Roller Bearings introduction and designs

Roller Bearings introduction and designs JSMEHTA

1. Rolling Contact Bearings

2. Plain bearings-Sleeve Bearing Advantages : It takes up less space. It has a rigid construction It will carry loads more effectively It is suitable for larger diameter shafts It is cheap to manufacture and cost less. They operate more silently. They have good shock load capacity . Disadvantages: It has higher frictional resistance It is more difficult to lubricate There are limited choice of designs available

3. Rolling Contact Bearings Two 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.

4. Types of Rolling contact Bearings

5. Bore Outer Race Inner Race Ball Cage or Separator Since the ball is a sphere , it only contacts the inner and outer race at a very small point, which helps it spin very smoothly . But 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 bearing . Less expensive and suitable for lighter loads and applications

6. Roller bearings : In these bearings, the roller is a cylinder, so the contact between the inner and outer race is not a point but a line . This spreads the load out over a larger area, allowing the bearing to handle much greater loads than a ball bearing. However, this type of bearing is not designed to handle much thrust loading.

7. Tapered roller bearings are used in car hubs, where they are usually mounted in pairs facing opposite directions so that they can handle thrust in both directions . Tapered roller bearings support both radial and axial loads, and generally can carry higher loads than ball bearings due to greater contact area. Taper roller bearings are extensively used in Machine spindles and gear boxes using helical gears The disadvantage of this bearing is that due to manufacturing complexities, tapered roller bearings are usually more expensive than ball bearings

8. Needle Bearing A 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. Advantages Smaller diameter rollers (Needles) enable larger area of contact and greater load carrying capacity. Less space is occupied Disadvantages More area of contact resulted in more frictional resistance to motion.

9. Ball Thrust Bearing Ball thrust bearings like the one shown are mostly used for low-speed applications and cannot handle much radial load. Lead screws and feed rods use this type of bearing at its end.

10. Designation of ball bearing 1-Extra light series 2-Light series 3-Medium series 4-Heavy series Bearing No.305 means bearing is of medium series whose bore is 05 X5=25 mm Bearing no. 411 Heavy series with bore 55 mm

11. Selection of radial ball bearings 1)Calculate dynamic Equivalent load

12. --- contd 2) Calculate design dynamic equivalent load by multiplying dynamic load by service factor 3)Calculate dynamic load capacity C 4 )Select suitable radial ball bearing from table according to dynamic load capacity from tables 5 )Write its designation

13. X and Y are functions of e (clearance)which is function of Fa/Co where Fa is axial thrust and Co is basic static load rating

14. General Selection Table