Flip flop hub and 2 chainrings?

I remember reading about a bike with flip-flop, fixed-free hub and a
double chainrings. The fixed set-up uses the smaller fixed cog and
the larger of the two chainrings for cruising. The free set-up uses a
larger (than the fixed) freewheeling cog and the smaller of the two
chainrings for hills. I'm thinking of experiment with one on a 1980s
Colnago Superissimo with horizontal drop-outs, and am looking for any
pointing in a helpful direction. Anyone know of tried and true gear
combinations for this type of set-up? Know of any web articles?
Thanks,
Larry

LF wrote:
I remember reading about a bike with flip-flop, fixed-free hub and a
double chainrings. The fixed set-up uses the smaller fixed cog and
the larger of the two chainrings for cruising. The free set-up uses a
larger (than the fixed) freewheeling cog and the smaller of the two
chainrings for hills. I'm thinking of experiment with one on a 1980s
Colnago Superissimo with horizontal drop-outs, and am looking for any
pointing in a helpful direction. Anyone know of tried and true gear
combinations for this type of set-up? Know of any web articles?
Thanks,
Larry

isn't differing chain length going to be a problem? you can calculate
what it would be for a range of permutations but i think any significant
chain ring differences are going to be tough to accommodate.

LF wrote:
I remember reading about a bike with flip-flop, fixed-free hub and a
double chainrings. The fixed set-up uses the smaller fixed cog and
the larger of the two chainrings for cruising. The free set-up uses a
larger (than the fixed) freewheeling cog and the smaller of the two
chainrings for hills. I'm thinking of experiment with one on a 1980s
Colnago Superissimo with horizontal drop-outs, and am looking for any
pointing in a helpful direction.

Just make sure the two gear combinations have the approximately same
number of teeth. Horizontal dropouts give you wiggle room, but a
smaller chainring reduces the angle at which the chain approaches the
rear cog, so theoretically, a shorter chain length is necessary. If you
going to mismatch the tooth counts, give the smaller ratio a few more teeth.

One other thing to think about: my experience suggests you should either
give the fixed side the preferred chainline, or compromise the two
(i.e., at least one of your chainlines will be off and tossing a chain
is less fun on a fixie).

Anyone know of tried and true gear
combinations for this type of set-up?

This would be purely personal preference. If I decided I wanted to do
this, I'd try about 5.7 m development (48x18 on setup) and 3.7 m dev.
(42 x 24). Depending on the length of your chain stays and dropouts,
Finding a 24 T rear cog might be tricky, so adjust accordingly suppose.
Also note that if I did this, I'd leave it on the 5.7 m dev. side and
possibly forget about the other ratio.


Know of any web articles?

http://sheldonbrown.com/articles.html

\\paul
--
Paul M. Hobson
..:change the f to ph to reply:.

On Apr 7, 9:33 pm, jim beam wrote:
LF wrote:
I remember reading about a bike with flip-flop, fixed-free hub and a
double chainrings. The fixed set-up uses the smaller fixed cog and
the larger of the two chainrings for cruising. The free set-up uses a
larger (than the fixed) freewheeling cog and the smaller of the two
chainrings for hills. I'm thinking of experiment with one on a 1980s
Colnago Superissimo with horizontal drop-outs, and am looking for any
pointing in a helpful direction. Anyone know of tried and true gear
combinations for this type of set-up? Know of any web articles?
Thanks,
Larry

isn't differing chain length going to be a problem? you can calculate
what it would be for a range of permutations but i think any significant
chain ring differences are going to be tough to accommodate.

The caveat with this setup is that the net teeth must stay the same.

Another option is a Surly Dingle cog, a fixed cassette with 2 cogs, a
17 and either a 19, 20, or 21. So say you got a 17-21, you could have
48-44 combo up front, giving 76" and 56" gears. Not only would chain
length remain the same, but chainline would be better maintained than
by flipping the wheel. You could probably even switch back and forth
without loosening the hub, depending on how tight the chain is.

On Apr 8, 4:53 pm, John Thompson wrote:
On 2008-04-08, LF wrote:

I remember reading about a bike with flip-flop, fixed-free hub and a
double chainrings. The fixed set-up uses the smaller fixed cog and
the larger of the two chainrings for cruising. The free set-up uses a
larger (than the fixed) freewheeling cog and the smaller of the two
chainrings for hills. I'm thinking of experiment with one on a 1980s
Colnago Superissimo with horizontal drop-outs, and am looking for any
pointing in a helpful direction. Anyone know of tried and true gear
combinations for this type of set-up? Know of any web articles?

Interesting idea, although I'd do it the other way around. Going uphill
on a fixed gear is seldom as much trouble as going down.

--

John )

Good point...I know I don't ever coast up hills...

On Apr 8, 9:31 am, "Paul M. Hobson" wrote:
LF wrote:
I remember reading about a bike with flip-flop, fixed-free hub and a
double chainrings. The fixed set-up uses the smaller fixed cog and
the larger of the two chainrings for cruising. The free set-up uses a
larger (than the fixed) freewheeling cog and the smaller of the two
chainrings for hills. I'm thinking of experiment with one on a 1980s
Colnago Superissimo with horizontal drop-outs, and am looking for any
pointing in a helpful direction.

Just make sure the two gear combinations have the approximately same
number of teeth. Horizontal dropouts give you wiggle room, but a
smaller chainring reduces the angle at which the chain approaches the
rear cog, so theoretically, a shorter chain length is necessary. If you
going to mismatch the tooth counts, give the smaller ratio a few more teeth.

