Preload and bearing arrangement
Basically, there are two types of preloading:
Spring preload Characteristics:
- Insensitive to different thermal expansion of shaft and housing
- Suitable for very high speeds
The drawing shows a spindle where bearing 1 has a fixed location, whereas the outer ring of bearing 2 is free to move axially. The spring force acts on the outer ring of bearing 2 and results in a permanent preload of both bearings almost independent of speed and temperature factors. Care must be taken to ensure easy movement of the adjusted outer ring. Bearings preloaded in this way can be used up to the limiting speed of single bearings if oil lubrication is used.
The spring has to be arranged to be effective in the same direction as the external axial load.
Rigid preload
Characteristics:
- Higher rigidity at radial loads
- Lower limiting speed compared to spring preload
- The magnitude of preload changes due to length variations as a result of temperature differences between shaft and housing.
- Distinct higher axial rigidity than with spring preload
With the spindle shown in the drawing both bearings are paired and mounted stationary in an axial direction. Bearings arranged like this have a defined axial pre-load.The sleeves shown in the drawing must be ground to identical lengths in one setting. RHD delivers the required bearing pairs with the necessary preload.
The change of the preload under operating conditions has to be considered.
Bearing arrangement: All bearing arrangements shown here after can be manufactured on request (depending on volume), or combined from universally matched bearings.
Back-to-back arrangement
Face-to-face arrangement
Tandem arrangement
Often, if a bearing is subjected to large loads or if a high degree of rigidity is required three or more bearings are used, assembled in sets shown here after. The bearing arrangements can be combined from universally matched bearings, or produced at sufficient lot sizes.
TDB
TDF
TDT
QDB
QDF
QDT
When using a single spring loaded bearing, a minimum preload must be observed to assure positive rotation of the balls and to prevent skidding. RHD application engineers will calculate the minimum preload for your application.
