Chain tensionning with vertical dropouts

On Fri, 15 Dec 2006 15:42:01 +0000, [email hidden] (Tom

S) may have said:

Hello,

Any ideas would be gratefully received about my conversion situation:

I've got a racing frame with vertical dropouts. I want to get rid of the
deraileurs and get two back wheels that i can interchange from time to
time. One wheel would have a flip flop fixed/free and one would have a
hub gear.

For the flip flop, the White Eccentric Hub looks good.

There have been mixed reports about it, but it's pretty much the only
real option out there.

Quoted message said:

But I'm not sure about the best way of tensionning the chain when using
a hub gear. I really want to avoid a chain tensioner if possible. I
think my preferred method would be to try and get a chain + chainring +
sprocket combo that would be just the right tension. It wouldn't matter
about not being able to get exactly the perfect gearing, because I'd
have a choice of gears from the hub.

As long as you will not be using a coaster-brake hub, you can use a
derailleur with a piece of piano wire in place of the cable
(permanently locking it into the required lateral alignment) as a
chain tensioner, but you may need to have two chains for the bike; one
for the flip/flop and one for the hub gear.

Quoted message said:

Sheldon Brown seems to think that this method would be "Kludgey", wheras
Eric House seems more into the idea. Are there any disadvantages of this
method apart from slightly fiddly set up to start with? Might the chain
get longer with time and cause problems later?

All chains wear! That's why you have to check them for "stretch" (a
misleading term, but to the eye that's what it looks like) and replace
them periodically. This is true for *any* kind of setup, though the
fully enclosed chains on many European bikes can be amazingly durable.

Quoted message said:

Or could I get an Eccentric Bottom Bracket that would solve the single
speed and the hub gears in one go? On the frame I'm trying to convert,
the diameter of the inside of the bottom bracket shell looks to be about
35mm.

There is no eccentric bottom bracket on the market as far as I know.
I am doubtful that such a construct could be made durable in any
event, as the amount of space inside the shell is already smaller than
the manufacturers would like; that's why the current high-end BB
assemblies have moved the bearings entirely outside the BB shell.

Sometimes the best solution is to shop around for the bits that will
do what is desired without resorting to exotic tech; I'd definitely
counsel trying to find a used frame with horizontal dropouts (or at
least long and usefully-angled ones) before trying what you're
proposing. In the long run, I believe that you'll be better off.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

Tom S said:

Hello,

Any ideas would be gratefully received about my conversion situation:

I've got a racing frame with vertical dropouts. I want to get rid of the
deraileurs and get two back wheels that i can interchange from time to
time. One wheel would have a flip flop fixed/free and one would have a
hub gear.

For the flip flop, the White Eccentric Hub looks good.

But I'm not sure about the best way of tensionning the chain when using
a hub gear. I really want to avoid a chain tensioner if possible. I
think my preferred method would be to try and get a chain + chainring +
sprocket combo that would be just the right tension. It wouldn't matter
about not being able to get exactly the perfect gearing, because I'd
have a choice of gears from the hub.

Sheldon Brown seems to think that this method would be "Kludgey", wheras
Eric House seems more into the idea. Are there any disadvantages of this
method apart from slightly fiddly set up to start with? Might the chain
get longer with time and cause problems later?

Or could I get an Eccentric Bottom Bracket that would solve the single
speed and the hub gears in one go? On the frame I'm trying to convert,
the diameter of the inside of the bottom bracket shell looks to be about
35mm.

Thanks in advance, and thanks to Sheldon "Awesome Website" Brown for the
erm... awesome website.

TomS

An idle chainring between the cranks and the cog. It simply floats
between the upper and lower portion of the chain. The closer it is to
the cog, the more slack it takes up. I have never done this but would be
interested to hear how well it works. I think it would be problematic on
a fixie - it would move up and down as you pedaled forward and backward.
Great conversation starter.

Anybody tried this?

