 Hello friends, I am Sanju Vinay, Assistant Professor in Mechanical Engineering Department, Walton Institute of Technology, Singapore. In this video, I am explaining rolling contact bearings. At the end of this session, learners will be able to identify the rolling contact bearings and also they will be able to select a suitable bearing according to the given application. Bering is a mechanical element which is used to guide the relative motion between two parts such as shaft and the housing with minimum friction and also to support the loads acting on the shaft. The friction between the elements of bearing is rolling 1 and as rolling friction is very less as you know, these bearings are also called as anti-friction bearings. The basic elements of the bearings are shown over here, you just find this is the inner race which is normally mounted on the shaft which is rotating. These are the balls in case of ball bearings or rollers in case of roller bearings which are being maintained in their radial position by cage or retainer. So, this is third element shown over here cage or retainer which used to separate the balls from each other and to maintain them in their radial position and that is why it is also called as a separator and then there is outer ring or outer race. So, this is the construction of the bearing for ball or roller bearings or as far as the classification of bearing is concerned basically these are classified as ball bearings and roller bearings. In case of ball bearings, there is a kinematically it has got a point contact between the ball and outer race and ball and inner race. So, point of contact is a just point of contact and that is why it has got very minimum frictional losses. So, temperature rise in such bearings is comparatively less and that is why they can be used for high speed applications but at the same time being the contact area is very less the load carrying capacity is also less. So, these are used for moderate to low load carrying capacities but for high speed applications. In case of roller bearings as you see over here there is a line contact between the roller and the races that is this is a outer race or inner race the line of contact is there because the area is more for contact the load carrying capacity of these bearings are very high. So, these are normal use for very heavy radial loads or thrust loads in case of thrust bearings. However, they can be used for moderate speeds further these bearings are classified as radial bearings and thrust bearings. So, in case of radial bearings we find is a radial load that is perpendicular to the axis of bearing or perpendicular to the axis of shaft these bearings are called as radial bearings. In case of thrust bearing we find that the load is acting along the axis of the shaft or axis of the bearing and that is called as a thrust bearing. So, accordingly there is a change in some constructional requirement. Now, here we find some types of rolling contact bearings. So, here I have shown some ball bearing types and roller bearing types. So, basically this is a deep groove ball bearing which has got a deep groove in the race inner and outer race in which the ball is fitted and there is a rolling friction of the ball with respect to the races. So, these bearings bring a deep groove they can sustain radial load as well as some moderate thrust load. So, these bearings are suitable for radial loads as well as a low value or moderate value of thrust load and being these are ball bearings they have got advantage of minimum friction and high speed application this can be very well used for household appliances or high speed applications having moderate or low capacities. This is a angular contact ball bearing. So, here the shape of the outer race and shape of the inner race is so adjusted that the balls have got a contact with the inner race and outer race the line of action is inclined that is the load is transmitted from inner race to outer race if at all it is transmitted along the inclined line and the line of action of load is in inclined plane rather or inclined line it can be resolved to components vertical and horizontal. So, it can sustain radial load as well as thrust load. So, whenever the bearings are subject to combined moderate radial and thrust loads then these bearings are best suitable that is angular contact bearings. This is a self aligning bearing. So, in which self aligning principle is used that is whenever there is expected misalignment between the shaft axis and the bearing axis then this has got assembly such that the shaft is fitted in the inner race and the ball. So, this is one assembly which itself rules according to the misalignment it rolls over the spherical surface over here and gets adjusted itself so that this misalignment is absorbed. And that is why whenever misalignment expected to exist then these bearings are best suitable. Same principle is used in case of roller self aligning bearings the principle is one at same however it is load carrying capacity is compared to more than these bearings. Then we see few of the roller bearings it is a cylindrical roller bearing in which there is a line contact and as a contact area is more the load carrying capacity is high. So, these are basically used for heavy radial loads acting on the bearing these bearings are used. This is a taper roller bearing in which the rollers are arranged along the conical axis like this one and because of they are arranged in conical axis along this line. They are subjected to radial and thrust loads. So, they can sustain very high radial and thrust load as a combined load on these bearings. So, these are used in machine tool spindles wherever we expect that the cutting forces are coming in all three XYZ axis then these are the best suitable bearings they give even rigidity to the system more and that is why taper roller bearings can be used. This is a needle roller bearing. In case of needle roller bearing the length of the roller is comparatively very high that is normally L by D is 4 to 6. And that is why the length of contact or the area of contact is very large being the area large it has got very high load carrying capacity. So, radial load they can sustain very high in this case and at the same time being the diameter of the rollers are less the overall radial dimension of these bearings are very very less. So, this is a most compact bearing in radial dimension carrying very high radial loads. So, these are also used in gear boxes or rigidity requirement wherever it is there and the radial space is a restriction these bearings are best suitable. However, the frictional losses are somewhat more. This is a thrust bearing in which the thrust load is applied and accordingly the construction will support the load. Now pause the video and think over this point that what type of bearing can be used for table frame. So, here I have given some comparison of ball bearings where factors are considered like radial load capacity. If I take a deep groove it has got a good radial load capacity, angular contact bearings also can good capacity that is low to moderate load they can sustain whereas a self-alarm bearing in comparison has got some low capacity. In case of thrust load deep groove ball bearing can take limited thrust load whereas angular contact bearings can take very high thrust load. So, they are excellent in that whereas self-alarm bearing cannot take thrust load as such. The combined load if I take combining these two once again it is a good in relationship where it has got excellent capacity as a combined load whereas good capacity. Life expectancy is excellent in this case deep groove ball bearing has got very good life and that is why they are used for high speed applications household applications. Alarm contact bearings are also excellent whereas comparatively self-alarm bearings are fair. So, as far as the speeds are concerned these two bearings can be used for very high speed whereas this can be used for somewhat comparatively less speed. So, this is the comparison of all the bearings. Here is the roller bearing. So, similarly I can consider roller bearings into account in which the same thing is here radial load capacity excellent everywhere thrust load is compared combined load is poor poor but taper roller is excellent. So, many of the machine tools spindles are used life expectancy is excellent almost operating speeds are better and here it is poor. So, this is the way one can compare all the bearings to select a proper for given application. So, these are my references. Thank you.