Steering Knuckle Grease

[Lifer]

They are. If I can get it to work, here's the full story:

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History of the CV Joint

In order to appreciate the history of constant velocity joints it is first necessary to understand that constant velocity joints are a special class of universal joint.

Although they did not know it at the time the principle of the universal joint was invented and used by the Chinese more than 2000 years ago. The Chinese made incense burner holders that used gimbals, essentially identical in principle to the modern gimbals that allow a ships compass to remain horizontal while the ship rolls.


An advance occurred when the great Italian mathematician and inventor Girolamo Cardano (1501 – 1576) took the Chinese gimbals (which by that time had spread beyond China) and described how it could be used to transmit rotary motion from one shaft to another. As a result, to this day, the ordinary universal joint is known as a Cardan Joint. Cardan however did not actually construct such a joint.


The next advance occurred when Sir Robert Hooke (1635 – 1703) a British physicist, astronomer and inventor had a need to make an adjusting mechanism for his helioscope. Sir Robert Hooke designed the universal joint, as we know it today with a cross or cruciform shaped component joining two yolks. Sir Robert was aware that such a joint does not transmit uniform or constant rotary motion and he used two such joints, separated by an intermediate shaft, to achieve constant velocity.

Sir Robert Hooke’s joint was identical in principle to the Cardan joint, merely different in construction and similarly Cardan’s joint was essentially identical to the Chinese gimbals but different in application, so neither man can be credited with the invention of the principle. Cardan however was the first to realize that gimbals could be used to transmit rotary motion through an angle. Sir Robert Hooke was the first to construct a Cardan joint (of different design) and Sir Robert was the first to address the problem of constant velocity.

After the advent of the industrial revolution and particularly after the invention of the steam engine and internal combustion engine, universal joints were used, but because they were not constant velocity and were poorly lubricated they regularly failed with the result that chains and belts were used in preference.


Between Hooke’s time and 1903 there was essentially no advance in universal joint technology. In 1903 Clarence Spicer was charged with designing a motor car, but did not want to use chain drive that was usual at the time, so he invented a universal joint with bearings sealed against dust. Spicer began production of his joint in 1904. He later took in Charles Dana as a partner and the firm Dana Spicer is today one of the world's largest companies with in excess of 70,000 employees.

Since Hooke, the shortcomings of the Cardan joint and the need for a constant velocity joint has been known, yet it was not until 1924 that two Frenchmen, Gregoire and Fenaille collaborated and invented the first practical constant velocity joint called the “Tracta Joint”.

The Tracta joint gained widespread usage in Britain, Europe and America and was still used widely during the World War II in light military vehicles including those made by Ford and Dodge. It was however a horrid thing, with large torque transmitting surfaces sliding inside forks. It had a high wear rate and a lot of friction however, with cheap petrol and no greenhouse concerns it gained acceptance.

In 1925 Carl Weiss patented a constant velocity joint that became known as the Bendix-Weiss joint. It consisted of two interlocking yolks and four steel balls situated in grooves formed in each yolk. This problem with this joint was that there were only four balls transmitting the torque through their line of contact and the balls skidded rather than rolled in the grooves with the result that wear rates, heat and friction were high however, this joint also gained widespread usage in light vehicles and applications.

In 1929 A. Rzeppa invented a constant velocity joint based upon the Bendix-Weiss principle, but rather than having interlocking yolks Rzeppa’s joint had an outer ring and an inner ring with grooves cut in each and six steel balls rather than four. It was noisy and tended to seize up however it was improved with advances in lubrication and also with changes to the angles of the grooves. It gained acceptance in 1959 when it was used in the front wheel drive of the famous Morris Mini and is today the joint that is found in all light front wheel drive vehicles.

Like the Bendix-Weiss joint the balls in the Rzeppa joint skid in the grooves when the joint is operated at an angle and even with modern lubricants the wear rate and friction is high, such that the life of these joints is reckoned in minutes when used at any appreciable angle and torque setting.

Between 1929 and 2000 there was no advance at all in constant velocity joints. The only advances were in the lubricants used to mitigate the wear inherent in the designs.

Because the Tracta, Bendix-Weiss and Rzeppa joints all had load bearing sliding surfaces and in the case of the Bendix-Weiss and the Rzeppa joints these, being the contact point of steel balls, were very small surfaces indeed. They were entirely unsuitable for the applications where they are most needed which are high load applications with the result that industry, agriculture and trucking still use the Cardan joint as improved by Clarence Spicer.
In about 1980 Glenn Thompson was using spherical geometry to design various products, including in particular a variable displacement pump/engine which was, in the final analysis, a particular application of a Cardan joint, but which could be improved if it were a constant velocity joint. While seeking to design the pump/engine in constant velocity form Glenn realized that by applying great circle geometry it was possible to construct a constant velocity joint without any load bearing sliding surfaces. However, the designs created at that time were cumbersome and could not be applied to the pump/engine, the task in hand. Although the inventive step in relation to providing a constant velocity joint was made in 1980, nothing was done about it at the time, as the resultant designs were too cumbersome.

By 2000, prototypes of Glenn’s pump/engine had been constructed, but when tested vibration proved to be of major concern so it became imperative to design a constant velocity joint, which could be incorporated into the pump/engine. Glenn again began considering constant velocity joints and in particular joints based upon great circle geometry.


Initially, the designs were cumbersome and could not be incorporated into the pump/engine. They did however hold promise as stand alone constant velocity joints.


A series of patent applications were made which disclosed and built upon the great circle geometry inventive step that had been made in about 1980. This series of patent applications culminated in the one which discloses a spherical pantograph on one side of the joint only and which is known as the Thompson Coupling.

The Thompson Coupling represents a great forward step in universal joints as it is the world’s first practical constant velocity joint which has no load bearing sliding surfaces. In addition, it is the first one that can withstand axial and radial loads without degradation and as such can be properly described as being the world's first and only constant velocity coupling, as distinct from joint.



Because of the limitations of existing constant velocity joints,they are entirely unsuitable for those applications where they are most needed. These applications are essentially all applications subject to high load where more than one shaft is used. Such applications include the driveshafts (tailshafts) of trucks, power transmission needs of industry generally and in particular agricultural PTO shafts. At the present time ordinary Cardan (ordinary universal) joints are used almost exclusively in these applications with the result that the vehicles and machines must be deigned to maintain strict geometric relationships in order to prevent damaging vibration and energy losses. This leads to expensive and limiting design constraints. Quite often the required relationship can only be approximately maintained with the result that vibration and energy loss does occur. In agricultural applications in particular the resulting vibration is often severe and damaging to machinery. Tests conducted to date indicate that the Thompson Coupling is suitable for these applications.




© 2008 Thompson Couplings Ltd
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Italics added by "Lifer" for emphasis.

[ELBUFO]

I use nothing but synthetic grease lubes and oil. Worth the price. I have been using AMSOIL for over 30 years. Worth checking into...John

[HingsingM37]

I got my front axle assembled this past weekend. Charles, you weren't kidding when you said you can get only some grease in during assembly. What a messy job. I needed one of those Hindu Gods with the six arms to help me hold everthing in place I also discovered that the axle yoke must be fully engaged to the curvature of the joint or you end up a lilttle too long. Fortunately I remembered that while inspecting the drive axles while apart. I am sure some folks would have gotten a hammer out.
All in all it went well. When I was done I stood there turning the input shaft watching the axles move. After such a long time apart it was silly fun to see it all moving again.

[HingsingM37]

On a side note it took @275 pumps of my grease gun to empty a 14.5oz grease cartridge.