6.8- Bearings Flashcards
Describe a plain bearing.
Load carrying cylindrical inserts, made from hard wearing materials.
What are the common uses for plain bearings?
Where the loads are light and the motion is continuous.
In view of frequent maintenance of plain bearings what are they now being replaced with?
Anti-friction bearings.
What are bearings used to support?
Journals of shafts and axles.
What are bearings used to support journals at right angles called?
Journal bearings or roller bearings.
Bearings for pivot journals which accept longitudinal direction are known as what?
Pivot bearings or axial bearings.
The journal of a sliding bearing operates in what?
Bearing box, bushing or bearing body.
What does the amount of bearing play depend on?
The demands of the bearing and the lubricant.
What are sliding bearings resistant too?
Push forces, operating with little noise.
What are two disadvantages of sliding bearings?
High starting resistance and high maintenance.
What are the bearing loads commonly experienced?
Radial and thrust.
What are the 5 basic types of anti-friction bearing?
Tapered Needle Ball Spherical Cylindrical.
What does an anti-friction bearing consist of?
Outer and inner raceway
Rolling element
Rolling element cage.
What are the raceways and rolling elements made from?
Chromium steel or Chromium Nickel Steel.
What contact do ball bearings have?
Point- this means all the stress is concentrated on one point.
What is the most popular ball bearing and what loads can it take?
Deep groove ball bearing and light radial loads only.
What is the most common use for cylindrical roller bearings?
Non-locating positions where it is necessary to deal with thermal expansion.
What does the self-aligning feature of spherical roller bearings allow?
Minor angular displacements between the shaft and housing to be accommodated.
Why must the cage around spherical roller bearings be robust?
To counteract the roller skewing effect which increases inertia.
Why is a tapered roller bearing the best?
Because it has all the benefits of the other types and many more of its own.
What materials are suitable for bearings? (6 examples)
Copper tin alloys copper tin zinc alloys lead tin alloys cast iron dry powdered metals synthetics
What’s a benefit of using dry powdered metals such as graphite for bearings?
They contain fluid or solid lubricants in their pores.
What are synthetic bearings lubricated with?
Water, it also acts as a coolant.
How does an air bearing work?
It utilizes a thin film of air to provide a zero friction load bearing.
