Top 10 Reasons – Why should one be a Mechanical Engineer?

1. You have a great opportunity to create something innovative and useful. Your creation solve
the problem of others and it gives you great feeling.

2.   It is really broad branch of engineering so career options are wide after graduation.

3.   Variety in the learning- you learn how to design the thing from safety pin to aircraft.

4.   Easy to understand the thing whatever you learn.

5.   You create a range of skills- you learn as a machine operator, a smith , a foundry man, a mechanic, a plant manager, a plant manager, a researcher and rule maker.

6.    You work with massive machines to tiny precious instruments , micro and nano devices.

7.   Every industry has a importance of your work because you are only human resources that required for the survival of any industry.

8.   Get paid very handsomely (after gaining little year experience.)

9.   Not much of girls hanging around. You do not have to worry about geeting dressed perfectly for class or for girls.

10.                It sounds and nice feeling to be called as a mechanical engineer.

DIFFERENTIAL

Introduction:-

The differential is an integral part of all four wheeler. Differential technology was invented centuries ago and is considered to be one of the most
ingenious inventions human thinking has ever produced.The differential is a device that splits the engine torque two ways, allowing each output to spin at a different speed. 

Why the Differential gear is used?

Wheels receive power from the engine via a drive shaft. The wheels that receive power and make the vehicle move forward are called the drive wheels. The main function of the differential gear is to allow the drive wheels to turn at different rpms while both receiving power from the engine.

The differential has three jobs:

• To aim the engine power at the wheels
• To act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before it hits the wheels
• To transmit the power to the wheels while allowing them to rotate at different speeds (This is the one that earned the differential its name.)

Parts of differential is shown in figure above :-

Differential Operation:-

Now let’s see how the differential manages to rotate the side gears (drive wheels) at different speeds as demanded by different driving scenarios.

The vehicle moves straight

In this case, the spider gear rotates along with the ring gear but does not rotate on its own axis. So the spider gear will push and make both the side gears turn, and both will turn at the same speed. In short, when the vehicle moves straight, the spider-side gear assembly will move as a single solid unit.

The vehicle takes a right turn

Now consider the case when the vehicle is taking a right turn. The spider gear plays a pivotal role in this case. Along with the rotation of the ring gear it rotates on its own axis. So, the spider gear is has a combined rotation. The effect of the combined rotation on the side gear is interesting.When properly meshed, the side gear has to have the same peripheral velocity as the spider gear. Technically speaking, both gears should have the same pitch line velocity. When the spider gear is spinning as well as rotating, peripheral velocity on the left side of spider gear is the sum of the spinning and rotational velocities. But on the right side, it is the difference of the two, since the spin velocity is in the opposite direction on this side.This means the left side gear will have higher speed compared to the right side gear. This is the way the differential manages to turn left and right wheels at different speeds.

The vehicle takes a left turn

While taking a left turn, the right wheel should rotate at a higher speed. By comparing with the previous case, it is clear that, if the spider gear spins in the opposite direction, the right side gear will have a higher speed.

DIFFERENT TYPES OF LAYOUT IN AUTOMOBILES

1.)Front engine front wheel drive 

Front-wheel drive is the most common form of engine/transmission layout used in modern passenger cars, where the engine drives the
front wheels only.In this layout a front mounted engine-clutch-gear box unit drives a beam type rear axle suspended on leaf sprints through a propeller shaft with two universal joints.  Most front wheel drive vehicles today feature transverse engine mounting, though many in prior decades were positioned longitudinally instead.

Advantages:-

•  Balanced weight distribution between the front and the rear wheels.
• Easy front wheel steering.
• Behind the rear seats, large luggage space is available.
•  Accessibility to various components like engine, gearbox and rear axle is better in  comparison to other layouts. The control linkages-accelerator, choke, clutch and gearbox are short and simple.
• Full benefits of the natural air stream created by vehicle’s movement is taken by the forward radiator resulting in reduced power losses from a large fan.
• Small length of the propeller shaft permits the angularity of the universal joints to be small and easily provided by simple types.

2.)Rear engine rear wheel drive

Rear-engine, Rear-wheel-drive layout places both the engine and drive wheels at the rear of the vehicle.It is shown in figure below

Advantages:-

• Better road adhesion preferably on steep hills and while accelerating with increased weight on the driving wheels.
• Generally a proportional part of weight of the car is transferred to the front wheels while braking. Therefore, due to the firm road surface contact maintained by rear engined car results in assistance to stopping of the vehicle.
• In this arrangement, front wheels are only for steering purposes.
• The necessaity of the propeller shaft is altogether eliminated due to the combination of engine, gear box and final drive. This also requires only one common oil sump.
• Good visibility and stream lining is provided by proper design of vehicle front.

3.)All wheel drive

An AWD vehicle (short for All-wheel drive vehicle) is one with a powertrain capable of providing power to all its wheels, whether full-time or on-demand.It appears in everything from supercars with out-of-this-world performance like the Audi R8 to family crossovers and SUVs like the Volvo XC90.

Advantages:-

• As compared to rear wheel driven car, there is a faster and safer travelling due to good road holding on curves.
• Gives sportier handling and traction to a broader range of cars.
• A lower flat floor lines is provided due to dispensing with the propeller shaft resulting in lowering of centre of gravity.
• The engine, clutch, gear box and final drive are combined similar to the rear engine car. This provides a more comfortable drive due to final drive spring. 
• Good road adhesion is obtained due to a large part of the vehicle’s weight being carried on the driving wheels under normal conditions.

ALL ABOUT GEARS

Gears are toothed wheels which are used to transmit force to other gears or toothed parts by meshing with minimal slip.
When two gears are meshed together, the smaller gear is called a pinion. The gear transmitting force is referred to as a drive gear, and the receiving gear is called the driven gear.

When pinion is the driver, it results in step down drive in which the output speed decreases and the torque increases. On the other hand, when the gear is the driver, it results in step up drive in which the output speed increases and the torque decreases.

Law of gearing:-

The angular velocity ratio of all gears of a meshed gear system must remain constant also the common normal at the point of contact must pass through the pitch point.

Screw thread terminology

Powder metallurgy

Powder metallurgy:-

Powder metallurgy is the process of blending fine powdered materials, pressing them into a desired shape or form (compacting), and then heating the compressed material in a controlled atmosphere to bond the material (sintering). The powder metallurgy process generally consists of four basic steps: powder manufacture, powder blending, compacting, and sintering. Compacting is generally performed at room temperature, and the elevated-temperature process of sintering is usually conducted at atmospheric pressure. Optional secondary processing often follows to obtain special properties or enhanced precision. The use of powder metal technology bypasses the need to manufacture the resulting products by metal removal processes, thereby reducing costs.

Powder metallurgy is also used in "3D printing" of metals.

CHOKE IN BIKES

Choke valve in bikes :-

A choke valve is sometimes installed in the carburetor of internal combustion engines. Its purpose is to restrict the flow of air, thereby enriching the fuel-air mixture while starting the engine. Depending on engine design and application, the valve can be activated manually by the operator of the engine (via a lever or pull handle) or automatically by a temperature-sensitive mechanism called an autochoke.

Why it is important?

Choke valves are important for naturally aspirated gasoline engines because small droplets of gasoline do not evaporate well within a cold engine. By restricting the flow of air into the throat of the carburetor, the choke valve reduces the pressure inside the throat, which causes a proportionally greater amount of fuel to be pushed from the main jet into the combustion chamber during cold-running operation. Once the engine is warm (from combustion), opening the choke valve restores the carburetor to normal operation, supplying fuel and air in the correct stoichiometric ratio for clean, efficient combustion.