Front Axle | Construction ,Function and Types Of Front Axle
The major unit on front part of the motor vehicle is front axle. It takes the weight of the front portion of the automobile. It gives steering facility and absorbs shocks. The weight of the front part of the vehicle is transmitted to the road surface through front wheels by the front axle of a vehicle. It also houses the mechanism for steering the vehicle to absorb shocks due to road surface variations.
Functions of Front Axle
1. It turns the front wheel easily.
2. It provides a cushioning effect though a spring.
3. It takes the weight of front vehicle.
4. It provides steering action.
S. The spring transmits cushion effect to the vehicle.
6. It controls the ride through shock absorber.
7. It takes the braking system.
8. It transmits power to the front wheels in case of four wheel drive.
9. It carries both the hub and wheels
Construction and Components of Front Axle
Axle beam is a major part of the front axle. It is used to transmit the vehicle weight to the front wheel through the spring. A typical front axle shown in Figure 4.31 elaborates the front axle components with steering linkage.
The ends of the axle beam are shaped in such way to assemble the stub axle. The ends of the axle beam are shaped either as a yoke or plain surface with drilled hole to hold a swivel pin connecting the stub axle portion of the assembly. The wheels are connected on stub axles.
The inclined steering arms are located to track rod ends. The third steering arm is connected to the drag link. The steering linkage is connected by the drag link to the drop arm of the steering box. The main axle beam is attached to stub axles by kingpins. The front road wheels are connected on these stub axles.
The components of the front axle are axle beam, stub axle, swivel pin and track load.
1. Axle beam:
Axle beams are made by drop forging of steel having 0.4% carbon or 1-3% nickel steel. The front axle beam is formed into l-section in the centre portion. The ends are made into either circular or elliptical. l-section construction carries bending loads caused by the load of
the vehicle and torque by braking of wheels. The centre portion of the front axle is provided a downward sweep to maintain the chassis height low. This axle beam is already hinged with stub axles. Springs are mounted on the axle beam at equi distance from its centre known Springs pads or seats.
2. Kingpin or Swivel pin:
The steering spindle and steering knuckle assemblies are pinned at the ends of axle beam in order to permit wheels to be turned by (he steering gear. This pin is known as kingpin or steering knuckle pin. It is also called swivel pins. The pins are made of good quality case
hardened steels used to secure the stub axle to the axle beam. It is exactly located and locked by cotter pins in position.
3. Track rod:
The two stub axles arms of the front axle are connected with ends of a track rod through knuckle or ball joints known as track rod ends. The connection is done by screws to ensure adjustments. In the stub axle, left hand and right hand threads are formed at each end. Toe-in
is increased by lengthening the rod and it is decreased by shortening the same.
4. Pull and push rod or drag link:
Pull and push rod also called drag link is connected between steering arm of the front axle and drop arm of the steering assemble. But the cross-section is tubular. Spring loaded ball sockets are provided at each end. One end is connected to the steering arm of the stub axle
whereas the other end is connected to the steering drop arm.
Types of Front Axles
There are two types of the front axles based on the rotation as follows.
1. Live front axle
2. Dead front axle.
Generally, the front axle is a dead axle. In heavy vehicles and most of cars, the front axle is a live axle. These types of axle are used in modern cars and heavier vehicles. The front axles are called as dead axles when they do not rotate but live axles transmit power to rear wheels. A live front axle also transmits the driving power to front wheels having different swiveling mechanisms. The dead front axle has enough rigidity and strength to transmit the weight of the vehicle from swings to front wheels.
There are two types of the front axles based on the axle beam as follows.
I. Straight axle
2. Double drop axle
3. Fully drop axle
Figure 4,33 illustrates these three types of front axle arrangements.
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