MTS Series 249G2 Swivels - Manual (Page 25)

Swivel Bearing Backlash
Series 249G2 Swivels Maintenance 25
Maintenance
Contents
Swivel Bearing Backlash 25
Checking for Swivel Bearing Backlash—Observation Method 26
Checking for Swivel Bearing Backlash—System Response Method 27
Adjusting Backlash 27
Considerations For Superbolt Torquenuts 30
Overview
Maintenance for the Series 249 Swivels consist of periodic checks and, if
necessary, adjusting the backlash. Series 249N are not backlash adjustable, and
therefore do not require maintenance of the clamping bolt system. They still,
however, should be periodically checked for excessive bearing movement and
noise. The spherical bearing used in the swivels should not be lubricated.
Series 249 Swivels are usually shipped from MTS with the backlash adjusted and
are ready for immediate use. However, the backlash should be checked and, if
necessary, adjusted prior to use in the field. Backlash should be checked again
after four to five hours of initial use and as often as necessary thereafter.
Operating a swivel with excessive backlash can result in system instability, poor
control of load when passing through zero, and rapid bearing wear due to shock
loading effects. Proper backlash adjustment will prolong the life of the swivel
and enhance the system’s performance and fidelity.
Swivel Bearing Backlash
The acceptable amount of backlash in a given test system depends on the forces
the swivel must react to and the sensitivity of the test. If a smooth transition
between tension and compression loads is not required, a small amount of
backlash might not affect test results. Determining whether or not the swivel
bearing backlash adjustment is compatible with the sensitivity requirements of
the test requires you to carefully consider the function of the swivel within the
test setup.
Testing systems that use the swivel primarily as a tool to align the components of
the force train during application of tensile or compressive forces, but not both,
will probably not be affected by a certain amount of swivel bearing backlash.
Testing systems that use the swivel during dynamic tensile and compressive
loading of a specimen/structure can be adversely affected by a swivel bearing
adjustment that is too loose or too tight.
The following describe the methods which can be used to determine if it is
necessary to adjust the swivel bearing backlash.