The Sanko F series was an affordable range of derailleurs offered by Sanko from 1957 until sometime towards the end of the 1960s. It was designed to sit below Sanko's all-conquering S series of mid-range derailleurs.

It was a simple, pull-chain device mounted using a plain hole that fitted on the axle. It had no b-pivot and had a p-pivot concentric with the guide pulley. The tension pulley was, in a first for Sanko, a simple, inexpensive, plastic, item with a plain bearing.

Despite being affordable, the F series was well made, with tight tolerances and high quality chrome. The sliding rod mechanism was identical to that in the mid-range Sanko S series.

There were two models:

• The 1957 Sanko F1, which has a normal cable adjuster and ball bearings in its guide pulley.
• The 1965 Sanko F2, which had been 'improved' with a truly weird and incomprehensible cable adjuster and a plain bearing in its guide pulley.

Some of the documentation appears to suggest that the F series was suitable for both 1/8" and 3/32" chains. All the F series derailleurs that I have ever seen have a toothed guide pulley that has teeth that are definitely too wide to fit a 3/32" chain. Perhaps there was a version with narrower teeth - let me know if you have ever touched one in the flesh.

This is a used, but repectable, example of a Sanko F1.

• Derailleur brands: Sanko
• Country: Japan
• Date of introduction: 1957?
• Date of this example: unknown
• Model no.: F1
• Weight: 237g including integral hanger plate
• Maximum cog: unknown
• Total capacity: unknown
• Pulley centre to centre: 49mm
• Index compatibility: friction
• Chain width: 1/8”
• Logic: low normal
• B pivot: none
• P pivot: sprung
• Materials: largely steel

Ref. 729