KNOW WHY CANALS ARE MOSTLY MADE IN TRAPEZOIDAL CROSS SECTION !!

Common types of cross-sections for irrigation canals are trapezoid, parabolic, triangular, circular, and irregular (natural). Square / rectangular cross sections are used normally for concrete ducts.Out of these trapezoidal cross section is widely used due to following reasons :-

1)Heavy rains - The trapezoid has its width gradually increasing towards the top. In case of heavy rains , since the water level increases ,the trapezoid geometry ensures that the channel doesn’t overflow as the water is accomodated in the larger areas at the top of the trapezoid.

2) Velocity - The ratio of flow area to the contact area with the wall is very high. This decreases the effect of viscous forces on the flow velocity of water,thus making it move faster.

3) Safety - If someone or something falls into the canal by mistake, it is easier to climb a wall with a gradual gradient like the trapezoid unlike a vertical wall.

4.)Discharge-The best thing about a trapezoidal channel is that it has maximum discharge i.e., maximum volume of water flows through it within 1 second, when compared to rectangular, circular and triangular channels.

5.)This trapezoidal section offers least frictional resistance. 

6.)It is easy to maintain such as dredging and tile work in trapezoidal canal can be done by even unskilled labour and less equipments.

CHECK OUT WHY 4 STROKE ENGINES ARE MORE PREFERRED OVER 2 STROKE ENGINE !!

Even though power of two stroke engine is more than four stroke engine then why four stroke engine are used more?

ADVANTAGES OF 4 STROKE ENGINE :-

1. More torque :- In general, 4 stroke engines always make extra torque than 2 stroke engine at low RPM. Although 2 stroked ones give higher torque at higher RPM but it has a lot to do with fuel efficiency.
2. More fuel efficiency :- 4 stroke engines have greater fuel efficiency than 2 stroke ones because fuel is consumed once every 4 strokes.
3. Less pollution :- As power is generated once every 4 strokes & also as no oil or lubricant is added to the fuel; 4 stroke engine produces less pollution.
4. More durability :- We all know that more the engine runs, quicker it wears out. 2 stroke engines are designed for high RPM. If an engine can go for 10000 rpm’s before it wears out; a 4 stroke engine with 100 rpm will run for 100 minutes than the other 2 stroke engine which has a higher rpm of 500 & will run for only 20 minutes.
5. No extra addition of oil :- Only the moving parts need lubrication intermediately. No extra oil or lubricant is added to fuel.

DISADVANTAGES OF 4 STROKE ENGINE :-

1. Complicated design :- A 4 stroke engine has complex valve mechanisms operated & controlled by gears & chain. Also there are many parts to worry about which makes it harder to troubleshoot.
2. Less powerful :- As power gets delivered once every 2 rotations of crankshaft(4 strokes), hence 4 stroke is less powerful.
3. Expensive :- A four stroke engine has much more parts than 2 stroke engine. So they often require repairs which leads to greater expense.

2 Stroke engines creates lots of noise and pollution this is one of the prominent reason why 2 stroke engines are not preferred. 

So, overall the 4-stroke engines have some minor disadvantages but a lots of advantages which are more relevant.

LEARN HOW TO READ ENGINE OIL SPECIFICATIONS !!

You might have seen something like 20W-50 or 10w40 on engine oil bottles.

Lets check out its meaning !!

Your engines rotating parts are protected from heat and friction by a thin layer of oil. Understanding the viscosity ratings and detergents used in today's modern oils is critical to keeping your engine running. As an owner there is no more critical maintenance item than regular oil changes with the proper oil for your car or truck.

Oil weight, or viscosity, refers to how thick or thin the oil is. The temperature requirements set for oil by the Society of Automotive Engineers (SAE) is 0 degrees F (low) and 210 degrees F (high).

Oil weight, or viscosity, refers to how thick or thin the oil is. The temperature requirements set for oil by the Society of Automotive Engineers (SAE) is 0 degrees F (low) and 210 degrees F (high).

Oils meeting the SAE's low temperature requirements have a "W" after the viscosity rating (example: 10W), and oils that meet the high ratings have no letter (example SAE 30). An oil is rated for viscosity by heating it to a specified temperature, and then allowing it to flow out of a specifically sized hole. Its viscosity rating is determined by the length of time it takes to flow out of the hole. If it flows quickly, it gets a low rating. If it flows slowly, it gets a high rating.

Your engine needs oil that is thin enough for cold starts, and thick enough when the engine is hot. Since oil gets thinner when heated, and thicker when cooled, most of us use what are called multi-grade, or multi-viscosity oils. These oils meet SAE specifications for the low temperature requirements of a light oil and the high temperature requirements of a heavy oil. This is the best of both worlds and is accomplished by using special additives to increase viscosity with increase temperature.

In a 10w-40 for example the 10w bit (W = winter, not weight or watt or anything else for that matter) simply means that the oil must have a certain maximum viscosity/flow at low temperature. The lower the "W" number the better the oil's cold temperature/cold start performance.

The 40 in a 10w-40 simply means that the oil must fall within certain viscosity limits at 100°C. This is a fixed limit and all oils that end in 40 must achieve these limits. Once again the lower the number, the thinner the oil: a 30 oil is thinner than a 40 oil at 100°C etc. Your handbook will specify whether a 30, 40 or 50 etc is required.

For more clarification watch the video :