Design Characteristics of Bearings – Review Flashcards

These flashcards cover key concepts from the lecture on bearing design characteristics: definitions, functions, load sources, bearing types and sub-types, specific bearing characteristics, materials, lubrication objectives, lubricant selection, and practical applications.

What is the basic definition of a bearing?

A machine element that constrains relative motion to only the desired motion and reduces friction between moving parts.

List three primary functions of bearings.

1) Carry load, 2) Reduce friction & wear, 3) Limit unwanted motion.

Name three common sources of radial loads on bearings.

1) Weight of gears, pulleys, and shaft, 2) Tension from belt or chain drives, 3) Forces between meshing gear teeth.

Which two broad families are bearings divided into?

1) Plain (slide) bearings, 2) Rolling-element bearings.

Why do plain (slide) bearings generally require greater lubrication than rolling bearings?

They have a larger contact area, resulting in higher sliding friction.

Give two alternative names for rolling-element bearings.

Rolling contact bearings or antifriction bearings.

Why are rolling-element bearings often called antifriction bearings?

Because rolling friction is much lower than sliding friction due to smaller contact area.

List the main sub-types of ball bearings mentioned.

Deep groove and angular contact (single-row and double-row).

List four main sub-types of roller bearings mentioned.

Cylindrical, spherical (single & double-row), tapered, and needle.

What is the purpose of the interference fit between the bearing races and the shaft/housing?

To make the inner race rotate with the shaft and keep the outer race stationary in the housing.

Which ball bearing type is most widely used and lowest in cost?

Deep groove (Conrad) ball bearing.

What loads can a deep groove ball bearing accommodate?

Excellent radial load and fair axial load.

Give three industrial applications of deep groove ball bearings.

Electric motors & power tools, gearboxes & transmissions, pumps & compressors.

How does an angular contact ball bearing differ from a deep groove ball bearing in axial capacity?

Angular contact bearings have greater axial (thrust) load capacity in one direction.

State two typical uses of angular contact ball bearings.

Pumps & compressors, machine-tool spindles (also electric motors, generators, automotive hub bearings).

What is a double-row angular contact ball bearing functionally equivalent to?

Two single-row angular contact bearings mounted back-to-back.

Which bearing family generally has higher load capacity than ball bearings?

Roller bearings.

Give three key characteristics of cylindrical roller bearings.

1) Very high radial load capacity, 2) Good speed capability, 3) Limited misalignment capability (rings can move axially).

Name two machines where cylindrical roller bearings are commonly used.

Large electric motors and gearboxes & transmissions (others: machine-tool spindles, steel rolling mills).

Why can spherical roller bearings handle misalignment without loss of capacity?

Their two-row barrel-shaped rollers allow angular adjustment (up to about 1.5°).

What mix of loads can spherical roller bearings carry?

Excellent heavy radial/impact loads and moderate axial loads.

List three applications of spherical roller bearings.

Steel mills, paper mills, large gearboxes (also continuous casting machines, large air handling equipment).

What distinguishes a tapered roller bearing’s cup and cone?

Outer ring is the cup; inner ring with rollers and retainer is the cone and is separable.

How does contact angle affect tapered roller bearing load capacity?

Shallow angle = larger radial capacity, steep angle = larger axial (thrust) capacity.

Why are tapered roller bearings often used in pairs or duplexed?

To handle axial loads in both directions and provide rigidity.

Name three typical applications for tapered roller bearings.

Automotive transmissions, heavy-duty wheel bearings, steel mill roll necks (also aircraft wheels, industrial gearboxes).

What physical feature gives needle roller bearings their name?

They use long, thin cylindrical rollers resembling needles.

State two advantages of needle roller bearings.

1) High radial load capacity in a small space, 2) Can operate at very high speed (with a cage).

Give two automobile components that commonly use needle roller bearings.

Pumps, compressors, or transmissions.

List two key advantages of white-metal (babbitt) plain bearing material.

High durability withstanding momentary high loads and good performance even with limited lubrication or slight misalignment.

Which plain-bearing alloy offers very high strength and temperature resistance compared with white metal?

Copper-lead alloys.

Why are tin bronzes valued for plain bearings in marine environments?

They provide corrosion resistance in seawater and brines.

State the two main objectives of bearing lubrication.

Reduce friction and prevent overheating & corrosion.

What are the ideal viscosity characteristics of a bearing oil?

Stable viscosity over a broad temperature range and good film strength to support loads.

Give three additional functions of lubricants beyond friction reduction.

Seal against contaminants, dissipate heat, protect against corrosion (also reduce noise, resist moisture).

When is grease preferred over oil for bearing lubrication?

When oil would not stay in place, a continuous oil supply is impractical, loads are low, operation intermittent, and speed is slow.

Under what operating conditions is oil lubrication generally recommended for bearings?

High loads, continuous operation, and high rotational speed.

How does a grease thickener aid rolling-element bearing lubrication?

It absorbs oil and releases it slowly to the bearing over a long period, allowing a small grease quantity to last a long time.

Why are additives blended into bearing oils?

To improve corrosion resistance, build protective layers under extreme conditions, and adjust viscosity behavior with temperature.