Is it possible to build a brushed DC motor with a ring magnet stator, instead of a stator with gaps as shown in the GIF below?
See my answer to your other question.
Yes, it is possible, and since permanent magnet DC motors have been around for well over 100 years, it's undoubtedly been done. There are many downsides:
- It would be difficult to magnetize such a magnet to be as powerful as a pair of correctly-magnetized magnets
- Magnetic materials -- even steels -- are brittle, hard to machine, and won't have thermal expansion characteristics that match whatever you want to use for a case.
- So getting one to match the size of the case would be difficult.
- And Once you got your magnet machined to match the case at room temperature, chances are low that it would stay matched, because of differences in thermal expansion coefficients.
- This, in turn, means that you can't press the magnet and case together -- you'd need to assemble them with glue or clips.
- And all of that means that except in very specific circumstances, a full-ring magnet would be more expensive, more trouble, less reliable, and very likely lower performance than a "traditional" arrangement.