The Incredible Mechanics of Driveshafts

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The evolution of automotive drivelines began centuries ago with horse-drawn implements, such as the Watkins and Bryson mowing machine, which introduced the first modern conceptualization of a driveshaft in 1861. Early automobiles primarily used chain drives, but by the turn of the century, gear-driven systems became more prevalent. The 1901 Autocar, designed by Louis S. Clarke, was considered the first shaft-driven automobile in the U.S., featuring a rear-end layout with a sliding-gear transmission, torque tube, and bevel gear assembly with an integrated differential. Autocar used a "pot type" universal joint, which was later superseded by the more robust Cardan universal joint, first used in the 1902 Spyker 60 HP race car.

Cardan universal joints, named after the Italian mathematician Gerolamo Cardano, consisted of two yokes connected by a cross-shaped intermediate journal, allowing power transmission between shafts at an angle. These joints used bronze bushings and later needle roller bearings to reduce friction and increase durability. Slip yokes were incorporated into the driveline assembly to accommodate axial movement. However, Cardan joints had limitations, such as non-uniform rotational speeds and increased friction at higher angles.

Throughout the 1920s, several design variations were developed to address these limitations. Ball and trunnion universal joints, like those used in the 1928 Chrysler DeSoto, allowed for greater angle misalignment and integrated slip characteristics. Double Cardan shafts, which used two universal joints connected by an intermediate propeller shaft, became a popular choice for rear-wheel drive vehicles due to their design flexibility, manufacturability, and torque capacity.

Constant velocity (CV) joints were introduced in the late 1920s to address the limitations of Cardan joints in front-wheel drive vehicles. The Tracta joint, invented by Jean-Albert Grégoire, was one of the first CV joints used in production vehicles. However, the most practical and popular design was the Rzeppa joint, invented by Ford engineer Alfred H. Rzeppa in 1926. Rzeppa joints used ball bearings to provide smooth power transfer at high angles. Tripod joints, developed in the 1960s, were commonly used on the inboard side of front-wheel drive half-shafts due to their affordability and ability to accommodate axial movement.

During the 1960s, manufacturers began experimenting with CV joints on propeller shafts for rear-wheel drive cars to achieve smoother power transfer. Double Cardan joints, which placed two Cardan joints back-to-back in a single unit, were also developed for use in high-articulation, high-torque applications.

Until the 1980s, drive shafts were primarily made from steel alloys. In 1985, the first composite drive shafts were introduced by Spicer U-Joint Division of Dana Corporation and GM. Composite drive shafts, made from carbon fiber or glass fiber in a polymer matrix, offered significant weight savings, high strength-to-weight ratios, and inherent damping properties.

As the automotive industry looks towards a future with alternative power sources, driveline components and universal joints remain crucial elements. Despite attempts to eliminate drivelines using hub electric motors, the traditional drivetrain layout is likely to remain dominant in the near future.

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