The following statements might seem simplified to the point of being naïve. They are not. These statements are very narrowly defined, are common to virtually all precision flexible shaft couplings used in motion systems today, and the basis for most of the detailed technical information in the rest of this web site.

 
We use flexible shaft couplings for one reason and one reason only: To preserve the integrity and extend the life of the load bearing devices supporting the shafts being coupled. Pretty Darn Simple.

 
Keep in mind that our subject is precision flexible shaft couplings for motion systems and we are largely ignoring power transmission (PT) flexible shaft couplings in this discussion. That being said the purpose of all flexible shaft couplings is this: To accurately transmit torque and rotary position from one shaft to another shaft. The list of things they should not do is just a bit longer and is discussed throughout this web site.

 
The simple answer is that there is no simple answer. Designs for flexible shaft couplings are as numerous as grains of sands on a beach and truth be told, the origins of most flexible shaft couplings can be traced back almost as far as the sand's. There are precious few new or unique designs in the world of flexible shaft couplings and that most of the considerable improvements made recently are due to new methods of manufacturing and modern materials being applied to tried and true designs some of which are over a century old.

In any given motion system the forces that act upon the flexible shaft couplings are the same regardless of the design or type, but the introduction of 2 different flexible shaft coupling with seemingly identical performance criteria can make a radical difference in the overall system performance. Fortunately the 80/20 principal applies here. By this I mean if you address the most common issues before your system design is done (the 20%), you will avoid most of the potential problems (the 80%) on the back end of your design.