6.8 Flashcards
What does a bearing do ?
Constrains relative motion to Desired motion and reduces friction between moving parts.
What does the design of a bearing provide ?
Provides linear movement / rotation around fixed axis
What is the role of gears ?
Transmits power, change drive directions and increases / decreases rotational speed.
What’s the two major groups of bearings ?
- Plain - made up of a plain cylinder or flat washer
2.Rolling - Made up of rolling components
What two good characteristics does bearings have ?
- Made from strong material
- Provides Quiet and efficient operation
What’s the two forces acting upon a bearing ?
- Axial
- Radial
( bearing can have combo of both )
What distributes lubricant over all of the bearing ?
Oil grooves/wells
What are synthetic bearings lubricated with ?
Water, whicch also acts as coolant
With sliding bearings, why is grease lube used ?
Used on stressed bearings to with large bearing play.
What loads does plain bearings take ?
Radial ( journal )
When are plain bearings used ?
When load is light a motion is continuous.
What’s pivot ( axial ) bearings used for ?
Longitudinal forces
What’s 3 advantages of roller and ball bearings ?
- Almost eliminate all friction
- Carry heavy loads
- Don’t heat as much as plain bearings
What the 5 types of anti-friction bearings ?
- Tapered
- Ball
- Needle
- Cylindrical
- Spherical
What separates the different raceways ?
Cage
What’s the raceways made from on anti-friction bearing ?
- Chromium steel
- Chromium - nickel steel
( tracks are polished )
What is the distinction between ball bearings and roller bearings ?
Ball bearings - low starting resistants, and high rotational speed.
Roller bearings - are used if stress is too much for ball bearings
What are the major components of ball bearing ?
- Outer ring
- Inner ring
- Rolling elements
- Retrainer
What’s the shields and sealants inside the races used for ?
To retain lubricant and protect bearing from contamination.
( races can be machined externally or internally to make them self angling )
What are ball bearings used for ?
Accessory drives, gearings
( anywhere narrow bearing is required )
What load is ball bearings poor at withstanding due to their point contact
Oscillating loads.
When is cylindrical bearings commonly used ?
Non-locating positions
What two types of bearings are placed at the end of shaft ?
- Locating (fixed)
- Non-locating (floats)
What does the cylindrical bearings line contact with races allow it to do over ball bearings ?
Carry more radial loads.
Why does the cylindrical bearing have lower lad capacity ?
Has heavier cage and few rollers in order to retain the rollers
What properties does a needles bearings long thin rollers give it ?
Very high radial load capacity
True or false, spherical roller bearings are self aligning ?
True
- self aligning allows it to make minor angle adjustments between shaft and housing.
What causes the skidding of rollers in a spherical roller bearing ?
Rolling motion only occurs in two contact points on each roller
What load does a spherical roller bearing take ?
Radial
- but stress isn’t evenly distributed when under heavy loads .
When is a spherical bearing best suited to be used?
- Risk of misalignment while assembly
- Where speed isn’t exacting
4 Advantage of tapered roller bearing ?
- Less vulnerable to contaminants due to natural pumping action
- Low fiction
- Loner service life
- Can take radial and axial loads
2 Advantages of air bearings ?
- Zero- friction
- Don’t need lubricant and don’t wear
How’s air bearings fluid film created ?
By applying flow of air through bearing face and into bearing gap.
What 3 bearings are designed purely for thrust loads ?
- Roller
- Ball
- Needle
How is a thrust bearing often mounted ?
Vertically
- this supports heavy machinery.
- used on propellers as well.
What loads do thrust bearings take ?
Axial loads, Limited radial loads
(They have high load capacity)
If radial load is expected, what is placed next to the thrust bearing ?
Another bearing
What is the function a bearing ?
Reducer friction between moving parts
