OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk Wipac Magister Condenser Discharge Ignition System

G'day folks,
Substantial new info located, so I'll reopen this thread to add it.

The notion to look in patent literature, for info on this system, occurred to me recently. It seemed to me, that it was innovative enough that it might have been worth patenting.
And it had been...

So this looks like the right thread for this information. The diagrams and info supplied by previous posters here has been invaluable, in selecting the most relevant patents.



This is the circuit diagram from US Patent 3037148, class 'Ignition Systems for Internal Combustion Engines', filed 28 Dec 1959, granted May 1962.
Invented by George Gayler, and assigned to Wipac Development Ltd.

The major components here are :
11. Flywheel
12. Feed Coil stator
13. Flywheel magnet
14. Feed Coil ~ 4-5,000 turns
15. Rectifier diode
16. Condenser/capacitor, 0.2 microfarad
17. Primary winding of 18
18. Voltage transformer coil, 70:1 turns ratio
19. Contact points
20. Points cam
21. Spark plug
22. Secondary winding of 18

The three Magister module low tension wires are connections from the feed coil 14 [to rectifier 15], points 19 [to the primary of the transformer coil 17], and chassis earth. This isn't shown very clearly in the circuit diagram as drawn, though. The next patent listed here, 3175122, does a better job of showing 'modular' construction.

Note that the transformer coil shown here is wired a bit differently ['autotransformer' configuration] to the production Magister in grumpy's earlier post, but the patent covers both variants. Production 'Magister' ignitions would very likely have differed a bit in construction detail from the patent examples; these aren't rigid specs. Production units would have been optimised for the mass production processes in use, and the situation they were to be used in.

The essential bits from this patent, summarised:

Operation: The capacitor is charged with the contact points open. When the points close, the capacitor discharges through the primary winding of the transformer coil, inducing a high voltage in the secondary winding and causing a discharge across the electrode gap of the spark plug.

The Feed Coil - details for two examples are given:
Type 1 was 5,000 turns of 36SWG aluminium wire. This generated increasing voltage to a peak of 250V at 2,000rpm, then declining to 225V at 3,000rpm.

Type 2 was 4,000 turns of 34SWG copper wire. This also generated 250V at 2,000rpm, but then kept on increasing, to 325V at 3,000rpm.

The transformer coil - specification of 70:1 turns ratio, and inductance of 20 microhenries measured across the primary winding.

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Gayler, and a Reginald Penn as coinventor, filed another patent in this class on the same date, which covers operation of this ignition circuit, and several variants of it, from any AC current source; US Patent 3175122, granted March 1965. The low voltage alternator variants had two transformer coils.

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The construction of the transformer coil is most probably along the lines of yet another patent, also filed on 28th Dec 1959, but not granted until August 1965. Inventor was Reginald Penn, US Patent 3202950, class 'Step-Up Voltage Transformer having High Tension Lead'.

This describes a very compact cylindrical transformer, wound on an insulating tubular former with a ferrite core, and the primary winding wound over the secondary.

In the patent, the 'working example' dimensions of the former tube are given as 0.75" long, 0.13" ID, 0.15" OD. Over this is wound the 47SWG enamelled copper wire secondary; described as one layer of three turns plus 15 layers of 193 turns, with paper insulation between layers. Then the primary winding, of 33 turns of 36SWG wire. This gives a turns ratio of ~88:1.
Again this was a 'concept' example, and not necessarily exactly the same as the production units. But it does look a very good match dimensionally for the known Magister examples.

There was also an article titled 'Magister Ignition system' in the UK 'Automobile Engineer' journal, vol 51 p240 (1961), if anyone can find that one.