Bearings

Bearing exploded view & parts

• shielf

• inner race

• balls

• retainer

• outer race

Bearing image

What are bearings?

• a machine element that constrains relative motion to only the desired motion

• experience loads in two basic directions: axial load and radial load

Axial load vs radial load

• axial load - thrust (back and forth)

• radial load - load pushing inwards towards the centre of the circle

Why are bearings used?

1. reduce friction between moving parts

2. provides free linear movement of the moving part or free rotation around a fixed axis

   • or it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts

Bearing types

1. ball

2. cylindrical roller

3. needle roller

4. tapered roller

5. symmetrical roller

6. unsymmetrical rolelr

Examples of bearing applications

• rolling track in airport security

• sliding doors (like closet doors)

• drill

• fidget spinner

• pillow block bearings - used to rotate a shaft

Ball bearings

• most common

• load: can handle both radial and thrust loads, usualyl found in applications where load is relatively small

  • load transmitted from outer race → ball → inner race

• since ball is a sphere, only contacts inner and outer race at small point which helps it spin very smoothly

  • however, also means not much is holding hte load; if bearing is overloaded, ball can deform, ruining bearing

Types of ball bearings

• deep groove ball

• angular contact ball

• self-aligning ball

Roller bearings

• used in applications like conveyer belt rollers

• load: can hold heavy radial load, but not much thrust (axial) load

• allows contact between inner and outer race in a line, which spreads load over larger area

  • much stronger than ball bearing

• variation of this type is a needle bearing, which uses cylinders w/ small diameter which allows it to fit into small places

Types of roller bearings

• barrel roller

• spherical roller

• cylindrical roller

• needle roller

Tapered roller bearigns

• roller bearing with a conical shape

• load: can support large radial and large thrust (axial) loads

• used in car hubs, where they are usually mounted in pairs facing opposite directions so they can handle thrust in both directions

Ball thrust bearings

• used for low speed applications

• load: cannot handle much radial load

• barstools and lazy susan turntables use these

Types of ball thrust bearings

• single direction thrust ball

• double direction thrust ball

• angular contact thrust ball

Linear bearings

• rollers provide low friction for heavy loads in a linear motion

Sleeve bearings

• a type of linear bearing

• made to slide over rods/shafts to provide an extremely low friction motion

• excellent for shock absorption

• minimize energy usage, noise, wear

Example of bearings in a car

wheel bearing hub