This weekend I saw my first DaVinci tandem, which has a bottom bracket mounted double freewheeling system which enables either rider to coast while the other is doing all of the work. So often, when we see a "new" idea, it is actually a reincarnation of something someone did -- or at least attempted -- decades ago.

So ... We have all seen tandems with either same-side or crossover gearing, but always with a timing chain which maintained consistent synchronization of the captain's and the stoker's pedals. (The default was a zero, or near-zero phase offset, but some savvy folks use a 90-degree offset to give the smoother torque output of a four-cylinder engine.) Has anyone in the past offered either variable captain/stoker timing or something akin to the DaVinci system, in which the bicycle itself imposes no timing relationship? (It was pretty weird to watch the couple with the DaVinci leaving the farmers market, for anyone accustomed to watching a normal tandem (or triple) team pedaling in sync with each other.)