How your car turns without shaking itself apart

Design · Published 9 October 2026 Swipe more like this →

In short: Standard universal joints allow shafts to bend, but they create speed fluctuations that cause violent vibrations. To solve this, engineers developed the constant-velocity (CV) joint. This mechanical marvel ensures that power flows at a steady speed even when wheels are steered at sharp angles.

The challenge of transmitting power between two rotating shafts at an angle began with the 16th-century universal joint, invented by Gerolamo Cardano. While functional, these joints suffer from a critical flaw: the output shaft's speed fluctuates relative to the input. As the angle between the shafts increases, these vibrations become more pronounced and the joints can become 'notchy' or difficult to rotate. To counteract this, Robert Hooke invented the double Cardan joint in the 17th century, which uses two universal joints offset by 90 degrees to cancel out speed variations.

Modern automotive engineering, particularly in front-wheel drive vehicles, relies on more sophisticated designs like the Rzeppa joint. Invented by Alfred H. Rzeppa in 1926, it uses a spherical inner shell with six grooves and a star-shaped gear to allow for high articulation—up to 54 degrees. This allows wheels to turn significantly while maintaining constant velocity. Variations like the Birfield joint, which uses elliptical tracks to confine ball travel, became standard in cars like the Mini to improve efficiency.

Other specialized designs exist for different needs. The tripod joint, developed by Michel Orain, is favored for its low cost and efficiency in rear-wheel drive or inboard applications where movement is limited to one axis and a 'plunge' motion is required. Meanwhile, the Tracta joint uses a 'double tongue and groove' principle to neutralize speed variations. Each of these mechanisms represents a different balance between torque capacity, angular range, and mechanical simplicity, ensuring that whether you are navigating a sharp turn or a rugged off-road trail, the power reaches the wheels smoothly.

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