Not much happened in the first five years of this decade - understandably as people were far too busy getting dressed up in idiotic uniforms, eating dried egg, digging for victory, inventing weapons of mass destruction and, of course, murdering each other in wholesale quantities.
Even the last five years of the decade were dominated by the wearying task of trying to restart normal life in a world of rationing and endless shortages. Despite this, the derailleur explosion of the late 1930s continued in the late 1940s.
The decade’s key derailleur model was the 1948 Simplex Tour de France - a drop-out mounting pull-chain design with two pulley wheels. It set the tone for affordable derailleurs for the next 10 years.
Browse the derailleurs from the 1940s...
Where you see a red link, this is for a derailleur model which I do not (yet?) have in my collection - but for which I do have some kind of real and relevant documentation.