Hydraulic Brake System

The Hydraulic brake system is a braking system which uses brake fluid usually includes ethylene glycol, to transmit pressure from the controlling unit, which is usually near the driver, to the actual brake mechanism, which is near the wheel of the vehicle.

The most common arrangement of hydraulic brakes for passenger vehicles, motorcycles, scooters, and mopeds, consists of the following

• Brake pedal or Brake lever
• Pushrod, also called an actuating rod
• Reinforced hydraulic lines
• Rotor or a brake disc or a drum attached to a wheel
• Master cylinder assembly includes:
    Piston assembly is made up of one or two pistons, a return spring, a series of gaskets or O-rings.
    Fluid reservoir
• Brake caliper assembly usually includes:
    One or two hollow aluminum or chrome-plated steel pistons called caliper pistons.
    Set of thermally conductive brake pads.

A glycol-ether based brake fluid regularly loads the system or some other fluids are also used to control the transfer of force or power between the brake lever and the wheel.

The automobiles generally use disc brakes on the front wheels and drum brakes on the rear wheels. The disc brakes have good stopping performance and are usually safer and more efficient than drum brakes. The four wheel disc brakes are more popular, swapping drums on all but the most basic vehicles. Many two wheel automobiles design uses a drum brake for the rear wheel.

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What is Lean-Manufacturing ?

Lean Manufacturing is a business initiative to reduce waste in manufactured products. The basic idea is to reduce the cost systematically, throughout the product and production process, by means of a series of engineering reviews.
The crucial insight is that most costs are assigned when a product is designed. Often an engineer will specify familiar, safe materials and processes rather than inexpensive, efficient ones. This reduces project risk, that is, the cost to the engineer, while increasing financial risks, and decreasing profits. Good organizations develop and review checklists to review product designs.
At the system engineering level, requirements are reviewed with marketing and customer representatives to eliminate costly requirements. Shared modules may be developed, such as multipurpose power-supplies or shared mechanical components or fasteners. Requirements are assigned to the cheapest discipline. For example, adjustments may be moved into software, and measurements away from a mechanical solution to an electronic solution. Another approach is to choose connection or power-transport methods that are cheap or that used standardized components that become available in a competitive market.
In mechanical engineering, the process usually begins with a team review of the materials and processes. The team will include a cost accountant, manufacturing and design engineers. Quite often, parts can be combined into a single injection-molded plastic or die-cast part reducing both fabrication and assembly costs. Fasteners are eliminated, reduced or commonized. Tolerances (critical dimensions) are eliminated, widened and adapted to production processes to achieve theoretical 100% yields. Adjustments are eliminated

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Main Components of Compressed Air Systems

Compressed air systems consist of following major components: Intake air filters, inter-stage
coolers, after-coolers, air-dryers, moisture drain traps, receivers, piping network, filters,
regulators and lubricators.

Intake Air Filters : Prevent dust from entering a compressor; Dust causes sticking valves,
scoured cylinders, excessive wear etc.
Inter-stage Coolers : Reduce the temperature of the air before it enters the next stage to
reduce the work of compression and increase efficiency. They are normally water-cooled.
After-Coolers: The objective is to remove the moisture in the air by reducing the
temperature in a water-cooled heat exchanger.
Air-dryers: The remaining traces of moisture after after-cooler are removed using air dryers,
as air for instrument and pneumatic equipment has to be relatively free of any moisture. The
moisture is removed by using adsorbents like silica gel /activated carbon, or refrigerant
dryers, or heat of compression dryers.
Moisture Drain Traps: Moisture drain traps are used for removal of moisture in the
compressed air. These traps resemble steam traps. Various types of traps used are manual
drain cocks, timer based / automatic drain valves etc.
Receivers : Air receivers are provided as stora ge and smoothening pulsating air output -
reducing pressure variations from the compressor.

Compressor Plant and its parts

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Flywheel Energy Storage

Flywheel energy storage systems store kinetic energy (i.e. energy produced by motion) by constantly spinning a compact rotor in a low-friction environment. When short-term back-up power is required (i.e. when utility power fluctuates or is lost), the rotor's inertia allows it to continue spinning and the resulting kinetic energy is converted to electricity.

