A high load capacity hydrodynamic journal foil bearing system is disclosed, which
comprises a top foil and a plurality of undersprings. Preload forces are transferred
from the undersprings to internal circumferential compressive forces within a top
foil, resulting in low preload forces against the shaft, allowing the shaft to
expand at high speeds without increasing the preload forces or overloading the
fluid film. One underspring may have a different spring rate than another underspring.
The top foil may be normalized to shaft shape and dimensions. These features may
be accomplished with using less mechanical parts than other journal foil bearing
system designs.