A universal joint, otherwise called a u-joint, is found in many automotive applications, as well as in other mechanics. For example, a u-joint is used in vehicles between the drive train bar and the transmission or axle where the bars meet at a right angle. There are three main designs of u-joints, each designed for a specific application.
The Hooke style universal joint is perhaps the most widely known joint in the United States. The joint consists of two rods that are connected at the centre by a four-pin attachment. The two rods are slender on the outer half and thicker on the inner half. The Hooke u-joint was designed by Robert Hooke, curator of experiments at the Royal Society in 1662. Hooke's work was primarily focused on the mechanics of clocks and other astronomical measuring tools.
Ring and Trunnion
The ring and trunnion universal joint is designed with a female and a male rod at either end of the centre cross point. The centre cross is an open circle with four protruding points that poke through the holes on the male and female rods. Within the centre of the ring and trunnion u-joint is a bushing and a lock ring that help maintain the centre cross between the rods. The ring and trunnion is often seen inside the driveshaft of a vehicle.
Bendix-Weiss is a universal ball joint that has a hollow centre containing four small metal balls. The two rods are formed to hook together at a cross section, and the metal balls sit in each corner socket. A a fifth, smaller ball is situated in the very centre of the cross point to help stabilise the entire device during rotations. The Bendix-Weiss joint is designed to carry the exact amount of torque on one arm of the joint as on each of the other arms. This equal balance is valuable to applications involving heavy and complex vehicles in the military, for example.