In specifying a bearing for its new Gator 500 pipe-welding machine, Derbyshire company Fusion Provida faced a dilemma.

The design called for a bearing with an inside diameter of 12in to support the trimmer and cutting blade. A standard bearing with this dimension would, however, be too large and heavy. A smaller diameter bearing on the other hand would have not met the design and performance requirements. So what was the alternative? The solution proved to be a standard product from the RA Rodriguez Kaydon range of Reali-Slim thin section bearings. The size selected was a 12in (305mm) diameter bearing with a cross section of only 0.375in (10mm). This allowed Fusion Provida to use a large diameter bearing and still keep the design compact. Fusion Provida designs and manufactures a range of machines for butt welding plastic pipes in the gas and water industries. The company's introduction of a new, fully automatic butt fusion machine, called the Gator 500, is an important development. This machine will trim, heat and join pipes in a single, computer-controlled process. Full cycle interlock ensures that each step in the fusion process is automatically controlled within pre-programmed parameters in a continuous operation. This gives the benefit of consistent and faster welds. Kaydon four-point contact ball bearings are designed to accept combinations of radial, thrust and moment loads. This is made possible by the unusual geometry of the raceways. The ball groove in each race has two radii that are larger than the ball radius and the centres of these two radii are offset from the centre of the ball radius. This results in a gothic arch configuration, allowing the two grooves to make contact with the ball at four points. For Fusion Provida, the slim profile of the large Kaydon KC120XPO bearing and its four-point contact ball geometry were indeed the main purchasing criteria. As Jason Roberts, one of the company's Design Engineers concludes: "These characteristics give the Gator 500's cutting and trimming mechanism excellent support and stability as it completes its circuit within the pipe". "It has also enabled us to keep the machine's overall design extremely compact".