"Tom S" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I've got a racing frame with vertical dropouts. I want to get rid of the
deraileurs and get two back wheels that i can interchange from time to
time. One wheel would have a flip flop fixed/free and one would have a
hub gear.

For the flip flop, the White Eccentric Hub looks good.

But I'm not sure about the best way of tensionning the chain when using
a hub gear.

I see these options:

a. Eccentric bottom bracket

b. Change the dropouts to something like the Rohloff sliding dropouts.
Apparently this isn't too expensive to do but in my situation I decided to
get a new custom frame with these dropouts for my hub gear.

c. Depending on how often you are changing hubs, you could use a chain
tensioner with the gear hub and not use it when using the flip-flop
eccentric hub. This would requiring splicing and unsplicing the chain with
some type of quick connect link to give you two different chain lengths.
Obviously, this wouldn't be very satisfactory if you are switching hubs very
often.

d. Two bikes?

BobT

Tom S said:

But I'm not sure about the best way of tensionning the chain when using
a hub gear. I really want to avoid a chain tensioner if possible. I
think my preferred method would be to try and get a chain + chainring +
sprocket combo that would be just the right tension. It wouldn't matter
about not being able to get exactly the perfect gearing, because I'd
have a choice of gears from the hub.

I did this for a while on my tandem. It worked fine. My problem there
was, with two people, the Shimano Nexus hub did not have enough bracing to
avoid counter-rotation. But with 2-3 cogs for the hub and a couple of
chainrings, you should be able to find a reasonable combination.

Quoted message said:

Or could I get an Eccentric Bottom Bracket that would solve the single
speed and the hub gears in one go? On the frame I'm trying to convert,
the diameter of the inside of the bottom bracket shell looks to be about
35mm.

Do they make eccentric bottom brackets that will fit the shell? If so,
that would be an elegant solution, but I doubt the part exists.

--

David L. Johnson

__o | It is a scientifically proven fact that a mid life crisis can
_`\(,_ | only be cured by something racy and Italian. Bianchis and
(_)/ (_) | Colnagos are a lot cheaper than Maserattis and Ferraris. --
Glenn Davies

Tom S? who said:

Any ideas would be gratefully received about my conversion
situation:

Quoted message said:

I've got a racing frame with vertical dropouts. I want to get rid of
the derailleurs and get two back wheels that i can interchange from
time to time. One wheel would have a flip flop fixed/free and one
would have a hub gear.

You might find a combination that gives correct chain slack but that
won't last for long. Even slight chain wear will make it too loose to
ride safely, the chain easily jumping off track and either falling off
or jamming the wheel. You'll be surprised what a few thousandths
(inch) of wear will do to chain sag. Of course you could compute it
and see if you care.

Once, when a stick tore off my derailleur, I put the remaining parts
in my bag along with the short piece of chain that I had to remove,
and found I had two gears available: 50-15 and 46-20, or something
like that, with my vertical dropouts. The higher gear had a bit of
sag and the lower barely tight. Conspicuous was how small changes in
position in the dropout altered the sag.

Jobst Brandt

On Fri, 15 Dec 2006 10:07:02 -0800, Dan <[email hidden]>

Quoted message said:

Tom S said:

Hello,

Any ideas would be gratefully received about my conversion situation:

I've got a racing frame with vertical dropouts. I want to get rid of the
deraileurs and get two back wheels that i can interchange from time to
time. One wheel would have a flip flop fixed/free and one would have a
hub gear.

For the flip flop, the White Eccentric Hub looks good.

But I'm not sure about the best way of tensionning the chain when using
a hub gear. I really want to avoid a chain tensioner if possible. I
think my preferred method would be to try and get a chain + chainring +
sprocket combo that would be just the right tension. It wouldn't matter
about not being able to get exactly the perfect gearing, because I'd
have a choice of gears from the hub.

