Bridge behind BB housing

[sergio]

I have recorded differring opinions from two different, famous!,
framebuilders,
whose identity I shall provisionally withold, about the usefulness of
having a bridge just behind the bottom bracket housing in a steel
frame.

Opinion n.1
It must be there to make the frame stronger; plus, it is so cheap.

Opinion n.2
It should not be there (unless one wants to attach fenders to it). It
makes the frame prone to cracking around the area where the bridge is
attached, more so than it would be around the BB housing.

Any learned opinion from you, expert builders?

Sergio
Pisa

[sergio]

On 28 Set, 19:41, futrino <fu...@qwest.net> wrote:

> trek 700 commuter 1990?
> broke last year and got it welded for $35 and still on the road.

Well, If I see right how it had been inplanted, that must have been
the very worst bridge on the continent.

Sergio
Pisa

[A Muzi]

> sergio wrote:
>> I have recorded differring opinions from two different, famous!,
>> framebuilders,
>> whose identity I shall provisionally withold, about the usefulness of
>> having a bridge just behind the bottom bracket housing in a steel
>> frame.
>> Opinion n.1
>> It must be there to make the frame stronger; plus, it is so cheap.
>> Opinion n.2
>> It should not be there (unless one wants to attach fenders to it). It
>> makes the frame prone to cracking around the area where the bridge is
>> attached, more so than it would be around the BB housing.
>> Any learned opinion from you, expert builders?

futrino wrote:
> http://img2.freeimagehosting.net/uploads/389e0163dc.jpg
> trek 700 commuter 1990?
> broke last year and got it welded for $35 and still on the road.

These may be a different failure from what Sergio asked about. This one
rusted through as it was not vented:
http://www.yellowjersey.org/photosfromthepast/NIMGADE.JPG
Was yours filled with brown water?
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

[John Thompson]

On 2007-09-28, futrino <futon@qwest.net> wrote:

> trek 700 commuter 1990?
> broke last year and got it welded for $35 and still on the road.

Back when I did warranty inspection for Trek, that would have won you a
new frame.

--

John (john@os2.dhs.org)

[sergio]

Andrew Muzi wrote:
> > These may be a different failure from what Sergio asked about.

To me, that bridge appeared to be inserted into the chain stay tubes,
and not brazed onto them. Is that good construction?

Since we are at it, here is a frame that I would otherwise regard as a
very nice one. It has got no bridge and it developed a crack where I
would have never expected.
Any opinion about this failure from you out there?
In fact, I am considering salvaging it to bring it to new life.

http://img233.imageshack.us/my.php?image=img1187rn2.jpg
http://img211.imageshack.us/my.php?image=img1188yz0.jpg
http://img216.imageshack.us/my.php?image=img1189tq1.jpg
http://img123.imageshack.us/my.php?image=img1190sl7.jpg
http://img406.imageshack.us/my.php?image=img1191np1.jpg
http://img505.imageshack.us/my.php?image=img1192fb6.jpg

Thanks for any thought about it you might have.

Sergio
Pisa

[A Muzi]

sergio wrote:
> I have recorded differring opinions from two different, famous!,
> framebuilders,
> whose identity I shall provisionally withold, about the usefulness of
> having a bridge just behind the bottom bracket housing in a steel
> frame.
>
> Opinion n.1
> It must be there to make the frame stronger; plus, it is so cheap.
>
> Opinion n.2
> It should not be there (unless one wants to attach fenders to it). It
> makes the frame prone to cracking around the area where the bridge is
> attached, more so than it would be around the BB housing.
>
> Any learned opinion from you, expert builders?

As a guy who replaces cracked chainstays regularly, it isn't all that
simple. After about 1977/1980, with cast BB shells, short chainstays
(which must be dented or ovalled more deeply), and thinner tubes, all of
which contribute, a pretty cast bridge can lead to chainstay cracks.
Those cast pieces are big (in terms of BTUs and braze time) then are
quite rigid and they often have squared sharp edges. A simple thin tube
is less likely to give any trouble.

Some builders such as 3Rensho used a small 'plate' extension behind the
BB, others added a 'rib' on the shell casting between the chainstays and
many builders simply skipped the thing entirely. All of those avoid
chainstay cracks pretty well.

Mounting mudguards on my fixie was harder without a chainstay bridge,
yes, but it was Jobst Brandt who pointed to the now-obvious problem of
tires wedging at wheel change. If you can live with that, leave it out.

I do not believe a closed figure (axle/QR, chainstays, BB shell) is
affected by that bridge or lack of it in any real sense of strength or
rigidity.

We can follow a history of breakage from the bikes of the early sixties
with fork blade/crown failures to the later lower headlug/downtube
cracks on until cast-BB-with-the-wrong angles breakage, then chainstay
at bridge cracks to later cast frame end failure. The designers got
after each problem in turn. Making one piece in a dynamic figure
ultra-rigid doesn't always solve problems and sometimes makes new ones.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

[Colin Campbell]

sergio wrote:
> I have recorded differring opinions from two different, famous!,
> framebuilders,
> whose identity I shall provisionally withold, about the usefulness of
> having a bridge just behind the bottom bracket housing in a steel
> frame.
>
> Opinion n.1
> It must be there to make the frame stronger; plus, it is so cheap.
>
> Opinion n.2
> It should not be there (unless one wants to attach fenders to it). It
> makes the frame prone to cracking around the area where the bridge is
> attached, more so than it would be around the BB housing.
>
> Any learned opinion from you, expert builders?
>
> Sergio
> Pisa
>
I am not an expert, but I have seen such bridges on many track bikes, as
well as a few road bikes, and I've never seen one of them with cracked
chainstays.

[jobst.brandt@stanfordalumni.org]

Sergio Servadio writes:

> I have recorded differing opinions from two different, famous!,
> frame builders, whose identity I shall provisionally withhold, about
> the usefulness of having a bridge just behind the bottom bracket
> housing in a steel frame.

> Opinion #1

> It must be there to make the frame stronger; plus, it is so cheap.

He may also believe in tying and soldering spoke crossings.

> Opinion #2

> It should not be there (unless one wants to attach fenders to
> it). It makes the frame prone to cracking around the area where the
> bridge is attached, more so than it would be around the BB housing.

