If you want to read quickly, you can buy Tianhao patented magnetic steel and Tianhao 35 pieces of straight axis cores, and wrap them with 0.7 double lines. Tianhao 1600 battery can run about 40 knots. They are sold in Shanghai.
Want torque, buy Audi rare earth thick magnetic steel, three-stage inclined shaft.
I hope you have a good time.