IMPELLER Vs. PROPELLER !! DIFFERENCE EXPLAINED !!

Propellers and impellers both provide thrust, but do it in different ways.Let us understand the difference between two with the help of examples.

PROPELLER:

If you have ever seen pictures of ships closely, you must have noticed small rotating fans on both sides of the ship. 

These are propellers that actually help in propelling the ship forward. A propeller is an open running device that has the function of providing a thrust force. There is always a propelling fan on the mouth of an aircraft also. If we go by definitions given in various dictionaries, a propeller is a device having a revolving hub with rotating blades to propel an airplane, ship etc. 

A propeller is a special type of fan with blades that convert rotational motion into a force that helps in movement forward. This is because of a pressure difference that gets created between the front and the rear surfaces of the blades. This pressure difference pushes both air and water behind the blade. This thrust or force can be easily explained with the help of Newton’s laws of motion as well as Bernoulli’s theorem. Propellers are made heavy use of both in aviation as well as in ships.

IMPELLER:

Have you ever paid attention to the working behind the water pump that is used at home that sucks water from the main pipeline passing through the main road and brings it inside your home and then lifts it to the over head tank?

The working principle behind this pump is the impeller inside a casing that creates a sucking force that draws in liquid at a great force and diverts it to your overhead tank. An impeller is always inside a casing as its purpose is to draw the liquid inside as against a propeller that provides an outward thrust and is always open. An impeller, because of its rotation and especially designed blades, increases the pressure of the fluid and thus its flow. A centrifugal pump used to draw fluid is the best example of an impeller.

In brief:

Propeller vs Impeller

• Both propeller and impeller are specially designed blades with a motor.
• While a propeller is designed to covert rotational motion into forward thrust, an impeller is designed to use rotational motion to suck fluid in.
• A propeller has an open design while an impeller is always inside a casing or housing.

UNDERWATER WELDING !! HOW IT IS DONE ?? EXPLAINED !!

Underwater Welding:-

Underwater welding is one of the most dangerous occupations in the world. Underwater, the odds are stacked against you. The pressure threatens to crush the body. Clouds of bubbles making any task difficult to perform by blocking visuals.Underwater welders are responsible for repairing pipelines, offshore oil drilling rigs, ships, dams, locks, sub-sea habitats and nuclear power facilities, to name a few.

Underwater welding is the process of welding at elevated pressures, normally underwater. Underwater welding can either take place wet in the water itself or dry inside a specially constructed positive pressure enclosure and hence a dry environment.So,it can be classified into two categories:

1. Wet Welding
2. Dry Welding

Wet Welding:

Wet underwater welding directly exposes the diver and electrode to the water and surrounding elements.Divers usually use around 300–400 amps of direct current to power their electrode, and they weld using varied forms of arc welding.This practice commonly uses a variation of shielded metal arc welding, employing a waterproof electrode.

Wet welding with a stick electrode is done with similar equipment to that used for dry welding, but the electrode holders are designed for water cooling and are more heavily insulated. They will overheat if used out of the water.The electric arc heats the workpiece and the welding rod, and the molten metal is transferred through the gas bubble around the arc. 

The hazards of underwater welding include the risk of electric shock to the welder. To prevent this, the welding equipment must be adaptable to a marine environment, properly insulated and the welding current must be controlled.

Dry Welding / Hyperbaric Welding:

Another method of welding underwater is hyperbaric welding or dry welding. Hyperbaric welding is the process by which a chamber is sealed around the structure that is to be welded. It is then filled with a gas (typically mixture of helium and oxygen, or argon), which then forces the water outside of the hyperbaric sphere.

In most cases, and most ideally, a dry chamber system is used. Temporary hyperbaric chambers are used to prevent water from entering the work area. The chambers house up to three welders at a time.

Underwater welding is one of the most difficult jobs on the planet and in the water. Though with advancing technologies in robotic capabilities, advancements are being made to protect underwater welders. Despite what the future may hold, today underwater welders help maintain the most integral components of many industries around the world.

DIFFERENCE BETWEEN ORTHOGONAL AND OBLIQUE CUTTING EXPLAINED !!

Metal cutting is “the process of removing unwanted material in the form of chips, from a block of metal, using cutting tool”.

Methods of Metal Cutting:

There are two basic methods of metal cutting based on cutting edge and direction of relative motion between tool and work:

(i) Orthogonal cutting process

(ii) Oblique cutting process 

(i) Orthogonal Cutting Process:

In orthogonal cutting process, the cutting edge is perpendicular (90 degree) to the direction of feed. The chip flows in a direction normal to cutting edge of the tool. A perfectly sharp tool will cut the metal on rack surface.

(ii) Oblique Cutting Process:

In oblique cutting process, the cutting edge is inclined at an acute angle (less than 90 degree) to the direction of feed. The chip flows sideway in a long curl. The chip flows in a direction at an angle with normal to the cutting edge of the tool.

Difference between the two is discussed in detail in the table below:

WHY V-SHAPED ENGINES ARE USED ?

A V engine, or Vee engine is a common configuration for an internal combustion engine. The cylinders and pistons are aligned, in two separate planes or 'banks', so that they appear to be in a "V" when viewed along the axis of the crankshaft.The primary reason to use a V-engine is largely packaging. They're shorter and more compact than an inline engine.

