Paris-Roubaix equipped Fossati frame from 1949-50

[Old Ned]

That is fantastic. How did the chain tension change on gear shift?

Gravity handles most of it.

It is the weight of the rider over the back wheel that pushes the wheel 'up' the rear dropout and the mesh of the teeth on the wheel spindle and the top edge of the dropout that keeps it all square. I suppose that if the rider was daft (or gymnastic!) enough to be able to change gear whilst out of the saddle then things could become complicated!

Dave Keeler broke the End-toEnd record using one of these gears - and he didn't half have backache by the time he'd finished.

 

[Citoyen du monde]

That is fantastic. How did the chain tension change on gear shift?

Gravity handles most of it.

It is the weight of the rider over the back wheel that pushes the wheel 'up' the rear dropout and the mesh of the teeth on the wheel spindle and the top edge of the dropout that keeps it all square. I suppose that if the rider was daft (or gymnastic!) enough to be able to change gear whilst out of the saddle then things could become complicated!

Dave Keeler broke the End-toEnd record using one of these gears - and he didn't half have backache by the time he'd finished.

Yes, as Ned writes it is the weight of the rider (gravity) that pushes the wheel backwards as far back as the chain will allow. This reminds me of a joke that I played on a former bike mechanic colleague of mine. Back in the 80's, when I worked with him, he was the "junior" mechanic. Over the years he has become the top local mechanic, the one that all the other mechanics turn to when they have a problem with a bike they can't get to work. I had a girlfriend call him up saying that one of the other local shops had directed her to him to resolve her problem. She had been given a Bee-An-Shee bicycle by her boyfriend and couldn't get the derailleur to work. It was a Camp-Ag-No-Lo derailleur. Of course, he said bring it by; at which point he immediately put the bike up in the work stand (a Park clamp). No matter what you do, it is not possible to get the derailleur to work in the stand as you need the weight of the rider. The mechanic had read and heard about the Paris Roubaix derailleur but had never seen one in the flesh. After letting him fiddle around for 15 minutes while the cute girl was watching him, I walked into the shop area (my first visit in about 5 years). He took one look at me, looked back at the bike and said. "FXXk you, this is your pile of crap isn't it?" He was completely frustrated to not be able to figure out what was wrong.