the speed and when load decreases engine need less fuel to supply. Governor performs the task to maintain the proper supply of fuel according to the need of the engine.

How mechanical Governor works

Mechanical Governor has two balls of equal weights attached to the arms of the Governor. These balls called Governor balls. These balls revolve when spindle of governor rotates.

The upper end of the arms is attached with the spindle. This makes the ball to move up and down while rotating with respect to vertical axis. The lower side arms are linked to the sleeve which revolves along with the spindle. This also makes the sleeve to move up and down while revolving.

When speed increases the sleeve goes upward and tends to go down wards with the decrease in speed. Stopper in the spindle controls the movement of sleeve and a lever will connect the sleeve to throttle valve. This mechanism controls the fuel supply appropriately.

Types of governor

 Governors mainly divided into two types, although they are further subdivided into several parts. Two main types of governor are following
1. Centrifugal governor
2. Inertia governor

Centrifugal governor

Centrifugal Governor detects change in speed with the help of gear and flyweight. This Governor balance the centrifugal force of the rotating Ball by equal and opposite radial for controlling force. Flyweight helps the Governor change in speed. The rotating balls will be opposite to each other and have the same weight.

If we operate a small, lightweight engine which beer is light load, then the carburetor will supply the amount of air fuel mixture to combustion chamber.
Then the crankshaft will start spinning and the centrifugal force cause the flyweight to open. the pressure is applied on governor and crank. The Crank is Linked with throttle valve and the action will cause the fly weights to pull the throttle valve to the closed position.

If the load Of the crankshaft is increased then it will cause the flyweight to spin slowly, and the centrifugal force will decrease and it will not completely pull the throttle valve to the closed position and therefore the air fuel supply will be increased

Inertia governor

Inertia Governor are quit different from centrifugal governor because it works on different principle. The Governor balls are arranged such that the inertia force generated from the angular acceleration of the Governor shaft tend to change their positions. The displacement of the balls is controlled by Spring and mechanism of governor. Through this the supply of air fuel mixture can be controlled.

In this governor the positions of the balls depends on the rate of change of speed of the Governor shaft. Because of this the quick response will be obtained as we change the load. This type of governor takes action due to acceleration and not due to finite change in speed.

 Centrifugal governor is preferred over inertia governor because inertia Governor have practical difficulty of arrangements expected balance of revolving parts.

Press working terminology

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Press is very important machine of manufacturing industry. The sheet metal industries fully dependent on press machines. Press provides Metal cutting operation in just one blow.

In the Press machines die is used.It is designed according to the design of the product that you want to manufacture. Press can perform many operations. To read these operations please click here.

The figure of a Press die is shown below

The main components of press machine are described below.


The lower part of press machine is called bed. It is like a table which bears all the load of press. It is stationery portion. Boister plate is mounted on this part.

Boister plate

The part which is used to Mount the die assembly is called boister plate. It support the die block and locate it at right place.

Die set 

It is an assembly which has two or more parts. It is Design according to the final product required. It is usually have one upper part and one lower part.

Die block

This part has the cavity of required part.

Lower Shoe

Die block is mounted on the lower Shoe and lower shoe is mounted on the boister plate. So basically it is the lower part of the shoe.


This part is fastened with the moving part Ram in the press. This is male part of die set which produce required shape in the component with the use of pressure.

Upper shoe

The upper part of die set is called upper shoe.

Punch plate 

The punch plate is one which uphold the punch. It is also called panch retainer.

Backup plate

This place is used tu prevent the excessive pressure that damages the die. This place distributes the pressure in a wide area of plate to decrease the intensity of pressure. Therefore it prevents the punch holder from crushing.


This is a plate used to hold the specimen on the die. It strip out the metal strip off the punches.

Classification Of Centrifugal Pumps ( Pump Types )

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The pumps are used to move the fluid by consuming the energy. The pump is a device that is used to transfer the fluids water, oil, gases, slurry by consuming and using mechanical work.

Energy used in a pump can be engine energy, electrical energy or other non conventional energy. Pump Works according to some mechanism (rotary or reciprocating). This mechanism converts energy into mechanical work.

