I was hoping I could have this question answered that has been on my mind for quite some time. I haven't found anything too conclusive on the topic in my searches online.

As far as I can tell the most popular construction of a brushless DC motor involves having a state (solid or layers of plates) that resembles the appearance of a wheel's spokes, in which the alternating magnetic field faces in/out, driving the motion along stationary permanent magnets - as you can see in the first image. I'm interested to find out why the orientation of the coils of the stator don't face parallel to the axle and similarly alternate the magnetic field for stationary magnets aligned parallel with the axel, as seen in the second image.
Is the a benefit to efficiency that I don't understand? Is there a warping of the magnetic fields I can't see? Is it cheaper ('cause it seems like it would be easier to construct the coils independently and place them parallel to the axle)?

A second question: Why don't we ever see modular construction of the perpendicularly aligned stators? Why don't we simply construct each coil separate and then combine them all together to form the stator? Wouldn't that be way easier than winding around all the tiny slits in the stator? What am I not understanding about this process?

Thanks for your time and future input!!

 

To a robot, I don't think winding the U-cores in the second pic would be any/much easier than winding the stator in the first pic.

 

I would think the magnetic force in the second motor would be higher with reference to the rotor. The elctromagets in that configuration are able to use both magnetic poles N and S. Where the first motor is only able to use one magnetic pole. The permanent magnets in the second rotor are also using two poles one above the other, one N and one S. The second motor is a better use of all magnetic force, so should be more efficient.

 

Constructive responses. I know a machine could wind a stator with ease, I was thinking more of manual winding. Also, I had a feeling it might have something to do with field direction and combination. Thanks you two!