Front Wheel Drive System is a basic and most used system in lightweight cars. The engine and the whole transmission assembly are introduced and powered by the front wheels only. The rear wheels in this type of drive system are just the driven wheels.
In this article, I will discuss the function and the details of the Front Wheel Drive system.
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Front Wheel Drive
Front-wheel drive (FWD) is a type of vehicle propulsion system in which the power from the engine is delivered to the front wheels. This means that the front wheels are responsible for both steering and moving the vehicle forward. Front-wheel drive is common in many compact and midsize cars and offers advantages such as better traction in certain driving conditions, space efficiency, and cost-effectiveness.
FWD vehicles generally offer better traction, especially in slippery conditions like rain or snow. This is because the weight of the engine is over the front wheels, providing additional grip. These cars tend to have understeer characteristics, meaning they are more likely to continue in a straight line when cornering if the driver applies too much steering input. This is in contrast to rear-wheel-drive cars, which may exhibit oversteer.
FWD systems are generally less complex and less expensive to manufacture than rear-wheel or all-wheel-drive systems. Many everyday passenger cars, hatchbacks, and smaller SUVs use front-wheel drive due to their practical advantages for daily commuting and fuel efficiency.
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Working of Front Wheel Drive System
The overall design of a front-wheel-drive system is characterized by its simplicity and efficiency. The engine and the whole transmission system are equipped in a single housing that powers the front wheels only. This power drives the vehicle and the rear wheel.
The process begins with the vehicle’s engine, which generates power through the combustion of fuel. The combustion of this fuel moves the crankshaft. The power is then directed to the transmission, a crucial component that manages power distribution to the wheels. In FWD vehicles, the transmission is typically located at the front of the vehicle.
In many front-wheel-drive setups, especially in smaller and more compact vehicles, the transmission is combined with the front axle into a single unit called a transaxle. This integrated unit helps reduce weight and improve space efficiency. The transaxle sends power to the front wheels through a pair of drive axles. Constant Velocity (CV) joints are used at both ends of the axles to allow flexibility and smooth rotation as the wheels move and turn.
The front-wheel-drive system includes a differential, which distributes power between the two front wheels. This ensures that both wheels receive an appropriate amount of power, especially when turning. As power is delivered to the front wheels, they rotate, propelling the vehicle forward.
Note- In a front-wheel-drive configuration, the same wheels responsible for propelling the vehicle are also used for steering. This is different from rear-wheel-drive systems where the front wheels only steer, and the rear wheels provide propulsion.
Components of Front Wheel Drive
The front-wheel drive mechanism uses several key components that work together to transmit the power to the front wheels. These components help to transmit the power to the wheels in front. These components are-
1. Engine
The engine is the component used in the system to generate power in the system. The main hero of this drive is the Engine. The engine generating power is transmitted to the other system that helps to drive the wheels. In the front-wheel drive system, the engine is mounted in front of the driver.
2. Transmission System
The transmission manages the power generated by the engine and transmits it to the wheels. In many front-wheel-drive vehicles, the transmission is integrated with the front axle into a unit called a transaxle. In the transmission system, there are clutch and gearbox are in a single housing.
The clutch is used in the transmission system to add or cut off the engine power to the gearbox. The gearbox here is used to carry the engine torque and the power.
3. Transaxle
Transaxles are commonly found in front-wheel-drive cars, where the engine is located at the front of the vehicle. In rear-wheel-drive vehicles, the transmission and axle are often separate components, and the differential is usually located in the rear of the vehicle. The transaxle configuration is not limited to front-wheel drive; it can also be used in some all-wheel-drive setups, providing a compact and efficient solution for delivering power to both the front and rear wheels.
#4. Drive Axles
Drive axles are components of a vehicle’s drivetrain responsible for transferring power from the transmission or transaxle to the wheels. In a front-wheel-drive (FWD) or rear-wheel-drive (RWD) configuration, there are typically two drive axles—one for each side of the vehicle. In all-wheel-drive (AWD) systems, there are usually both front and rear drive axles.
#5. CV Joints
Drive axles include CV(Constant Velocity Joints) joints at both ends. These joints allow for flexible movement and rotation of the axles as the wheels move, turn, or go through suspension travel. CV joints are crucial for maintaining a constant speed and efficient power transfer, especially during turns.
#6. Spline Shaft
Spline shafts are often used in the design of drive axles. These shafts have a series of ridges (splines) that fit into corresponding grooves in other components, ensuring a secure and efficient transfer of power.
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Advantages of Front Wheel Drive
Regardless of the engine position, front-wheel drive has numerous advantages given as follows-
- Good drive-off and sufficient capacity with only a few people in the vehicle.
- Understeering in cornering, therefore self-braking.
- The front axle is loaded due to the weight of the drive unit, although the steering is not necessarily heavier(in comparison with standard cars) during driving.
- Long wheelbase making high ride comfort possible.
- Good engine cooling(radiator in front), and an electric fan can be fitted.
- Smooth can floor pan.
- A large boot with a favorable crumple zone for rear-end crash.
- There remains the load well distributed on steered and driven wheels.
- Good road holding, especially on wet roads and in winter conditions. Thus the car is pulled and not pushed.
- Insensitive to side wind.
- Simple rear axle design(a rigid axle is not necessarily a disadvantage).
- Short power flow because of the engine, gearbox, and differential from a compact unit.
- Effective heating due to short paths.
- Exhaust system with long path(important on cars with catalytic converters).
Disadvantages of Front Wheel Drive System
The disadvantages are-
- With powerful engines, the increasing torque and vibration influence the steering and also the engine length is limited.
- The power plant mounting has to absorb the engine moment times the total gear ratio.
- There is bending stress on the exhaust system from the power plant movements during drive-off and braking(with the engine).
- The turning and track circle is restricted due to the limited bending angle of the drive joints.
- There is higher tire wear in front because the highly loaded front wheels are both steered and driven.
- In the front-wheel drive, under the full load, poorer drive-off capacity on wet and icy roads and no inclines.
- With high front axle load, a high steering ratio or power steering is necessary.
- With high located, dash panel mounted rack and pinion steering, center take-off tie-rods become necessary, insignificant kinematic toe-in change partially inevitable.
Conclusion
It’s worth noting that while front-wheel drive is prevalent, there are also other drivetrain configurations like rear-wheel drive, all-wheel drive, and four-wheel drive, each with its own set of advantages and disadvantages depending on the vehicle’s intended use and design.
Frequently Asked Questions(FAQ’S)
Are all compact cars front-wheel drive?
While many compact cars use front-wheel drive, it’s not a universal rule. Some compact cars, as well as larger vehicles, may have rear-wheel drive or all-wheel drive configurations.
How does front-wheel drive differ from rear-wheel drive?
In front-wheel drive, the power is sent to the front wheels, while in rear-wheel drive, it’s sent to the rear wheels. This affects handling characteristics and the distribution of weight in the vehicle.
Is front-wheel drive better than rear-wheel drive?
The superiority of front-wheel drive versus rear-wheel drive depends on factors such as driving conditions, vehicle type, and personal preferences. Front-wheel drive is often preferred for everyday commuting due to its practical advantages.
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