I shall attempt to mask the poverty of my knowledge about Sun-Bow, by remarking on the strange tendency for the Sun to pop up in the names of derailleur brands. Sun-Bow, SunRace, SunRun, SunTour and I think I have even seen Golden Sun, Sunrise and Sunset - what is it all about? Is this solar fixation common to many products from the Far East - or is it peculiar to derailleurs? Why doesn’t the Moon get a look in? Mars and Venus make an appearance but what about Jupiter, Pluto or even Uranus?
The little that I do know about Sun-Bow is that one derailleur that I acquired had a brown card label attached to it saying ‘Yamashita Iron Works Ltd. YA-100 Rear Derailleur’. Coincidentally, the only S.Y. derailleur that I have seen has the words ‘Yamashita Japan’ stamped on its inside parallelogram plate. It also shares some small parts with Sun-Bow derailleurs.
Based on these tiny crumbs of evidence, my pitiful researches on Google have thrown up two possible companies who may possibly have manufactured the Sun-Bow brand.
The strength of the first possibility is that the company definitely made bicycle components in the relevant period. The strength of the second possibility is that the company definitely had ‘Iron Works’ in its name.
Sun-Bow is vaguely interesting in that the brand is a rare example of a Japanese manufacturer producing cheap derivatives of the products of another Japanese manufacturer (SunTour in the case of the derailleur in this collection). In the early days, Japanese manufacturers often copied European designs, and latterly the Taiwanese, Chinese, Indians and finally the Europeans have copied Japanese designs, but it is unusual for the Japanese to copy other Japanese designs.
I have no solid information on dates, but I vaguely remember seeing a Sun-Bow on a no-name Japanese bike in about 1977.