> Any learned opinion from you, expert builders?

It was there on bicycles that never used fenders on older frames with
with horizontal road dropouts, because knocking the rear wheel forward
for quick removal, jammed the tire between the chainstays, and when
pulling the wheel free caused it to re-register in the dropouts. This
little back-and-forth exercise was an annoying loss of time in the
days of yore. Today most bicycles are so short that the tire strikes
the seat tube before it can get jammed between the chainstays.

Jobst Brandt

[datakoll]

I swabbed and swished rusto into that pipe after a thinner rinse. It
runs with a tape of duct fastened to the back side with the hole side
free to breathe under the looped tape. you know, in case of rain.

[Jay Beattie]

On Sep 27, 4:36 pm, A Muzi <a...@yellowjersey.org> wrote:
> sergio wrote:
> > I have recorded differring opinions from two different, famous!,
> > framebuilders,
> > whose identity I shall provisionally withold, about the usefulness of
> > having a bridge just behind the bottom bracket housing in a steel
> > frame.
>
> > Opinion n.1
> > It must be there to make the frame stronger; plus, it is so cheap.
>
> > Opinion n.2
> > It should not be there (unless one wants to attach fenders to it). It
> > makes the frame prone to cracking around the area where the bridge is
> > attached, more so than it would be around the BB housing.
>
> > Any learned opinion from you, expert builders?
>
> As a guy who replaces cracked chainstays regularly, it isn't all that
> simple. After about 1977/1980, with cast BB shells, short chainstays
> (which must be dented or ovalled more deeply), and thinner tubes, all of
> which contribute, a pretty cast bridge can lead to chainstay cracks.
> Those cast pieces are big (in terms of BTUs and braze time) then are
> quite rigid and they often have squared sharp edges. A simple thin tube
> is less likely to give any trouble.
>
> Some builders such as 3Rensho used a small 'plate' extension behind the
> BB, others added a 'rib' on the shell casting between the chainstays and
> many builders simply skipped the thing entirely. All of those avoid
> chainstay cracks pretty well.
>
> Mounting mudguards on my fixie was harder without a chainstay bridge,
> yes, but it was Jobst Brandt who pointed to the now-obvious problem of
> tires wedging at wheel change. If you can live with that, leave it out.
>
> I do not believe a closed figure (axle/QR, chainstays, BB shell) is
> affected by that bridge or lack of it in any real sense of strength or
> rigidity.
>
> We can follow a history of breakage from the bikes of the early sixties
> with fork blade/crown failures to the later lower headlug/downtube
> cracks on until cast-BB-with-the-wrong angles breakage, then chainstay
> at bridge cracks to later cast frame end failure. The designers got
> after each problem in turn. Making one piece in a dynamic figure
> ultra-rigid doesn't always solve problems and sometimes makes new ones.

What was the deal with headlug/downtube joint? That seems like a
pretty benign joint. -- Jay Beattie.

[John Thompson]

On 2007-09-27, A Muzi <am@yellowjersey.org> wrote:

> As a guy who replaces cracked chainstays regularly, it isn't all that
> simple. After about 1977/1980, with cast BB shells, short chainstays
> (which must be dented or ovalled more deeply), and thinner tubes, all of
> which contribute, a pretty cast bridge can lead to chainstay cracks.
> Those cast pieces are big (in terms of BTUs and braze time) then are
> quite rigid and they often have squared sharp edges. A simple thin tube
> is less likely to give any trouble.

A piece of 1/2" electrical conduit works just fine. You can buy enough
for 50 frames for a couple bucks at the hardware store.

> Some builders such as 3Rensho used a small 'plate' extension behind the
> BB, others added a 'rib' on the shell casting between the chainstays and
> many builders simply skipped the thing entirely. All of those avoid
> chainstay cracks pretty well.

Some people claim the bridge stiffens the rear triangle. I've built and
ridden frames with and without and frankly, I can't tell a difference.

--

John (john@os2.dhs.org)

[* * Chas]

"A Muzi" <am@yellowjersey.org> wrote in message
news:13fofii8hjl33ae@corp.supernews.com...
> sergio wrote:
> > I have recorded differring opinions from two different, famous!,
> > framebuilders,
> > whose identity I shall provisionally withold, about the usefulness of
> > having a bridge just behind the bottom bracket housing in a steel
> > frame.
> >
> > Opinion n.1
> > It must be there to make the frame stronger; plus, it is so cheap.
> >
> > Opinion n.2
> > It should not be there (unless one wants to attach fenders to it). It
> > makes the frame prone to cracking around the area where the bridge is
> > attached, more so than it would be around the BB housing.
> >
> > Any learned opinion from you, expert builders?
>
> As a guy who replaces cracked chainstays regularly, it isn't all that
> simple. After about 1977/1980, with cast BB shells, short chainstays
> (which must be dented or ovalled more deeply), and thinner tubes, all of
> which contribute, a pretty cast bridge can lead to chainstay cracks.
> Those cast pieces are big (in terms of BTUs and braze time) then are
> quite rigid and they often have squared sharp edges. A simple thin tube
> is less likely to give any trouble.
>
> Some builders such as 3Rensho used a small 'plate' extension behind the
> BB, others added a 'rib' on the shell casting between the chainstays and
> many builders simply skipped the thing entirely. All of those avoid
> chainstay cracks pretty well.
>
> Mounting mudguards on my fixie was harder without a chainstay bridge,
> yes, but it was Jobst Brandt who pointed to the now-obvious problem of
> tires wedging at wheel change. If you can live with that, leave it out.
>
> I do not believe a closed figure (axle/QR, chainstays, BB shell) is
> affected by that bridge or lack of it in any real sense of strength or
> rigidity.
>
> We can follow a history of breakage from the bikes of the early sixties
> with fork blade/crown failures to the later lower headlug/downtube
> cracks on until cast-BB-with-the-wrong angles breakage, then chainstay
> at bridge cracks to later cast frame end failure. The designers got
> after each problem in turn. Making one piece in a dynamic figure
> ultra-rigid doesn't always solve problems and sometimes makes new ones.
> --
> Andrew Muzi
> www.yellowjersey.org
> Open every day since 1 April, 1971

The melting point of many brazing alloys is very close to the temperature
where alloy steels can be permanently damaged from overheating. It's very
easy to quickly overheat thin wall tubing even when using silver brazing
alloys with lower melting temperatures.