Sheldon Brown seems to think that this method would be "Kludgey", wheras
Eric House seems more into the idea. Are there any disadvantages of this
method apart from slightly fiddly set up to start with? Might the chain
get longer with time and cause problems later?

Or could I get an Eccentric Bottom Bracket that would solve the single
speed and the hub gears in one go? On the frame I'm trying to convert,
the diameter of the inside of the bottom bracket shell looks to be about
35mm.

Thanks in advance, and thanks to Sheldon "Awesome Website" Brown for the
erm... awesome website.

TomS

An idle chainring between the cranks and the cog. It simply floats
between the upper and lower portion of the chain. The closer it is to
the cog, the more slack it takes up. I have never done this but would be
interested to hear how well it works. I think it would be problematic on
a fixie - it would move up and down as you pedaled forward and backward.
Great conversation starter.

Anybody tried this?

Dear Dan,

Bah! Who needs a floating sprocket for chain tension?

With a floating chain and a freewheel, you don't even need chain
tension . . .

http://i16.tinypic.com/4gj8g2c.jpg

Click on the lower right for full-size image of Vernon Blake riding
with a floating chain in 1919, from "The Dancing Chain," p. 64, 2nd
edition, Frank Berto.

Here's the explanation:

"The Floating Chain"

"The floating chain was the ultimate in simplicity. Intent on reducing
any form of drag, Vélocio [Paul de Vivie] put weaker and weaker
springs on the tension arms he used with his variable gear devices.
But under muddy conditions, this loose chain had a tendency to climb
onto the tips of the sprocket teeth and slip."

"One day in 1911, having suffered more than usual from these chain
slippages, Vélocio thought of a way to stop the links from climbing on
to the teeth. He installed a small steel roller, which he called the
'steel finger' just below the freewheel. The thing worked! Of course,
this required a single-sprocket freewheel. Finally, in January 1912,
he removed the tension-arm and pulley altogether, just letting the
chain dangle. People warned him that he was losing his chain."

"By combining a floating chain with a triple chainwheel and a rear
wheel with a sprocket on either side of the wheel, the touring cyclist
had the simplest possible six-speed gear set. Shifting across the
chainwheels with the fingers gave three gears for flat country.
Reversing the rear wheel gave three moutain-climbing gears.
Flottantistes (riders who used the floating chain) generally used
three chainwheels, but some had up to five."

"The Dancing Chain," p. 79, 2nd edition, Frank Berto

Cheers,

Carl Fogel

THANKS

....to everyone who has replied so far. It's great to get your
experience and ideas.

Didn't want to make loads of new posts, so I've mixed up the replies to
your posts below:

--

Quoted message said:

I did this for a while on my tandem. It worked fine. My problem there
was, with two people, the Shimano Nexus hub did not have enough bracing to
avoid counter-rotation. But with 2-3 cogs for the hub and a couple of
chainrings, you should be able to find a reasonable combination.

excellent. this is encouraging.

in terms of the rotation, did you have Anti-Rotation washers installed?

eg the ones on this page, a 3rd of the way down:

http://sheldonbrown.com/harris/shimano-nexus.html

--

Quoted message said:

You might find a combination that gives correct chain slack but that
won't last for long. Even slight chain wear will make it too loose to
ride safely, the chain easily jumping off track and either falling off
or jamming the wheel. You'll be surprised what a few thousandths
(inch) of wear will do to chain sag. Of course you could compute it
and see if you care.

oh dear. this sounds nasty. maybe this is why S.B. describes it as a
"kludge"

--

Quoted message said:

There have been mixed reports about it [the White Eccentric Hub] but it's pretty much the only
real option out there.

ok.

Quoted message said:

As long as you will not be using a coaster-brake hub, you can use a
derailleur with a piece of piano wire in place of the cable as a
chain tensioner,

don't like this idea, probably just for aesthetic and spiritual
reasons. what if i become a spy or a ninja? people would hear me coming
a mile off!

