Rolling Contact Bearing: A Vital Component in Mechanical Systems

Rolling contact bearings play a crucial role in various mechanical systems, ranging from automobiles to industrial machinery. These bearings facilitate the movement of rotating parts by reducing friction and enabling smooth operation. The ability to support radial and axial loads while minimizing energy loss makes rolling contact bearings indispensable in modern engineering applications. In this article, we will explore the fundamentals of rolling contact bearings, their types, working principles, and applications.

Understanding Rolling Contact Bearings:

Rolling contact bearings are mechanical devices designed to reduce friction between moving parts. Unlike plain bearings, which rely on sliding surfaces, rolling contact bearings employ rolling elements that separate the bearing races and enable relative motion. This rolling action significantly reduces frictional losses and extends the life of the bearing.

Types of Rolling Contact Bearings:

1. Ball Bearings: Ball bearings are the most common type of rolling contact bearings. They consist of steel balls arranged between two concentric rings known as the inner and outer races. The balls facilitate smooth rotational motion by rolling between the races, reducing friction. Ball bearings are suitable for moderate radial and axial loads and find extensive use in applications such as electric motors, automotive wheels, and household appliances.
2. Roller Bearings: Roller bearings are designed to handle higher radial loads compared to ball bearings. They utilize cylindrical, tapered, or spherical rollers instead of balls. The larger contact area between the rollers and races allows roller bearings to withstand heavy loads while maintaining low friction. These bearings are commonly found in industrial machinery, such as conveyor systems, gearboxes, and large rotating equipment.

Working Principles of Rolling Contact Bearings:

Rolling contact bearings operate on the principle of separating moving parts by using rolling elements. When a load is applied to the bearing, the rolling elements distribute the load evenly, minimizing stress concentration. As the inner race rotates, the rolling elements roll along the raceways, reducing friction and facilitating smooth motion.

The lubrication of rolling contact bearings is vital to ensure their proper functioning. Lubricants, such as grease or oil, are used to minimize friction, dissipate heat, and prevent wear and corrosion. Regular maintenance and appropriate lubrication intervals are necessary to prolong the life of rolling contact bearings.

Applications of Rolling Contact Bearings:

Rolling contact bearings are utilized in numerous applications across various industries. Some notable applications include:

1. Automotive Industry: Rolling contact bearings are extensively used in automobiles for wheel hubs, transmissions, engines, and suspension systems. They contribute to efficient power transmission, reduced friction, and enhanced vehicle performance.
2. Industrial Machinery: Rolling contact bearings find widespread use in industrial machinery, including pumps, compressors, turbines, and manufacturing equipment. These bearings enable smooth operation, reduce downtime, and improve overall productivity.
3. Aerospace and Defense: The aerospace and defense sectors rely on rolling contact bearings for critical applications such as aircraft engines, landing gear systems, and missile guidance systems. The bearings used in these applications must withstand extreme conditions and provide reliable performance.
4. Power Generation: Rolling contact bearings are vital components in power generation equipment, including wind turbines, hydroelectric generators, and gas turbines. They facilitate the rotation of turbine shafts, ensuring efficient power production.

Interview questions on bearing

Combination of bearing use in equipment

Three types of combination of bearings mentioned below

• O type of arrangement (DB) back to back
• X type of arrangement (DF) face to face
• Tendon arrangement

O type of arrangement (Back to Back)

The distance or (pressure point) between inner and outer cage is more because the smaller deformation occurs due to moment loads this type of arrangement bearing can take a larger moment load than X type of arrangement.
Two angular contact ball bearing or two taper rollers bearing which take combine loads and can be paired in combination of X arrangement, O arrangement and tendon arrangements. O arrangement two bearing uses for directional and axial load

X type of arrangement (Face to Face)

X type of arrangement is used if the shaft is going hot during the operation, to prevent bearing damage from this pre-load given during mounting of bearing on shaft increases.
But in O type of arrangement the co-efficient of thermal expansion for bearing and other part will be same. Because the axial and radial thermal expansions cancel out each other, and in this condition given pre-load during installation does not change.

X type of arrangement bearing can tolerate the inaccuracy of housing and it can tolerate shaft deflection due to poor shaft rigidity.
Tandem arrangement is used for heavy loads with low speeds.

What is cage bearing and full complement bearing?

full complement bearing

Full complement without cage bearing has a greater number of rolling elements. It can support very large loads. But mutual contact with rolling elements increases friction with each other. It runs at relatively low speed or to slewing motions.

Caged bearing

Caged bearing has a smaller number of rolling elements. It can support fewer loads as compared to full complement bearing. But in caged bearing, mutual contact of rolling elements has less friction with each other, rolling element are separate in it. It can run high at speeds.

Where full complement bearing used?

High load with very low speed.

Types of Bearing internal clearance

Zero operational clearance and slight pre-load, some positive clearance, arrangement has some pre-load.

What happens if clearance is less than required for a spherical roller bearing after mounting on the shaft?

Bearing life reduced and creating noise during operation due to thermal expansion. What do you mean of bearing pre-load.

why it is important?

• Enhance the bearing stiffness
• Enhance the accuracy of shaft guidance
• Compensation for wear and settling in operation
• Give a long service life

Radial load

Cylindrical roller Double row angular contact Deep grove

List of Axial load bear bearing

Single row angular contact,  Taper roller bearing,  Deep groove.

The rolling contact bearing materials are silicon nitrite, 52100 steel, 440c stainless steel, M50 steel.

Question

Most of ball bearing are made of ?

A) 20MC5, B) SAE2100, C) Silicon Nitrite, D) 440c stainless steel.

Code for bearing

Bearing code is a combination of three terms (letter and number), which is prefix, basic code, suffix.

Prefix

There are 4 different prefixes used in bearing nomenclature,
R means ring of cylindrical or taper roller bearing with rolling element and cage but not separable ring.
WS means ring and ball of thrust ball bearing.
GS is a housing washer of thrust ball bearing.
K means cage with rolling elements. Go for the code of bearings.

Suffix

E high capacity bearing,
UA, UO AND UL means universal design of single row angular contact ball bearing with closed axial preload, no clearance and light preload respectively.
ZR and 2ZR bearing with one or two shields.
RSR and 2RSR bearing one or two shields,
J, Y, M, F, L, T and TV pressed steel, pressed brass, machined brass, machined light alloy and plastic cage.
K means bearing with taper bore, taper 1:12 ratio.
PN (PO), P6, P5, P4, P2 tolerance class.
C1, C2, CN(CN), C3, C4, and C5 bearing clearance.

For know, about inside bore, multiply last two digit with 5, and if D = 10, 12, 15, 17 then code number will be 00, 01, 02, 03 respectively.
If the d is more than 480 mm then written directly on bearings.

Full bearing code description with example 22320K EJW 33 C33 C3 Means spherical roller bearing, straight bore, clearance is more than normal clearance, bore diameter is 120 mm, machined brass cage, high capacity bearing.