There are several application that pump offers like pumping water from pounds or well, filtering of pond or swimming pool, aeration in the car etc.Pumps comes in many sizes from microscope pumps to large industrial pumps

Although, there are many type of pumps but we will discuss the important one i.e. Centrifugal pump.

Fig. Centrifugal Pump

Centrifugal Pump

Centrifugal pump uses the centrifugal force to pump the fluid. it is the kinetic energy type of pump. It is a type of dynamic axisymmetric pump machinery. The centrifugal pump increases the head of fluid by converting its kinetic energy into hydrodynamic energy. this kinetic energy is rotational type. The rotational motion in the fluid will come through the energy source like engine electricity etc.

Centrifugal pump is used widely because of it's Simple design, high capacity, high head and large efficiency etc.

How Centrifugal Pumps are classified

1. Based on Flow of Fluid

Pumps help different types in which the fluid flow happens differently. The types of Fluid flow in the pumps are as follows

1. Radial flow
2. Axial flow
3. Mixed flow

Radial Flow Pumps

Pumps in which the fluid enters at the centre of impeller and the impeller blades directs the flow at right angles outwards to the pump shaft are calles radial flow type pumps. This type of pumps provides high head and high efficiency.

Axial Flow Pump

Axial flow pump provides low head but large quantity of water. In this type of pump the impeller pushes the fluid parallel to the shaft. Axial flow pump also called propeller pump because of its operation is analogous to the propeller of boat.

Mixed Plow Pumps

these pumps has Qualities of both radial and axial flow pumps. When the fluid travels through the impeller the Blades of impeller will push the fluid outwards from the pump shaft to the pump suction angle greater than 90 degree. Mixed flow pumps mainly used for irrigation purposes.

2. Type of Casing

There are two type of casing

Volute Casing

In the volute casing the area of casing will be increased from impeller to outlet. This will cause the decrease in the velocity of the fluid. The decreased velocity will finally increase the head.

Vortex Casing

In this casing a circular chamber is introduced between the impeller. This circular chamber is called vortex and casing is called vortex casing.

3. Number of Impellers Used Per Shaft

In the centrifugal pump one or more than one impeller shaft can be used. Based on this pumps can be classified in following categories

Single Stage Centrifugal Pump

In the single stage centrifugal pump one impeller is used in the pump shaft. The type of pump is used where low head is required.

Two stage Centrifugal Pump

To get a medium head as a result of pump output, the two impeller are used in series in a single shaft

Multistage Centrifugal Pump

When high head and high discharge output is required. Multiple number of impeller can be used in a single shaft.

4. Based on Working Head

The potential of water or water head is the desired output of a pump so we can classify according to the head Obtained from the pump.

Low Lift Centrifugal Pump

The pumps which can provide head up to 15 M are called low lift centrifugal pump.

Medium Lift Centrifugal Pump

The pumps which can provide head more than 15 M and less than 40 M are termed as medium lift centrifugal pump.

High lift Centrifugal Pumps

The pumps which are able to produce head more than 40 M are referred as high lift centrifugal pumps.

5. Type of Liquid to be Pumped

Pumping of Pure Liquid

When pure liquid pumping is required, the closed impeller pump is used because they have higher efficiency

Pumping of Little Impure Liquid

In this case the semi open impeller is used if the liquid contains some impurities

Pumping of Liquid Contains Solid Matter

If the liquid contains solid matter to pump then the open impeller is used.

6. Based on Shaft Orientation

Horizontal Shaft

If the shaft is placed horizontal it will provide ease of orientation and maintenance.

Vertical Shaft

If the space is less then the shaft is placed vertically.

Frequently asked question ( FAQ)

What is casing of centrifugal pump

The volute Which receives the liquid pumped by the impeller is called casing of a centrifugal pump. Volute is funnel shaped element of increasing area. It slow downs the rate of flow of liquid.

Why centrifugal pump is used and how it works

To move the fluid from small quantity to large quantity centrifugal pump is used. The centrifugal pumps uses the rotating impeller to create vacuum. Vacuum causes the movement, then this movement drives the fluid to the outside of the pump housing. Then the pressure is increased and the liquid is moved towards the discharge.