A poorly mitered tube takes a lot more brazing material to fill the gaps
between the tubes. Most silver brazing alloys work best with a gap of
..001" to .003". Brass will fill a larger gap.

I've seen some chainstays crack at the BB joint but a lot more right side
chainstays that were cracked at 2" to 6" out from the BB. I only recall
seeing 1 or 2 cracked left side chainstays.

Also, an anecdotal observation: I've seen very few cracked Reynolds
chainstays. Most of the cracked ones were Columbus or Super Vitus tubing.
I asked several local frame builders about this and they agreed. Except
for breaks at the dropouts or BB they've seen very few cracked Reynolds
chainstays. Over the years Columbus decreased then increased the wall
thickness of the tubing in their SL chainstays .6mm - .7mm?

On frames with short chainstays the bridge may not be necessary and it may
just serve as a point to attach fenders. It seems logical that the bridge
would add some rigidity on frames with long chainstays. I heard once that
the bridge distributes some of the stresses at the BB joints.

Chas.

[A Muzi]

>> sergio wrote:
>>> I have recorded differring opinions from two different, famous!,
>>> framebuilders,
>>> whose identity I shall provisionally withold, about the usefulness of
>>> having a bridge just behind the bottom bracket housing in a steel
>>> frame.
>>> Opinion n.1
>>> It must be there to make the frame stronger; plus, it is so cheap.
>>> Opinion n.2
>>> It should not be there (unless one wants to attach fenders to it). It
>>> makes the frame prone to cracking around the area where the bridge is
>>> attached, more so than it would be around the BB housing.
>>> Any learned opinion from you, expert builders?

> A Muzi <a...@yellowjersey.org> blathered:
>> As a guy who replaces cracked chainstays regularly, it isn't all that
>> simple. After about 1977/1980, with cast BB shells, short chainstays
>> (which must be dented or ovalled more deeply), and thinner tubes, all of
>> which contribute, a pretty cast bridge can lead to chainstay cracks.
>> Those cast pieces are big (in terms of BTUs and braze time) then are
>> quite rigid and they often have squared sharp edges. A simple thin tube
>> is less likely to give any trouble.
>> Some builders such as 3Rensho used a small 'plate' extension behind the
>> BB, others added a 'rib' on the shell casting between the chainstays and
>> many builders simply skipped the thing entirely. All of those avoid
>> chainstay cracks pretty well.
>> Mounting mudguards on my fixie was harder without a chainstay bridge,
>> yes, but it was Jobst Brandt who pointed to the now-obvious problem of
>> tires wedging at wheel change. If you can live with that, leave it out.
>> I do not believe a closed figure (axle/QR, chainstays, BB shell) is
>> affected by that bridge or lack of it in any real sense of strength or
>> rigidity.
>> We can follow a history of breakage from the bikes of the early sixties
>> with fork blade/crown failures to the later lower headlug/downtube
>> cracks on until cast-BB-with-the-wrong angles breakage, then chainstay
>> at bridge cracks to later cast frame end failure. The designers got
>> after each problem in turn. Making one piece in a dynamic figure
>> ultra-rigid doesn't always solve problems and sometimes makes new ones.

Jay Beattie wrote:
> What was the deal with headlug/downtube joint? That seems like a
> pretty benign joint. -- Jay Beattie.

Ideally, the joint is brazed tube-to-tube with the lug supporting that
joint. A straight-angled chop or two at the downtube can't mate
properly to the head tube.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

[Donald Gillies]

Jay Beattie <jbeattie@lindsayhart.com> writes:

>What was the deal with headlug/downtube joint? That seems like a
>pretty benign joint. -- Jay Beattie.

That's just about the highest stresspoint on the bike. The downtube
is by far the most-stressed main tube, since both seat tube and top
tube are under compression ~ the downtube alone is suffering enormous
pulling forces. If there is one tube you should not add braze-ons to,
it's the downtube. Many times, braze-on gear levers or even bottle
mounts lead to cracking and tearing and self-destruction of the downtube.

Look at any modern aluminum bike. there's a good reason why the
downtube looks 2x beefier than any other tube.

- Don Gillies
San Diego, CA

[Gary Young]

On Thu, 27 Sep 2007 21:53:22 -0500, A Muzi wrote:

>>> sergio wrote:
>>>> I have recorded differring opinions from two different, famous!,
>>>> framebuilders,
>>>> whose identity I shall provisionally withold, about the usefulness of
>>>> having a bridge just behind the bottom bracket housing in a steel
>>>> frame.
>>>> Opinion n.1
>>>> It must be there to make the frame stronger; plus, it is so cheap.
>>>> Opinion n.2
>>>> It should not be there (unless one wants to attach fenders to it). It
>>>> makes the frame prone to cracking around the area where the bridge is
>>>> attached, more so than it would be around the BB housing.
>>>> Any learned opinion from you, expert builders?
>
>> A Muzi <a...@yellowjersey.org> blathered:
>>> As a guy who replaces cracked chainstays regularly, it isn't all that
>>> simple. After about 1977/1980, with cast BB shells, short chainstays
>>> (which must be dented or ovalled more deeply), and thinner tubes, all of
>>> which contribute, a pretty cast bridge can lead to chainstay cracks.
>>> Those cast pieces are big (in terms of BTUs and braze time) then are
>>> quite rigid and they often have squared sharp edges. A simple thin tube
>>> is less likely to give any trouble.
>>> Some builders such as 3Rensho used a small 'plate' extension behind the
>>> BB, others added a 'rib' on the shell casting between the chainstays and
>>> many builders simply skipped the thing entirely. All of those avoid
>>> chainstay cracks pretty well.
>>> Mounting mudguards on my fixie was harder without a chainstay bridge,
>>> yes, but it was Jobst Brandt who pointed to the now-obvious problem of
>>> tires wedging at wheel change. If you can live with that, leave it out.
>>> I do not believe a closed figure (axle/QR, chainstays, BB shell) is
>>> affected by that bridge or lack of it in any real sense of strength or
>>> rigidity.
>>> We can follow a history of breakage from the bikes of the early sixties
>>> with fork blade/crown failures to the later lower headlug/downtube
>>> cracks on until cast-BB-with-the-wrong angles breakage, then chainstay
>>> at bridge cracks to later cast frame end failure. The designers got
>>> after each problem in turn. Making one piece in a dynamic figure
>>> ultra-rigid doesn't always solve problems and sometimes makes new ones.
>

It sounds as if the typical failures have gotten more benign over time? Am
I just reading that into what you wrote, or do you think that's actually
the case? Also, do you think failures have gotten more rare (as, say, a
percentage of all of the frames you sell)?