Active Power's CleanSource® Flywheel Technology, as shown below, integrates the function of a motor, flywheel rotor and generator into a single integrated system. The motor, which uses electric current from the utility grid to provide energy to rotate the flywheel, spins constantly to maintain a ready source of kinetic energy. The generator then converts the kinetic energy of the flywheel into electricity. This integration of functionality reduces the cost and increases product efficiency. 

            A flywheel, in essence is a mechanical battery - simply a mass rotating about an axis. Flywheels store energy mechanically in the form of kinetic energy. They take an electrical input to accelerate the rotor up to speed by using the built-in motor, and return the electrical energy by using this same motor as a generator. Flywheels are one of the oldest and most common mechanical devises in existence. They may still prove to serve us as an important component on tomorrow's vehicles and future energy needs. Flywheels are one of the most promising technologies for replacing conventional lead acid batteries as energy storage systems for a variety of applications, including automobiles, economical rural electrification systems, and stand-alone, remote power units commonly used in the telecommunications industry. Recent advances in the mechanical properties of composites has rekindled interest in using the inertia of a spinning wheel to store energy. 

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Vapour Compression Refrigeration Cycle

Vapour compression refrigeration systems are the most commonly used among all refrigeration systems. As the name implies, these systems belong to the general class of vapour cycles, wherein the working fluid (refrigerant) undergoes phase change at least during one process. In a vapour compression refrigeration system, refrigeration is obtained as the refrigerant evaporates at low temperatures. The input to the system is in the form of mechanical energy required to run the compressor. Hence these systems are also called as mechanical refrigeration systems. Vapour compression refrigeration systems are available to suit almost all applications with the refrigeration capacities ranging from few Watts to few megawatts. A wide variety of refrigerants can be used in these systems to suit different applications, capacities etc. The actual vapour compression cycle is based on Evans-Perkins cycle, which is also called as reverse Rankine cycle.

Vapour Compression Refrigeration System

Compression: In this process vapour is drawn in the compressor cylinder during its suction stroke and is isentropically compressed to pressure P2 during its compression stroke. Hence temperature of vapour increases. 

Condensation: The vapours after leaving the compressor enters the condenser where is is condensed to high pressure liquid. cooling water is supplied to remove heat from the vapour.

Expansion: high pressure liquid is now expanded through throttle valve and the liquid at stage 3 is throttled to lower pressure P1 and has a low temperature. After throttling we get vapours at low temperature.

Vapourization: After the throttle valve the wet vapours are passed through the evaporator. The vapour absorbs the heat from the surrounding hence reach the condition 1.

Figure shows the schematic of a standard, saturated, single stage (SSS) vapour compression refrigeration system and the operating cycle on a T s diagram. As shown in the figure the standard single stage, saturated vapour compression refrigeration system consists of the following four processes:

Process 1-2: Isentropic compression of saturated vapour in compressor
Process 2-3: Isobaric heat rejection in condenser
Process 3-4: Isenthalpic expansion of saturated liquid in expansion device
Process 4-1: Isobaric heat extraction in the evaporator

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Mechanical Parts Drawing for practice

Here i am sharing some mechanical parts industrial drawing solely for practice and understanding.

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Marine Engines Or Parts of Internal Combustion Engine

Here i am sharing the simple marine engine; 9 hp; for small ship:

Marine engine and its parts ( please enlarge to view clearly)

Description of important parts:

