FITTING THE COIL FORMER AND CHEEK PIECES

BUTTERFLY NUTS

WINDING WIRE

 

Jigs for the rotors

PCD jig for drilling holes

The magnet rotors are mounted on a bearing hub (see diagram 1 0). The hub has a flange with holes in it. For example there may be four holes on a 1 02mm (4 inch) 'pitch circle diameter' (PCD). Or you may have some other arrangement. This will depend on what kind of hub it is. Here we shall say 1 02mm PCD.

10. THE BEARING HUB PCD

PCD

REAR ROTOR

FRONT ROTOR

The PCD jig will be used to drill holes in the rotors etc.

It will also be used to balance the rotors.

The holes must be marked and drilled very precisely. (See diagram 1 1.)

• Cut a square piece of steel plate 1 25mm by 1 25mm.

• Draw diagonal lines between the corners and mark the exact centre with a punch.

• Set your compasses at 51 mm radius (or to suit whatever PCD). Draw a circle.

• The diameter of the circle is the PCD of the holes in the hub.

• Punch both places where one line meets the circle.

• Set your compasses at 72mm. Mark two points exactly this distance from the
first two, on the circle. (If you have a different PCD, this size would not be 72mm.
Find the size by trial and error.)

• Drill four holes exactly 72 mm apart on the circle. Use a small drill first and then
a larger one.

 

1 1 . MARKING AND DRILLING THE PCD JIG

Magnet positioning jig (See diagram 12)

This jig is for putting the magnet blocks into the correct places on the steel disks. Only one jig is needed. Make the jig from 250x250 mm plywood or aluminium sheet (not steel).

12. THE MAGNET POSITIONING JIG

• Mark the centre of the workpiece.

• Draw three circles, with diameters 50mm, 1 02mm and 200mm, on this centre.

• Draw a pair of parallel straight lines, as tangents to the 50mm circle as shown.

Draw 3 more pairs of straight lines at 45 and 90 degree angles to the first pair.

Using these lines, mark the magnet positions, and cut out the jig along the bold

lines as shown in the diagram.

Draw a line connecting two opposite magnet centres.

Place the PCD jig on top of the 1 02mm circle, aligned with the magnet centres,

and drill four holes to match the four holes in the steel disks.

Making the moulds

Make moulds for the stator and rotor castings. They can be turned from wood or aluminium. Another method is to make plaster or clay plugs on a wheel, like a pot. The shape of the plug would be the shape of the outside of the stator. Then make a fibreglass mould on the plug. The surface of each mould must be perfectly flat.

The moulds need to be strong and smooth. It is not easy to separate the stator casting from the moulds. Hammer blows are usually needed.

It is a good idea to wind one coil (see section 4) before making the stator mould. This coil should fit neatly in the mould.

Here is one way to make the moulds, from composite wooden floorboard sheets, using wood-turning.

Stator Outer mould

• Cut out several disks of flooring sheet (see diagram 13), approximately 500mm diameter.

13. DISKS

Take all but one of the disks, and cut circular hole in each, 360mm diameter to form rings (see diagram 14).

14. RINGS

Draw a circle 360 mm diameter on the remaining disk

Drill a 12 mm hole at the centre of this disk, to help with centring.

Glue the rings on top of the remaining disk, to form a stack, with a hole 60mm

deep (diagram 1 5). Use plenty of glue at the insides of the rings.

Cut out a small disk of 1 5 mm plywood, 1 40 mm in diameter, and drill a 1 2 mm

hole at its centre.

Placing a 1 2 mm bolt through both holes, glue the small disk into the exact centre

of the hollow. Use plenty of glue at the edge of the disk.

60 DEEP 15. STACK

Mount another piece of wood or board onto a lathe, a motor or the wheel hub of a

small vehicle (for example a 3-wheel taxi). This is a the faceplate (see diagram

16).

Spin the faceplate and use a pencil to make a very small circle at the centre.

Drill a 12mm hole precisely at this centre. Hold the drill parallel to the shaft.

Screw the glued stack onto the faceplate, using a 1 2mm bolt to centre it. Use four

woodscrews through the disk and into the faceplate.

Check that the face of the mould runs true. You can do this by holding a pencil

close to it while it spins. Where the pencil makes marks, the face is 'high'. Loosen

the screws and insert pieces of paper between the faceplate and the stack, on the

opposite side from the pencil marks. Tighten the screws and check again.