adminUNIVERSAL JOINT
A universal joint (U-joint) also known as a cardan joint is a mechanical coupling that connects two rotating shafts whose axes are not in a straight line with each other. It transmits torque and rotational motion even when the shafts are at an angle, allowing for flexibility in the drive train system.
There are several types of universal joints and they are; cardan/single universal, double cardan or universal, constant velocity (CV), tracta or tripod, Thompson coupling and bendix-weiss joint.
Cardan/single universal joint is the most basic type of universal joint. Cardan joints consist of two yokes and a cross/spider assembly. Single or cardan universal joints are simple and strong and cause velocity fluctuations at large angles when it rotates. They are primarily used in driveshafts of trucks and RWD cars.
Double cardan (double U-joints) joints are two cardan or U-joints placed back to back with a centering socket between them. Double Cardan joints cancel out velocity fluctuations as it rotates. They find use in heavy duty trucks, front axles of 4WD vehicles.
Constant velocity (CV) joints are designed to transmit torque at constant speed regardless of angle. They are used extensively in FWD and AWD vehicles.
Tracta or tripod joints use three rollers in a tulip-shaped housing. Tracta joints allows both angular and axial (plunge) movement. They allow for smooth power transmission between shafts.
Thompson coupling is a precision velocity joint used in industrial and specialized vehicle applications. They maintain exact constant velocity at any angle.
Bendix-weiss joints uses balls in curved grooves to achieve near constant velocity. They find use in older vehicles and some steering columns.
The advantages of universal joints are; they transmit power even when shafts are misaligned or positioned at angles to each other. Universal joints have few parts that are easy to manufacture and maintain. They can handle very high torque loads, cost effective and can accommodate suspension travel with ease. Universal joints are capable of operating at wide operating angles with smooth power delivery.
The disadvantages of universal joints are; they can cause vibration and wear at large angles. Universal joints require periodic lubrication to function properly or effectively. They are often limited by low operating angles of between 15-20 degrees for smooth operations in most types of universal joints. Some universal joints like constant velocity joints are complex and expensive. Also velocity variation in cardan joints causes energy loss as heat at large angles.
Universal joints find applications in the following; rear wheel drive shaft as single/double cardan universal joints. Front wheel drive axle shafts as Rzeppa constant velocity joints. Steering column as cardan or bendix-weiss universal joints. 4WD/AWD front axles as double cardan or contant velocity universal joints. Truck propeller shafts as heavy duty cardan universal joints. Independent rear suspension as constant velocity (tripod + rzeppa) universal joint. Off-road vehicles front axles as double cardam universal joints.
The future of universal joints is based on the advances and development of the following technologies; electric vehicles since in their design they eliminate traditional driveshaft in many configurations such as motors at each wheel. However constant velocity will remain essential for driven front/rear axles in single motor electric vehicles. The incorporation of in-wheel motor technology will eliminate the need for long drive shafts such that the use of universal joints will reduce proportionally or considerably. Future universal joints will use carbon fiber yokes, ceramic bearings and self-lubricating materials to reduce weight and extend service life. In the future universal joints will be maintenance free, sealed for life universal joints will be the order of the day and some designs will approach zero-maintenance after 300,000 plus kilometer. Research is ongoing into wide angle constant velocity joints (capable of 50 degrees plus), thus enabling more aggressive suspension designs and tighter turning radii. Integration of vibration sensors and internet of things (IOT) diagnostics will allow real-time monitoring of universal joints wear thus predicting failure before it occurs.
SOURCES:
- Universal joints and driveshafts: Analysis, design, applications by Hans-Christoph Seherr-Thoss, Friedrich Schmetlz and Erich Auckor.
- Manual Drivetrains and axles by James D. Halderman.
- Automotive drivetrain and manual transmissions by Keith Santini and Kirk T. VanGelder.
- Automotive transmissions: Fundamentals, selection, design and application by Harald Naunhezmer, Bernd Bertsche, Joachim Ryborz and Wolfgang Novak.
- Automotive powertrain science and technology by Allan Bonnick.
