Once upon a time, I converted a tandem from this arrangement to a conventional eccentric for my buddy the great frame painter Les Lunas. Les had a lovely tandem built by one of the Portland (OR) frame builders of back then, with the "floating" chainring to take up chain slack. It was an elegant solution: you just moved the ring closer to a BB when the chain stretched, and it looked just great.
But one day Les and his wife Sue were competing in the NJ state time trial, when Les noticed as chainring rolling down the road, pretty well matching their pace. It seems that if you jump hard, you can compress things and on the rebound the ring can pop out. After that, we put in an eccentric, and sacrificed the lovely visuals.
harvey sachs mcLean VA, where we still have a fabulous tri-color fade Les did in Imron, so subtle you can't find the fade areas. ++++++++++++++++++++++++++++++++++++++ Jim Merz wrote: One can do this to adjust the chain tension without an eccentric BB.
after Peter Brueggeman pointed out:
In Dale's GP Wilson photos, there's a tandem photo showing an unattached
chainring in the tandem chainline located between the captain and stoker
chainrings. That's a new one to me. It looks like it is a couple of
teeth larger than the front and rear chainrings. Is this something
others have seen done, and does it accomplish anything other than looks?
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