Check out this shot - singe mag on 1906 car firing 2 plugs per cyl.

[mikewest]

I don't see how a single wire jumped from one plug to another effectively fired 2 plus at once. Maybe it didn't... Maybe it only fired one plug that had the least resistance??Ane the second plug was insurance??? in case one fouled? Mike

[Craig Gillingham]

I have to state from the start that I've got no experience running a 2-spark engine. I do know that there were spark plugs made to run in series so that they provided a simultaneous spark to two plugs in series. Lodge were probably the best know, Su-Dig and Bosch Germany made them as well, and I'm sure there were others. I think the idea was that they would both fire together, however, I remember reading --somewhere-- that running two plugs in series wasn't as desirable as having two separate spark sources (2 Spark magneto or 2 distributors), possibly because the spark wasn't as strong in both plugs, or because of an uneven spark quality between the two? These dual sparkplugs died out around WW1. I haven't come across anyone nowadays of running two plugs in series. There are a few 2 Spark magneto engines running, but no single-spark-magneto-2-plug engines that I can find.

 

 

Edited September 9, 2018 by Craig Gillingham (see edit history)

[mikewest]

Hi Craig, I think you nailed it! Wow - a great deal of information! Thank you! Mike

[Craig Gillingham]

Mike, no worries. I suppose the basic concept is that the double-pole plug has two electrodes and doesn't earth to the engine, it sparks across the electrodes, one of the electrodes leads to the second standard plug that's earthed to the engine.