single speed roadie conversions

"RU12?" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I am looking for a forum where single speed conversions are discussed.

Thanks

Carl

The following is brilliant. I've read every word on this guys blog at least
once:

http://bikesnobnyc.blogspot.com/2007/08/if-many-fixed-gear-bicycles-on.html

Including this prophetic article:

http://bikesnobnyc.blogspot.com/2007/06/seven-signs-of-fixed-gear-apocalypse.html

The above column stopped me in my tracks from building up a track frame I
had just got cheap cheap, and convinced me to wait a couple of years for
things to blow over.

RU12? said:

I am looking for a forum where single speed conversions are discussed.

Single speed or fixed gear? Road, mountain, recumbent or other? Ginger
or MaryAnne?

I've got a Schwinn Le Tour that I've built up as a single speed. I've
also got a Landshark track bike that I've put a brake on to ride on
the road. Watcha want to know?

Here's the full deal on the Portland fixed gear case:
http://bikeportland.org/cats/news/fixed-gear-ruling/

Jeff

"RU12?" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I am looking for a forum where single speed conversions are discussed.

Thanks

Carl

This non-forum probably has more info than you will be able to use in your
lifetime.

http://sheldonbrown.com/fixed/index.html

I wish Sheldon still posted here.

In article <N%MAi.98704$rX4.87831@pd7urf2no>,

Dave Mayer said:

"RU12?" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I am looking for a forum where single speed conversions are discussed.

Thanks

Carl

The following is brilliant. I've read every word on this guys blog at least
once:

http://bikesnobnyc.blogspot.com/2007/08/if-many-fixed-gear-bicycles-on.html

Including this prophetic article:

http://bikesnobnyc.blogspot.com/2007/06/seven-signs-of-fixed-gear-apocalypse.h
tml

The above column stopped me in my tracks from building up a track frame I
had just got cheap cheap, and convinced me to wait a couple of years for
things to blow over.

Dave:

Put a Nexus-8 in there. Conceal the shifter and cables as best you can.
Drag Race the fixie riders up steep hills. Enjoy.

--
Ryan Cousineau [email hidden] http://www.wiredcola.com/
"I don't want kids who are thinking about going into mathematics
to think that they have to take drugs to succeed." -Paul Erdos

RU12? said:

I am looking for a forum where single speed conversions are discussed.

You've found one. Any technical questions?

RU12? said:

I am looking for a forum where single speed conversions are discussed.

SS or fixed (the latter being considerably more rewarding)?

It's a UK forum, but try

www.anothercyclingforum.com and navigate to the "Velo Fixe" board.

Drooling over the bikes at www.fixedgeargallery.com is obligatory.

RU12? said:

I am looking for a forum where single speed conversions are discussed.

Sheldon Brown has covered this completely. These days, though, if
you've got around six bills, there are pre-built fixies from Kona,
Redline, and Bianchi that are tremendous values. Unless you've got
buckets of parts (guilty!) or are desperate for some sort of imaginary
cred--off the shelf is often cheaper and better.

Zog The Undeniable said:

SS or fixed (the latter being considerably more rewarding)?

What's more rewarding than a nice coast?

I find fixed gears to be more confining than rewarding. I mean, they
are better than nothing... I say this as a long time track bike rider.

I think the fixed gear Thing jumped the couch about five or seven
years ago.

Robert

Quoted message said:

Zog The Undeniable said:

SS or fixed (the latter being considerably more rewarding)?

What's more rewarding than a nice coast?

I find fixed gears to be more confining than rewarding. I mean, they
are better than nothing... I say this as a long time track bike rider.

I think the fixed gear Thing jumped the couch about five or seven
years ago.

SS doesn't make climbing easier, you need to keep two brakes (OK, some
people do this on fixed, but it's not *mandatory*) and you don't get the
fringe benefits such as trackstands, feedback on slippy roads, easy
speed moderation in traffic yadda yadda. SS is certainly easier
downhill until you develop the ability to take your legs "out of gear"
on fixed and push towards 200rpm (hint: ankling helps because it means
your heavy legs don't get so involved).

Fixed on the road is quite different from on the velodrome, and I prefer
the former (I do both).

