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.)

All I can tell you is DaVinci tandems have a huge fan club, and it looks really strange when you see a couple riding them.

So the ubiquitous joke about the stoker not pedaling could actually be true!

Not sure I would like that. Being in sync is part of the fun.

Do not inform my wife of this.
She will want one.

Counterpoint Opus offered the independent-coasting. Very interesting bike with the captain riding upright in the rear position and the stoker recumbent in the front. I think Bilenky bought the rights to the design and still produces a version. Pic from the webs below.

Well, you're obviously not familiar with the recumbent world. Since you don't need to worry about pedal strike, independent pedaling and/or independent shifting is practical. For a back-to-back tandem, independent drivetrains eliminate the long (lllloooonnngggg) chain run from front to back. Here's an M5 carbon-fiber back-to-back:



If that's not wacky enough, my friend Gary Dinsmore built a both-wheel-drive, both-wheel-suspended, moving-(front)-bottom-bracket tandem. This is Gary riding alongside the original WYMS designer Bill Patterson with their spouses:

While I haven't seen a prior application of a tandem, this could easily have been attained using a couple of Shimano FFS (Front Freewheel System) cranksets that came out in 1977. I imagine that somebody probably tried it, back in the day.

Yes, the system reminded me vaguely of the short-lived FFS when I saw it.

I always enjoy seeming something novel in bicycle transmissions, and the DaVinci system certainly qualifies.

The DaVinci system is as normal as Sunday School compared to some of the stuff I've seen tried on high-speed streamlined bicycles. Graeme Obree's "Beastie" is in the middle of the weird-o-meter:

Egad!!!!!! Put a fender on that front wheel and keep the grit off your chin!

Hey! He hit 55mph and he's still smiling!

The story of his building the Beastie and his attempt at Battle Mountain was filmed. Here's the trailer:
https://vimeo.com/130621871

I think they're trying to find a U.S. distributor.