Bearings Flashcards
What are plain bearings?
Light loads only, continuous motion
Frequent maintenance
Support journals of shafts and axis
Called journal or roller bearing
What are sliding bearings?
Operate in bearing box, bearing bushing, or directly on the bearing body
Resistant to ‘push’ forces, operate with very little noise
High starting resistance, continuous maintenance
What are anti-friction bearings?
Ball bearings have slow start resistance but roller bearings can take higher loads
Ball bearings - all types have a point of contact
Deep groove - most popular bearing
Light, radial loads only
What are cylindrical roller bearings?
Allows axial (floating) to accommodate thermal expansion Line contact rather than spot contact of ball bearing Heavier cage, fewer rollers = lower load capacity
What are needle roller bearings?
Long, thin, compact rollers
High radial load capacity
Very light axial load capacity
What are spherical roller bearings?
Self-aligning, allowing for minor angular displacement
High radial load capacity
Robust cage
Operates where lower speeds are not important
What are tapered roller bearing?
Combined radial and thrust load Longer life with reduced size Adjustable for either end play or preload values Less sensitive to contamination High speeds Low price for long use
What are the bearing materials?
Advantages?
Copper tin alloys
Copper tin zinc casting alloys
Lead tin alloys
Cast iron
Good sliding properties
Good lubricant = longer life
What is Radial?
Accept forces acting radially to the shaft axis
Can be subjected to small axial loads
What is Axial?
Accept forces acting in the direction of the shaft axis
Can be subjected to small radial loads
What are air bearings?
Use a thin film of pressurised air to provide a zero friction interface
Avoid traditional bearing problems such as friction wear
Very quiet
