Duplexed bearings are type A bearings that are delivered as matched sets in a back-to-back, face-to-face or tandem configuration. Individual bearings within a duplexed set are closely matched for bore size, outside diameters and furnished with the appropriate race faces ground with a predetermined preload gap. The figures above show the race faces that are ground for each style of duplexed set. When the bearings are installed and axially clamped, the gap will be closed and the preload established. It should be noted that the outboard faces of duplexed sets are not normally controlled. Bearing sets should be universally ground in order to control outboard face flushness. Duplexed sets are marked with a “V” across the inside and outside diameters at the high point of radial runout.
APG will supply matched ground inner ring and outer ring spacers along with duplexed sets to meet existing envelope requirements or improve the moment capability and moment stiffness of the set. Multiple individual bearings can be provided as matched sets for applications limited in the radial direction but requiring additional capacity. Consideration should be given to load sharing effectiveness when multiple bearings are used together. The radial and thrust capacities for the set are calculated based upon multiplying the individual bearing capacities by N0.7, where N is the number of bearings in the set which are resisting the applied load. Therefore, the radial load in a typical duplexed pair is calculated by multiplying the single bearings radial capacity by (2)0.7. A tandem set with three bearings would have a thrust capacity equivalent to the single bearings thrust capacity multiplied by (3)0.7.
Back-to-back duplexed sets have a larger moment arm resistance and therefore offer greater rigidity under moment loads. The face-to-face configuration offers additional compliance in the moment direction and is more forgiving of shaft and housing misalignments.
APG offer both styles of duplexed sets with our High Performance Low Drag Outboard Seals or Shields. APG Sealed Duplexed sets can provide significant advantages in terms of achieving consistent, low torque performance with high stiffness in a tight envelope.
