As an add-on to the above, I just went through this process. Here's what I got:

47/50T chainrings
Nuovo Record front derailleur - should be a piece of cake for range, shifting ease and no chain rub even at the extremes of the ranges.

13, 15, 17, 20, 23, 26T freewheel
Nuovo Record rear derailleur - I'm a little concerned about 26T cog but I'm going to try it out and see how it goes.

This table shows the ratios. You can also see the shifting pattern.

rear...frt...gear
cog....ring...ratio
26...47...1.69
26...50...1.72
23...47...1.74
23...50...1.77
20...47...1.80
20....50..1.83
17...47...1.87
17...50...1.90
15...47...1.93
15...50...1.95
13...47...1.99
13...50...2.02

This is also a decent shifting pattern - single shift then double shift.


What do you think? Do I have this right? I "know" several of these ratios like old friends, so those are good to go. The real question is what about the others? In my opinion, the all-too-common 42/52T chainring pair never worked all that well for me. Vintage freewheels and chainrings aren't cheap, so I don't want to make a mistake.