Chain tensionning with vertical dropouts
Tom S
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
Werehatrack
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.
>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.
>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.
>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.
BobT
news:1hqe8vq.13f6rf217lj98gN%f-nl1....@netfocus.co.uk...
> 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
Dan
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?
David L. Johnson
> 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.
> 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
jobst....@stanfordalumni.org
> 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 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
carl...@comcast.net
wrote:
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
bric...@gmail.com
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:
--
>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
--
>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"
--
>There have been mixed reports about it [the White Eccentric Hub] but it's pretty much the only
>real option out there.
>
ok.
>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!
>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.
>
>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.
----
>b. Change the dropouts to something like the Rohloff sliding dropouts.
>Apparently this isn't too expensive
>
I'll look into this avenue, thanks.
>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
>often.
yes, this definitely might be a good compromise. i could just keep 2
chains.
>
>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.
--
>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.
--
John Thompson
> 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.
> 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
> 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 (jo...@os2.dhs.org)
Dan
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
carl...@comcast.net
<jo...@vector.os2.dhs.org> wrote:
>On 2006-12-15, Tom S <f-nl1....@netfocus.co.uk> wrote:
>
>> 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
dusto...@mac.com
Tom S wrote:
> 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
carl...@comcast.net
wrote:
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
LF
> 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
Jim Higson
> 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.
Kinky Cowboy
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
bric...@gmail.com
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
amit....@gmail.com
bric...@gmail.com wrote:
> 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.
John Thompson
> On Fri, 15 Dec 2006 14:19:26 -0600, John Thompson
><jo...@vector.os2.dhs.org> wrote:
>>
>>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.
> 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 (jo...@os2.dhs.org)
John Thompson
>>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
> 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 (jo...@os2.dhs.org)
carl...@comcast.net
<jo...@vector.os2.dhs.org> wrote:
>On 2006-12-15, carl...@comcast.net <carl...@comcast.net> wrote:
>
>> On Fri, 15 Dec 2006 14:19:26 -0600, John Thompson
>><jo...@vector.os2.dhs.org> wrote:
>>>
>>>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.
>
>> 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).
Dear John,
As far as I've been able to tell, the simple trailing-arm
chain-tensioner is as unknown to RBT as the wheel was in the New
World.
It's been standard on trials motorcycles since the early 1970's on
Bultaco, Montesa, Ossa, Honda, Yamaha, Kawasaki, Suzuki, GasGas,
Sherco, Beta, Scorpa, Fantic, and other brands.
Usually when I mention the trailing-arm chain-tensioner, the reaction
is either blank incomprehension or fierce denial, so it's nice that
someone else finally sees how it works.
It could be welded or brazed onto the chainstay, but a pair of
hose-clamps holding a short length of half-pipe will serve as a mount.
Indeed, that's how chain-tensioners were added to a lot of pre-1972
trials machines. The stress on the lever amounts to little more than
the resistance of the coil spring, and the chain promptly drags the
lever back into alignment whenever it tries to bounce to either side.
It works fine for "fixie" trials machines with several inches of rear
suspension travel and heavy motorcycle chains, so it would seem likely
to work on rigid-frame fixie bicycles with light chains.
Of course, there may be some detail that makes it inefficient or even
pointless, but the usual objection that braking would instantly rip
the chain-tensioner off only shows how the simple trailing-arm is a
dark and bloody mystery in these parts.
Curiously, lots of old derailleur bicycles used trailing-arm
chain-tensioners with small idler sprockets on the ends of huge arms
before the compact modern two-lever tensioner-and-derailleur design
triumped.
The difference was that they pushed the chain away from the chainstay,
not toward it like a modern trials motorcycle chain-tensioner. The
reason is that the old bicycles were dealing with the enormous amount
of chain slack needed for derailleur gearing--a trials-type
chain-tensioner would have hit the chainstay before it gathered up all
the extra chain. That's one reason why the double-arm triumphed--all
that extra slack is gathered up into the S-bend.
A modern fixie bicycle has scarcely any chain slack compared to a
derailleur, so the trials-style tension-toward-the-chainstay design
would work.
Berto's "The Dancing Chain" includes numerous examples of bicycles
with these single-lever trailing-arm chain-tensioners from the 1920's
through the 1950's:
http://i17.tinypic.com/2lxf9k6.jpg
Click on the lower right in Explorer for full-size. Berto notes that
it was produced from 1936 to 1954 and was based on an earlier French
design. Similar models in Berto's book are sometimes mounted further
back on the chainstay. You can see the evolution from this monster
single-arm chain-tensioner pushing the chain away from the chainstay,
to more complicated two-arm tensioners that gather the chain into the
neater S-bend, to the modern two-arm tensioner integerated on the
parallelogram that moves the chain from side to side while taking up
the slack.
In all likelihood, no one uses such chain tensioners on fixie bicycles
because it's reasonably easy to adjust the chain tension by moving the
axle on horizontal dropouts, just as chain tension is adjusted on
typical motorcycles, which lack chain-tensioners.
