6.8 Flashcards
What are axial and radial loads
Axial ( thrust ) loads are a sideways load
Radial ( journal ) loads are a downwards load
What is special about dry powder and synthetic bearings?
Dry powder bearings are self lubricating as their pores contain fluid or solid lubricants which comes out when heated.
Synthetic bearings can be lubricted by water which also acts as a coolant.
Sliding bearings
Use a grease pump to lube the machine before use
Plain bearings
Take very light radial loads with relatively continuous motion
Regular maintenance is necessary to avoid contamination
To work effieciently clearance is required for lube.
5 basic types of roller element bearings
Tapered
Cylindrical
Ball
Spherical
Needle
Ball bearings
Light radial loads
Capable of withstanding very high speeds
Shields or seals can be fitted
Point contact so can not take heavy oscillating force
Cylindrical roller bearing
Line contact
Take heavier radial loading as a result
Allows limited axial loading
Heavier
Needle roller bearings
Long thin rollers
Compact and lighter
High radial loads
Very light axial loads
Spherical roller bearings
Self aligning
Very high radial load capacity
Higher friction
Under heavy loafing stress is not evenly distributed
Tapered roller bearing
Long life
Very high radial and axial loads
Reduced size
Low friction coefficient
Less sensitive to contamination
Low price for long use
Air bearings
Use a thin film of pressurised air to provide a zero friction interface
Avoids traditional bearing problems
Thrust bearings
Designed for combination of radial and axial loads
Found in variable pitch propellers
