Rewinding Magneto Coils - Materials
This page describes all the materials The Magneto Guys use when rewinding magneto coils . We hasten to point out that we do not supply these materials. Yes, this is what we use to repair magnetos so we have stocks here but they are for our own use. We do not have the time or the facilities to become mail order parts or materials suppliers. As always, we are happy to make suggestions of where these items are available - just contact us
and let us know what you are looking for!
Side cheek insulation: 0.015" thick Presspahn. Class A, produced from 100% electrical grade kraft wood pulp. We buy this in large sheets and cut into strips using a paper guillotine.
Polyester tape: Class B 130°C polyester tape with a rubber thermosetting adhesive. Used for electrical installation and repair work; soldered joints and seams; insulation of soldered joints, and terminals. It has high electrical strength - breakdown voltage 4.5kV and good resistance to solvents.
Primary winding interleaving insulation: Kraft paper, usually 0.003” thick - sometimes 0.002” thick on smaller coils. We buy this in a large roll and cut to the required width with a paper guillotine.
Primary winding: Solderable polyurethane enamelled copper wire. The number of layers and size of wire used depends on the magneto. Typically three to six layers of 19 to 24swg.
Wire sleeving used for primary wires:
Class F, 3kv rated, very flexible, glass fibre braided, acrylic coated sleeving. Used to insulate the ends of the primary winding. We use two sizes - 1mm i/d when covering a single wire and 1.5mm i/d when covering a pair of wires.
Secondary winding interleaving insulation:
Usually kraft paper, 0.002” thick. We buy this in rolls of different widths from 34mm to 50mm to suit different magnetos. Sometimes we use 0.001” thick Glassine on small coils. This is on a 6" wide roll which we cut to the required width using a paper guillotine.
Secondary winding: Solderable polyurethane enamelled copper wire. The number of turns and size of wire used again depends on the magneto. Typically 9,000 to 14,000 turns of 44 to 47swg .
Silvered Copper Foil: This was originally made for use in the stained glass trade. We came across this tape a few years ago and tried it out. The silvered surface is very easy to solder to and the fact that it is self adhesive makes it very versatile. We use it at the end of the secondary winding where it is joined to the HT connection. Available in a range of widths, we use the 1/2" wide version.
Tinned copper wire: We use 22swg wire on the end of the secondary winding to connect to the slip ring - what we call the HT spout.
Wire sleeving used for HT spout:
PVC sleeving to BS2848 Type 3 105T. We use a double sleeve for the HT spout insulation. The grey is 1mm inside diameter and the blue is 2mm inside diameter
Egyptian cotton tape: This is chosen for the tape's highly absorbent ability to soak up varnish and resins. When wrapping the coil, each turn half overlaps the previous turn - the single red line along the centre of the tape makes this job much easier. We use 1/2" wide tape.
Plain cotton tape: Probably the cheapest item on the list. The plain cotton tape we use for the intermediate layer is torn into strips from old sheets and pillow cases....
Approximately 1/2" wide, a 30" length is about right although we usually shorten this on very small coils.
Varnish:
Dolphon CC1305 High flash, solventless polyester resin with high thermal conductivity. Cured by baking at 120°C for four hours. Once cured, provides excellent electrical insulation properties. It also provides mechanical support to the winding so that it is not affected by vibration or the centrifugal forces experienced by rotating coil magnetos.
