Design Characteristics of Bearings – Review Flashcards

A comprehensive set of Q&A flashcards covering definitions, types, applications, materials, and lubrication principles for bearings, designed to aid exam preparation.

What are the three primary functions of a bearing?

Carry load, reduce friction & wear, and limit unwanted motion.

Where do most radial loads on bearings typically originate?

(1) Weight of parts such as gears, pulleys, and the shaft itself; (2) Tension from belt or chain drives; (3) Forces between meshing gear teeth.

How does a plain (slide) bearing support a rotating shaft?

The shaft slides directly on the stationary bearing surface, creating a large contact area that requires significant lubrication.

Why are rolling-element bearings often called antifriction bearings?

Because their point or line contact greatly reduces rolling friction compared with the large sliding area of plain bearings.

Name the two main families of rolling-element bearings.

Ball bearings and roller bearings.

List four common sub-types of ball bearings.

Deep groove, single-row angular contact, double-row angular contact, and (general) radial/thrust variants.

List four common sub-types of roller bearings.

Cylindrical, spherical, tapered, and needle roller bearings.

What is the purpose of the inner and outer races in a rolling bearing?

To house the rolling elements; the inner race rotates with the shaft (interference fit) while the outer race remains stationary in the housing.

Why are deep groove ball bearings called "Conrad" bearings?

Because of the Conrad assembly method used to insert the balls, allowing one-piece deep grooves in both races.

Which loads can deep groove ball bearings accommodate well and moderately?

They accommodate radial loads well and axial (thrust) loads moderately.

Give three industrial applications of deep groove ball bearings.

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

What load advantage do angular contact ball bearings have over deep groove versions?

Higher axial (thrust) load capacity in one direction due to the contact angle between balls and races.

Why are double-row angular contact ball bearings equivalent to two single-row bearings mounted back-to-back?

Because they incorporate two rows of balls with opposing contact angles in a single assembly, carrying radial loads and axial loads in both directions.

Which three industries commonly use double-row angular contact ball bearings?

Centrifugal pumps, electric motors, and blowers/fans (also transmissions & gearboxes).

Why do roller bearings generally have higher load capacity than ball bearings?

Rollers have a larger contact area (line contact) with the races, distributing loads over a bigger surface.

State two key features of cylindrical roller bearings.

Very high radial load capacity and good speed capability; they are also separable and allow limited axial movement.

Name two typical applications for cylindrical roller bearings.

Large electric motors and machine-tool spindles (also gearboxes, steel mills).

What unique ability makes spherical roller bearings suitable for misaligned shafts?

They can accommodate angular misalignment (up to about 1.5°) without loss of load-carrying capacity.

Which combination of loads can spherical roller bearings carry?

Heavy radial loads/impact loads and moderate axial loads.

Give three machines that often use spherical roller bearings.

Steel mills, paper mills, and continuous casting machinery (also large gearboxes, air-handling equipment).

How are the outer and inner rings of a tapered roller bearing commonly named?

Outer ring = cup; inner ring with rollers & cage = cone.

How does the contact angle of a tapered roller bearing affect its capacity?

A shallow angle favors higher radial load capacity; a steeper angle favors higher axial load capacity.

Why are tapered roller bearings usually used in pairs?

To support axial loads in both directions and to control shaft alignment/preload.

List three applications of tapered roller bearings.

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

What distinguishes a needle roller bearing from other roller bearings?

It uses long, thin rollers (needles), offering high radial load capacity in a very small cross-section (space-saving).

Name two automotive components that often employ needle roller bearings.

Pumps (oil/fuel) and transmissions (gear clusters, planetary sets).

Why is white metal (Babbitt) a popular plain-bearing material?

High durability, good friction resistance, can endure high loads momentarily, and works fairly well with minimal lubrication or slight misalignment.

Which plain-bearing alloy offers high temperature resistance and higher load capacity than white metal?

Copper-lead alloys.

Give two desirable properties of tin bronze for plain bearings.

High load-carrying capacity and good wear resistance; also corrosion resistance in seawater.

State the primary objective of bearing lubrication.

To reduce friction and prevent overheating & corrosion of bearing surfaces.

What are the two main classes of bearing lubricants?

Oil and grease.

List four ideal properties of a lubrication oil for bearings.

Stable viscosity over a wide temperature range, good film strength, long service life, and non-corrosiveness/compatibility with adjacent components.

When is grease preferred over oil for bearing lubrication?

When maintaining a continuous oil supply is difficult, when lubricant must stay in place (wheel bearings, chassis), or when sealing against contaminants is important.

Under what operating conditions is oil lubrication generally recommended?

High loads, continuous operation, and high rotational speed.

Give two advantages of grease in hard-to-reach bearing locations.

Reduces lubricant loss/lubrication frequency and provides rust protection by staying in place.

Why are additives blended into bearing oils?

To enhance corrosion resistance, provide protective surface layers under extreme conditions, and improve viscosity behavior across temperatures.

What role does a thickener play in greases for rolling-element bearings?

It holds the oil and releases it gradually to the bearing contact over a long period.

How much grease is typically required for a rolling-element bearing, and why is that sufficient?

Only a few grams; because the grease slowly releases oil, providing long-term lubrication under modest loads.