Quoted message said:

All chains wear! That's why you have to check them for "stretch" and replace
them periodically. This is true for *any* kind of setup

OK, i suppose you just spend 15 quid every year or so on a new one.

Quoted message said:

Sometimes the best solution is to shop around for the bits that will
do what is desired without resorting to exotic tech; I'd definitely
counsel trying to find a used frame with horizontal dropouts

probably very sensible. i might well end up doing this after a long
period of struggling and end up spending more time and money on trying
to hack the current cheap frame i've found.

----

Quoted message said:

b. Change the dropouts to something like the Rohloff sliding dropouts.
Apparently this isn't too expensive

I'll look into this avenue, thanks.

Quoted message said:

c. Depending on how often you are changing hubs, you could use a chain
tensioner with the gear hub and not use it when using the flip-flop
eccentric hub. This would requiring splicing and unsplicing the chain...

.... Obviously, this wouldn't be very satisfactory if you are switching
hubs very

Quoted message said:

often.

yes, this definitely might be a good compromise. i could just keep 2
chains.

Quoted message said:

d. Two bikes?

no! one bike. part of the fun. two bikes sounds like a slippery slope,
before you know it it'll turn into a herd.

--

Quoted message said:

An idle chainring between the cranks and the cog. It simply floats
between the upper and lower portion of the chain. The closer it is to
the cog, the more slack it takes up.

like it. very original.

--

Tom S said:

Any ideas would be gratefully received about my conversion situation:

I've got a racing frame with vertical dropouts. I want to get rid of the
deraileurs and get two back wheels that i can interchange from time to
time. One wheel would have a flip flop fixed/free and one would have a
hub gear.

For the flip flop, the White Eccentric Hub looks good.

But I'm not sure about the best way of tensionning the chain when using
a hub gear. I really want to avoid a chain tensioner if possible.

You can't use a chain tensioner with a fixed gear; it would be destroyed
the first time you tried to push back on the pedals to slow down.

Basically, you have very limited options in adjusting chain tension on a
single speed/fixed gear bike with vertical dropouts. This will be
particualarly problematic if you intend to use different size cogs on
your flip-flop hub.

Quoted message said:

I think my preferred method would be to try and get a chain +
chainring + sprocket combo that would be just the right tension.

You can get half-links for 1/8" chain that can gain you some leeway. But
the best method might be these eccentric hubs:

http://www.sheldonbrown.com/harris/white-hubs.html

Quoted message said:

Or could I get an Eccentric Bottom Bracket that would solve the single
speed and the hub gears in one go? On the frame I'm trying to convert,
the diameter of the inside of the bottom bracket shell looks to be about
35mm.

Eccentric BBs are generally sized for tandems and will not fit in a
standard BB shell. I'm sure someone will jump in to correct me if I'm
wrong.

--

John ([email hidden])

Quoted message said:

On Fri, 15 Dec 2006 10:07:02 -0800, Dan <[email hidden]>

Quoted message said:

Tom S said:

Hello,

Any ideas would be gratefully received about my conversion situation:

I've got a racing frame with vertical dropouts. I want to get rid of the
deraileurs and get two back wheels that i can interchange from time to
time. One wheel would have a flip flop fixed/free and one would have a
hub gear.

For the flip flop, the White Eccentric Hub looks good.

But I'm not sure about the best way of tensionning the chain when using
a hub gear. I really want to avoid a chain tensioner if possible. I
think my preferred method would be to try and get a chain + chainring +
sprocket combo that would be just the right tension. It wouldn't matter
about not being able to get exactly the perfect gearing, because I'd
have a choice of gears from the hub.

Sheldon Brown seems to think that this method would be "Kludgey", wheras
Eric House seems more into the idea. Are there any disadvantages of this
method apart from slightly fiddly set up to start with? Might the chain
get longer with time and cause problems later?

Or could I get an Eccentric Bottom Bracket that would solve the single
speed and the hub gears in one go? On the frame I'm trying to convert,
the diameter of the inside of the bottom bracket shell looks to be about
35mm.

