This one is "hors categorie" TreasureBike stuff. Calling it a chain tensioner is a bit of a misnomer. However, functionally speaking, that's about all its good for. Aesthetically, and as a statement, however, its pure treasure.
My dad bought this 20+ years ago when it was already NOS. He had plans of building up a lightweight super-bike, or French-ish super-bike anyway. This would be controlled via Simplex Retro-friction shift levers (which he is still using on his bike). Eventually, the dream of that project slipped away with the acceptance of the Jubilee's limited functionality. I have never seen one on a working bike -- probably because the design (pivots) wasn't great. Though we didn't know it then, it turns out the special frame hanger was missing, so it never would have worked right.
I had it in a TreasureBox for a long time. I was cleaning up a while back and offered it to the shop I had worked at years ago -- a "thank you" for still offering me discounts -- in case someone needed it. The "boss" (owner and still friend) looked at it and said simply "for a single speed". Many might not have understood the significance of that fragment, but I did. How did I not see it previously? Ah, the wisdom: use it as a chain tensioner for a single-speed conversion. Brilliant.
Now with "the" pedals, a TreasureBike is starting to take shape. Next up, some thoughts on brakes. Then musings on frames.
