USCG Exam PracticeBearings, lubrication, and care of machine parts
In a reduction gear installation, journal (sleeve) bearings support the radial load of a rotating shaft by means of which mechanism?
- A. A grease-packed rolling element that prevents metal-to-metal contact
- ✓ A hydrodynamic oil wedge that keeps the metal surfaces apartCorrect
- C. Direct metal-to-metal contact with a sacrificial babbitt surface
- D. Magnetic repulsion generated by the shaft's rotation through the oil film
Why B is correct
NAVEDTRA 14075 §4-1 states that journal (sleeve) bearings carry the radial weight of a shaft on a thin film of pressurized oil — a hydrodynamic wedge — that keeps the metal surfaces apart. Rolling-element bearings are a separate category used where loads and speeds suit them.
Cited:NAVEDTRA 14075 §4-1