From: Craig Sandvik <distracticon@yahoo.com> <snip> Were sprung derailleurs (as we know them) common in these years? How were chains tensioned on vertical dropouts otherwise? Tell us more please.
Ah, the mind's eye travels back to the late '60s, when I was asked to do some work on a friend's new British tandem. If memory serves, it is a late (I hope) example of the breed: a small vertical drop-out, without derailleur hanger. The derailleur, which moved in-and-out on a straight rod with a helical traveller, was mounted to the chain stay about 5 cm in front of the dropout. Chain tension was maintained by a doorspring from the top of the idler assembly to an anchor under or near the bottom bracket. Similar effects (but with parallelograms) were achieved by an Altenberger in the 1950s (shown on a Cinelli at Dale's spring event at least twice), and a last-gasp Suntour assembly. Don't try dropping the wheel out if the chain isn't on the smallest rear cog!
harvey sachs
mcLean VA