Sean Kelly rides Tourmalet in wool kit on 1910 bike! pics!

[PIGEON]

Didn't they use double sided hubs with large and small sprockets, stopping to turn the wheel around at the top and bottom of climbs?

How would they have made up for chain slack? Did they have two front chainwheels too, and did they manually move the chain to the bigger one when they turned the wheel around to use the smaller sprocket and the other way around?

They just moved the wheel forwards or backwards in the dropouts/track ends. Just as you would today if you had a flip-flop hub.

That wouldn't allow for a difference much greater than 2 ot 3 teeth then unless the bikes had 5 inch dropouts, hardly a change in ratio that would allow for comfortable climbing and descending.. Regardless whether Henri Desgrange meant "single speed" or "fixed wheel", he was wrong