What are taper roller bearings, and why are they so useful?
Taper roller bearings were invented in America over a hundred years ago. But since bearing technology had improved little for many years prior to their invention, they represented quite a leap forward in the applications to which they were best suited.
So, what are taper roller bearings, and how do they differ from other types of bearing with which we may be more familiar? Picture the axle of a large vehicle; it may be an agricultural vehicle like a combine harvester, a plant vehicle like a road grader or planer, a mining vehicle, or similar. The axle is a shaft which passes through a cylindrical, tube like bearing which forms a ring around the axle, and that bearing is then attached to the chassis of the vehicle, possibly through other components such as a suspension assembly. As the vehicle is loaded, the load on the bearing increases, so the bearing must be strong. Then as the vehicle moves away, the axle rotates in the bearing.
What happens when the vehicle turns a corner? In addition to the load pressing down on the axle through the bearing (radial force), a second force now comes into play. As the weight of the load on the vehicle moves sideways (axial force), it tries to force the axle to slide sideways through the bearing towards the wheel. Bearings are made to be very strong to stand up to a high radial force so vehicles can carry a large amount of weight. But the axial force is pressing on the weak side wall of the bearing, trying to force the axle to pop out the side of the vehicle. How can you make a bearing which supports the axle but is also resistant to a high axial force? Enter the taper roller bearings.
Taper roller bearings are slightly different from the tube like bearings described above. Instead of being cylindrical, they are smaller at one end and therefore resemble a cone with the point cut off. Whereas regular cylindrical bearings are very strong in bearing forces which press down on them from above, taper roller bearings are effectively set at an angle, and therefore can bear both radial and axial forces. When used in pairs, it’s as if the taper roller bearings form the top and bottom of an enclosed cylinder, in which sits the axle. In this way, the axle is held in place, and the high forces are borne by the strongest parts of the bearing.
Why are rollers used in taper roller bearings, instead of ball bearings? Ball bearings take all the weight on one point of the ball, leading to high wear. The rollers in taper roller bearings spread this weight, leading to greater load carrying capacity and increased reliability. Taper roller bearings are the accepted first solution for many industrial and automotive applications, and follow the designation system defined by ISO355.