2 BEARINGS- INTRODUCTION Bearings are machine elements which are used to support a rotating member called as shaft.They transmit the load from a rotating member to a stationary member known as frame or housing.
3 Bearing Motions Axial rotation e.g. shaft rotation Common motions permitted by bearings are:Axial rotation e.g. shaft rotationLinear motion e.g. Carriage over the bed, drawer in the tablespherical rotation e.g. ball and socket jointHinge motion e.g. door
5 Bearing Loads-Radial load The bearings that support the shafts of motors and pulleys are subject to a radial load.
6 Bearing Loads-Thrust load The bearings in this stoolare subject to a thrust load
7 Bearing Loads-Combination of Radial &Thrust load The bearings in a car wheel are subjectto both thrust and radial loads.
8 Bearing Classification On the basis of contact they have between the rotating and the stationary memberPlain bearings(Sliding contact)Rolling bearings(Rolling contact)
9 Plain bearings-Sleeve Bearing Advantages :It takes up less space.It has a rigid constructionIt will carry loads more effectivelyIt is suitable for larger diameter shaftsIt is cheap to manufacture and cost less.They operate more silently.They have good shock load capacity.Disadvantages:It has higher frictional resistanceIt is more difficult to lubricateThere are limited choice of designs available
10 Sliding contact- Sleeve Bearing Split SleeveSuitable for large diameters shaftsSolid SleeveSuitable to radial load onlySlit SleeveAdjustable to compensate wear
11 Rolling Bearings Things roll better than they slide The concept behind a ball bearing is very simple:Things roll better than they slideTwo surfaces can roll over each other, the friction is greatly reduced.Bearings reduce friction by providing smooth metal balls or rollers, and a smooth inner and outer metal surface for the balls to roll against.These balls or rollers "bear" the load, allowing the device to spin smoothly.
12 Rolling Bearings Advantages The rolling bearings have a lower frictional resistance than plain bearingsThe Lubrication of rolling bearings is easier because they can be "grease packed'A greater choice of roller bearing designs are available than for plain bearingsDisadvantagesIt takes up more space than plain bearingsThe rolling bearings are not as rigid as plain bearingsMore nosier in operation than plain bearings
13 Types of rolling Bearings Ball bearings,Roller bearings,Tapered roller bearings.Ball thrust bearings,Roller thrust bearings and
15 Ball bearingsIn a ball bearing, the load is transmitted from the outer race to the ball and from the ball to the inner raceSince the ball is a sphere, it only contacts the inner and outer race at a very small point, which helps it spin very smoothlyBut it also means that there is not very much contact area holding that load, so if the bearing is overloaded, the balls can deform and spoil the bearingLess expensive and suitable for lighter loads and applications
16 Rolling Element Bearing Parts Outer RaceInner RaceBallCage or SeparatorBore
17 Roller bearingCommon roller bearings use cylinders of slightly greater lengththan diameter.Roller bearings typically have higher radial load capacity thanball bearings, but a low axial capacity and higher friction underaxial loads.If the inner and outer races are misaligned, the bearing capacityoften drops quickly compared to either a ball bearing
18 Roller bearing Advantages They can carry greater radial loads The geometric shape of the rolling element can be variedThey are having greater area of contact with the race waysDisadvantagesNot suitable to take much thrust loadExpensive
19 Taper Roller BearingsTapered roller bearings use conical rollers that run on conical races.Tapered roller bearings support both radial and axial loads, andgenerallycan carry higher loads than ball bearings due to greater contact area.Taper roller bearings are extensively used in Machine spindles andgear boxes using helical gearsThe disadvantage of this bearing is that due to manufacturingcomplexities, tapered roller bearings are usually more expensive thanball bearings
20 Needle BearingA variation of the roller type of bearing is called a needle bearing, uses cylinders with a very small diameter.This allows the bearing to fit into tight places.AdvantagesSmaller diameter rollers (Needles) enable larger area of contact and greaterload carrying capacity.Less space is occupiedDisadvantagesMore area of contact resulted in more frictional resistance to motion.
21 Ball Thrust BearingBall thrust bearings like the one shown are mostly used forlow-speed applications and cannot handle muchradial load.Lead screws and feed rods use this type of bearing at its end.
22 Roller Thrust BearingRoller thrust bearings like the one illustrated can support large thrust loads.They are often found in gear sets like machine transmissions between gears, and between the housing and the rotating shafts.The helical gears used in most transmissions have angled teethand this causes a thrust load that must be supported by this type of bearing