That was an amazing and very interesting video. My Father joined the RAF in 1921 as an Engine Mechanic. I still have his beatuifuly written note book of the Gnome Monosoupape when he was on a course,firrst dated April 3rd 1923.. Watching the video and with this notebook in front of me I was able to folow his notes easily.. I remember him telling me that the plug leads were piano wire and needed constant re-tensioning due to the centrifical force on them. I still have, somewhere, the gauge he made while on that course to check tension. The wire is placed in and around a pillar, that moves against a scale when tension is increased.
Keith.