Abstract:
This paper summarizes the early developments that led to laminated elastomeric bearings becoming the principal load-bearing elements in modern helicopter rotor heads. Early helicopters used conventional ball or roller bearings to allow the rotor blade pitch, flap, and lead-lag motions. These rolling element bearings were not well-suited to the small, oscillatory motions required in helicopter rotors. Laminated elastomeric bearings were conceived in the mid-1950s as a better alternative. The basic operating principles of elastomeric bearings for helicopters are explained. Five key innovations, developments, and milestone achievements are identified. These include patents issued to Hinks, Schmidt, and Gorndt et al. The first successful helicopter elastomeric bearing projects are also described. These include the Enstrom F-28 centrifugal force thrust bearing, the Scheutzow Flexhub rotor head, and the Boeing-Vertol Triskelion rotor head. These key early developments led to the first production spherical elastomeric bearing rotor heads and eventually revolutionized helicopter rotor design. Almost all modern helicopter rotor heads use spherical elastomeric bearings to accommodate the blade pitch, flap, and lead-lag motions.