Well, I think I can make out a timing chain to the right, that connects both cranksets. Which in turn means there's got to be some double-hub-shenanigans going on on the rear, otherwise the whole thing won't move.
Yeah timing chain outside the triple chainrings up front but cranks are definitely out of sync. Could just be poor setup.
Don’t know about the double hub, looks like a normal hub to me with the stoker cranks bolted on the outside of the dropouts but don’t know how that’d work.
Double hub could be possible with the center hub around a large hollow axle, and the outer hub with a smaller solid axle running through the first one.
Well, I think I can make out a timing chain to the right, that connects both cranksets. Which in turn means there's got to be some double-hub-shenanigans going on on the rear, otherwise the whole thing won't move.