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Differential is an integral part of all four wheelers. Wheels receive power from the engine via a drive shaft and the main function of the differential is to allow these wheels to turn at different rpms, while receiving power from the engine.
Consider these wheels which are negotiating a turn. Clearly that the left wheel has to travel more distance than the right wheel which means the left wheel has to rotate at a higher speed. If these wheels were connected using a solid shaft as shown, the wheels have to slip to accomplish the turn. This is exactly where a differential comes in. The ingenious mechanism in a differential allows left and right wheels to turn at different rpms, while transferring power to both the wheels.
Step by step we will learn how differential achieves this feat using its simplest configuration. Power from the engine is transferred to the ring gear through a pinion gear. The ring gear is connected to a spider gear which is at the heart of the differential. The spider gear is free to rotate in two different ways, one along the ring gear and two on its own axis. The spider gear is meshed with 2 side gears. So, power from the engine flows from the pinion to the left and right wheels as shown.
Now let’s consider different cases. When the vehicle moves straight the spider gear rotates along with the ring gear but it does not rotate on its own axis. The spider gear will push and make both side gears turn at the same speed. When the vehicle is moving straight, the spider-side gear assembly will move as a single solid unit.
Now consider the case when the vehicle is taking a right turn. The spider gear plays a pivotal role here. Along with the rotation of the ring gear, the spider gear spins on its own axis. In fact the spider gear is forced to do the second spin to meet the demands of the right and left wheels differing speeds. So the spider gear is having a combined rotation. The effect of 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. When the spider gear is spinning and rotating, the peripheral velocity at the left side of spider gear is the sum of spinning and rotational velocity. However, on the right side it is the difference of the two. The left side gear will have higher speed compared to the right side gear. Which is how the differential manages to turn left and right wheels at different speeds.
Consider these wheels which are negotiating a turn. Clearly that the left wheel has to travel more distance than the right wheel which means the left wheel has to rotate at a higher speed. If these wheels were connected using a solid shaft as shown, the wheels have to slip to accomplish the turn. This is exactly where a differential comes in. The ingenious mechanism in a differential allows left and right wheels to turn at different rpms, while transferring power to both the wheels.
Step by step we will learn how differential achieves this feat using its simplest configuration. Power from the engine is transferred to the ring gear through a pinion gear. The ring gear is connected to a spider gear which is at the heart of the differential. The spider gear is free to rotate in two different ways, one along the ring gear and two on its own axis. The spider gear is meshed with 2 side gears. So, power from the engine flows from the pinion to the left and right wheels as shown.
Now let’s consider different cases. When the vehicle moves straight the spider gear rotates along with the ring gear but it does not rotate on its own axis. The spider gear will push and make both side gears turn at the same speed. When the vehicle is moving straight, the spider-side gear assembly will move as a single solid unit.
Now consider the case when the vehicle is taking a right turn. The spider gear plays a pivotal role here. Along with the rotation of the ring gear, the spider gear spins on its own axis. In fact the spider gear is forced to do the second spin to meet the demands of the right and left wheels differing speeds. So the spider gear is having a combined rotation. The effect of 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. When the spider gear is spinning and rotating, the peripheral velocity at the left side of spider gear is the sum of spinning and rotational velocity. However, on the right side it is the difference of the two. The left side gear will have higher speed compared to the right side gear. Which is how the differential manages to turn left and right wheels at different speeds.
While taking a left turn, the spider gear will spin in the opposite direction. In order to carry load one more spider gear is usually added. 4 spider gear arrangement is also used for heavy load vehicles.
Apart from allowing wheels to rotate at different rpms, the differential has got 2 more functions. The first of these alternate functions is speed reduction at pinion ring gear assembly which will result in torque multiplication. The other function is to turn the power flow direction by 90 degrees.
The differential we have gone through so far is known as open or standard differential. It is capable of turning wheels at different rpms, but it has one major drawback. Consider a situation where one wheel of a vehicle is on a surface with good traction and another wheel on a slippery track. In this case a standard differential will send the majority of the power to the slippery wheel, so the vehicle won’t be able to move.
To overcome this problem Limited Slip Differentials were introduced. We will learn more about them in a separate video. Thank you.
Apart from allowing wheels to rotate at different rpms, the differential has got 2 more functions. The first of these alternate functions is speed reduction at pinion ring gear assembly which will result in torque multiplication. The other function is to turn the power flow direction by 90 degrees.
The differential we have gone through so far is known as open or standard differential. It is capable of turning wheels at different rpms, but it has one major drawback. Consider a situation where one wheel of a vehicle is on a surface with good traction and another wheel on a slippery track. In this case a standard differential will send the majority of the power to the slippery wheel, so the vehicle won’t be able to move.
To overcome this problem Limited Slip Differentials were introduced. We will learn more about them in a separate video. Thank you.