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The rotor has been the hardest and most stressful part to construct. Purely due to the facts of speed, lateral forces from the stator magnets and tolerances. My initial plan of 10mm acrylic for the body was quickly changed to 12mm polycarbonate after some discussion on the forum regarding how well acrylic holds up at high speeds. 12mm polycarbonate is considered 'bulletproof' and far more rigid than acrylic. Therefore it will withstand the high speed centripetal forces and lateral vibrations.
The first step is to route the circle, this was done using a centre pin guide attached to the router. Cut in 2mm steps, increasing the depth of cut every complete revolution. All the centre pin requires is a small dimple at the centre of the piece. This was drilled with a 1.5mm drill to a depth of 1mm. giving a very small 'cup' with a 'V' cross section. This becomes the datum point for all other markings. After the disk is cut a CAD template was overlaid and fixed down.
The centre was positioned to the datum point with a pin. Each of the 8 radial centres was transferred to the disk using the same method. I then marked each 'spoke' from the centre datum to the edge through the magnet hole centres. The 'spokes' after drilling has been completed.
A jig was made for the router footplate to allow easy positioning of each magnet centre. A centre line marked on the jig allowed each 'spoke' to be positioned correctly before clamping.
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