Modern automobiles use various half-shaft support types, with fully floating and semi-floating being the two most common. Some sources also classify them into three types: fully floating, 3/4 floating, and semi-floating.
A fully floating half-shaft is characterized by bearing only torque during operation, with no force or bending moment at either end. The outer end of this half-shaft is bolted to the wheel hub, which is then mounted on the half-shaft sleeve via two distant bearings. The inner end features a specially designed spline, while the outer end is a flange with several drilled holes. Due to its simple structure and reliable operation, the fully floating half-shaft is widely used in commercial vehicles.
4. Floating Half-Shaft
In addition to bearing all torque, this type of half-shaft also bears some bending moment. Its unique feature is that it has only one bearing at the outer end, which supports the wheel hub. Because the supporting stiffness of a single bearing is relatively weak, the 3/4 floating half-shaft must not only handle torque but also withstand the bending moments caused by the vertical force, driving force, and lateral force between the wheel and the road surface. However, this type of half-shaft is relatively rarely used in automobiles.
Semi-floating Half-shaft
In the design of a semi-floating half-shaft, its outer end journal is directly mounted on a bearing in the inner bore of the outer end of the axle housing. The end of the half-shaft is connected to the wheel hub via a tapered journal and a key, or directly to the wheel disc and brake drum via a flange. Therefore, this type of half-shaft is responsible not only for transmitting torque but also for withstanding the bending moments generated by the vertical force, driving force, and lateral force transmitted from the wheel. Due to its simple structure, light weight, and affordable cost, the semi-floating half-shaft is widely used in passenger cars and some light vehicles.