Thanks in advance, and thanks to Sheldon "Awesome Website" Brown for the
erm... awesome website.

TomS

An idle chainring between the cranks and the cog. It simply floats
between the upper and lower portion of the chain. The closer it is to
the cog, the more slack it takes up. I have never done this but would be
interested to hear how well it works. I think it would be problematic on
a fixie - it would move up and down as you pedaled forward and backward.
Great conversation starter.

Anybody tried this?

Dear Dan,

Bah! Who needs a floating sprocket for chain tension?

With a floating chain and a freewheel, you don't even need chain
tension . . .

http://i16.tinypic.com/4gj8g2c.jpg

Click on the lower right for full-size image of Vernon Blake riding
with a floating chain in 1919, from "The Dancing Chain," p. 64, 2nd
edition, Frank Berto.

Here's the explanation:

"The Floating Chain"

"The floating chain was the ultimate in simplicity. Intent on reducing
any form of drag, Vélocio [Paul de Vivie] put weaker and weaker
springs on the tension arms he used with his variable gear devices.
But under muddy conditions, this loose chain had a tendency to climb
onto the tips of the sprocket teeth and slip."

"One day in 1911, having suffered more than usual from these chain
slippages, Vélocio thought of a way to stop the links from climbing on
to the teeth. He installed a small steel roller, which he called the
'steel finger' just below the freewheel. The thing worked! Of course,
this required a single-sprocket freewheel. Finally, in January 1912,
he removed the tension-arm and pulley altogether, just letting the
chain dangle. People warned him that he was losing his chain."

"By combining a floating chain with a triple chainwheel and a rear
wheel with a sprocket on either side of the wheel, the touring cyclist
had the simplest possible six-speed gear set. Shifting across the
chainwheels with the fingers gave three gears for flat country.
Reversing the rear wheel gave three moutain-climbing gears.
Flottantistes (riders who used the floating chain) generally used
three chainwheels, but some had up to five."

"The Dancing Chain," p. 79, 2nd edition, Frank Berto

Cheers,

Carl Fogel

Dear Carl,

Bah! yourself. That's the Christmas spirit.

I feel that my floater is much more elegant than the one that yourefer
too, see:
http://www.geocities.com/banquo_lives/singlespeed.html

As far as the image you linked goes:
Really very poor photography
Looks dangerous

In my photo you can see that it is a really nice fallish sort of day and
I should be out riding my bike. You can also see that unless you remove
the drive side chainstay, you can't put in a big enough cog or chain
wheel to get much adjustment.

Dan

John Thompson said:

Tom S said:

Any ideas would be gratefully received about my conversion situation:

I've got a racing frame with vertical dropouts. I want to get rid of the
deraileurs and get two back wheels that i can interchange from time to
time. One wheel would have a flip flop fixed/free and one would have a
hub gear.

For the flip flop, the White Eccentric Hub looks good.

But I'm not sure about the best way of tensionning the chain when using
a hub gear. I really want to avoid a chain tensioner if possible.

You can't use a chain tensioner with a fixed gear; it would be destroyed
the first time you tried to push back on the pedals to slow down.

[snip]

Dear John,

True, a chain-tensioner based on a foolishly cannibalized double-lever
derailleur won't work on a fixed gear.

But single-lever trailing-arm chain-tensioners have been used for over
forty years on much heavier and more powerful "fixies" like this one:

http://i13.tinypic.com/479xidi.jpg

This kind of chain-tensioner is as reliable as a brick. In Explorer,
click on the lower right for the full-size picture.

No matter how hard the lower chain-run straightens under massive
engine braking, the chain just pushes the trailing-arm tensioner down
an inch or two against the coil spring, which is out of sight on the
other side of the metal arm.