1. Cylinder head: In an internal combustion engine, the cylinder head (often informally abbreviated to just head) sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket. In most engines, the head also provides space for the passages that feed air and fuel to the cylinder, and that allow the exhaust to escape. The head can also be a place to mount the valves, spark plugs, and fuel injectors.
2. Intake valve & Exhaust valve: The valves through which fresh fuel enters into the combustion chamber is called intake valve and valve through which residual gases leave are called exhaust valve. These valves are controlled by CAM shaft.
3. Valve rocker arm: Generally referred to within the context of the internal combustion engine of automotive, marine, motorcycle and reciprocating aviation engines, the rocker arm is an oscillating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it.
4. Pre-combustion chamber: This chamber is located at the cylinder head and is connected to the engine cylinder by small holes. It occupies 40% of the total cylinder volume. During the compression stroke, air from the main cylinder enters the pre-combustion chamber. At this moment, fuel is injected into the pre-combustion chamber and combustion begins. Pressure increases and the fuel droplets are forced through the small holes into the main cylinder, resulting in a very good mix of the fuel and air. The bulk of the combustion actually takes place in the main cylinder. This type of combustion chamber has multi-fuel capability because the temperature of the pre-chamber vaporizes the fuel before the main combustion event occurs.
5. Intake Silencer: It serves the purpose of silencing the air intake in engine.
6. Mixing Elbow:  Its function is to cool the engine exhaust gases by mixing them with the cooling water discharged from the engine heat ex-changer  It requires no regular maintenance, but neither should it be completely forgotten. Over time, the exhaust mixer elbow can become restricted with accumulated soot from the engine exhaust, resulting in increased exhaust gas back pressure and loss of engine power.
7. Camshaft: A camshaft is a shaft to which a cam is fastened or of which a cam forms an integral part.
8. Tappet: A tappet is a projection which imparts a linear motion to some other component within a mechanism.
9. Pushrod: An overhead (OHV) engine, also informally called pushrod engine or I-head engine, is a type of piston engine that places the camshaft within the cylinder block (usually beside and slightly above the crankshaft in a straight engine or directly above the crankshaft in the V of a V engine), and uses pushrods or rods to actuate rocker arms above the cylinder head to actuate the valves.
10. Piston:  In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. 
11. Connecting rod: In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts reciprocating motion into rotating motion.
12. Crankshaft: The crankshaft, sometimes abbreviated to crank, is the part of an engine that translates reciprocating linear piston motion into rotation. To convert the reciprocating motion into rotation, the crankshaft has "crank throws" or "crankpins", additional bearing surfaces whose axis is offset from that of the crank, to which the "big ends" of the connecting rods from each cylinder attach.
13. Flywheel: A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia and thus resist changes in rotational speed. The amount of energy stored in a flywheel is proportional to the square of its rotational speed. Energy is transferred to a flywheel by applying torque to it, thereby increasing its rotational speed, and hence its stored energy. Conversely, a flywheel releases stored energy by applying torque to a mechanical load, thereby decreasing its rotational speed.

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Let's Prepare for Technical Interview (Part-6)

Mechanical engineering interview questions:

Que: What is bending moment?
Ans: When a moment is applied to bend an element, a bending moment exists in the element.

Que: What are the points in the Stress Strain curve for Steel?
Ans: Proportional limit, elastic limit or yield point, ultimate stress and stress at failure.

Que: Define Reynolds number?
Ans: Reynolds number is the ratio of inertial force and viscous force. It is a dimensionless number. It determines the type of fluid flow.

Que: What is a Newtonian fluid?
Ans: A Newtonian fluid possesses a linear stress strain relationship curve and it passes through the origin. The fluid properties of a Newtonian fluid do not change when any force acts upon it.

Que: How many Joules is 1 BTU?
Ans: 1 BTU is equal to 1055.056 joules.

Que: What is PS?
Ans: PS is Pferdestarke, the German unit for Horsepower.

Que: Explain Otto cycle?
Ans: Otto cycle can be explained by a pressure volume relationship diagram. It shows the functioning cycle of a four stroke engine. The cycle starts with an intake stroke, closing the intake and moving to the compression stroke, starting of combustion, power stroke, heat exchange stroke where heat is rejected and the exhaust stroke. It was designed by Nicolas Otto, a German engineer.

Que: Explain the nomenclature of a 6203-ZZ bearing?
Ans: 6 is the type code, which shows it is a single-row ball bearing, 2 is the series, means light, 03 is the bore, which is 17 mm and ZZ is the suffix meaning double shielded bearing.

Que: What is Gear ratio?
Ans: It is the ratio of the number of revolutions of the pinion gear to one revolution of the idler gear.

