The Shimano Positron AX (AX10) manages to bear two of the most infamous monikers in Shimano History - ‘Positron’ and ‘AX’. All it needs is ‘Biopace’ shaped pulley wheels and the set would be complete. In marketing terms, it is the kind of laughing stock that gets laughed at by other laughing stocks.

This benighted derailleur was further cursed by being fitted to some of the most hilarious bikes of all times. I particularly remember a Huffy Aerowind, that managed to combine a suite of low-end, steel, ‘aerodynamic’ Shimano AX components with an aerodynamic frame with ovalised tubing that unfortunately had a wall thickness measured in centimeters. The whole confection was topped of with a dusting of spot welding and fork ends made by crushing the tubing flat. You had to be careful to book yourself onto the waiting list for Hernia surgery before attempting to lift this high speed aerodynamic gem.

Despite all this I have a soft spot for the Shimano Positron AX (AX10). Unlike the other Positrons it used a single, normal, Bowden cable instead of a complex arrangement of two cables or the loathsome, rigid, piano wire. I set up a few Shimano Positron AX’s, and they seemed to work surprisingly well.

When you come across unbearably self-confident children called Giles or Jocasta, you wonder what they would have been like if they had been christened John or Mary. How would we view the Positron AX if it had been sent out into the world as the Skylark IV?

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• Derailleur brands: Shimano
• Categories: Shimano - Positron indexing insanity, Shimano - the turbulent AX story
• Country: Japan
• Date of introduction: 1981
• Date of this example: 1981 (two letter date code FG)
• Model no.: AX10
• Weight: 324g including hanger plate
• Maximum cog: 28 teeth (Shimano)
• Total capacity: 28 teeth (Shimano)
• Pulley centre to centre: 58mm
• Index compatibility: 6 speed
• Chain width: 3/32”
• Logic: top normal
• B pivot: sprung
• P pivot: sprung
• Materials: steel