What is Suction Head of a Pump

Suction head is the vertical distance from the centre line of pump shaft to the level of fluid to be pumped.

What is Impeller of a Pump

The rotating part of centrifugal pump is called impeller. It takes energy to rotate and pump the fluid outwards. It is made of metals like steel, aluminium, brass, also made of rubber and plastic.

What is Head

Pump head is the ability of pump to deliver air pressure to make the fluid to reach at the maximum height. Head of pump is measured in height. The height upto which water can be raised by pump is called head.

What is Priming

Priming is removing the air entrapped In The suction line and the pump, before starting operation of the pump. For this purpose the water is filled throughout the casing to remove the air present.

Water Sensor

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 Water in Fuel Sensor or WiF sensor indicates the presence of water in the fuel. It is installed in the fuel filter and when the water level in the water separator reaches the warning level, the Wif sends an electrical signal to the ECU or to dashboard (lamp). The WiF is used especially in the Common Rail engines to avoid the Fuel injector damage.The WiF sensor uses the difference of electric conductivity through water and diesel fuel by 2 electrodes.

First generation WiF sensors use a potting resin to isolate the electronic circuit, while the latest generation of Wif sensors (the WS3 sensor in Surface-mount technology) are made totally without leakage using an innovative co-moulding process.

The latest generation of WiF sensors have a high resistance to vibrations and to thermal excursion cycles.

The main automotive WiF designer and producer is SMP Poland.
A level sensing device is designed to measure the level of flow substances including liquids, slurries and granular materials. Ther are also continuous level sensors; however, these sensing modules can only detect the level of flow of a substance with a specific range.

A water sensor is a device used in the detection of the water level for various applications. Water sensors are of several types that include ultrasonic sensors, pressure transducers, bubblers, and float sensors.

Working Method

Ultrasonic sensors operate by transmitting sound waves that reflect from the liquid surface and are obtained by the sensor. The sensor measures the time interval between the transmitted and received signals, which is then converted into distance measurement with the help of electronic circuits within the sensor thereby measuring the level of the liquid.

Float sensors work based on the change in resistance of a potentiometer within the sensor by the turning of a pulley or a spring-loaded shaft.

Bubbler sensors, on the other hand, measure water level by detecting the pressure of air-filled tubes with an open, submerged bottom end. The static pressure at the end of the tubes is more when the water level is high, and therefore more air pressure is required to fill the tube.


Water sensors find applications in nuclear power plants, automobiles for measuring the amount of gasoline left in the fuel tank, engine oil, cooling water, and brake/power steering fluid.
Industrial applications of water level sensors include water level sensing in transport and storage tanks and water treatment tanks. Wess Global Inc. manufacture different types of level instruments for their use in municipal areas and also in the food and beverage industry.

