Rear Axle and its types are discussed in this article. The axle is the central shaft on which a pair of wheels or shafts rotates. The axle is a very important component as it gives support to the wheels. So read the types and the importance of axles in an automobile vehicle.
What is a Rear Axle
In between the differential and the driving wheels is the rear axle to transmits power from the differential to the driving wheels. It is clear from the construction of the differential, that the rear axle is not a single piece, but it is in two halves connected by the differential, one part is known as a half shaft.
The inner end of the half shaft is connected to the sun gear of the differential, and the outer end of the driving wheel. In rear-wheel drive vehicles, the rear wheels are the driving wheels, whereas in front-wheel drive vehicles, the front wheels are the driving wheels.
Almost all rear axles on modern passenger cars are live axles, that is, they revolve with the wheels. Dead axles simply remain stationary, and do not move with the wheels. A housing completely encloses the rear axles and the differential, protecting them from water, dust, and injury, in addition to mounting their inner bearings and providing a container for the lubricant.
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Loads on a Rear Axle
When the wheels have plain bearings on the axle casing, the rear shafts merely transmit the driving torque from the differential to the wheels. But this is not always so. The shafts sometimes play an essential part in supporting the axle casing and thus the weight of the body.
The vertical load, which comes onto the axle casing, through the springs, is transmitted through these bearings to the shafts and hence through the wheels to the ground. The reaction of this load between the wheel and the ground acts upward on the wheel.
This force tends to bend the overhanging part of the shaft, as at (a), and the shear it as at (b) in Fig. P4-1. Again, if a side force acts upon the wheel due to any reaction, it will tend to push the shaft into the axle casing. This tendency is resisted by the thrust bearing situated at the center of the axle. If the force acts outwards the end thrust becomes a pull. The force tends to bend the hanging part of the axle, as at (c).
Therefore, it is concluded that depending upon the arrangement of the bearings the rear axle or the axle casing must support:
- The total rear weight of the vehicle, causing both bending and shearing action.
- Side thrust on the wheels when cornering, which imposes a bending load and an end thrust or a pull.
- Driving torque.
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Rear Axle and Its Types
Types of rear axles. Depending upon the methods of supporting the rear axles and mounting the rear wheels, the rear axles are of three types:
- Semi-floating axle.
- Full floating axle.
- Three-quarter floating axle.
#1. Semi Floating Axle
A semi-floating axle has a bearing located on the axle and inside the axle casing. It has to support all the loads listed above. Therefore, it needs to be larger, for the same torque output, than any other type. The inner end of the axle is supported by the differential side gear.
It is thus relieved of the Job of supporting the weight of the car by the axle housing. The outer end has to support the weight of the car and take end thrust. The inner end of the axle is splined to the differential side gear. The outer end is flanged so that the wheel can be bolted directly to it.
In some designs, the hub of the wheel is keyed to the outer end of the axle. The vehicle load is transmitted to the axle through the casing and the bearing, which causes the bending or shearing of the axle. The semi-floating axle is the simplest and cheapest of all other types and is widely used on light goods vehicles.
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#2. Full Floating Axle
bas to support all the loads as listed above. Therefore, it needs to be larger, for the same torque output, than any other type. The inner end of the axle is supported by the differential side gear. It is thus relieved of the Job of supporting the weight of the car by the axle housing.
The outer end has to support the weight of the car and take end thrust. The inner end of the axle is splined to the differential side gear. The outer end is flanged so that the wheel can be bolted directly to it. In some designs, the hub of the wheel is keyed to the outer end of the axle.
The vehicle load is transmitted to the axle through the casing and the bearing, which causes the bending or shearing of the axle. The semi-floating axle is the simplest and cheapest of all other types and is widely used on light goods vehicles.
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#3. Three Quater Floating Axle
A three-quarter floating axle has a bearing located between the hub and the axle casing. Thus, the weight of the vehicle is transferred to the axle casing, and only the side thrust is driving torque are taken by the axle. The axle is keyed rigidly to the hub, thus providing the driving connection and maintaining the alignment of the wheel.
The inner end of this axle has the same construction as that of the semi-floating axle. Although the three-quarter floating axle is more reliable it is not as simple as the semi-floating axle.
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Maintenance of Axle
Maintenance of the axle is important to run the wheels on the road perfectly. Visual inspection is important to spot the wear of the components. The moving parts are equipped with the system only, so there is a high probability of breaking down.
Proper lubrication is important to run without any friction. Also, smooth movement is required for anti-heat conductivity. Also, the leakage in any hydraulic system causes damage to the system. The brake system is also connected to the axle housing and these brakes also need maintenance.
Misalignment of axles can lead to premature wear of tires and other components. Periodically check and adjust the alignment of axles to ensure they are properly aligned with the vehicle chassis. For complex maintenance tasks or repairs, consider consulting a qualified mechanic or technician with experience in axle systems. They can provide expert diagnosis and ensure proper maintenance procedures are followed.
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Conclusion
Axles come in various configurations depending on the vehicle’s design, including solid axles, independent axles, and drive axles. Solid axles connect both wheels on the same side of the vehicle and are commonly found in rear-wheel-drive and heavy-duty vehicles. Independent axles allow each wheel to move independently.
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