> Jay Beattie wrote:
>> What was the deal with headlug/downtube joint? That seems like a
>> pretty benign joint. -- Jay Beattie.
>
> Ideally, the joint is brazed tube-to-tube with the lug supporting that
> joint. A straight-angled chop or two at the downtube can't mate
> properly to the head tube.

[A Muzi]

>>>> sergio wrote:
>>>>> I have recorded differring opinions from two different, famous!,
>>>>> framebuilders,
>>>>> whose identity I shall provisionally withold, about the usefulness of
>>>>> having a bridge just behind the bottom bracket housing in a steel
>>>>> frame.
>>>>> Opinion n.1
>>>>> It must be there to make the frame stronger; plus, it is so cheap.
>>>>> Opinion n.2
>>>>> It should not be there (unless one wants to attach fenders to it). It
>>>>> makes the frame prone to cracking around the area where the bridge is
>>>>> attached, more so than it would be around the BB housing.
>>>>> Any learned opinion from you, expert builders?

>>> A Muzi <a...@yellowjersey.org> blathered:
>>>> As a guy who replaces cracked chainstays regularly, it isn't all that
>>>> simple. After about 1977/1980, with cast BB shells, short chainstays
>>>> (which must be dented or ovalled more deeply), and thinner tubes, all of
>>>> which contribute, a pretty cast bridge can lead to chainstay cracks.
>>>> Those cast pieces are big (in terms of BTUs and braze time) then are
>>>> quite rigid and they often have squared sharp edges. A simple thin tube
>>>> is less likely to give any trouble.
>>>> Some builders such as 3Rensho used a small 'plate' extension behind the
>>>> BB, others added a 'rib' on the shell casting between the chainstays and
>>>> many builders simply skipped the thing entirely. All of those avoid
>>>> chainstay cracks pretty well.
>>>> Mounting mudguards on my fixie was harder without a chainstay bridge,
>>>> yes, but it was Jobst Brandt who pointed to the now-obvious problem of
>>>> tires wedging at wheel change. If you can live with that, leave it out.
>>>> I do not believe a closed figure (axle/QR, chainstays, BB shell) is
>>>> affected by that bridge or lack of it in any real sense of strength or
>>>> rigidity.
>>>> We can follow a history of breakage from the bikes of the early sixties
>>>> with fork blade/crown failures to the later lower headlug/downtube
>>>> cracks on until cast-BB-with-the-wrong angles breakage, then chainstay
>>>> at bridge cracks to later cast frame end failure. The designers got
>>>> after each problem in turn. Making one piece in a dynamic figure
>>>> ultra-rigid doesn't always solve problems and sometimes makes new ones.

>> Jay Beattie wrote:
>>> What was the deal with headlug/downtube joint? That seems like a
>>> pretty benign joint. -- Jay Beattie.

> A Muzi wrote:
>> Ideally, the joint is brazed tube-to-tube with the lug supporting that
>> joint. A straight-angled chop or two at the downtube can't mate
>> properly to the head tube

Gary Young wrote:
> It sounds as if the typical failures have gotten more benign over time? Am
> I just reading that into what you wrote, or do you think that's actually
> the case? Also, do you think failures have gotten more rare (as, say, a
> percentage of all of the frames you sell)?

Yes, absolutely!
Surviving steel bike makers build, overall, a much higher quality
product in every way. Not only fewer 'stupid' errors but uniformly
better alignment, threading, finish, etc.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

[russellseaton1@yahoo.com]

On Sep 28, 4:06 pm, A Muzi <a...@yellowjersey.org> wrote:
> >>>> sergio wrote:
> >>>>> I have recorded differring opinions from two different, famous!,
> >>>>> framebuilders,
> >>>>> whose identity I shall provisionally withold, about the usefulness of
> >>>>> having a bridge just behind the bottom bracket housing in a steel
> >>>>> frame.
> >>>>> Opinion n.1
> >>>>> It must be there to make the frame stronger; plus, it is so cheap.
> >>>>> Opinion n.2
> >>>>> It should not be there (unless one wants to attach fenders to it). It
> >>>>> makes the frame prone to cracking around the area where the bridge is
> >>>>> attached, more so than it would be around the BB housing.
> >>>>> Any learned opinion from you, expert builders?
> >>> A Muzi <a...@yellowjersey.org> blathered:
> >>>> As a guy who replaces cracked chainstays regularly, it isn't all that
> >>>> simple. After about 1977/1980, with cast BB shells, short chainstays
> >>>> (which must be dented or ovalled more deeply), and thinner tubes, all of
> >>>> which contribute, a pretty cast bridge can lead to chainstay cracks.
> >>>> Those cast pieces are big (in terms of BTUs and braze time) then are
> >>>> quite rigid and they often have squared sharp edges. A simple thin tube
> >>>> is less likely to give any trouble.
> >>>> Some builders such as 3Rensho used a small 'plate' extension behind the
> >>>> BB, others added a 'rib' on the shell casting between the chainstays and
> >>>> many builders simply skipped the thing entirely. All of those avoid
> >>>> chainstay cracks pretty well.
> >>>> Mounting mudguards on my fixie was harder without a chainstay bridge,
> >>>> yes, but it was Jobst Brandt who pointed to the now-obvious problem of
> >>>> tires wedging at wheel change. If you can live with that, leave it out.
> >>>> I do not believe a closed figure (axle/QR, chainstays, BB shell) is
> >>>> affected by that bridge or lack of it in any real sense of strength or
> >>>> rigidity.
> >>>> We can follow a history of breakage from the bikes of the early sixties
> >>>> with fork blade/crown failures to the later lower headlug/downtube
> >>>> cracks on until cast-BB-with-the-wrong angles breakage, then chainstay
> >>>> at bridge cracks to later cast frame end failure. The designers got
> >>>> after each problem in turn. Making one piece in a dynamic figure
> >>>> ultra-rigid doesn't always solve problems and sometimes makes new ones.
> >> Jay Beattie wrote:
> >>> What was the deal with headlug/downtube joint? That seems like a
> >>> pretty benign joint. -- Jay Beattie.
> > A Muzi wrote:
> >> Ideally, the joint is brazed tube-to-tube with the lug supporting that
> >> joint. A straight-angled chop or two at the downtube can't mate
> >> properly to the head tube
> Gary Young wrote:
> > It sounds as if the typical failures have gotten more benign over time? Am
> > I just reading that into what you wrote, or do you think that's actually
> > the case? Also, do you think failures have gotten more rare (as, say, a
> > percentage of all of the frames you sell)?
>
> Yes, absolutely!
> Surviving steel bike makers build, overall, a much higher quality
> product in every way. Not only fewer 'stupid' errors but uniformly
> better alignment, threading, finish, etc.

