WHAT DO YOU KNOW ABOUT
FRACTURED OUTER RING BALL BEARING?
Fracture outer ring ball bearing design permits the use of extra balls into the bearing complement. The extra balls increase the static and dynamic capacities of the bearing and allows a smaller boundary bearing (smaller chassis) to be used in applications where size and mass/weight is very important.
• The first patent for a split outer ball bearing was filed in November 1955 (U.S. Patent No. 2,702,216).
• A second patent was filed in January 1975 (U.S. Patent No. 3,858,288) which split the outer from the inside diameter/raceway.
• A third patent was filed in February 1987 (U.S. Patent No. 4,643,595) which was designed for a full complement bearing adapted to cope with high radial loading.
• Problems arise in the fabrication of fracture bearing rings by conventional methods. Particularly, unless the ring cracks cleanly there is a danger that small loose metallic particles could be created which could become defects and significantly reduce the bearing life. It is estimated that the production yield is 60% or less of the total order for most manufacturers.
• Phoenix Aerospace Components Inc. (PAC) has developed a proprietary method of making such a fracture ring with 90%, or better, yield. The rings manufactured by this method assures that the outer roundness and runout to bore meet the ABMA ABEC class requirements. Also, the bearings tested with an Anderon meter (a dynamic bearing analyzer) shows noise values very similar to a regular one-piece outer ring ball bearing.
In aerospace application this design is used in ALLISON (Rolls Royce) 250 engine (and US military designations T63 and T703), Starter, and Pneumatic Shutoff Valve. Since the early 1960's more than 30,000 Allison 250 engines had been built. They are used in the following fixed and rotary-wing aircraft:
FAA-PMA Fractured Outer Ring Ball Bearing made by Phoenix Aerospace:
• After the life test of the fractured outer ring ball bearings produced by PAC, the noise test comparison between PAC PMA bearings and OEM bearings was carried out. The vibration test results of PAC bearings were very good at the same level as OEM products.