Angular misalignment

Moment caused by contact-point shift. This moment acts in the angular misalignment plane and tends to straighten the coupling. It can be expressed... 

Moment caused by coupling friction. This moment acts in a plane at a right angle relative to the angular misalignment. It has the magnitude... 

Moment caused by angular misalignment. This results in bending of the diaphragm... 

Angular misalignment can take several signature forms and excites the fundamental (lx) and secondary (2x) components. It can excite the third (3x) harmonic frequency depending on the actual phase relationship of the angular misalignment. It also creates a strong axial vibration. 

For comparison, see Figure 54.3, which shows two shafts that have angular misalignment, but are not offset. Figure 54.9 shows how an offset measurement for non-parallel shafts can vary, depending upon where the distance between two shaft centerlines is measured. Again, note that theoretical offset is defined at the coupling face. 

Both angular misalignment and offset can occur in the vertical plane. Vertical misalignment, which is corrected... 

Figure 54.9 Offset measurement for angularly misaligned shafts...

Both offset and angular misalignment can occur in the horizontal plane. Shims are not used to correct for horizontal misalignment, which is typically illustrated in a top-view drawing as shown in Figure 54.11. This type of misalignment is corrected by physically moving the machine to be moved (MTBM). 

The primary requirement for making any connection is to minimise the optical power that is lost in it. Intrinsic losses result from technological variations of the fibres to be connected i.e. core area mismatch, numerical aperture mismatch, and profile mismatch. These obvious errors can only be omitted by proper matching of connected fibres or additional optical elements should be used. Contrary to the intrinsic losses, extrinsic ones can be corrected by a mechanical alignment. Extrinsic losses are caused if ends of the fibres are in some distance and the light from the input fibre cannot be collected by the sink fibre. A similar situation with power losses occurs in lateral displacement and angular misalignment. 

Figure 16. Tolerances of the a-Si Q (jRIN coupler efficiency with respect to (a) input mode angular misalignment, (h) input mode displacement, (c) input wavelength, and (d) polarization.

Figure 1.13 Percentage error in measured d spacing as a function of scattering angle arising from a constant angular misalignment of A0 for a well aligned (0.001°), a typically aligned, (0.01°) and a poorly aligned (0.05°) diffractometer.

TTie corrugated joint, when well designed and constructed, has advantages if the installation is inaccessible and maintenance of the joint is difficult or impossible. It is also useful when the piping is subject to lateral and angular misalignment as weU as axial motion. However, it is important to select and install the joint properly so that the corrugations will not be overstressed. 

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