How engine is connected to wheels? | How does an engine connect to a transmission?

The running automobile always makes me curious to think about that How engine is connected to wheels? Hence I did a small research to find the relation between engine and wheels, the outputs of which I have mentioned in this article.

The engine is connected to wheels for the purpose of power transmission. The engine shaft is coupled to the gearbox using a clutch which permits engagement and disengagement between them. The gearbox output is connected to the differential by means of the propeller shaft. The differential divides the power from the propeller shaft to both driving wheels which are connected by half axles on both sides.

Why engine is connected to the wheels?

The engine is the heart of the vehicle. When the engine generates power by burning the fuel, power transmits from the engine to the wheel and a vehicle runs. Therefore to power transmission from the engine to the wheels, they are connected through some mechanisms that we will discuss below.

How engine is connected to wheels?

How engine is connected to wheels

1) The output shaft of the engine is connected to the clutch while the output of the clutch is connected to the input of the transmission gearbox.

2) The clutch allows engagement and disengagement between the engine and gearbox.

3) The transmission gearbox fulfils the different torque and speed requirements as per driving conditions like climbing on hills, racing on straight roads etc.

4) The output of the gearbox is connected to the propeller shaft which transmits power from the transmission gearbox to the final drive.

5) Final drive help to transmit power from the propeller shaft to the perpendicular rear axle. Its main purpose is to transmit the power between the shafts which are perpendicular to each other.

6) The final drive is associated with the differential unit which helps to rotate both driving wheels at different speeds which is necessary while moving on a curved road.

7) Output shafts of the differential unit are connected to the wheels using two half rear axles.

8) The rear axle and propeller shaft has a universal joint and slip joint to allow angular and linear disturbance.

Role of each component in connecting engine and wheels:

In general, the components required to connect the engine and the wheels for the transmit power from the engine to the wheel are listed below:-

  1. Clutch
  2. Gearbox
  3. Propeller shaft with a universal joint and slip joint
  4. Final drive with differential unit
  5. Rear axle

Now let’s see in detail what is the role of each component that helps in connecting the engine and wheels and the transmission of power from the engine to the wheel.

A] clutch:-

  1. This device controls the engagement and disengagement between the engine and gearbox.
  2. Whenever the clutch is in the engaged condition it allows the gearbox input shaft to rotate with the speed of the engine shaft.
  3. Whenever the clutch is in the disengaged condition the engine gets isolated from the further transmission system and the power of the engine is not transmitted to the gearbox shaft.

What is need for a clutch?

  1. To engage and disengage the transmission gearbox from the engine
  2. It is easy to stop the vehicle while the engine is in running condition.
  3. To prevent damage to the gearbox from shocks and allow smooth engagement.

B] Transmission gearbox:-

  1. It is the type of gearbox which gives multiple stages of output speed and torque by changing the gear ratios.
  2. The gear ratios can be changed by shifting the transmission lever which changes the engagement between gears.

Why gearbox is required?

  1. The engine generally provides low torque with low speed and high torque with higher speed.
  2. But while moving on a straight road the vehicle requires higher speed with less torque and while climbing onto the hills, the vehicle requires higher torque with less speed.
  3. Hence to fulfil this requirement the transmission gearbox has different stages with different torque and RPM.
  4. It also has the provision of reverse gear to move vehicles in the backward direction.

C] Propeller shaft:-

  1. The propeller shaft is fitted between the gearbox and the final drive.
  2. It transmits power from the gearbox output to the final drive.
  3. At both ends of the propeller shaft, the universal joint is fitted to allow angular Transmission of power.
  4. It also has a slip joint because of which the length of the propeller shaft can easily fluctuate.

Need of propeller shaft:-

  1. It is used to connect the gearbox output shaft to the final drive shaft.
  2. It also allows angular disturbance and linear displacement while power transmission.

D] Final drive:-

  1. The final drive is used to transmit the power from the propeller shaft to the rear axle which is perpendicular to each other.
  2. Another use of the final drive is to give fixed speed reduction using pairs of gears.
  3. It can give the reduction up to 10:1.
  4. The gears used are bevel gears, hypoid gears, and worm and worm wheels.

What is the need for the final drive?

  1. To transmit power from the propeller shaft to the rear axle which is perpendicular to each other.
  2. To provide the fixed speed reduction.

E] Differential:-

  1. It is connected between the final drive and the rear axle.
  2. The purpose of the differential is to allow an equal amount of power transmission to both driving wheels with a slight change in speed of both tyres.
  3. It consists of two sun gears mounted on each half axle shaft.
  4. The pinion gear meshes with both sun gears.
  5. The cage holds all pinion gears together.

What is the need for the differential?

  1. It helps vehicles while moving on curved roads. using the differential unit both axle shaft rotates at different speeds which helps to change the vehicle direction.
  2. When the vehicle is on a bumpy road the differential allows both wheels to rotate at different speeds.

F] Rear axle:-

  1. It is used to connect the output of Differential to the wheels.
  2. It also bears the maximum load of vehicles.
  3. It also has a universal joint to allow angular power transmission to the wheel.

What wiill happen if engine and wheels are not connected?

I know some will definitely think that what will happen if the engine is someway not connected to the wheels? Obviously, Vehicles will not run since no power will be transmitted from the engine to the wheels. Wheels will remain idle until they do not receive power from the engine.

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Pratik is a Graduated Mechanical engineer. He enjoys sharing the engineering knowledge learned by him with people.

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