Most shafts are supported at 2 bearings. These bearings have to provide axial and radial support in a manner that does not over-constrain the shaft.

Over-constraint may take place where 2 bearings may endeavor to provide the same function. If proper tolerances are not provided such bearings may in fact provide a load for each other.

Large conveyor drive pulleys

The use of shaft mounted gearbox as shown here, have become very popular. This is largely because if the box and the shaft are not mounted separately their alignment is difficult to guarantee. The weight due to the box typically causes an insignificant increase in shaft stresses.

Locomotive drive motor and axle set. Note motor is fixed to chassis while wheel move with the track.

Ring gear coupling

Pin and rubber coupling

An example of a shaft (or may be called hinge pin, even an axle) where shear stresses may be as significant as bending stresses.