Tapered roller bearings can be fixed and preloaded using shims and an end cap. There is a setting procedure to ensure the desired preload is achieved and the amount of end play (axial clearance) is within acceptable parameters. But these traditional components can be replaced using a wave spring and spiral ring, resulting in cost savings in both assembly and field maintenance.
Tapered bearings are capable of accommodating high axial forces. They are used on a variety of equipment and machinery, including automobile wheel bearing assemblies, agriculture, construction and mining equipment, gear boxes, engine motors, and reducers.
Under the standard method, it is necessary to determine the number of shims needed to take up the required amount of end play. This is usually accomplished by tightening the end cap without the shims until there is a slight drag on the bearing. The gap between the end plate and shaft (or housing, depending on the application) is measured. This result, along with the amount of end play required, will determine the number of shims needed for the bearing to function effectively.
Shims and an end cap are used to secure these tapered roller bearings on a shaft at the desired preload.
(Source: Rotor Clip)
Two-turn spiral ring replaces end cap
The two-turn spiral ring can replace the end plate, the screws (to fix the end plate), and the lock wire as a fixing element. There is only the need to design a slightly longer shaft with a machined groove that offers a suitable seat for the spiral ring. The two-turn spiral ring creates a 100% real shoulder for the spring element by offering a 360-degree closed surface (compared to conventional retaining rings or snap rings).
Immediate advantages include reduced costs and ease of handling on the assembly line due to fewer components. Service in the field will be quicker, because only one ring (versus multiple screws) must be handled.
Wave spring replaces shims for bearing preload
Single or multiple turn flat wire wave springs are viable replacements for screws and shims, and they offer the advantage of compensating for axial play in the application. Shims can statically compensate only for axial play, but a wave spring can continually adjust for play when thermal expansion occurs during the running time of the application.
Flat wire wave springs can be designed with extremely low spring rates, so that the provided loads during changes in the axial cavity are more constant than they are with shims adjusted by screws. In addition, the use of a wave spring combined with a two-turn spiral ring minimizes the risks of assembly errors, because screws (to fix and preload the shim) can be pulled with too much or too little torque.
The consequences are as follows:
- Too much torque: The bearing is preloaded in such a way as to cause wear, which reduces the lifetime of the bearing.
- Too little torque: The bearing is not preloaded with a sufficient axial force, and noise-vibration-harshness problems occur.
Given the necessity to reduce weight and assembly time and to consolidate vendors, Rotor Clip's two-turn spiral rings and TruWave wave springs will assist designers in achieving these important cost reduction goals.
Elmar Kampmann is technical sales manager and global wave spring engineer for Rotor Clip Co.