In case the clutter is confusing, the chain-tensioner is the black arm
screwed onto the swing-arm, just above the footpeg in the picture. The
hard pad can be replaced with an idler sprocket, but the engine has
power to spare and a pad is even more reliable than a sprocket.

A mousetrap is more complicated.

Cheers,

Carl Fogel

Tom S said:

Any ideas would be gratefully received about my conversion situation:

I've got a racing frame with vertical dropouts. I want to get rid of the
deraileurs and get two back wheels that i can interchange from time to
time. One wheel would have a flip flop fixed/free and one would have a
hub gear.

Suggestions include getting a different frame with horizontal DO's.
Old-fashioned longer pattern DO's give more room for adjustment, so you
might save yourself some money in one area-- if you already have
various chainrings and cogs in the parts box. Longer DO's also might
allow using different size cogs, going from fixed to flipflop or
whatever, without changing chain length.

You might be able to use a double chainring and have a wheel with
correct chainline for each.

You've already seen this? http://www.sheldonbrown.com/chainline.html

Here's another picture:
http://businesscycles.com/tr-refspec.htm#chainline
--D-y

On Fri, 15 Dec 2006 14:56:31 -0800, Dan <[email hidden]>

Quoted message said:

Quoted message said:

On Fri, 15 Dec 2006 10:07:02 -0800, Dan <[email hidden]>

Quoted message said:

Tom S wrote:
> Hello,
>
> Any ideas would be gratefully received about my conversion situation:
>
> I've got a racing frame with vertical dropouts. I want to get rid of the
> deraileurs and get two back wheels that i can interchange from time to
> time. One wheel would have a flip flop fixed/free and one would have a
> hub gear.
>
> For the flip flop, the White Eccentric Hub looks good.
>
> But I'm not sure about the best way of tensionning the chain when using
> a hub gear. I really want to avoid a chain tensioner if possible. I
> think my preferred method would be to try and get a chain + chainring +
> sprocket combo that would be just the right tension. It wouldn't matter
> about not being able to get exactly the perfect gearing, because I'd
> have a choice of gears from the hub.
>
> Sheldon Brown seems to think that this method would be "Kludgey", wheras
> Eric House seems more into the idea. Are there any disadvantages of this
> method apart from slightly fiddly set up to start with? Might the chain
> get longer with time and cause problems later?
>
> Or could I get an Eccentric Bottom Bracket that would solve the single
> speed and the hub gears in one go? On the frame I'm trying to convert,
> the diameter of the inside of the bottom bracket shell looks to be about
> 35mm.
>
> Thanks in advance, and thanks to Sheldon "Awesome Website" Brown for the
> erm... awesome website.
>
> TomS
>
An idle chainring between the cranks and the cog. It simply floats
between the upper and lower portion of the chain. The closer it is to
the cog, the more slack it takes up. I have never done this but would be
interested to hear how well it works. I think it would be problematic on
a fixie - it would move up and down as you pedaled forward and backward.
Great conversation starter.

Anybody tried this?

Dear Dan,

Bah! Who needs a floating sprocket for chain tension?

With a floating chain and a freewheel, you don't even need chain
tension . . .

http://i16.tinypic.com/4gj8g2c.jpg

Click on the lower right for full-size image of Vernon Blake riding
with a floating chain in 1919, from "The Dancing Chain," p. 64, 2nd
edition, Frank Berto.

Here's the explanation:

"The Floating Chain"

"The floating chain was the ultimate in simplicity. Intent on reducing
any form of drag, Vélocio [Paul de Vivie] put weaker and weaker
springs on the tension arms he used with his variable gear devices.
But under muddy conditions, this loose chain had a tendency to climb
onto the tips of the sprocket teeth and slip."

"One day in 1911, having suffered more than usual from these chain
slippages, Vélocio thought of a way to stop the links from climbing on
to the teeth. He installed a small steel roller, which he called the
'steel finger' just below the freewheel. The thing worked! Of course,
this required a single-sprocket freewheel. Finally, in January 1912,
he removed the tension-arm and pulley altogether, just letting the
chain dangle. People warned him that he was losing his chain."

