John, my hat is off to you .. thanks .. as I had nothing to compare this assembly too or even a detailed picture of a good assembly, I was at a loss as to what it should look like or what may be missing. 10-to-1 when the ring broke in 3-pieces, I am guessing one of the pieces took out the hall effect.. although it is small enough, I did not even see the remnants around when I pulled the shell.
So in summary I will order a new DC Motor with flywheel & sensor (6SP8590040) from either Lionel or Timko. Looking on0line Lionel still shows it available.
Again, many thanks for your help and guidance
I will let you know the results, once I get the part and install it