You're dead right about it being a bandwagon. Here in the UK anything
old and steel seems to get converted to fixed, although I've just added
a fixed 1993 Cannondale MTB to my roadified Fuji Track.

I noted a number of the frames that had vertical dropouts but no
tensioner (and no ENO rear hub). Are they just lucky with their bb to
dropout distance or is a tensioner not necessarily necessary?

D'ohBoy, who's considering a conversion of a cyclic nature

D'ohBoy said:

I noted a number of the frames that had vertical dropouts but no
tensioner (and no ENO rear hub). Are they just lucky with their bb to
dropout distance or is a tensioner not necessarily necessary?

D'ohBoy, who's considering a conversion of a cyclic nature

Okay, read Sheldon's bits.

Sorry.

D'ohBoy

http://eehouse.org/fixin/ and hope you get lucky. I did on my '03 Jamis
Aurora frame. 39/12, 40/13, 41/14, 42/15 all worked perfectly (if you sized
your chain using a half-link). I cut the chain shorter than the 39/12 and
then used two quick links along with little sections of chain, each 1/2 link
longer than the next, when I swapped my gearing around.

"D'ohBoy" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I noted a number of the frames that had vertical dropouts but no
tensioner (and no ENO rear hub). Are they just lucky with their bb to
dropout distance or is a tensioner not necessarily necessary?

D'ohBoy, who's considering a conversion of a cyclic nature

In article <[email hidden]>,

D'ohBoy said:

I noted a number of the frames that had vertical dropouts but no
tensioner (and no ENO rear hub). Are they just lucky with their bb
to dropout distance or is a tensioner not necessarily necessary?

Eric House wrote a computer application called "FixMeUp" that would
calculate the combination of chainwheel and cog that would allow this.
It is probably still out there on the Web somewhere. Also many of those
bikes use a half-link to fine-tune the chain tension.

Wait a minute, here is the link to FixMeUp:

http://www.eehouse.org/fixin/

HTH!

Peter Cole said:

I'm not sure how well such a device would work on a bicycle. Bicycle
torques are high, with reverse torque being as high as forward during
leg braking on a fixed gear.

That last part is simply not true. Think about standing up and mashing
while going uphill. There is no equivalent downhill. No way can
reverse torque be close to forward torque. If it were, the rear wheel
would be skidding all the time. But the only way you can skid a fixed
gear is to jump and lock your leg.

--

David L. Johnson

Arguing with an engineer is like mud wrestling with a pig...
You soon find out the pig likes it!

David L. Johnson said:

Peter Cole said:

I'm not sure how well such a device would work on a bicycle. Bicycle
torques are high, with reverse torque being as high as forward during
leg braking on a fixed gear.

That last part is simply not true. Think about standing up and mashing
while going uphill. There is no equivalent downhill. No way can
reverse torque be close to forward torque. If it were, the rear wheel
would be skidding all the time. But the only way you can skid a fixed
gear is to jump and lock your leg.

Yes, but when you do that the torque is proportional to the dynamic
coefficient of friction. None of us mortals can generate enough forward
torque to spin a tire, so max forward torque is less than static
coefficient of friction, whether it's greater/lower than dynamic, I
don't know, nor do I know the difference between static & dynamic
coefficients off the top of my head (sure it's out there, no time to
look now). My guess is that they're (max fwd & rev torques) in the same
range, I could be wrong.

Quoth Carl Fogel:

Quoted message said:

Quoted message said:

Quoted message said:

The venerable trailing-arm chain tensioner is a mystery only on RBT.

Quoted message said:

Quoted message said:

Pictures and details are explained here:

Quoted message said:

Quoted message said:

http://groups.google.com/group/rec.bicycles.tech/msg/bef0db8649e24801

Quoted message said:

B) A trailing-arm chain tensioner will work fine with a friction block
or a nearly frictionless bicycle-style idler pulley. Replacing the
crude friction block with an elegant derailleur-style pulley makes no
difference to the reliability and tensioning power of the mechanism.

If you use a pulley, a leading-arm tensioner works as well (or as
poorly) as a trailing-arm one, and has the advantage of a convenient
place to attach it, the hanger made for a derailer.

