Let me try and explain how this wondrous AutoBike derailleur actually works.

The large round (solid steel) object protruding towards the viewer from the rear knuckle is a weight that is split into two halves. This weight spins on a spindle that runs through the knuckle and has a small v-belt pulley on the other end of it. This pulley is very near the spokes of the rear wheel. A plastic plate is fitted behind the freewheel, much like a conventional spoke protector. This plate, however, has a v-belt groove around its outer edge, and the v-belt runs from this groove over the small pulley on the derailleur.

As the rear wheel turns, the weight is spun at a ferocious speed. As the weight spins, the two halves move apart (due to the mythical ‘centrifugal force’) and - much like the governor on a Victorian steam engine - they operate the two steel arms running on either side of the rear knuckle. These arms, working against the parallelogram spring, drive the derailleur towards higher gears.

The faster the rear wheel turns, the more the derailleur moves to a higher gear. When the rear wheel stops the derailleur always moves to the low gear position. All this without any direct intervention by the rider.

The Allen bolt that is mounted on the top of the front knuckle controls the parallelogram spring tension. As you increase the tension you increase the speed required to move the derailleur - so it effectively tends to change up into any particular gear at a higher wheel speed.

This AutoBike derailleur does appear to have some kind of provision for the derailleur to operate, or be operated by, a cable, but I have never seen this in action. It could be a way that you could limit the gear range (like in an automatic car) or it could be a way that the derailleur could operate a gear indicator, perhaps on the handlebars. I prefer to think of this feature as an evolutionary relic much like the appendix in the human digestive system.

But seriously, the strangest thing about this design is that it is not indexed in any way. When you are travelling at a speed that would naturally cause the derailleur to be between two gears - then the derailleur happily positions itself between the two gears. The one person who I have spoken to who has ridden this system extensively seemed unbothered by this - apparently you soon learn to tune your speed to suit. Somehow I can’t imagine this being easy when descending or climbing steep hills - exactly the time when I, as a not overly thin, not overly fit, person, seem to most need my gears to function accurately. Perhaps they don’t have steep hills in Muskogee (a place where even squares can have a ball).

Unlike the AutoBike SmartShift 2000 in this collection, this example has a flamboyant mounting bracket and its 'p knuckle' is rivetted to the parallelogram (on the AutoBike SmartShift 2000 the pivots are held in place by removable circlips). Unlike the later LandRider Auto Shift, it has a short pulley cage. It is manufactured by Falcon and has ‘Falcon’ branded pulley wheels.

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• Derailleur brands: AutoBike, manufactured by Falcon
• Country: USA, manufactured in Taiwan
• Date of introduction: 1997?
• Date of this example: unknown
• Model no.: unknown
• Weight: a record breaking 573g including hanger plate, but excluding drive belt and drive disc
• Maximum cog: 28 teeth?
• Total capacity: 28 teeth?
• Pulley centre to centre: 56mm
• Index compatibility: friction
• Chain width: 3/32”
• Logic: low normal
• B pivot: sprung
• P pivot: sprung
• Materials: largely steel, with an aluminium rear knuckle