KNOW WHY FIRING ORDER IS 1-4-3-2 , RATHER THAN 1-2-3-4 !!

Every engine cylinder must fire once in every cycle. This requires that for a four-stroke four cylinder engine the ignition system must fire for every 180 degrees of crank rotation. For a six cylinder engine the time available is only 120 degrees of crank rotation. The order in which various cylinders of a multi cylinder engine fire is called the firing order. The number of possibilities of firing order depends upon the number of cylinders and throws of the crankshaft.

Let us see firing order of various engine configurations:

For 4-Cylinder engines the possible firing orders are: 1-3-4-2 or 1-2-4-3

For 3 Cylinder engine 1-3-2

8 Cylinder in-line engine 1-6-2-5-8-3-7-4

For a 6-Cylinder engine firing orders can be: 1-5-3-6-2-4 or 1-5-4-6-2-3

You might be wondering why firing order is not in sequence.Why for a four stroke engine firing order is 1-3-4-2 rather than 1-2-3-4 ? We will discuss about factors on which firing order depends in this article.


Following factors must be considered before deciding the optimum firing order of an engine. These are:

(i) Engine vibrations

(ii) Engine cooling


Consider that the cylinder number 1 of the four-cylinder engine, is fired first. A pressure generated in the cylinder number 1 will give rise to a force on the bearings. If the next cylinder fired is cylinder number 2, this imbalance in load on the two bearings would further aggravate the problem of balancing of the crankshaft vibrations & would result in severe engine vibrations. If we fire cylinder number 3 after cylinder number 1, the load may be more or less evenly distributed as cylinder 3 is far from cylinder 1 so vibrations will be distributed evenly due to symmetry of engine.

Further, consider the effect of firing sequence on engine cooling. When the first cylinder is fired its temperature increases. If the next cylinder that fires is number 2, the portion of the engine between the cylinder number 1 and 2 gets overheated.This results in uneven heating as half engine is heated.If we fire cylinder 3 after cylinder 1 then this results in equal heating of the engine which reduces thermal stress and aids in efficient cooling.

KNOW THE MEANING OF CROSS MARK AT THE END OF BOGGIE OF TRAIN !!

You might have noticed a mark X on the last bogie of a train once in a life. According to a rule, now every train must have this mark on its last bogie. Also, observe the board with letters LV written on it beside the letter X and a red light below the letter X.But do you know what that means? We will discuss about this X mark in this article.

• It indicates that wagon consisting of this letter X is the last wagon of the train.
• The Letter “X” is used during morning whereas Red light below it is used to indicate during night.
• If the last wagon of the train doesn’t contain this symbol, then it indicates that the train is in trouble and also it can be known that train is running without some wagons.
• It can easily alert the railway officials so that they can save from the accident.
• In addition, a small board with ‘LV’ (black on yellow) is often attached to the rear of the vehicle (it stands for Last Vehicle).

There are some cases where a last vehicle indication is not required — for instance, when the number of coaches or wagons in a train can be passed on to each block section after verification from the previous block section at the time the line clear indication is obtained (and with exchange of private numbers). The information is also provided to the section controllers. In some cases when working entirely within one block section, an 'LV' sign is not needed if the number of coaches or wagons is communicated by telephone to the next station.

KNOW WHAT YELLOW OR WHITE STRIPS ON COACHES OF INDIAN RAILWAY MEAN !!

On 16 April, 1853, Indian Railways started its services and the first train travelled at a distance of 33 km from Mumbai to Thane. While travelling through train, you may have seen coloured coaches and different coloured stripes on the train coaches such as yellow or white etc. Have you ever thought why these coloured stripes are given to some of the train coaches, what does it mean? Let us study through this article about the stripes and about the colour coaches & their significance.

On the blue ICF coach, the lines or stripes of yellow or white colour are placed on top of the window at the end of the coach, which is actually used to separate the coach from another coach. These lines indicate the unreserved coach of the second class. When a train arrives at the station, there are many people who are confused about the General Bogie, but by looking these yellow stripes, people can easily understand that this is the General Coach. Coach with white strip shows reservation class.

Similarly, the yellow stripes on blue / red are used for the handicapped and sick people. Similarly, green stripes on the grey indicate that the coach is for women only. These colour patterns are included only for the new Auto Door Closing EMU in Mumbai, Western Railway.Similarly, the red colour stripe indicates the first-class coach.

KNOW WHY TURBOCHARGERS ARE MOSTLY USED IN DIESEL ENGINE !

Turbochargers are rarely used with petrol engines but mostly used in diesel engines.We will discuss the reason behind this in this article.

A turbo charger is a device which uses exhaust heat from an Engine to get more air into the Cylinder during Induction stroke.More air translates to increased ability to burn more fuel which in turn increases the Power output (brake horse power) of the Engine.Turbocharging is common in modern car and truck Diesel engines to produce higher power outputs, lower emissions levels, and improved efficiency from a similar capacity of engine. Turbo-Diesels in automobiles offer a higher refinement level than their naturally aspirated counterparts.

Basically turbocharger compresses the air and forces into the engine cylinder so in short, we are putting more air into cylinder which results in more power.Compression of air by TURBOCHARGER INCREASES THE PRESSURE AND TEMPERATURE INSIDE THE CYLINDER.