One other thing to think about: my experience suggests you should either
give the fixed side the preferred chainline, or compromise the two
(i.e., at least one of your chainlines will be off and tossing a chain
is less fun on a fixie).

Anyone know of tried and true gear
combinations for this type of set-up?

This would be purely personal preference. If I decided I wanted to do
this, I'd try about 5.7 m development (48x18 on setup) and 3.7 m dev.
(42 x 24). Depending on the length of your chain stays and dropouts,
Finding a 24 T rear cog might be tricky, so adjust accordingly suppose.
Also note that if I did this, I'd leave it on the 5.7 m dev. side and
possibly forget about the other ratio.

Know of any web articles?

http://sheldonbrown.com/articles.html

\\paul
Thanks much,
For my purposes, I could try a 52/42 chain rings with a 20 fixed and
30 free (If I can find one). The 52x20 fixed would be a good general
purpose gear for me (64 inches) and New England's rolling terrain. I
would use that most of the time, and set up the chain line to work
best with that combo. The 42x30 (34 inches) I'd have for the
occasional big climb. Both combos are 72 teeth total.

Best,
Larry "saved by Sheldon once again, Fieman
Marblehead, MA

On Mon, 7 Apr 2008 20:57:30 -0700 (PDT), LF wrote:

I remember reading about a bike with flip-flop, fixed-free hub and a
double chainrings. The fixed set-up uses the smaller fixed cog and
the larger of the two chainrings for cruising. The free set-up uses a
larger (than the fixed) freewheeling cog and the smaller of the two
chainrings for hills. I'm thinking of experiment with one on a 1980s
Colnago Superissimo with horizontal drop-outs, and am looking for any
pointing in a helpful direction. Anyone know of tried and true gear
combinations for this type of set-up? Know of any web articles?
Thanks,
Larry

This may help:

cd = cl - (z1+z2)/2 + sqrt{([cl - z1+z2)/2)^2 - 8*((z2-z1]^2)/4pi^2}

where
cd = centre distance in pitches
cl = chain length in pitches
z1 = n0 teeth in small sprocket
z2 = n0 teeth in large sprocket

On Apr 7, 10:57*pm, LF wrote:
I remember reading about a bike with flip-flop, fixed-free hub and a
double chainrings. *The fixed set-up uses the smaller fixed cog and
the larger of the two chainrings for cruising. *The free set-up uses a
larger (than the fixed) freewheeling cog and the smaller of the two
chainrings for hills. *I'm thinking of experiment with one on a 1980s
Colnago Superissimo with horizontal drop-outs, and am looking for any
pointing in a helpful direction. * Anyone know of tried and true gear
combinations for this type of set-up? * Know of any web articles?
Thanks,
Larry

Two chainrings and a flip flop hub? Four gears possibly. You do know
White Industries has a double freewheel cog (16-18 or 17-19) you could
use instead. Then it would be 6 gears or 8 gears possibly. Seems to
me your double freewheel flip flop hub thing is about like having a
normal geared bike except its less useful. Why not just stick with
the normal single speed or the normal geared bike. Why create an
abberation midway between the two.

snip
Seems to
me your double freewheel flip flop hub thing is about like having a
normal geared bike except its less useful. Why not just stick with
the normal single speed or the normal geared bike. Why create an
abberation midway between the two.

Russell,
I find myself preferring my fixed gear bike. It's fun. But, I am
weak. It's great for rolling terrain, but I'm fearful of large
hills. I remember reading about some British guy who set up a bike
with a flip-flop hub and double chain ring. I'm only looking for two
gears, no more. I'm hoping that I could use this set up to mostly
ride fixed, but also have the option of a free wheeling, bail out gear
for that too long climb. In general, I'm too lazy to get off my bike
and flip the floppable wheel. So far, I never have. Sloth forces me
to bludgeon over the obstacle. However, cowering in the looming
shadow of a seemingly insurmountable mogul, I might give it a whirl.
I guess I could always get off and walk -- again. It would be easier
an simpler than flopping. But, I imagine my self on a long ride, and
when I cross the great plains, and come to the foothills of the
rockies, I could flip it.
Best,
Larry

On Apr 7, 9:57*pm, LF wrote:
I remember reading about a bike with flip-flop, fixed-free hub and a
double chainrings. *The fixed set-up uses the smaller fixed cog and
the larger of the two chainrings for cruising. *The free set-up uses a
larger (than the fixed) freewheeling cog and the smaller of the two
chainrings for hills. *I'm thinking of experiment with one on a 1980s
Colnago Superissimo with horizontal drop-outs, and am looking for any
pointing in a helpful direction. * Anyone know of tried and true gear
combinations for this type of set-up? * Know of any web articles?
Thanks,
Larry

Dear Larry,

Sorry, I suspect that I hit the wrong button and somehow sent you an
email instead of a post to this thread.

Here's a chain calculator for the distance between sprocket centers,
given the number of teeth and the links:

http://www.wa4dsy.net/robot/sprocket

For anyone interested in testing the equation, which takes a bit of
patience to put into a spreadsheet, any two same-size sprockets will
eliminate the tricky geometry, leaving only reassuringly simple
arithmetic behind.

For example, 112 half-inch links wrapped around a pair of 53-tooth
sprockets will put the sprocket centers 29.5 links or 14.75" apart.

Each half-sprocket of chain requires 53/2 links, so you subtract that
from the 112 links available.

Then you need to split the remaining 59 links into the upper and lower
vertical runs, which means that the centers are 29.5 half-inch links
apart.

Cheers,

Carl Fogel