Electronic – How is the shaft of a motor fixed in its position

electric-machinemechanicalmechanical-assemblymotor

Consider for example a brushed DC motor.
1- Is the shaft of the motor (which is rotor in this case), actually floating mid-air because of magnetic field of stator? Why doesn't it fall down due to gravity?
And what about other types of motors?
I mean, How can we fix a rotating bar inside a cylinder without somehow mechanically coupling them?

2- For outrunner BLDC motors, shaft is mechanically attached to the surrounding magnets around stator. How is stator and all its windings fixed in its position and not falling down?

A Maxon DC motor
Cutaway of a motor

Best Answer

Is the shaft of the motor (which is rotor in this case), actually floating mid-air because of magnetic field of stator?

Your pictures show ball bearings. Cheaper motors will use bushings - ideally made of oil-impregnated sintered bronze, but perhaps in throwaway items just a cheap bronze or even brass alloy. In very cheap items a shaft may even run in a low friction plastic.

For outrunner BLDC motors, shaft is mechanically attached to the surrounding magnets around stator. How is stator and all its windings fixed in its position and not falling down?

In an outrunner motor, the laminations of the stator are basically the part of the motor which is physically mounted to the rest of the machinery. This might be done by means of screws, or some cylindrical stub which is press fit or glued or has a snap retaining ring.

What you didn't ask, and that gets closer to some of what you have imagined, is how the shaft and rotor of an outrunner motor are retained. Sometimes there's a groove in the shaft behind the rear bearing with a snap ring or "e-clip" capturing it. But sometimes in light duty applications it's just the powerful attraction of the magnets holding the rotor bell over the motor, and you can actually pull it right off.