Exactly how many surviving steel bike makers are there in the world?
Talking only about factory bike makers, not 1-2 man custom makers such
as Sachs, Kellogg, Wiegle, etc. I think Serotta and maybe Colnago and
Pinarello still offer a steel frame. Waterford of course makes steel
frames but has only been a business of its own for about 15 years.
Other steel makers such as Surly(QBP), Soma, Kogswell are all new
companies that owe much of their existence to the internet publicity.
Guerciotti, Ciocc, Tomassinni, Gios, Pegorretti, Mondonico, and a few
other Italian or companies with Italian names probably still make
steel frames but are hardly seen or sold in the US. They are pretty
much special order.



> --
> Andrew Muziwww.yellowjersey.org
> Open every day since 1 April, 1971- Hide quoted text -
>
> - Show quoted text -

[A Muzi]

>>>>>> sergio wrote:
>>>>>>> I have recorded differring opinions from two different, famous!,
>>>>>>> framebuilders,
>>>>>>> whose identity I shall provisionally withold, about the usefulness of
>>>>>>> having a bridge just behind the bottom bracket housing in a steel
>>>>>>> frame.
>>>>>>> Opinion n.1
>>>>>>> It must be there to make the frame stronger; plus, it is so cheap.
>>>>>>> Opinion n.2
>>>>>>> It should not be there (unless one wants to attach fenders to it). It
>>>>>>> makes the frame prone to cracking around the area where the bridge is
>>>>>>> attached, more so than it would be around the BB housing.
>>>>>>> Any learned opinion from you, expert builders?
>>>>> A Muzi <a...@yellowjersey.org> blathered:
>>>>>> As a guy who replaces cracked chainstays regularly, it isn't all that
>>>>>> simple. After about 1977/1980, with cast BB shells, short chainstays
>>>>>> (which must be dented or ovalled more deeply), and thinner tubes, all of
>>>>>> which contribute, a pretty cast bridge can lead to chainstay cracks.
>>>>>> Those cast pieces are big (in terms of BTUs and braze time) then are
>>>>>> quite rigid and they often have squared sharp edges. A simple thin tube
>>>>>> is less likely to give any trouble.
>>>>>> Some builders such as 3Rensho used a small 'plate' extension behind the
>>>>>> BB, others added a 'rib' on the shell casting between the chainstays and
>>>>>> many builders simply skipped the thing entirely. All of those avoid
>>>>>> chainstay cracks pretty well.
>>>>>> Mounting mudguards on my fixie was harder without a chainstay bridge,
>>>>>> yes, but it was Jobst Brandt who pointed to the now-obvious problem of
>>>>>> tires wedging at wheel change. If you can live with that, leave it out.
>>>>>> I do not believe a closed figure (axle/QR, chainstays, BB shell) is
>>>>>> affected by that bridge or lack of it in any real sense of strength or
>>>>>> rigidity.
>>>>>> We can follow a history of breakage from the bikes of the early sixties
>>>>>> with fork blade/crown failures to the later lower headlug/downtube
>>>>>> cracks on until cast-BB-with-the-wrong angles breakage, then chainstay
>>>>>> at bridge cracks to later cast frame end failure. The designers got
>>>>>> after each problem in turn. Making one piece in a dynamic figure
>>>>>> ultra-rigid doesn't always solve problems and sometimes makes new ones.

>>>> Jay Beattie wrote:
>>>>> What was the deal with headlug/downtube joint? That seems like a
>>>>> pretty benign joint. -- Jay Beattie.

>>> A Muzi wrote:
>>>> Ideally, the joint is brazed tube-to-tube with the lug supporting that
>>>> joint. A straight-angled chop or two at the downtube can't mate
>>>> properly to the head tube

>> Gary Young wrote:
>>> It sounds as if the typical failures have gotten more benign over time? Am
>>> I just reading that into what you wrote, or do you think that's actually
>>> the case? Also, do you think failures have gotten more rare (as, say, a
>>> percentage of all of the frames you sell)?

> A Muzi <a...@yellowjersey.org> wrote:
>> Yes, absolutely!
>> Surviving steel bike makers build, overall, a much higher quality
>> product in every way. Not only fewer 'stupid' errors but uniformly
>> better alignment, threading, finish, etc.

russellseaton1@yahoo.com wrote:
> Exactly how many surviving steel bike makers are there in the world?
> Talking only about factory bike makers, not 1-2 man custom makers such
> as Sachs, Kellogg, Wiegle, etc. I think Serotta and maybe Colnago and
> Pinarello still offer a steel frame. Waterford of course makes steel
> frames but has only been a business of its own for about 15 years.
> Other steel makers such as Surly(QBP), Soma, Kogswell are all new
> companies that owe much of their existence to the internet publicity.
> Guerciotti, Ciocc, Tomassinni, Gios, Pegorretti, Mondonico, and a few
> other Italian or companies with Italian names probably still make
> steel frames but are hardly seen or sold in the US. They are pretty
> much special order.

