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General Chat (Vincent Related)
Greg Brillus Racer
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<blockquote data-quote="greg brillus" data-source="post: 100251" data-attributes="member: 597"><p>The twin spark ignition we are going to run is quite clever...........Basically the mag is a Joe Hunt (Fairbanks Morse) twin outlet wasted spark magneto......Pretty common on older race bikes, especially on Pre-unit Triumph's, Bsa's and so on. There is an accessory that is produced by "Morris magneto's" in the USA that is a HT lead that splits from one into two with a junction box similar to a standard one into two throttle on a Vincent twin. This junction box houses two very high rating diodes set up in reverse polarity to one another. Some may not know, but a magneto is an AC device, that is, that as the armature rotates, the polarity reverses every 180 degrees. Because the magneto has twin outlets that fires both at every crank revolution, this polarity leaving each HT lead is opposite and alternating. As the spark travels to the junction box, the polarity of the spark is sent down only one of the output leads due to the diode that allows the direction of voltage to flow though it. Because there are two of these used, there are twin sparks available at the alternating output leads. Obviously the magneto needs to be timed correctly and the pairs of leads need to be checked and "Paired" before an engine run to prevent cross firing or failure to start. I have tested it by hooking up the HT leads to the four plugs in both heads whilst they were sitting on the bench, and you can clearly see both plugs spark at the same time as you rotate the magneto shaft back and fourth. For me it is a better alternative to running electronic ignition, with twin outlet coils, battery, and so on. Far less complication and weight saving as well.</p></blockquote><p></p>
[QUOTE="greg brillus, post: 100251, member: 597"] The twin spark ignition we are going to run is quite clever...........Basically the mag is a Joe Hunt (Fairbanks Morse) twin outlet wasted spark magneto......Pretty common on older race bikes, especially on Pre-unit Triumph's, Bsa's and so on. There is an accessory that is produced by "Morris magneto's" in the USA that is a HT lead that splits from one into two with a junction box similar to a standard one into two throttle on a Vincent twin. This junction box houses two very high rating diodes set up in reverse polarity to one another. Some may not know, but a magneto is an AC device, that is, that as the armature rotates, the polarity reverses every 180 degrees. Because the magneto has twin outlets that fires both at every crank revolution, this polarity leaving each HT lead is opposite and alternating. As the spark travels to the junction box, the polarity of the spark is sent down only one of the output leads due to the diode that allows the direction of voltage to flow though it. Because there are two of these used, there are twin sparks available at the alternating output leads. Obviously the magneto needs to be timed correctly and the pairs of leads need to be checked and "Paired" before an engine run to prevent cross firing or failure to start. I have tested it by hooking up the HT leads to the four plugs in both heads whilst they were sitting on the bench, and you can clearly see both plugs spark at the same time as you rotate the magneto shaft back and fourth. For me it is a better alternative to running electronic ignition, with twin outlet coils, battery, and so on. Far less complication and weight saving as well. [/QUOTE]
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General Chat (Vincent Related)
Greg Brillus Racer
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