Universal joint

A universal joint

A universal joint, U joint, Cardan joint, Hardy-Spicer joint, or Hooke's joint is a joint in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion. Clarence W Spicer is known for inventing the Spicer joint a type of Universal joint. A joint is the location at which two or more Bones make contact It consists of a pair of ordinary hinges located close together, but oriented at 90° relative to each other. A hinge is a type of bearing that connects two solid objects typically allowing only a limited angle of Rotation between them

1 History
2 Angular speed
3 Double cardan
4 See also
5 References
6 External links

History

The concept of the universal joint is based on the design of gimbals, which have been in use since antiquity. A gimbal is a pivoted support that allows the rotation of an object about a single axis One anticipation of the universal joint was its use by the Ancient Greeks on ballistae. The ballista ( Latin, from Greek βαλλίστρα - ballistra, from - βάλλω ballō, "to throw" plural ballistae The first person known to have suggested its use for transmitting motive power was Gerolamo Cardano, an Italian mathematician, in 1545, although it is unclear whether he produced a working model. Christopher Polhem later reinvented it and it was called "Polhem knot". Christopher Polhammar ( December 18, 1661 - August 30, 1751) better known as, which he took after his Ennoblement, was In Europe, the device is often called the Cardan joint or Cardan shaft. Robert Hooke produced a working universal joint in 1676, giving rise to an alternative name, the Hooke's joint. Robert Hooke, FRS (18 July 1635 – 3 March 1703 was an English Natural philosopher and Polymath who played an important role in the Though the first use of the name universal joint is sometimes attributed to American car manufacturer Henry Ford, the term appeared in patent documents as early as 1884 when Charles H. Henry Ford ( July 30, 1863 &ndash April 7, 1947) was the American founder of the Ford Motor Company and father of Amidon was awarded United States Letters Patent No. 298,542 for a bit brace.

Angular speed


Angular output shaft speed $\omega_2\,$ for different angles $\beta\,$ of the input shaft	Output shaft angle for different angles $\beta\,$ of the input shaft

When the two shafts are at an angle other than 180° (straight), the driven shaft does not rotate with constant angular speed in relation to the drive shaft; the more the angle goes toward 90° the jerkier the movement gets (clearly, when the angle $\beta\,$ = 90° the shafts would even lock). This happens primarily because the plane containing the four arms of the centre piece constantly changes the angle it makes with the axis of each rotating shaft. However, the overall average speed of the driven shaft remains the same as that of driving shaft, and so speed ratio of the driven to the driving shaft on average is 1:1 over multiple rotations. Speed is the rate of motion, or equivalently the rate of change in position often expressed as Distance d traveled per unit of

The angular speed $\omega_2\,$ of the driven shaft, as a function of the angular speed of the driving shaft $\omega_1\,$ and the angle of the driving shaft $\phi_1\,$ , is found using:

Universal joints in a driveshaft

$\omega_2 = \frac{\omega_1\cos\beta}{1-\sin^2\beta\sin^2\phi_1}$

and the angular acceleration,

$\alpha_2 =\frac{\alpha_1\cos\beta}{1-\sin^2\beta\sin^2\phi_1}- \frac{\omega_1^2\sin^2\beta\cos\beta\sin 2\phi_1}{(1-\sin^2\beta\sin^2\phi_1)^2}$

Double cardan

A configuration known as a double cardan joint drive shaft partially overcomes the problem of jerky rotation. Do not confuse with Angular velocity In Physics (specifically Mechanics and Electrical engineering) angular frequency Angular acceleration is the rate of change of Angular velocity over Time. In this configuration, two U-joints are utilised where the second U-joint is phased in relation to the first U-joint in order cancel the changing angular velocity, and an intermediate shaft connects the two U-joints. In this configuration, the assembly will result in an almost constant velocity, provided both the driving and the driven shaft are parallel and the two universal joints are correctly aligned with each other - usually $\beta\,\le$ 45°. This assembly is commonly employed in rear wheel drive vehicles.

Even when the driving and driven shafts are parallel, if $\beta\,>$ 0°, oscillating moments are applied to the three shafts as they rotate. These tend to bend them in a direction perpendicular to the common plane of the shafts. This applies forces to the support bearings and can cause "launch shudder" in rear wheel drive vehicles. ^[1] The intermediate shaft will also maintain a sinusoidal angular velocity, which contributes to vibration and stresses.

In practice, it is often impossible to maintain a strict geometric relationship between the driving and driven shafts, and the intermediate shaft, giving rise to greater vibrations and mechanical stresses. The stresses can be reduced by the use of a smaller and lighter intermediate shaft, ensuring the driven and driving shafts share as close to the same angle in relation to the intermediate shaft, and reducing the angle of the joints.

Joints have been developed utilizing a floating intermediate shaft and centering elements to maintain equal angles between the driven and driving shafts, and the intermediate shaft. This overcomes the problem of differential angles between the input and output shafts.

A recent innovation, the Thompson coupling is a further development of the double cardan joint, which doesn't rely on friction or sliding elements to maintain a strict geometric relationship within the joint, and which is capable of transmitting torque under axial and radial loads with low frictional losses. The Thompson coupling is a type of Universal joint that unlike traditional universal joints has true constant velocity between the drive and driven shaft

References

Theory of Machines 3 from National University of Ireland

^ http://www.patentstorm.us/patents/6345680/description.html

External links

Joint by Sándor Kabai, The Wolfram Demonstrations Project. Constant-velocity joints (aka homokinetic or CV joints) allow a rotating shaft to transmit power through A gear coupling is a mechanical device for transmitting Torque between two shafts that are not Coaxial. The Thompson coupling is a type of Universal joint that unlike traditional universal joints has true constant velocity between the drive and driven shaft A rag joint refers to certain flexible joints found on Automobiles They are typically found on Steering shafts that connect the Steering Dr Ing Leonhard Geislinger invented the torsionally Elastic coupling or also called flexible coupling in 1958
DIY: Replacing Universal Joints, About. com.

Dictionary

-noun

A coupling that allows different parts of a machine not in line with each other some freedom of movement at the same time as transmitting rotary motion.

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
network: | |

Contents