DIFFERENTIALS
The general purpose of the differential is to split the torque coming from the engine to each individual wheel of an axle so that they can rotate at different speeds irrespective of each other. In the early days of the automobile during the start of the 20th century when the concept of the differential was not invented, only one of the rear wheels was connected to the engine.
As a matter of fact, very few electric cars have to hassle of differentials, those EVs that have only one motor for an axle, include differential otherwise they have one motor for each wheel. But for gasoline-powered engines, it is a better idea to transfer the power generated from the engine through the gears as ICE produces torque at a variable rate and so the power is transferred with increasing gear ratios.
Generally, electric cars tend to be heavy as the batters add a lot of weight but in some cases, they are saving weight. In hybrid cars, they have gone far as a replacement for the reverse gear which in turn saves a considerable amount of weight.
The shortcoming of a normal mechanical differential is very radical. In the usual case, the power is transferred to the tire that has the least traction, that’s why whenever the tire that has gone airborne in off-road situations spins endlessly, sometimes making the situation dangerous.
Many modifications have been made to tackle this situation as discussed below:-
1.Open Differential
It is the most basic type of differential that simply allows for the torque to pass to the wheels from the gearbox. The torque split is held 50/50 to both wheels of an axle by default. This is the most common type of differential system that you’ll find in your car.
A massive drawback of this system is that when one wheel is lifted then the maximum torque is sent to the lifted wheel, and very little torque stays with the well-settled wheel.
2. Locking Differential
Locking diffs falls in the opposite spectrum of the open differential. The primary purpose of this system is to split torque 50/50 between the 2 wheels no matter the conditions and situation are. Usually, an option is there inside the vehicle in the form of a switch to switch from an open differential to a closed differential.
It basically locks the diff. and makes both the wheels spin at the same rate even when one wheel is in the air, this system results in superior traction in offroad conditions.
3.Limited-Slip Differential (LSD)
These types of differentials are becoming a common thing as it is also tackling the common problem of open diff. It allows for a proper split of torque even when the wheel is in the air in unfavorable conditions. It mains the proper 50/50 split in all conditions.
It limits the spinning and slippage of the wheel on demand. It purposefully restricts the excessive power going to one wheel. It is an electronic system rather than a mechanical one.
4.Torque Vectoring Differential
This system is kind of an advanced one as it is mostly used in high-end performance cars. Torque vectoring system alone is there in very few cars. Let alone a torque vectoring system which ultimately becomes even rarer.
It electronically provides the engine torque to each wheel in a differential. This is done on demand and can be altered between the wheels in a fraction of a second. The wheel with the least traction in a turn is given more traction.
5.Active Differential
It is very much like the limited-slip differential. This system still employs mechanisms to provide the bare resistance needed to transfer torque from one side to another but rather than relying on purely mechanical force, clutches can be electronically activated.
Other Important Engineering Terms
1.Prop-Shaft
The bar connecting the front engine to the rear differential. It is long and cylindrical in shape. The bar is only found in RWD and AWD cars and not in AWD cars.
If ever the bar breaks down, then the vehicle becomes completely immobile to the point that it can’t move an inch. If it breaks in the middle of the road then you are doomed. There can be many possible reasons for this, a truck carrying more capacity than it should be carrying, overloading can be one of the reasons. Applying more pressure in off-road conditions can be another reason.
2. Understeer & Oversteer
The concept of understeer and oversteer is very simple and radical at the same time. All cars suffer these sets of situations in their lifetime. The stress that tires handle in these situations is beyond immense. These situations are the primary reason for abnormal wear and tear.
Understeer is a situation when the front tires lose grip and increase the turning radius of the car under hard cornering.
Oversteer is a situation when the rear tires lose grip and sometimes spins under hard cornering.
Understeer is the most common of the two because it can happen in a front-engined car at a considerable high speed whereas oversteer generally happens in rear-engine cars because of excess power in rear wheels or the engine being at the back. Oversteer can be fun sometimes as some people use this to drift the car. Drifting is basically controlling the car on the edge and making it go sideways in a completely controlled manner.
Drifting is also a situation of controlled oversteer.
INTERESTING FACTS ABOUT DIFFERENTIAL
- Mercedes’ G-wagon has buttons inside its cabin to open or close front and rear differentials. It has a total of 3 buttons for the job, the 1st one locks the front diff. the second button locks the rear diff. and the 3rd button locks all the wheels at the same time. It does everything electronically with the help of a central computer. All these modifications make it a beast in off-road capability.
- Many cars have the option of shifting to a low gear ratio which allows for improved capability in off-roading capability. Lower gear ratios help achieve the instant pick-up of the vehicle even greater but compromise on gaining high speed.
