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  UV Joint History

Universal Joint History

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 Hookie’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 motorcar, but did not want to use chain drive that was usual at the time, so he invented a universal joint with bearings and 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 worlds 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 Second World War 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 the Rzeppa joints all had load bearing sliding surfaces and in the case of the Bendix-Weiss and the Pzeppa 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.

 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.

 <Notes> This article is quoted by the courtesy of Thomson Coupling's website.

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