I have no idea how many. Lots more than 'special order'!!
You left out the wonderful Hodaka as well as Panasonic, Brigestone and
all the Keirin builders. British; Jackson-Hetchins, Thorne, Mercian come
to mind.
And what about the Dutch builders (Batavus, Gizelle, etc) ?
Bianchi/Milano still makes volume steel bikes for their market, just not
for ours. (Bianchi/Bergamo doesn't do steel now) And Bianchi/Santiago
Chile, probably another couple dozen operations like that (Cspel, Steyr
etc).
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

[Donald Gillies]

"russellseaton1@yahoo.com" <russellseaton1@yahoo.com> writes:

>Exactly how many surviving steel bike makers are there in the world?
>Talking only about factory bike makers, not 1-2 man custom makers such
>as Sachs, Kellogg, Wiegle, etc. I think Serotta and maybe Colnago and
>Pinarello still offer a steel frame. Waterford of course makes steel
>frames but has only been a business of its own for about 15 years.

One could argue that Waterford is the oldest of all steel bike
makers. Mercian probably comes in second place, or maybe tied with
Dawes ?? Doesn't Dawes still manufacture steel frames ??

- Don Gillies
San Diego, CA

[M-gineering]

A Muzi wrote:

> And what about the Dutch builders (Batavus, Gazelle, etc) ?

There are some smaller factories still building steel frames, but AFAIK
all the big ones have sold of the frame building lines and outsourced to
the (far) east. Most 45 pound roadsters now feature 'lightweight'
aluminium frames
--
/Marten

info(apestaartje)m-gineering(punt)nl

[Donald Gillies]

A Muzi <am@yellowjersey.org> writes:

>> A Muzi <a...@yellowjersey.org> wrote:
>>> Yes, absolutely!
>>> Surviving steel bike makers build, overall, a much higher quality
>>> product in every way. Not only fewer 'stupid' errors but uniformly
>>> better alignment, threading, finish, etc.

>russellseaton1@yahoo.com wrote:
>> Exactly how many surviving steel bike makers are there in the world?

Whoops, let me try again :

Gazelle : 100+ (?) years old
Bianchi : 100+ (?) years old
Waterford : 70+ (?) years old (1930's)
Mercian : 60+ (?) years old (1940's)
Dawes : 50+ (?) years old (1960 ?)

Then there are all those young'uns like other americans and italian
pantographors (pornographers ..) etc ...

- Don Gillies
San Diego, CA, USA

[Kinky Cowboy]

On 29 Sep 2007 01:08:46 -0700, gillies@cs.ubc.ca (Donald Gillies)
wrote:

>Jay Beattie <jbeattie@lindsayhart.com> writes:
>
>>What was the deal with headlug/downtube joint? That seems like a
>>pretty benign joint. -- Jay Beattie.
>
>That's just about the highest stresspoint on the bike. The downtube
>is by far the most-stressed main tube, since both seat tube and top
>tube are under compression ~ the downtube alone is suffering enormous
>pulling forces. If there is one tube you should not add braze-ons to,
>it's the downtube. Many times, braze-on gear levers or even bottle
>mounts lead to cracking and tearing and self-destruction of the downtube.
>
>Look at any modern aluminum bike. there's a good reason why the
>downtube looks 2x beefier than any other tube.
>

Yes, and it's nothing to do with the tensile load, which can be (and
has been, on some designs) resisted by a suitable sized wire. The very
large diameter down tube is there to resist torsional loads.

Kinky Cowboy*

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

[sergio]

On 29 Set, 12:54, Kinky Cowboy <u...@domain.com> wrote:

> Yes, and it's nothing to do with the tensile load, which can be (and
> has been, on some designs) resisted by a suitable sized wire.

About tension, and tensile stregth that is needed down there, I have a
question.

What wire would be adequate?
How about a brake cord?

I ask since I repaired, and put back into service, a Colnago Carbitubo
that had unglued at the joint by adding a bike brake cord. The cord
did elongate to the point that I was forced to tension it again; and
this time I improved the fix by implanting a couple of splines
(english?) through the tubes.

To be honest, I was rather surprised that a brake cord would elongate
that much, and probably it would have kept getting longer and longer.

Sergio
Pisa

[jim beam]

Kinky Cowboy wrote:
> On 29 Sep 2007 01:08:46 -0700, gillies@cs.ubc.ca (Donald Gillies)
> wrote:
>
>> Jay Beattie <jbeattie@lindsayhart.com> writes:
>>
>>> What was the deal with headlug/downtube joint? That seems like a
>>> pretty benign joint. -- Jay Beattie.
>> That's just about the highest stresspoint on the bike. The downtube
>> is by far the most-stressed main tube, since both seat tube and top
>> tube are under compression ~ the downtube alone is suffering enormous
>> pulling forces. If there is one tube you should not add braze-ons to,
>> it's the downtube. Many times, braze-on gear levers or even bottle
>> mounts lead to cracking and tearing and self-destruction of the downtube.
>>
>> Look at any modern aluminum bike. there's a good reason why the
>> downtube looks 2x beefier than any other tube.
>>
>
> Yes, and it's nothing to do with the tensile load, which can be (and
> has been, on some designs) resisted by a suitable sized wire. The very
> large diameter down tube is there to resist torsional loads.

indeed.


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

[carlfogel@comcast.net]

On Sat, 29 Sep 2007 06:08:11 -0700, sergio <servadio@df.unipi.it>
wrote:

>On 29 Set, 12:54, Kinky Cowboy <u...@domain.com> wrote:
>
>> Yes, and it's nothing to do with the tensile load, which can be (and
>> has been, on some designs) resisted by a suitable sized wire.
>
>About tension, and tensile stregth that is needed down there, I have a
>question.
>
>What wire would be adequate?
>How about a brake cord?
>
>I ask since I repaired, and put back into service, a Colnago Carbitubo
>that had unglued at the joint by adding a bike brake cord. The cord
>did elongate to the point that I was forced to tension it again; and
>this time I improved the fix by implanting a couple of splines
>(english?) through the tubes.
>
>To be honest, I was rather surprised that a brake cord would elongate
>that much, and probably it would have kept getting longer and longer.
>
>Sergio
>Pisa

Dear Sergio,

Here's a bike with two wire chainstays and a single wire downtube:

http://www.flickr.com/photo_zoom.gne?id=452139683&size=o

The thick wires (thin rods) go right past the inch-pitch chain and
gear teeth, so you can get a good idea of the thickness.

