The flexible disk ( flexible disk ), also Guibokupplung, is usually made of rubber or other resilient material plate with mostly vulcanized bushings made of metal, which at cardan shafts ( propeller shafts ) ensures that for slight misalignments of the two axes, ie misalignment, balanced and at the same torque impulses are dampened which arise when changing the speed or the start of the wave. Often it is necessary that the flexible disk is then held in addition by means of a centering, eg for very long waves or at very high speed rotating shafts.
In contrast to the functionally similar universal joint Hardy discs are only used when no angular offset and alignment errors should be corrected. A Hardy disc, which circumferentially strong twists would be destroyed in no time by internal heat from the flexing. A permissible angular misalignment of up to 3 degrees for flexible disks with textile reinforcement, wherein Hardy discs of pure rubber even less, since the torque transfer to take place only via the elastomer.
The mainly common in the German language name goes back to the Englishman John Leslie Hardy, who through his firm Hardy Spicer & CO LTD. the construction in 1938 as the inventor at the Royal Patent Office in the UK could enter under the number GB497903. In English, the disc is usually referred to as " flexible joint disc" or " flex disc", without going into Hardy.
Classic Hardy disks are inserted into the drive technology of automobiles; their typical application is the transmission output of rear wheel drive vehicles, such as BMW and Mercedes -Benz. In industry and agriculture Hardy discs are used on all rotating shafts. These will be decoupled from vibrations and spared from hard knocks, so attachments can be designed with smaller dimensions. Examples include harvesters, tractors, forklifts and vibration in the drive train of engine test benches. Also ship drives can be equipped with Hardy slices, which are then correctly identified as a strip joint discs. Another application of the flexible disk can also be found in the steering wheel and from the steering gear.
Is mounted the flexible disk by the screwing of the sleeves with the shafts to be connected, in each case alternately, a socket to the drive and the other terminal is connected to the output shaft in order to ensure that the forces pass through the flexible plate.
There are also Hardy discs without vulcanized bushings. You will not screwed, but only plugged between tap washers. Due to the centrifugal force, however, a metal ring on the rubber member ( flexible disk ) is frontally inserted in the most cases. The shaft drive on the gearbox output of BMW motorcycles in the 1950s and 1960s is an example: BMW R 25/ 3, BMW R 26, BMW R 27 Today ( 2008) is a Russian company, Ural is the only motorcycle manufacturer still Hardy discs in his current model range begins.