Cheers,
Carl Fogel
Earl Bollinger
news:slrneo8pu...@vector.os2.dhs.org...
Well this is surely fascinating. So one simply takes an appropriate diameter
sprocket and place it in between the chain like depicted in the photos and
that works ok.
You can acheive a decent chain tension that way.
Does the loose sprocket stay in that place OK? It doesn't have an axle on
the chainstay there anyplace?
Dan
loose due to wear or mishap and then it simply plops out- hopefully not
into the spokes. The real difficulty is that the chainstay passes
through the loop of the chain which limits the space available for the
sprocket. The one in the photo of my red bike is as big as it can be.
Also, it cannot be moved forward since it will rub on the chainstay and
it cannot be moved back because it will engage the rear cog. Maybe a
really large chainwheel would fit around the chainstay on some bicycles
but I suppose you would have to hacksaw a cut in it so that you could
fit the chain wheel around the chainstay.
When it grinds its teeth on the chainstay, it doesn't make as nice of a
noise as cards in the spokes do.
jobst....@stanfordalumni.org
>>> 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.
> Well this is surely fascinating. So one simply takes an appropriate
> diameter sprocket and place it in between the chain like depicted in
> the photos and that works OK.
> You can achieve a decent chain tension that way. Does the loose
> sprocket stay in that place OK? It doesn't have an axle on the
> chainstay there anyplace?
It doesn't need any other support than the chain, but it isn't easy to
find the right size that will fit the bicycle. Chains come in
integral inch length. I've never seen a half-link for bicycle chains,
but motorcycles have them for that purpose.
It's more theoretical than practical. You may have a hard time
finding a CW the size you need that will fit in the space
available... and then it befalls the same chain wear problem as after
starting with an exact fit on just two sprockets. Wear will get you
nowhere. It doesn't take much chain wear to make excessive slack.
That happens with the idling chainwheel the same way.
Jobst Brandt
carl...@comcast.net
[snip]
>I've never seen a half-link for bicycle chains,
>but motorcycles have them for that purpose.
[snip]
Dear Jobst,
"NEW! 3/32" Half Links $3.95 "
"If you are having trouble fitting the desired gears onto a bike with
vertical dropouts, this link will let you add or subtract 1/2 a link
(1/2 inch) from your chain, allowing you to move the axle 1/4" forward
or backward. We never used to be able to get half-links for the narrow
chain, this is a new item!"
http://sheldonbrown.com/harris/chains.html
Or at Bike Tools Etc:
Cheers,
Carl Fogel
b...@mambo.ucolick.org
> John Thompson <jo...@vector.os2.dhs.org> wrote:
>
> >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).
>
> chain-tensioner is as unknown to RBT as the wheel was in the New
> Usually when I mention the trailing-arm chain-tensioner, the reaction
> is either blank incomprehension or fierce denial, so it's nice that
>
> The difference was that they pushed the chain away from the chainstay,
> not toward it like a modern trials motorcycle chain-tensioner. The
> reason is that the old bicycles were dealing with the enormous amount
> of chain slack needed for derailleur gearing--a trials-type
> chain-tensioner would have hit the chainstay before it gathered up all
> the extra chain. That's one reason why the double-arm triumphed--all
> that extra slack is gathered up into the S-bend.
>
> A modern fixie bicycle has scarcely any chain slack compared to a
> derailleur, so the trials-style tension-toward-the-chainstay design
> would work.
>
> Berto's "The Dancing Chain" includes numerous examples of bicycles
> with these single-lever trailing-arm chain-tensioners from the 1920's
> through the 1950's:
>
> http://i17.tinypic.com/2lxf9k6.jpg
> because it's reasonably easy to adjust the chain tension by moving the
> axle on horizontal dropouts, just as chain tension is adjusted on
> typical motorcycles, which lack chain-tensioners.
Among singlespeeders, it is somewhat well known that it's
better to run a chain tensioner as push-up rather than push-down,
if your setup allows it. This allows the chain to engage more
of the cog.
Fixed-gear conversions and the vertical dropout problem are
a relatively recent development. Trackies, of course, actually
need the adjustment provided by horizontal dropouts (since
they change rings and cogs) and most road bikes had horizontal
dropouts anyway until the last 10 years or so.
What I don't quite know is what distinguishes a trailing-arm
chain tensioner from a leading-arm tensioner like the
Surly Singleator http://www.surlybikes.com/parts/singleator_pop.html
Why is it important that the motorcycle chain tensioner
be trailing arm? Does it have something to do with its
behavior as the rear suspension is compressed? Or the
friction between pad/idler and chain?
When you put backpressure on the pedals of a fixie, you put
tension into the lower chain run, but the chain is still moving
in the "normal" direction. It seems reasonable that this would
foul up a derailleur, but it's not obvious to me that it would
destroy a Singleator in push-up mode, as the increased
tension pushes the Singleator down but probably doesn't
carry it backwards into the cog. I would imagine that
somebody's tried this and it failed for some reason I have
not thought of - maybe the tensioner isn't sturdy enough?