Quoted message said:

Motorcycles don't bother with the idler-pulley enhancement, since the
power loss of a crude friction block is insignificant with 10-20
horsepower.

C) I have no idea how _well_ a spring-loaded trailing-arm
chain-tensioner would work on a bicycle fixie.

No chain tensioner works well on a fixed gear bicycle.

Quoted message said:

I'm just baffled by the repeated claims
on RBT that braking on a fixie will instantly destroy any chain
tensioner. A glance at the brick-simple trailing-arm chain tensioners
used on trials machines will show why they've been working reliably
for decades. I suspect that most bicyclists are thinking of a much
more complicated leading-arm double-jointed derailleur-style chain
tensioner, which would indeed be destroyed by a fixie.

You're correct, a spring-loaded tensioner is not at risk of getting
pretzeled by reverse torque. That's not the actual problem.

The main reason you don't want a chain tensioner on a fixed-gear
drivetrain is that there's a serious risk of derailing the chain from
the chainring when the upper run goes slack as the rider resists.

Derailment of the chain from the chainring on a fixed gear bike can be
VERY dangerous. It is possible for the chain to then get doubled up
on the rear sprocket, leading to sudden rear-wheel lockup.

The motorcycle example shown in the photo avoids this by having a
guide around the front sprocket that would act like a front derailer,
preventing the chain from moving sideways.

Motorcycle chain is wider and more laterally rigid than bicycle
chain. Also, as a rider is resisting hard on a fixed gear, the bike
tends to get tossed from side to side, much as it would when climbing
out of the saddle. This increases the risk of derailment as the upper
run of chain goes slack.

It would be possible to use a stationary front "derailer" on a bicycle
for this, but it would be an even uglier kludge than a spring loaded
tensioner.

The other issue is that a fixed-gear cyclist spends a fair amount of
riding time in quasi "coasting" mode, applying little torque to the
drive train. The play in the drivetrain that would result from using
a spring loaded tensioner (or even just having the chain adjusted too
loose) would be very irritating and unpleasant.

Sheldon "No Tensioners For Fixed Gear" Brown
+--------------------------------+
| Atheists do not believe in |
| "I before E except after C." |
+--------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

On Thu, 30 Aug 2007 12:07:03 -0700, Sheldon Brown
<[email hidden]> wrote:

[snip]

Quoted message said:

Derailment of the chain from the chainring on a fixed gear bike can be
VERY dangerous. It is possible for the chain to then get doubled up
on the rear sprocket, leading to sudden rear-wheel lockup.

The motorcycle example shown in the photo avoids this by having a
guide around the front sprocket that would act like a front derailer,
preventing the chain from moving sideways.

[snip]

Dear Sheldon,

No argument about the bicycle side of things . . .

But the slotted cover over the motorcycle's front sprocket is
_emphatically_ not a chain guide.

Here's the original picture:

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

The chain never touches the slotted cover over the front sprocket. If
the chain ever did touch that cover, it would chew through the thin
aluminum in few seconds.

Anyone with a bicycling background can be pardoned for mistaking the
purpose of the slotted cover. Bicyclists are used to pushing chains
sideways with flimsy front derailleurs made of thin sheet metal.

That bizarre front derailleur action puzzles many motorcyclists, until
they realize that bicycle chains have so little speed and power when
shifting that there's no danger that they'll chew sideways through the
delicate shifting cage.

In contrast, the side of a trials motorcycle chain is the equivalent
of a dull chainsaw--a chainsaw with a 10 to 20 horsepower engine.

The slotted sprocket cover is just a safety cover, not a chain guide.
It keeps your foot from being chewed off by that engine-powered
buzz-saw next to the footpeg.

The exposed big ring of a bicycle also puzzles motorcyclists--okay, it
frightens them--until they realize that the bicycle pedal is fixed in
relationship to the teeth and powered only by the foot. There's no
engine-powered buzz-saw whirling dangerously next to a bicycle shoe,
as I occasionally remind myself when I glance down at all those naked
teeth right next to my right foot on my daily ride. The teeth are
indeed very close to my foot, but my shoe moves in the same circle as
the sprocket and the pedal arm serves as an effective safety bar.