Cheers,

Carl Fogel

[jim beam]

carlfogel@comcast.net wrote:
> On Sat, 29 Sep 2007 06:08:11 -0700, sergio <servadio@df.unipi.it>
> wrote:
>
>> On 29 Set, 12:54, Kinky Cowboy <u...@domain.com> wrote:
>>
>>> Yes, and it's nothing to do with the tensile load, which can be (and
>>> has been, on some designs) resisted by a suitable sized wire.
>> About tension, and tensile stregth that is needed down there, I have a
>> question.
>>
>> What wire would be adequate?
>> How about a brake cord?
>>
>> I ask since I repaired, and put back into service, a Colnago Carbitubo
>> that had unglued at the joint by adding a bike brake cord. The cord
>> did elongate to the point that I was forced to tension it again; and
>> this time I improved the fix by implanting a couple of splines
>> (english?) through the tubes.
>>
>> To be honest, I was rather surprised that a brake cord would elongate
>> that much, and probably it would have kept getting longer and longer.
>>
>> Sergio
>> Pisa
>
> Dear Sergio,
>
> Here's a bike with two wire chainstays and a single wire downtube:
>
> http://www.flickr.com/photo_zoom.gne?id=452139683&size=o
>
> The thick wires (thin rods) go right past the inch-pitch chain and
> gear teeth, so you can get a good idea of the thickness.
>
> Cheers,
>
> Carl Fogel

that chain is either /massively/ worn out, or not quite the right pitch
- there's some serious mis-mesh going on with that chain wheel.

[Ryan Cousineau]

In article <ra7tf3hnistj6bc381nvlt9qub3gjstuob@4ax.com>,
carlfogel@comcast.net wrote:

> On Sat, 29 Sep 2007 06:08:11 -0700, sergio <servadio@df.unipi.it>
> wrote:
>
> >On 29 Set, 12:54, Kinky Cowboy <u...@domain.com> wrote:
> >
> >> Yes, and it's nothing to do with the tensile load, which can be (and
> >> has been, on some designs) resisted by a suitable sized wire.
> >
> >About tension, and tensile stregth that is needed down there, I have a
> >question.
> >
> >What wire would be adequate?
> >How about a brake cord?
> >
> >I ask since I repaired, and put back into service, a Colnago Carbitubo
> >that had unglued at the joint by adding a bike brake cord. The cord
> >did elongate to the point that I was forced to tension it again; and
> >this time I improved the fix by implanting a couple of splines
> >(english?) through the tubes.
> >
> >To be honest, I was rather surprised that a brake cord would elongate
> >that much, and probably it would have kept getting longer and longer.
> >
> >Sergio
> >Pisa
>
> Dear Sergio,
>
> Here's a bike with two wire chainstays and a single wire downtube:
>
> http://www.flickr.com/photo_zoom.gne?id=452139683&size=o
>
> The thick wires (thin rods) go right past the inch-pitch chain and
> gear teeth, so you can get a good idea of the thickness.

The contemporary example is, of course, the Slingshot:

http://www.slingshotbikes.com/bikes/1

Here's a road-ish version:

http://www.slingshotbikes.com/bikes/6

You will notice that Slingshot now sells a conventional-downtube
cyclocross bike, perhaps for UCI-related reasons (as in, I'm pretty sure
the cable downtube isn't UCI-legal). I noticed that the folding
cable-downtube road bike has huge bracing plates above and below the top
tube's connection to the head tube.

--
Ryan Cousineau rcousine@sfu.ca 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

[Michael Press]

In article
<1191103420.655166.323230@g4g2000hsf.googlegroups.c om>,
sergio <servadio@df.unipi.it> wrote:

> Andrew Muzi wrote:
> > > These may be a different failure from what Sergio asked about.
>
> To me, that bridge appeared to be inserted into the chain stay tubes,
> and not brazed onto them. Is that good construction?
>
> Since we are at it, here is a frame that I would otherwise regard as a
> very nice one. It has got no bridge and it developed a crack where I
> would have never expected.
> Any opinion about this failure from you out there?
> In fact, I am considering salvaging it to bring it to new life.
>
> http://img233.imageshack.us/my.php?image=img1187rn2.jpg
> http://img211.imageshack.us/my.php?image=img1188yz0.jpg
> http://img216.imageshack.us/my.php?image=img1189tq1.jpg
> http://img123.imageshack.us/my.php?image=img1190sl7.jpg
> http://img406.imageshack.us/my.php?image=img1191np1.jpg
> http://img505.imageshack.us/my.php?image=img1192fb6.jpg
>
> Thanks for any thought about it you might have.

I still hold that a bridge here is part of the
chain stay to bottom bracket joint. Properly done
the bridge will better transfer torsion loads from
the bottom bracket to the chain stays, with less
flexing of the chain stays.

--
Michael Press

[datakoll]

yeah down here on the ground. adjusting chainstays for greater or
narrower axle widths falls into Andrew Muzi's scenario? and a
chainstay brace taking off the stress for these shinnanigains before
the stress arrived at the BB's complexity would seem like a good idea.
That may be after the fact or avoiding future calamity in PR given
self knowledge of your BB's strength - as a welder.
How many posts ask: I wanna spread my Aluminium chainstays...? more
than the mean.

