Bearings 1

Question 1

Types of Bearings

Answer 1

1. Rolling Element Bearings (Rolling Motion) 2. Plain Bearings (Sliding Motion).

Question 2

What is the function of a bearing?

Answer 2

A bearing allows two parts to move independently of each other.

Question 3

What motion do most bearings allow?

Answer 3

Most bearings allow rotational motion, but some allow linear motion.

Question 4

Operating Mechanism of Plain Bearings

Answer 4

Sliding between surfaces, which can generate friction and wear.

Question 5

What are the loading types for plain bearings?

Answer 5

Some take radial load only, others thrust load (axial load), and some can take both radial and thrust loads.

Question 6

Types of Lubrication for Plain Bearings

Answer 6

1. Partial Lubrication (Boundary, Dry, None) 2. Film Fluid Lubrication (Hydrostatic, Hydrodynamic).

Question 7

Characteristics of Boundary Lubrication

Answer 7

Grease/oil film applied, carries part of the load, surfaces still in contact leading to wear. Suitable for moderate loads/speeds.

Question 8

Examples of Boundary Lubrication Applications

Answer 8

Linkages, children’s bicycle wheels.

Question 9

Features of Dry Lubrication

Answer 9

Uses graphite powder, suitable for low loads/speeds, surfaces in contact leading to wear.

Question 10

Applications of Dry Lubrication

Answer 10

Locks, sliding mechanisms.

Question 11

Hydrodynamic Lubrication in Plain Bearings

Answer 11

Uses a wedge of lubricant film, no surface contact, suitable for high loads/high speeds.

Question 12

Examples of Hydrodynamic Lubrication Usage

Answer 12

Crankshafts, turbine shafts.

Question 13

Hydrostatic Lubrication Characteristics

Answer 13

Pressurized lubricant film, requires external pump, no surface contact, suitable for high loads/low to moderate speeds.

Question 14

Applications of Hydrostatic Lubrication

Answer 14

Machine tools, measuring instruments.

Question 15

Materials used in Plain Bearings

Answer 15

Shaft - hardened steel; Bearing - soft materials like white metals, copper alloys, aluminum alloys, polymers, porous sintered metals.

Question 16

Design Considerations for Plain Bearings

Answer 16

Magnitude and direction of forces, relative velocity, misalignment, operating environment, bearing length relative to shaft diameter.

Question 17

Calculating Pressure x Velocity (PV) Value in Bearing Design

Answer 17

Determine the mean bearing pressure and sliding velocity, then double the PV value for safety.

Question 18

Example Calculation in Bearing Design

Answer 18

Consider radial load, shaft diameter, bearing length, and running speed to calculate PV value and select suitable bearing material.

Question 19

Summary of Plain Bearings

Answer 19

Sliding motion generates wear and heat, selection based on shaft speed and load, calculate PV value and consult supplier’s chart.

Question 20

Factors in Selecting Bearing Material

Answer 20

PV value, maximum load capacity, operating temperature, coefficient of friction and expansion, application needs.

Question 21

No Lubrication

Answer 21

Polymer used as the bearing surface
* No maintenance (i.e. no re-lubrication)
* Surfaces are still in contact
Low Loads/Low Speed