Bellows and Spiral(helical) Beam type couplings are basically one piece couplings and so have very high torsional rigidity and zero backlash, so they are ideal for reversing operations. They are best suited to accomodate angular misalignment, which can be quite large if they are long enough. If used in this way there is no variation in angular velocity between the input and output shafts (as you would get when using conventional universal Hook type joints). If they are long enough they can also accept lateral errors. There is nothing to wear and fatigue is only a factor when angles or misalignment are considerable. Multiple disk couplings are good for small angular errors, but not lateral misalignment and are torsionally rigid and can work in very dirty conditions.
Multi part Cross-Joint or Oldham couplings are better where the shafts are parallel but not concentric and if of good quality, will be backlash free. However, not being "solid state" they will be subject to wear on the sliding surfaces, especially in dusty conditions and can develop backlash and noise.
There are other types of elasomeric one piece couplings, they are simple and can cope with most general mounting errors but are torsionally flexible. (I have even used a piece of hosepipe and a couple of jubilee clips in an emergency).
None of the above coupling types should be used for axial location and both input and output shafts should take all thrust loads, leaving the couplings without significant compression or tension.
Trevor Clarke. (R & D) Scientific Instruments.Somerset. UK
SW2007x64 SP3.0 Pentium P4 3.6Ghz, 4Gb Ram ATI FireGL V7100 Driver: 8.323.0.0
SW2007x32 SP4.0 Pentium P4 3.6Ghz, 2Gb Ram NVIDIA Quadro FX 500 Driver: 6.14.10.7756
