Today’s invention is a bike chain which acts as its own simple gearing mechanism.
Imagine two conventional, fixed-size sprockets, one attached to the pedals and one to the rear wheel hub.
The chain connecting these has links which are sprung so that they would naturally compress together into a shape like vvvvv rather than – - – - – - (Shown at the top in yellow).
As the pedal wheel rotates, two C-shaped diverters are moved in and out independently. Moving in flattens the vvvvv shape into – - – - – - around one or both of the sprockets.
This change in radius provides four gear ratios, as indicated, without needing any kind of derailleur mechanism (beyond the small, sprung tensioner wheel shown).