Jan. 13, 2025
A drive shaft, also known as a driveshaft, driving shaft, or propeller shaft is a mechanical component designed for transmitting torque and rotation. It typically connects parts of a drivetrain that are too far apart or need to move relative to one another. It is especially named after Girolamo Cardano for its flexibility in operation.
As a torque carrier, the drive shaft is subject to torsion and shear stress, resulting from the difference between the input torque and the load. Therefore, it needs to be robust enough to handle this stress while minimizing additional weight to avoid increasing inertia.
To accommodate variations in alignment and distance between the driving and driven components, drive shafts often feature one or multiple universal joints, jaw couplings, rag joints, or occasionally splined joints or prismatic joints.
The term driveshaft was first mentioned in the mid-19th century. An early instance appears in Stover's patent reissue concerning a planing machine, where it references the belt-driven shaft propelling the device. Although not present in his original patent, variations of the term were also noted in patents for horse-drawn mowing machines, denoting shafts that transmitted power from the machine's wheels to the cutting mechanism.
By the 20th century, the concept began to align more closely with its contemporary understanding. For instance, in 1919, Battles described the shaft in his Climax locomotive as a drive shaft, while Stillman identified the shaft coupled to his bicycle's rear axle as a drive shaft as well. Furthermore, in different contexts, the term was used to detail power transmission mechanisms in various machinery.
In 1899, Autocar became the first automotive manufacturer to implement a drive shaft in gasoline-powered vehicles, and today this historical vehicle can be found in the Smithsonian Institution collection.
Automobiles often deploy a longitudinal shaft for power delivery from the engine/transmission to the wheels. Alternatively, they can also utilize shorter drive shafts to channel power from a central differential or transaxle to the wheels.
In front-engine, rear-wheel drive vehicles, a longer drive shaft orchestrates power delivery along the length of the vehicle. Two principal types are prevalent: the torque tube equipped with a single universal joint and the more conventional Hotchkiss drive with multiple joints, commonly referred to as Système Panhard.
Most of these vehicles have the clutch and gearbox mounted on the engine, pushing power through the drive shaft to the rear axle’s final drive. When at a standstill, the drive shaft remains unmoving. Some performance-oriented models, like the Chevrolet Corvette and Porsche 924, utilize a rear transaxle configuration, impacting the drive shaft's operational dynamics.
A drive shaft that connects a rear differential with a rear wheel is also termed a half-shaft, as two of these shafts work together to complete a rear axle. Earlier vehicles often relied on chain or belt drive systems, while some implemented electrical generators and motors for power transmission.
In British English, the term drive shaft typically refers to a transverse shaft for power transmission to the front wheels. Conversely, the shaft linking the gearbox to the rear differential is called a "propeller shaft." A prop-shaft assembly encompasses the propeller shaft, a slip joint, and one or more universal joints, especially in four-wheel and rear-wheel drive setups.
Various drive shaft types utilized in the automotive industry include:
The innovative slip-in-tube drive shaft enhances crash safety by compressing to disperse energy during a collision, thus known as a "collapsible drive shaft."
These systems evolved from traditional front-engine, rear-wheel drive designs, introducing a transfer case between the transmission and the final drive systems of both axles—splitting traction while potentially integrating low-range gearing or differentials. Typically, at least two drive shafts link the transfer case to each axle, contributing to the vehicle's overall drivetrain integrity.
In the automotive industry, drive shafts are routinely used in testing facilities. In engine test labs, a drive shaft transmits specific speeds or torques from an internal combustion engine to a dynamometer. Moreover, shaft guards are implemented at connections to ensure safety and detect failures.
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At transmission test stands, drive shafts connect prime movers with transmissions.
Typically, a drive shaft in a vehicle can last roughly 120,000 kilometers. However, drivers experiencing any of the following symptoms should have it inspected promptly:
Cardan shaft park brakes engage on the drive shaft rather than the wheels, commonly utilized in small trucks. These braking systems are susceptible to malfunction, contributing to safety alerts regarding runaway vehicles on inclines.
Drivers face risks like parking heavily loaded on steep slopes, ineffective force application on the brake, or unstable load changes while parked. Using wheel chocks can prevent unwanted vehicle movement on inclines.
Drive shafts have been a component in motorcycles since before WW1, providing a clean, low-maintenance alternative to chain drives. However, they often necessitate helical or spiral bevel gearing to transmit power 90 degrees to the rear wheel, generating some power loss.
BMW has incorporated shaft drive technology in their motorcycles since 1923, while Moto Guzzi has implemented this in their V-twins since the 1960s. Other notable manufacturers, including Triumph and several Japanese brands, also produce shaft-driven motorcycles.
Notably, motorcycles with longitudinally-aligned crankshaft designs simplify the conversion of power due to requiring only a single 90-degree turn in power transmission. However, these motorcycles may experience a phenomenon known as the 'shaft effect,' causing the chassis to lift under power, which can be mitigated by systems like BMW's Paralever.
In power-driven vessels, the drive shaft, or propeller shaft, typically bridges the internal driving machinery and the external propeller, traversing at least one shaft seal as it exits the hull. The thrust from the propeller is conveyed through the thrust block or bearing, integral in larger vessels.
The section of the drivetrain connecting directly to the propeller is referred to as the tail shaft.
During the late 19th century, Shay, Climax, and Heisler locomotives utilized quill drives, effectively connecting power from a centrally located engine to each of the supporting trucks. Each drive shaft incorporates universal joints, enabling movement along the length to accommodate curves.
In contemporary setups, Cardan shafts find their place in diesel locomotives and some electric classes, aiding in power delivery of multiple units.
The drive shaft serves as an alternative to chain drives in bicycles, presenting distinct advantages and disadvantages:
PTO drive shafts assist in transferring power from an engine and PTO to vehicle-mounted accessories, such as air compressors, when space limitations exist along the engine. This assists in positioning accessories optimally away from the engine compartment.
Modern advancements in production processes, such as filament winding for composite drive shafts, are gaining traction in the automotive sector as manufacturers look to improve efficiency in high-volume production scenarios.
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