The first thing to consider is an engine as a purely rotational system. Imagine a one cylinder engine; the rotating crankshaft is massively out of balance. Even if the actual crankshaft was perfectly balanced, the motion of the piston and the forces it applies will never cancel out. This is why most one cylinder engines run a balance shaft; a weighted shaft geared into the crankshaft to mitigate the out-of-balance effects. A balance shaft can be run on other out of balance engines as well.

A V-engine, on the other hand, can be made to be inherently balanced. This means that no matter what speed the engine's running at, the forces from the rotating assembly will always cancel out. Most notably, a 90 degree V4 or V8 engine can be easily balanced and many race motorcycle engines use this configuration (Honda and Ducati in MotoGP). V6s and V12s run balanced at 60 degree bank angle.

Apart from this other advantages of V configuration are as follows:

1. Dimensions are compact - which are appreciated either in construction of road cars or race cars
2. The compact dimensions mean that more cylinders can be packed in, as comparable to an inline/straight engine of similar dimensions.
3. Can accommodate higher displacement cylinders, and therefore that extra power
4. Its a strong engine - which makes it ideal for racing applications
5. Can accommodate higher compression
6. High levels of refinement.

An interesting note: because a V12 is essentially two inline 6 engines stuck together they're naturally balanced regardless of bank angle. This is why V12 Jaguars have a reputation for smoothness. V6s, being two 3 cylinders stuck together, are inherently out of balance.

Talking about the limitations of V configuration engines,there are few yet they play and important role.These are mentioned below:

1. Contains more moving parts, resulting in higher cost/complexity
2. Weight. The same technicality above makes a V-engine heavy.

LEARN TO READ BOLT SPECIFICATIONS !!

A bolt is a type of threaded hardware fastener that is used to position two workpieces in specific relation to each other. Bolts come in several configurations for their application and specification variances.

Each bolt is specified with some coding in it which revels the information about that bolt such as M9X1.2X1.5 .Many metric bolts denote the use of metric measurements with an "M" at the start of the bolt designation, such as "M9x1.2x15." Metric bolts list measurements in millimeters. Besides using metric measurements, a metric bolt uses the distance between the threads rather than the thread pitch, used in American measurements, which is the number of threads per inch.

How to read these specifications:

For reading the specifications of the bolt follow these steps:

Determine the diameter of the bolt by looking at the first number. For example, if the metric bolt was M10x1.25x33, it would have a diameter of 10 millimeters.


Determine the distance between threads by looking at the second number. For example, if the metric bolt was M10x1.25x33, it would have 1.25 millimeters between threads.This is also known as pitch.


Determine the length of the metric bolt by looking at the third number. For example, if the metric bolt was M10x1.25x33, it would have a length of 33 millimeters.


Look on the bolt head for the number denoting the strength of the bolt. The bigger the number, the stronger the bolt.

Hope,you got to learn something from this article.

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BAJAJ V15 AND V12 !! WHAT IS DIFFERENCE ???

Bajaj Auto launched its first bike under the V brand in March 2016. The 150cc motorcycle with cafe racer styling, made with metal from the dismantled aircraft carrier, INS Vikrant, of the Indian Navy has become a runaway success. The V15 has recorded sales figures of 2 lakh units within eight months of its launch.

Encouraged by the response, Bajaj Auto just added a younger sibling to the V15,  the V12. At first glance, both motorcycles seem identical. Both feature the cafe racer design, removable rear cowl, and curved headlamps design. However, there are a few differences between the two V models.

Here is how the two are different from each other:

Engine: Both V models are powered by single-cylinder air-cooled DTS-i engines. However, the 149.5cc motor in the V15 generates 11.8bhp at 7,500rpm and 13Nm of torque at 5,500rpm. On the other hand, the V12's 124.5cc mill comes with an output of 10.5bhp at 7,500rpm and 11.2Nm of torque at 5,500rpm.

Suspension: The V15 is equipped with 33mm telescopic forks up front. On the other hand, the V12 gets slightly thinner 31mm forks. V12's suspension is also rated 110mm of fork travel.

Brakes: The V15 boasts of a 240mm disc brake for front tyres and 130mm drum brakes at rear. The V12 is offered without disc brakes up front. Instead it gets 130mm drum brakes for both front and rear wheels.

Tyres: While the V15 is equipped with 120/80-16 tyre at the rear and 90/90-18 tyre at front, the V12 comes with skinnier 100/90-16 rear tyre. The V15 also gets tubeless tyres while the V12 misses out on tubeless tyres, which is a very important feature.

Headlight: The V15 gets bright 55/60 W headlight that provides impressive illumination. On the other hand, the new V12 gets a 35/35 W headlamp, which is very common in other commuter motorcycles.

Dimension: The V15 measures 2044mm in length, 780mm in width and has a height of 1070mm. The V12 measures 2040mm in length, 785mm in width and 1066 in height. This means the V12's length and height are slightly less than that of the V15, while it has a bit more width. Both versions come with 165mm of ground clearance and 1315mm of wheelbase.

Price: The V15 has been priced at Rs 62,132 while the V12 costs Rs 56,283, both ex-showroom, Delhi. The difference in price is Rs 5,849.