Rear live axle shaft supporting mechanism
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In rear-wheel drive, we transmit engine power to wheels with the help of axle shafts via the differential. Depending on the capacity of vehicles, rear axle shaft supporting has been varying with conventional mechanisms. Generally, these rear live axle shafts have subjected to some stresses including,
- Torsional stress - driving torque have generated due to power transmission to the road wheels
- Vertical bending stress - bending moment takes place due to weight and load acting on the vehicle
- Horizontal bending stress - end thrust is built due to side force and cornering force act on the wheels
Types of Rear axles :
Semi-floating rear axle
Here, the rear live axle shaft is directly connecting to the wheel hub with the help of a flange containing bolt pattern sticks, which has coupled at the outer end of the axle shaft, and the inner end is splined to mesh with the drive gear. The bearing has placed between the axle shaft and casing at the edge. In this axle shaft, all the forerunning stresses are continuously acting along entirely that to transfer the same torque output to the wheels, the diameter of the semi-floating axle is larger when considering other axles. If we want to takeout the axle shaft from the casing incases of any failure, we need to rip out the wheel fittings. This semi-floating rear axle is simple in design and inexpensive so that it is mostly adopting in cars, SUVs, and mid-size trucks, like light-duty pickups.
Three-quarter floating rear axle
Similar to the above axle, a three-quarter floating axle is connected with the wheel hub using a flange. Only a placement of bearing differs., ( i.e.) the roller bearing is placed between the axle casing and wheel hub. So the axle shaft eliminates bending movement caused by vertical loads and has to withstand end thrust and driving torque. In case of any failure, the wheel housing needs to remove for taking out the axle shaft. This three-quarter floating axle is expensive compared to the previous one, so it is using in particular cars and light commercial vehicles.
Full-floating rear axle
In this type, the name itself briefs the functioning of a rear axle, in which the axle shaft floats without undertaking any kinds of vehicle loads. The axle shafts have splines on both ends, so the outer end of the axle shaft meshes with splines placed inside the flanged sleeve housing, and the inner end meshes with the drive gear. Here two taper roller bearings are placed between the axle casing and flanged sleeve housing, which has bolted with the wheel hub. These bearings take up all side forces and vertical loads and give it to the axle casing, so the axle shafts can withstand only torsional stress due to carrying a driving torque to wheels. If the axle shaft tends to fail, instead of jacking up the vehicle, the axle shaft can eject without dismantling their housing on the wheel. This full-floating rear axle is very firm, so it is using in light trucks with towing capabilities and heavy-duty vehicles.
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