"By combining a floating chain with a triple chainwheel and a rear
wheel with a sprocket on either side of the wheel, the touring cyclist
had the simplest possible six-speed gear set. Shifting across the
chainwheels with the fingers gave three gears for flat country.
Reversing the rear wheel gave three moutain-climbing gears.
Flottantistes (riders who used the floating chain) generally used
three chainwheels, but some had up to five."

"The Dancing Chain," p. 79, 2nd edition, Frank Berto

Cheers,

Carl Fogel

Dear Carl,

Bah! yourself. That's the Christmas spirit.

I feel that my floater is much more elegant than the one that yourefer
too, see:
http://www.geocities.com/banquo_lives/singlespeed.html

As far as the image you linked goes:
Really very poor photography
Looks dangerous

In my photo you can see that it is a really nice fallish sort of day and
I should be out riding my bike. You can also see that unless you remove
the drive side chainstay, you can't put in a big enough cog or chain
wheel to get much adjustment.

Dan

Dear Dan,

Humbug!

Or so the market said to using a large idler sprocket between the
drive sprockets as a chain tensioner:

http://i11.tinypic.com/29wv9jn.jpg

"Figure 466 illustrates a method used at one time by Messrs. Hobart,
Bird & Co. When the chain required to be tightened, the loose chain
wheel was placed nearer the hub chain-wheel."

--"Bicycles & Tricycles," p. 433, Archibald Sharp, 1896.

Trying to promote your antiquated notions by use of lurid modern
photography, coupled with a flamboyant red frame will not deceive the
cycling public!

Of course, if you use really big sprockets in the middle, you can
dispense with the chain altogether and have a multi-speed:

http://i12.tinypic.com/49j06bk.jpg

--"The Dancing Chain," 2nd edition, p. 46, Frank Berto

The 3-gear transmission requires some interesting extra tubes for
bracing the--uh, the--

Well, it's not a chain-stay any more, is it?

Click on lower right to expand pictures in Explorer.

Cheers,

Carl Fogel

(Tom S) said:

Any ideas would be gratefully received about my conversion situation:
I've got a racing frame with vertical dropouts. I want to get rid of the
deraileurs and get two back wheels that i can interchange from time to
time. One wheel would have a flip flop fixed/free and one would have a
hub gear.

Tom,

IMO, you are making things difficult. Getting an old steel frame with
horizontal dropouts could easily solve your problem. If you insist on
solving this problem with vertical dropouts, be prepared for trial(s)
and error(s).

Here are a few thoughts:

1. Its quite possible to run a fixed gear bike or a single-speed
freewheel bike on a bike with vertical dropouts. The easiest and
cheapest way is careful measurement and math, and a half-link. If you
look on Sheldon's magnificent site, you'll find a link to a calculator
for figuring which gear combos will work with what chain length for a
given chainstay length. Andrew Muzi set up a fixie like this, and just
changes the chain annually. I havn't done it yet, but might in the
spring.

2. Skip the flip-flop hub. To tell you the truth, I'm to lazy to flip
the hub, and find that I leave mine fixed -- even if it means walking
up a hill or two. If you haven't used a flip-flop hub before, it
might not work the way you hope it will. You too may find that it is
simply just not worth the effort. Like many products, they can be
better in theory than in actual use.

Now, if you want to set up a flip-flop hub on this same bike, and you
want the flip to have a different size cog than the flop, you have to
find two combinations that allow for the same chain length, but result
if different gear inches. That will be difficult, indeed. Some people
have done this with horizontal dropouts, and left two different sized
chainrings on to accommodate this goal. I suppose you could carry a
spare length of chain and a chain tool to accommodate this fetish --
but seriously, I doubt it would be worth it to take the time to adjust
the chain length on the road.

