Rolling Contact

Figure 6.2 Roller bearing with return path

The most common sort of bearing used in industry is the ball bearing. They are typically mounted in a track concentric to that of the shaft they are supporting and follow the same rotary path. In a linear machine this would require either a return path to be provided, shown in Figure 6.2, or seriously reduce the amplitude of oscillation allowed, which is unlikely to be acceptable in this application.

Stud bearings, whereby a set of roller bearings is used to make a wheel and track type arrangement, are used widely in industry for heavy duty applications. Figure 6.3 shows a typical configuration with a flat contact surface. 'V' shape surfaces can be used up to a speed of 5 ms-1 if axial forces are present [84].

Track rollers can, theoretically, be designed for a life of 106 km if they are well lubricated and the load factor is kept very low, i.e. the expected load on each bearing is less than 10% of its rated maximum [84]. Totally unlubricated bearings, however will have a life time of the order of 104 km.

Figure 6.3: Stud bearing

A well designed track bearing can take the loads speeds and annual distances associated with this type of application if proper provision for lubrication is made. Rolling contact bearings, however, can suffer from catastrophic instant failure. It is customary to rate rolling elements in terms of total distance and average (L-50) and minimum (L-10) life. The former of these is the life that can be expected from 50% of the bearings whereas the latter is the minimum life expected from 90% of samples. The implication is that 10 % will not reach minimum life expectancy and could theoretically fail well anytime after installation.

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

Get My Free Ebook


Post a comment