What is Propeller Shaft in Cars and What are Its Components?

There are numerous components in a car working in unison to ensure a seamless driving experience. One such important element is the propeller shaft. It plays a crucial role in transmitting power from the engine to the wheels. 

In this piece, we will discuss the propeller shaft in automobiles - its characteristics, types, materials, advantages and so on.

The propeller shaft, also known as the Drive Shaft is a component in a car that is used to transfer the engine's torque from the transmission to the differential axle. Its main work is to transfer the power from one end of the car to the other even when separated by a distance.

Here are some of the notable characteristics of the propeller shaft.

• The main role of the propeller shaft is to transfer the engine’s rotational power in the gearbox output shaft to the differential axle. 
• RPM or Revolutions per minute remains consistent during power transmission and hence there are minimal to no power losses.
• The shaft is capable of adjusting itself while the car runs through obstacles like speed breakers. 
• It has the capability to transfer power between components that are located at varying heights.

The Propeller shaft comprises three main components that are given below:

1. Universal Joint

 is an integral part of a propeller shaft. There are typically two universal joints in a single-piece shaft while the number can go up to three or four depending on the type of propeller shaft.

2. Slip Spline Joint

It is often situated at the output end of the propeller shaft. The major role of slip spline joints is to facilitate torque transmissions over different shaft lengths.

3. Tubular Shafts

The primary role of tubular shafts is to lessen the gap between the rear axle and the gearbox. The shaft size depends on the distance from the gearbox to the axle.

• As the engine generates power, it sends rotational energy to the transmission which then transmits it to the propeller shaft.
• This is further transmitted to the differential which distributes the power among the wheels, allowing the vehicle to move smoothly.
• Based on the road conditions, whether flat surface or uneven, the propeller shaft moves up and down such that the length of the shaft changes and the transmission system’s distance is maintained safely.

The two fundamental types of propeller shafts are:

1. Single-piece Propeller Type

• Comprises two universal joints, one tubular shaft and one slip spline joint.
• Used for short-distance transmission in cars.
• More durable than two-piece propeller types owing to friction welding techniques.

2. Two-piece Propeller Type

• Comprises three universal joints, two tubular shafts and one slip spline joint.
• Ideal for long-distance transmission such as buses.
• Exhibits lower strength due to increased number of joints.

The propeller shaft is generally made using steel, kevlar epoxy and epoxy composite material Alloys of aluminium and stainless steel. Discussed below are some of them:

• SM45C Steel: It is a high-quality and low-carbon structural steel known for its excellent wear resistance, a critical attribute for propeller shafts.
• Epoxy Composite Material: These composites are ideal for developing high-precision shafts due to their exceptional tensile strength ranging from 800-1300 MPa.
• Alloys of Aluminium and Stainless Steel: These materials are known to withstand torsional vibrations and exhibit high tensile strength.

The propeller shaft offers several benefits: 

• There is minimal to no power loss during power transmission.
• The tubular structure contributes to the lightweight design of the shaft.
• The construction of the shaft is simple which means it is easy to maintain leading to overall improved reliability.
• The Propeller shaft produces minimal noise even when subjected to high torques.

Here are some of the disadvantages of propeller shafts:

• If the RPM is too high, it can lead to potential damage to the shaft.
• The hollow propeller shaft comes with higher price tags.
• There may be signs of oil leakage at the spline collection which are often due to inadequate sealing mechanisms in the sealing components.

The propeller shaft finds its application in the following areas:

• It is used in the construction of motor vehicles and heavy-duty machinery.
• Their utilisation extends to commercial vehicles as well.
• Propeller shafts were initially used in aircraft designs.

Thus, it is quite evident that the propeller shaft is a crucial part of the drive axle. It executes the key task of transmitting torque and rotational power to the propellers from the engine, and thus, it must work smoothly and be taken care of at regular intervals.