I run a double on my Brompton 3 speed folding bike,
its a planetary low gear,
they make an overdrive one too 1.6x and the 2.5x
that the mountain drive is the inverse of..
my 16" wheel Has a 54t chainring, the low is like 21.6t,
so the 3 speeds have 2 ranges,
the gears in the hub are used twice .. 4th is low in high gear ,
3rd is high gear in low range.
still no derailleurs at all..
Since I am a novice in regards to mechanics/components, I could be missing a perfectly reasonable explanation for why it won't work. What am I missing? Seems like the advantage of a double with a low enough gear for climbing.
do the math, and see if the ratios are suitable,
A touring companion 20+ years ago rode a French TA crankset,
2 rings 50t and a 28t.
14-28 or 32 tooth freewheel.
bail out low.. big upshift right at the crest of the hill,
where the pedal forces
were let up as much as possible.
triple cranksets work out well for most people ,
thats why there are so often OEM bike specs including them
But buy what gear suits your curiosity ..
What works out best for me at present,
is Rohloff's speedhub..
those are a 7 speed hub used twice..