Turbocharged direct injection

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Turbocharged direct injection or TDI is a design of turbodiesel engines featuring turbocharging and cylinder-direct fuel injection that was developed and produced by the Volkswagen Group (VW AG). These TDI engines are widely used in all mainstream Volkswagen Group marquesof passenger cars and light commercial vehicles made by the company (particularly those sold in Europe). They are also used as marine enginesin Volkswagen Marine and Volkswagen Industrial Motor applications.
Some TDI engines installed in 2009 to 2015 model year Volkswagen Group cars sold through 18 September 2015 had an emissions defeat device, which activated emissions controls only during emissions testing. The emissions controls were suppressed otherwise, allowing the TDI engines to exceed legal limits on emissions. VW has admitted to using the illegal device in its TDI diesel cars.
In many countries, TDI is a registered trademark of Volkswagen AG.
The TDI designation has also been used on vehicles powered by Land Rover-designed diesel engines. These are unrelated to Volkswagen Group engines.
The TDI engine uses direct injection, where a fuel injector sprays atomised fuel directly into the main combustion chamber of each cylinder, rather than the pre-combustion chamber prevalent in older diesels which used indirect injection. The engine also uses forced induction by way of a turbocharger to increase the amount of air which is able to enter the engine cylinders, and most TDI engines also feature an intercooler to lower the temperature (and therefore increase the density) of the 'charged', or compressed air from the turbo, thereby increasing the amount of fuel that can be injected and combusted. These, in combination, allow for greater engine efficiency, and therefore greater power outputs (from a more complete combustion process compared to indirect injection), while also decreasing emissions and providing more torque than the non-turbo and non-direct injection petrol engined counterpart from VAG.
Similar technology has been used by other automotive companies, but "TDI" specifically refers to these Volkswagen Group engines. Naturally aspirated direct-injection diesel engines (those without a turbocharger) made by Volkswagen Group use the Suction Diesel Injection(SDI) label.
Because these engines are relatively low displacement and quite compact, they have a low surface area. The resulting reduced surface area of the direct injection diesel engine reduces heat losses, and thereby increases engine efficiency, at the expense of slightly increased combustion noise. A direct injection engine is also easier to start when cold, because of more efficient placing and usage of glowplugs.
Direct injection turbodiesel engines are frequent winners of various prizes in the International Engine of the Year Awards. In 1999 in particular, six out of twelve categories were won by direct injection engines: three were Volkswagen, two were BMW, and one Audi. Notably that year, the Volkswagen Group 1.2 TDI 3 L beat the Toyota Prius to win "Best Fuel Economy" in its class. The TDI engine has won "Green Car of the Year" award in the years 2009 (Volkswagen Jetta 2.0-litre common-rail TDI clean diesel) and 2010 (Audi A3 TDI clean diesel) beating other various electric cars.

Emissions testing falsification

On 18 September 2015 the US EPA and California Air Resources Board served notice to VW that approximately 480,000 VW and Audi automobiles equipped with 2.0 TDI engines sold in the US between 2009 and 2015 had an emissions compliance defeat device installed. The defeat device, in the form of specially crafted engine management unitfirmware, detects emissions testing conditions, and in such conditions will cause the vehicle to comply with emissions regulations by properly activating all emissions controls. However, under normal driving conditions, the emissions controls are suppressed, allowing the engine to produce more torque and get better fuel economy, at the expense of emitting up to 40 times more nitrogen oxides than allowed by law. Such NOx emission levels are not in compliance with US regulations. VW has since admitted to these allegations, and said that the illegal software was in use in its diesel cars worldwide, affecting some 11 million vehicles.


The fuels required for TDI engines include diesel fuel (also known as petrodiesel), or B5, B20, or B99 biodiesel, depending on emissions equipment, location dependent.
A 2007 Volkswagen Jetta Mk5 with a 1.9 TDI engine and a five-speed manual transmission achieves 5.2 litres per 100 kilometres (54 mpg‑imp; 45 mpg‑US) on the European combined-cycle test (an US EPA test of the same vehicle would achieve around 34 MPG), while a six-speed direct-shift gearbox (DSG) automatic version reaches 5.9 litres per 100 kilometres (48 mpg‑imp; 40 mpg‑US).
Newer TDI engines, with higher injection pressures, are less forgiving about poor-quality fuel than their 1980s ancestors. Volkswagen Group's warranty does not cover damage due to bad fuel (diesel or bio), and has in the past recommended that only mixtures up to 5% biodiesel (B5) be used. Volkswagen Group has recently permitted mixes up to B20, and has recommended B5 be used in place of 100% petroleum-based diesel because of biodiesel's improved lubricating properties.
In North America, No. 2 diesel fuel is recommended, since it has a higher cetane number than No. 1 fuel, and has lower viscosity (better ability to flow) than heavier fuel oils. Some owners in North America, where cetane levels are generally poor (as low as 40), use additives, or premium diesel, to get cetane numbers closer to the standard levels found in the European market (at least 51) where the engine is designed. Improved cetane reduces emissions while improving performance, and may increase fuel economy.
New ultra low-sulphur petroleum-only diesels are known to cause some seals to shrink, and may cause fuel pump failures in TDI engines used in 2006 to 2009 models. TDI engines from 2009 on and before 2006 are designed to use ULSD exclusively; biodiesel blends are reported to prevent that failure