Que: What is Annealing?
Ans: It is a process of heating a material above the re-crystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material.

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Let's Prepare for Technical Interview (Part-5)

Mechanical Engineering Interview Questions:

Que: The purpose of jigs and fixtures are to: a. Increased production rate
b. Increased machining accuracy
c. Facilitate interchangeable manufacturing
d. Enable employ less skilled operators
e. All of the above
Ans: All of the above.

Que: Which one of the following methods produces gear by generating process
a. Hobbing
b. Casting
c. Punching
d. Milling
e. Broaching
Ans: Hobbing

Que: Tool life of the cutting tool is most affected by
a. Cutting speed
b. Tool geometry
c. Cutting feed and depth
d. Micro-structure of material being cut
e. Not using coolant and lubricant
Ans: Cutting speed

Que: Metal in machining operation is removed by
a. Tearing chips

b. Distortion of metal
c. Shearing the metal across a zone
d. Cutting the metal across a zone
e. Pushing the metal with tool
Ans: Shearing the metal across a zone.

Que: A feeler gauge is used to check
a. Radius
b. Screw pitch
c. Surface roughness
d. Unsymmetrical shape
e. Thickness of clearance
Ans: Thickness of clearance.

Que:The property of a material which enable it to resist fracture due to high impact loads is known as
a. Elasticity
b. Endurance
c. Strength
d. Toughness
e. Resilience
Ans: Toughness

Que: Spring index is
a. Ratio of coil diameter to wire diameter
b. Load required to produce unit deflection
c. Its capability of storing energy
d. Indication of quality of spring
e. Nothing
Ans: Ratio of coil diameter to wire diameter.

Que: Nodular iron has
a. High machinability
b. Low melting point

c. High tensile strength
d. Good fluidity
e. All of the above
Ans: All of the above.

Que: Explain the Second Law of Thermodynamics.?
Ans: The entropy of the universe increases over time and moves towards a maximum value.

Que: How do you measure temperature in a Wet Bulb Thermometer?
Ans: Wet bulb temperature is measured in a wet bulb thermometer by covering the bulb with a wick and wetting it with water. It corresponds to the dew point temperature and relative humidity.

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Let's Prepare for technical interview (Part-4)

Mechanical engineering interview questions:

Que:What is the importance of thermodynamics in the field of mechanical engineering ?
Ans:All the mechanical engineering systems are studied with the help of thermodynamics. Hence it is very important for the mechanical engineers.

Que: How many laws of thermodynamics are there?
Ans: There are three laws of the thermodynamics:

First Law: Energy can be neither created nor destroyed. It can only change forms.In any process in an isolated system, the total energy remains the same.

Second Law: When two isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium in itself, but notin equilibrium with each other at first, are at some time allowed to interact, breaking the isolation that separates the two systems, and they exchange matter or energy, they will
eventually reach a mutual thermodynamic equilibrium. The sum of the entropies of the initial, isolated systems is less than or equal to the entropy of the final exchanging systems. In the process of reaching a new thermodynamic equilibrium, entropy has increased, or at least has not decreased.

Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum.

Que: State law of conservation of energy ?
Ans: According to the laws of conservation of energy, “energy can neither be created nor be destroyed. It can only be transformed from one form to another.”

Que: Is boiler a closed system ?
Ans: yes, boiler is definitely a closed system.

Que: What is carnot engine?
Ans: It was being designed by Carnot and let me tell you that Carnot engine is an imaginary engine which follows the Carnot cycle and provides 100% efficiency.

Que:which formula forms a link between thermodynamics and electro-magnetism?
Ans: Gibbs Helmholtz formula is the formula which forms the link between the thermodynamics and electromagnetism.
ΔHs/R = [∂ lnp /∂ (1/T)]x

Que:Which is the hardest compound known?
Ans: diamond.

Que:What is hess law?
Ans:According to the Hess law the energy transfer is simply independent of the path being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed.

Que: Which engine is more efficient diesel engine or petrol engine?
Ans: Diesel engine

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