Ben
carl...@comcast.net
<b...@mambo.ucolick.org> wrote:
Dear Ben,
A leading under-the-arm chain-tensioner rarely lasts an hour on a
trials bike. The chain heading toward the rear sprocket hits it in the
face, so to speak, and soon bends it backward.
(I had one for about a week in the early 1970's.
In contrast, the chain slaps a trailing chain-tensioner back into
alignment.
Think of dangling an oar off the back of a boat--the current keeps
pushing it back into line.
The Singleator looks like a leading arm designed for convenient
attachment to the derailleur hanger. Since it's for a street bicycle
with no suspension, it may work well enough.
Cheers,
Carl Fogel
Dan O
b...@mambo.ucolick.org wrote:
> Trackies, of course, actually
> need the adjustment provided by horizontal dropouts (since
> they change rings and cogs) and most road bikes had horizontal
> dropouts anyway until the last 10 years or so.
>
Do they adjust the chain length when switching gears? Moving the wheel
appreciably back or forward alters the geometry and handling, doesn't
it?
Kinky Cowboy
<jo...@vector.os2.dhs.org> wrote:
>On 2006-12-15, carl...@comcast.net <carl...@comcast.net> wrote:
>
>> On Fri, 15 Dec 2006 14:19:26 -0600, John Thompson
>><jo...@vector.os2.dhs.org> wrote:
>>>
>>>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.
>
>> 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).
I'm sure something could be arranged by a small modification to a DH
type chain keeper mounted between the fixed cup and the BB shell. Mine
already has the arm holding the lower roller on a pivot if you remove
one bolt, all it needs is a spring from a hardware store. I have an
old, no longer available, Truvativ model but this DMR device looks
ready to modify
http://www.bikedock.com/posit/images/products/0000001845.jpg
Kinky Cowboy
I see your half link and I raise you a bicycle chain which is ALL half
links
http://www.wiggle.co.uk/ProductDetail.aspx?W=0&Manufacturer=&UberCatName=&Cat=cycle&CategoryName=Chains&ProdID=5360021268&UberCat=0
carl...@comcast.net
wrote:
Dear Kinky,
I fold!
I like the round tin that your all half-link chain comes in, along
with flatter chain profile for smoother grinding on stunt bikes.
But the name "Reluctant" could stand improvement.
Cheers,
Carl Fogel
Solvang Cyclist
news:lc6bo218ruq44hgd9...@4ax.com:
This chain brings up the obvious question: What is the disadvantage of
using half links for a complete chain? Why wouldn't all chains be made
this way?
David
jobst....@stanfordalumni.org
>> I fold!
>> I like the round tin that your all half-link chain comes in, along
>> with flatter chain profile for smoother grinding on stunt bikes.
>> But the name "Reluctant" could stand improvement.
> This chain brings up the obvious question: What is the disadvantage
> of using half links for a complete chain? Why wouldn't all chains be
> made this way?
See if you can make a sleeveless chain that way. The upset-collar
4-part chain, is less expensive and possibly stronger. We, with
deragliatore's, don't need no steenkin half link chains.
Jobst Brandt
b...@mambo.ucolick.org
> > On Sun, 17 Dec 2006 13:05:04 +0000, Kinky Cowboy <us...@domain.com>
> >>I see your half link and I raise you a bicycle chain which is ALL half
> >>links
> >>http://www.wiggle.co.uk/ProductDetail.aspx?W=0&Manufacturer=&UberCatNam
> >>e=&Cat=cycle&CategoryName=Chains&ProdID=5360021268&UberCat=0
> >>
> This chain brings up the obvious question: What is the disadvantage of
> using half links for a complete chain? Why wouldn't all chains be made
> this way?
That's a 1/8" singlespeed chain. While it would probably be easy
to make a 3/32" version, I suspect that it would be more difficult
to make it narrow enough to fit modern 8/9/10 speed drivetrains
or to use the shaped side plates which are claimed to aid
shifting in the modern era. And if you have a derailleur, you
don't need half links - but good luck inventing a Powerlink
that works on the half link chain.
Ben
Tim McNamara
Solvang Cyclist <ne...@NOshierSPAM.com> wrote:
> This chain brings up the obvious question: What is the disadvantage of
> using half links for a complete chain? Why wouldn't all chains be made
> this way?
At least by reputation these chains weigh more than regular chains.
I've never weighed either type, however, so I don't know if it's true.
carl...@comcast.net
Dear Tim,
When I looked, there didn't seem to be any significant weight
difference.
Wiggle lists half-link heavy duty BMX 1/8 x 1/2 Reluctant chain at 442
grams:
Nashbar lists normal heavy-duty BMX 1/8 x 1/2 KMC chain at 440 grams:
The similar weights do seem odd, since the Reluctant chain has one
side flat for smoother grinding, instead of curved--the extra metal
should make it weigh more.
Maybe the extra-weight theory included a cotter-pin for each link,
like the ones used on motorcycles?
Cheers,
Carl Fogel