[carlfogel@comcast.net]

On Sat, 29 Sep 2007 19:54:48 -0700, jim beam
<spamvortex@bad.example.net> wrote:

>carlfogel@comcast.net wrote:
>> On Sat, 29 Sep 2007 06:08:11 -0700, sergio <servadio@df.unipi.it>
>> wrote:
>>
>>> On 29 Set, 12:54, Kinky Cowboy <u...@domain.com> wrote:
>>>
>>>> Yes, and it's nothing to do with the tensile load, which can be (and
>>>> has been, on some designs) resisted by a suitable sized wire.
>>> About tension, and tensile stregth that is needed down there, I have a
>>> question.
>>>
>>> What wire would be adequate?
>>> How about a brake cord?
>>>
>>> I ask since I repaired, and put back into service, a Colnago Carbitubo
>>> that had unglued at the joint by adding a bike brake cord. The cord
>>> did elongate to the point that I was forced to tension it again; and
>>> this time I improved the fix by implanting a couple of splines
>>> (english?) through the tubes.
>>>
>>> To be honest, I was rather surprised that a brake cord would elongate
>>> that much, and probably it would have kept getting longer and longer.
>>>
>>> Sergio
>>> Pisa
>>
>> Dear Sergio,
>>
>> Here's a bike with two wire chainstays and a single wire downtube:
>>
>> http://www.flickr.com/photo_zoom.gne?id=452139683&size=o
>>
>> The thick wires (thin rods) go right past the inch-pitch chain and
>> gear teeth, so you can get a good idea of the thickness.
>>
>> Cheers,
>>
>> Carl Fogel
>
>that chain is either /massively/ worn out, or not quite the right pitch
>- there's some serious mis-mesh going on with that chain wheel.

Dear Jim,

It's fairly typical of photos of old inch-pitch chain on the front
sprocket--you can often see daylight through the sprocket where the
chain engages at the top.

Cheers,

Carl Fogel

[jim beam]

carlfogel@comcast.net wrote:
> On Sat, 29 Sep 2007 19:54:48 -0700, jim beam
> <spamvortex@bad.example.net> wrote:
>
>> carlfogel@comcast.net wrote:
>>> On Sat, 29 Sep 2007 06:08:11 -0700, sergio <servadio@df.unipi.it>
>>> wrote:
>>>
>>>> On 29 Set, 12:54, Kinky Cowboy <u...@domain.com> wrote:
>>>>
>>>>> Yes, and it's nothing to do with the tensile load, which can be (and
>>>>> has been, on some designs) resisted by a suitable sized wire.
>>>> About tension, and tensile stregth that is needed down there, I have a
>>>> question.
>>>>
>>>> What wire would be adequate?
>>>> How about a brake cord?
>>>>
>>>> I ask since I repaired, and put back into service, a Colnago Carbitubo
>>>> that had unglued at the joint by adding a bike brake cord. The cord
>>>> did elongate to the point that I was forced to tension it again; and
>>>> this time I improved the fix by implanting a couple of splines
>>>> (english?) through the tubes.
>>>>
>>>> To be honest, I was rather surprised that a brake cord would elongate
>>>> that much, and probably it would have kept getting longer and longer.
>>>>
>>>> Sergio
>>>> Pisa
>>> Dear Sergio,
>>>
>>> Here's a bike with two wire chainstays and a single wire downtube:
>>>
>>> http://www.flickr.com/photo_zoom.gne?id=452139683&size=o
>>>
>>> The thick wires (thin rods) go right past the inch-pitch chain and
>>> gear teeth, so you can get a good idea of the thickness.
>>>
>>> Cheers,
>>>
>>> Carl Fogel
>> that chain is either /massively/ worn out, or not quite the right pitch
>> - there's some serious mis-mesh going on with that chain wheel.
>
> Dear Jim,
>
> It's fairly typical of photos of old inch-pitch chain on the front
> sprocket--you can often see daylight through the sprocket where the
> chain engages at the top.
>
> Cheers,
>
> Carl Fogel

that's the mis-match of the teeth. at both the top and bottom of the
sprocket, the roller is high up on the tooth and can't seat properly.

[sergio]

On 30 Set, 06:25, Michael Press <rub...@pacbell.net>
> > Thanks for any thought about it you might have.
> I still hold that a bridge here is part of the
> chain stay to bottom bracket joint. Properly done
> the bridge will better transfer torsion

I would second your thought.
There is no uinique answer to which solution is better than the other:
it is a matter of how it is implemented from an overall prospective.

Sergio
Pisa

[jim beam]

jobst.brandt@stanfordalumni.org wrote:
> Sergio Servadio writes:
>
>> I have recorded differing opinions from two different, famous!,
>> frame builders, whose identity I shall provisionally withhold, about
>> the usefulness of having a bridge just behind the bottom bracket
>> housing in a steel frame.
>
>> Opinion #1
>
>> It must be there to make the frame stronger; plus, it is so cheap.
>
> He may also believe in tying and soldering spoke crossings.

that's totally unwarranted ad hominem.


>
>> Opinion #2
>
>> It should not be there (unless one wants to attach fenders to
>> it). It makes the frame prone to cracking around the area where the
>> bridge is attached, more so than it would be around the BB housing.
>
>> Any learned opinion from you, expert builders?
>
> It was there on bicycles that never used fenders on older frames with
> with horizontal road dropouts, because knocking the rear wheel forward
> for quick removal, jammed the tire between the chainstays, and when
> pulling the wheel free caused it to re-register in the dropouts. This
> little back-and-forth exercise was an annoying loss of time in the
> days of yore. Today most bicycles are so short that the tire strikes
> the seat tube before it can get jammed between the chainstays.

of course, you know all about metal fatigue don't you jobst. oh, wait...

[Jambo]

"jim beam" <spamvortex@bad.example.net> wrote in message
news:QNydnS6bmvdOXJzanZ2dnUVZ_o3inZ2d@speakeasy.ne t...
> jobst.brandt@stanfordalumni.org wrote:
>>> It must be there to make the frame stronger; plus, it is so cheap.
>>
>> He may also believe in tying and soldering spoke crossings.
>
> that's totally unwarranted ad hominem.

Oh, the irony....

>> It was there on bicycles that never used fenders on older frames with
>> with horizontal road dropouts, because knocking the rear wheel forward
>> for quick removal, jammed the tire between the chainstays, and when
>> pulling the wheel free caused it to re-register in the dropouts. This
>> little back-and-forth exercise was an annoying loss of time in the
>> days of yore. Today most bicycles are so short that the tire strikes
>> the seat tube before it can get jammed between the chainstays.
>
> of course, you know all about metal fatigue don't you jobst. oh, wait...

And of course, with your "metelalrugist" background from "metarials skool",
you know better, dontcha?

Oh wait....