Now, let us take the case of Diesel Engine:

Diesel as a fuel is not as combustible as petrol. The air-fuel mixture inside the cylinder should be at higher pressures for effective combustion of diesel. To withstand higher combustion pressures a diesel engine is built with strong, heavy parts.So,heavier parts can withstand higher pressure generated by turbocharger.Also,the heavier components of a diesel engine cannot rotate at higher RPMs.Lesser RPM means lesser air intake into combustion chambers. Hence a turbo charger helps a diesel engine to get more air into the combustion chamber.

Now come to Petrol Engine:

Petrol is more combustible than diesel and hence at lower pressures combustion can take place.If we add turbocharger to petrol engine then rise in pressure inside the engine cylinder may lead to problem of knocking.Also the parts of petrol engine is lighter than diesel engine so they may not withstand the pressure rise inside the engine cylinder.These are the reasons why turbochargers are not used with petrol engines. 

Also read:

DIFFERENCE BETWEEN KNOCKING AND DETONATION EXPLAINED !!

KNOW WHY THESE EQUIPMENTS ARE USED ON THE ROOF OF FACTORIES??

 You might have seen this type of rotating equipment on the roof of factories.In this article we will discuss what is this,what is does and how it works.

These are known as roof extractors. 

In summers, high temperatures build up inside small workshops and factory units making them extremely unpleasant to work in. As a temporary measure portable fans are installed to provide relief for workers, however while portable fans cool small areas of the building, the rest remains stiflingly hot.

Roof extractor fans provide a simple, low cost method of cooling for small buildings or rooms of upto approximately 1400 cubic meter (50,000 cubic feet).

It provides ventilation, fresh air and remove stale or contaminated air.Hot air is exhausted from the building and cooler outside air is sucked in though open doors and windows. As a result the temperature inside the building is held close to the outside temperature.

Using roof extractor fans to cool buildings of upto 1400 cubic meter has proved to be a very cost effective. By rapidly removing hot air from the building and sucking cooler air in through open doors and windows, the temperature inside can be kept close to the ambient (outdoor) temperature. 

KNOW WHY WIND TURBINES ARE ALWAYS PAINTED WHITE !!

You might have noticed that almost every wind turbine is painted white in colour.We will discuss reasons behind the white colour in this article.

1.)Generally wind turbines are painted white to be more aesthetically pleasing than otherwise. Painting them white or light grey helps the entire structure "blend" into the background, especially when the sky is cloudy. By making the entire structure white, the wind turbine is less visually obtrusive, in theory at least. White, after all, is a pretty neutral color.

2.)White, with an absence of colour, reflects sunlight and therefore reflect heat. Heat causes expansion, drying up of lubrication, and blistering. Consequently any colour would either shorten the life of a wind turbine by introducing increased wear and tear, or be more expensive in terms of maintenance. 

3.)Third reason is to make them visible from the sky.From the sky looking down, planes and aircraft will be able to see them standing out in the grass below them. This rule was implemented for safety reasons, and it is actually required by law that pilots must have a clear view of all wind turbines from above to avoid any accidents. 

 So these are the basic reasons why wind turbines are painted in white colour.If you liked this article then share it with your friends and if you have any doubt then feel free to ask in comment section.

KNOW WHY CARBON FIBER IS EXPENSIVE !!

Stronger than steel and a fraction of the weight, carbon fiber is a brilliant invention. Since its first use as a motor case on space rockets in the 1960s, it's often proclaimed as the ticket to better performance. It costs enough that it better. Despite 50 years of advancements carbon fibre remains expensively high end. But 50 years later, carbon fiber is still rare and expensive (starting at $10/pound.The rate of steel is $0.38/pound.)

FEW FACTS ABOUT CARBON FIBER:

1.)Carbon fiber -- sometimes known as graphite fiber -- is a strong, stiff, lightweight material that has the potential to replace steel and is popularly used in specialized, high-performance products like aircrafts, racecars and sporting equipment.

2.)The next generation of carbon-fiber composites could reduce passenger car weight by 50 percent and improve fuel efficiency by about 35 percent without compromising performance or safety.

3.)Carbon fiber can be woven into a fabric that is suitable for use in defense applications or added to a resin and molded into preformed pieces, such as vehicle components or wind turbine blades.

WHY CARBON FIBER IS EXPENSIVE: 

The main reason for high cost of carbon fiber is its manufacturing process.Let us see how it is made and what makes it expensive.

Before carbon fiber becomes carbon fiber, it starts as a base material—usually an organic polymer with carbon atoms binding together long strings of molecules called a polyacrylonitrile(similar to the acrylics in sweaters and carpets).To get the carbon part of carbon fiber, half of the starting material's acrylic needs to be removed. "The final product will cost double what you started with because half burns off,"This is responsible for a big part of the costs.

Then there are two major processing steps. The first is called oxidization stabilization. Here the fibers are fed through very long ovens with temperatures of several hundred degrees. The process takes hours to complete and is therefore a massive energy eater.

The second step is carbonization where the material is again placed in an oven, but this time the temperatures rise over thousand degrees. This step will also increase the power bill. It doesn’t end there.

Manufactures also have to take care of the off-gases to make sure they do not poison the environment, which needs lot’s of energy, real estate and large equipment. All steps are just for the manufacturing of the individual filaments themselves.

To get to the final product, the fibers and the resin have to be shaped and cured in an autoclave, again a time and energy consuming process.

So,the process of manufacturing is time taking and energy eating also only half of the raw material is used in final product.This leads to the high cost of carbon fibre.