Here's a picture with the motorcycle's slotted countershaft cover
removed, showing an obviously untouched inside surface:

http://i11.tinypic.com/4u14sra.jpg

The shiny edges of the slotted cover show how pitifully thin it is.
Thin, that is, for dealing with a motorcycle chain. Hammered into the
shape of a front derailleur, it would be thick enough to shift
shifting a slowly moving bicycle chain back and forth sideways.

A few numbers illustrate the difference. An impressive bicycle
sprinter can put out over a thousand watts for a few seconds, or maybe
even the ~1500 watts that is two horsepower. But he's not likely to
try shifting with a front derailleur under that load.

A motorcycle routinely puts out up to ten times that much power.

As for chain speed, the gear ratios are roughly reversed. At 20 mph, a
52x14 bicycle's chain is moving at about 1.7 mph and a cadence of
about 70 rpm, but a 14x52 motorcycle's chain is moving at about 6.3
mph with a front sprocket "cadence" of about 950 rpm.

So even at only 2 mph, a near-stall in trials riding, the front
sprocket is spinning at close to 100 rpm when a 200-lb machine topples
over and pins your foot against the rocks. This is why a safety cover
over the front sprocket is a good idea.

Here's that second picture again:

http://i11.tinypic.com/4u14sra.jpg

With the slotted safety cover off, another chain safety cover is
revealed. Again, it's a cover, not a guide--if the chain ever touches
it, you'll be replacing the broken cover, but you'll be glad that
you're not replacing something much more expensive.

The second safety cover is the C-shaped flange about a finger's width
away from the chain. It's made of much thicker metal and stops the
chain from jamming things between the front of the front sprocket and
the transmission case. Jamming things between the sprocket and the
transmission case is a bad thing because the engine will happily smash
a hole in its own transmission case if anything carried forward on the
chain jams in that space.

"Anything" includes rocks, branches, bags filled with metal tools,
parts knocked off the back of the motorcycle, broken chains, and my
favorite, which shows how hard it is for bicyclists and off-road
motorcyclists to understand each other--

Barbed wire.

The chains of motorcycles ridden off-road in the U.S. will eventually
drag rusty barbed wire into the front sprocket. Unlike bicycles,
motorcycles have the power to do this. When debris is dragged into the
covered area, that C-shaped internal flange is what breaks instead of
the expensive metal transmission case.

The C-shaped internal flange also stops debris from destroying the
delicate pair of ignition wires on the upper left, which aren't as
badly placed as you'd think. They have to go somewhere, it's hard to
design a way to lead them through better protected areas, and other
locations turn out to be even more exposed.

Anyway, the slotted cover is no more a chain guide than the frame
itself. It's just a safety cover to keep feet out of the machinery.

As for the slots themsevles, they're not the absurd weight-saving
gesture that bicyclists might imagine, due to the bicycle world's
weight obsession. The slots illustrate again how different the two
worlds are. The engine-powered chain of the trials motorcycle drags
enormous amounts of mud into the covered area, far more mud than a
dainty bicycle chain can ever carry. The slots let muck like this
squeeze out:

http://i7.tinypic.com/5z5r8ee.jpg

Bicycles simply can't ride through that kind of stuff. And that's why
you see that huge black plastic chain guard in the original picture:

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

Again, it's another guard, not a guide. It's just to keep the massive
amounts of sticky mud clinging to the rear tire off the chain.

Cheers,

Carl Fogel

D'ohBoy said:

I noted a number of the frames that had vertical dropouts but no
tensioner (and no ENO rear hub). Are they just lucky with their bb to
dropout distance or is a tensioner not necessarily necessary?

D'ohBoy, who's considering a conversion of a cyclic nature

If the bikes in question are truly *fixed* gear (as opposed to single
freewheel), you wouldn't be able to use a tensioner on them anyway.

--

John ([email hidden])

How about putting a coaster break hub on the back wheel? There is no need to turn the bike into a fixie to get that cool sleek minimalist look.
To learn how to build the wheel I used the instructions on wheel building on Sheldon Brown's website. Check out my blog: Syracuse Bicycle Works
I have a post on the advantages of using a coaster break. Go there, and ask me any question.

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