3. The hub gear will work on the same bike if the cog is the same size
and the one that works in thought #1. If you have a hub-geared wheel
and a fixed-gear wheel, I say forget about the flip-flop hub. It makes
the project too difficult.

4. See what my e-friend, and your neighbor, Will has to say:
http://www.63xc.com/reviews/reviews.htm

All the best,
Larry

Werehatrack said:

There is no eccentric bottom bracket on the market as far as I know.

Thorn in the UK make bikes with them. I don't know if they are sold on their
own though, or if they even fit in a standard shell.

Jim Higson said:

Werehatrack said:

There is no eccentric bottom bracket on the market as far as I know.

Thorn in the UK make bikes with them. I don't know if they are sold on their
own though, or if they even fit in a standard shell.

Big shell, like a tandem front BB shell. The best ones seem to be
Bushnell, as they don't rely on a split BB shell, but they won't solve
the OP's problem.

Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary

Ok, thanks for all your thoughts and information everyone.

So it sounds like the Eccentric BB is going to be a no-no.

And there's a problem that even once you've figured out a good
chainring + sprocket + chain length setup, it will probably still need
some sort of tensionning due to chain wear or changing the chain.

I think I'll go ahead and get a hub gear, and try and get enough play
out of the DOs to keep the chain tight. This would be by filing the
sides of the dropouts a little bit, flat siding the axel, and getting a
little extra movement from the very slight angle of the dropouts. Maybe
I could get about 4mm of play this way. So the "kludge" method:

http://www.sheldonbrown.com/fixed-conversion.html

Then I can add a fixed wheel with a similar sprocket and chainring, and
use the same method for tensionning. Or if I did want to get a flip
flop, then I'd build this wheel with a White Hub so that I could still
sort the chain out with the two different sprocket sizes. As you can
tell, I'm new to this whole business, so I like the idea of messing
around with a flip flop, even if I don't use it that much.

I'm pretty confident this plan will do what I want, and I've learned a
lot already trying to make it work.

Thanks,

Tom S

Quoted message said:

I think I'll go ahead and get a hub gear, and try and get enough play
out of the DOs to keep the chain tight. This would be by filing the
sides of the dropouts a little bit, flat siding the axel, and getting a
little extra movement from the very slight angle of the dropouts.

If you're free to choose your chainring and cog sizes you can get close
and you can get quite a bit of tension adjustment just by filing the
dropouts a bit.

Quoted message said:

John Thompson said:

You can't use a chain tensioner with a fixed gear; it would be destroyed
the first time you tried to push back on the pedals to slow down.

Quoted message said:

Dear John,

True, a chain-tensioner based on a foolishly cannibalized double-lever
derailleur won't work on a fixed gear.

But single-lever trailing-arm chain-tensioners have been used for over
forty years on much heavier and more powerful "fixies" like this one:

http://i13.tinypic.com/479xidi.jpg

Very nice. Are similar items readily available for bicycles? It would be
fairly trivial to cobble one up, but a secure mount would have to be
welded/brazed/whatever onto the chainstay. This makes it less than ideal
for a quick 'n' easy home fixie conversion unless you happen to already
have welding equipment (which I do, but that's beside the point).

--

John ([email hidden])

Quoted message said:

Quoted message said:

Dear Carl,

Bah! yourself. That's the Christmas spirit.

I feel that my floater is much more elegant than the one that yourefer
too, see:
http://www.geocities.com/banquo_lives/singlespeed.html

Quoted message said:

Or so the market said to using a large idler sprocket between the
drive sprockets as a chain tensioner:

http://i11.tinypic.com/29wv9jn.jpg

"Figure 466 illustrates a method used at one time by Messrs. Hobart,
Bird & Co. When the chain required to be tightened, the loose chain
wheel was placed nearer the hub chain-wheel."

--"Bicycles & Tricycles," p. 433, Archibald Sharp, 1896.

I do like this solution. I have many old freewheel cogs and chainrings
of various sizes.

--

John ([email hidden])