The addition of spacers between the bearings
of a set may be necessary when the following is required:
- increased angular rigidity by separating the bearing
- heat generated by the bearings is to be dissipated more
effectively
- the space is required for oil jet nozzles.
Spacer manufacture requires good accuracy to ensure:
- parallel and planar faces within reduced tolerance limits
(Cf. Bearing tolerances)
- equal width outer and inner spacers to keep bearing original
preload unchanged (simultaneous grinding is recommended)
- well balanced rotated spacer.
The use of appropriate surface hardened (45HRc) or through
hardening material is normally recommended. This treatment
prevents the risk of spacer surface damage during assembly
and wear during subsequent operation.
Many materials are suitable for producing spacers, including
the following:
- ISO 100 Cr6 (SAE 52100) : through hardened
- UNI 38 Ni Cr Mo 4 (SAE 9840) : through hardened/tempered
- UNI 18 Ni Cr Mo 7 (SAE 4320) : case hardened
Spacer configuration complexity depends on any other function
it may have.
The rotating or static spacer of oil lubricated bearings
may, for instance, be deflector shaped to facilitate oil flow
through the bearings to ensure good oil drainage and disposal
via the discharge channels. It must never restrict lubricant
flow.
Spacer configuration in grease lubricated bearings plays
a secondary role. The spacer shape must however be such as
to allow dispersal of the excess grease expelled by the bearings,
especially during the running stage.
Preload arrangements of Back to Back (DD) or Face to Face
(FF) can be modified by changing outer or inner space width.
For instance, reducing the width of the spacer placed between
the outside rings, causes:
- reduced preload in DD sets
- increased preload in FF sets
The opposite occurs by reducing the width of the spacer between
the inner rings.
The following calculation is used for proper adjustment:
|
GRW
Product Desc.