[DampRobot]

One of my favorite ways to retain elements on shafts is to just use spacers stacked up between them. Yes, you usually have to manufacture them yourself, but they can make assembly and disassembly much easier. They maintain components the correct distance apart without a long alignment process (shaft collars) or weakening the shaft (retaining clips). In my designs, there is usually just a stack up of spacers and components captured between two bearings, or there is a shaft collar that you just press up against one end of the stack up.

On a side note, if you do decide to use shaft collars, use two piece ones. It can be a life saver to be able to drop a shaft collar off a shaft to get at something rather than disassemble a whole mechanism to get it off.