Why two top tubes ?

[Rik O'Shea]

Why two top tubes ?

http://tinyurl.com/37sbwo

[Coaster]

Rik O'Shea wrote:
> Why two top tubes ?
>
> http://tinyurl.com/37sbwo
>
Two tubes are better than one:
http://tinyurl.com/2wghpd

[unforgiven99@juno.com]

On Oct 25, 6:18 am, Rik O'Shea <rikos...@yahoo.com> wrote:
> Why two top tubes ?
>
> http://tinyurl.com/37sbwo

They must have given up on the "laterally stiff but vertically
compliant" nonsense.

[M-gineering]

Rik O'Shea wrote:
> Why two top tubes ?
>
> http://tinyurl.com/37sbwo
>

two tubes are twice as stiff as a single tube
It's easy to build as you can use the same tubes and lugs (with a bit of
grinding on the seatlugears)


--
/Marten

info(apestaartje)m-gineering(punt)nl

[Koert Marinissen]

Rik O'Shea schreef :
> Why two top tubes ?
>
> http://tinyurl.com/37sbwo

A strong man needs a strong bike!

http://picasaweb.google.com/koertmarinissen/Fiets/photo#5016259047640721090

Koert

[Bill Sornson]

Rik O'Shea wrote:
> Why two top tubes ?
>
> http://tinyurl.com/37sbwo

Why not?

(Oh, and those freakishly long, thin head tubes, too.)

[carlfogel@comcast.net]

On Thu, 25 Oct 2007 10:18:15 -0000, Rik O'Shea <rikoshea@yahoo.com>
wrote:

>
>Why two top tubes ?
>
>http://tinyurl.com/37sbwo

Dear Rik,

Partly for style, since double top tubes were popular around 1910:

http://www.fixedgeargallery.com/morley/04.jpg

http://www.fixedgeargallery.com/morley/06.jpg

Partly for strength for carrying loads slung across the top tube, a
popular habit in what the caption refers to as developing countries,
where riders may sling 200-300 pounds of cargo across the top tube and
trundle down a bumpy dirt road.

Cheers,

Carl Fogel

[Donald Gillies]

Rik O'Shea <rikoshea@yahoo.com> writes:

>Why two top tubes ?

>http://tinyurl.com/37sbwo

On this particular bike, i think it's a mistake, as the frame seems to
be a 23" (58.5cm) c-t frame. The top tube is the least-stressed tube
on the bicycle, because it's under compression. The downtube is the
most-stressed tube.

However, when the seat tube and head tube get very long, I think there
are a lot of twisting stresses on these tubes (because, for example,
all my indexed / spalled / fretted / whatever headsets are on bikes
24" or larger ... whereas none of my smaller bikes ever had this
problem.)

- Don Gillies
San Diego, CA

[clare at snyder.on.ca]

On Thu, 25 Oct 2007 10:18:15 -0000, Rik O'Shea <rikoshea@yahoo.com>
wrote:

>
>Why two top tubes ?
>
>http://tinyurl.com/37sbwo
Retro? Lots of olde bikes had dual top tubes.

--
Posted via a free Usenet account from http://www.teranews.com

[Bill Sornson]

Rik O'Shea wrote:
> Why two top tubes ?

Like this? http://mydoggyplace.com/images/sw-ftt.gif

[Chris M]

On Oct 25, 3:18 am, Rik O'Shea <rikos...@yahoo.com> wrote:
> Why two top tubes ?
>
> http://tinyurl.com/37sbwo

Regardless of the materials and dimensions, it will always be more
rigid along the plane defined by the 2 tubes relative to the plane
rotated 90 degrees from that first plane. *And* you can control the
relative amount of difference by the distance apart from the tubes. It
is actually a brilliant design for bikes, especially custom frames
built for a rider with known power and weight stats. The Colnago twin
down-tube models that had the tubes side-by-side are the perfect
example of a frame that exploits these benefits. The width between the
tubes could be (though I don't think many of them were custom built)
adjusted along with the properties of the tubes to build a frame with
just the blend of lateral and vertical stiffness / compliance
properties that the builder or designer would like. Compared to
traditional frames, these properties would be much easier to
manipulate. I am actually a bit surprised that there were not a lot
more of these designs built this way and if it were not for carbon
fiber's excellent tuning potential, I think that at some point Colnago
and or some others would have developed this scheme much more than the
few that were actually built. I can't recall in what order Colnago
offered them, but the first and second models were titanium and steel,
and the third model (in subsequent model years) was the same frame
scheme in carbon fiber. The titanium models were probably the most
widely sold, but they (many of them) also were made with inferior
titanium that often broke. I really think that carbon fiber
development that was happening in parallel to these models is the only
reason that Colnago gave up on this scheme. There were a few seasons
when at least 3 sponsored European Pro teams were using one or more of
these 3 twin-downtube frames.

[* * Chas]

"Coaster" <manypeny@mac.com> wrote in message
news:ffpr42$16ir$1@news2.ipartners.pl...
> Rik O'Shea wrote:
> > Why two top tubes ?
> >
> > http://tinyurl.com/37sbwo
> >
> Two tubes are better than one:
> http://tinyurl.com/2wghpd


Here's an even better solution:

http://www.classicrendezvous.com/Rarest/prison_bike.htm

Chas.

[Coaster]

unforgiven99@juno.com wrote:
> On Oct 25, 6:18 am, Rik O'Shea <rikos...@yahoo.com> wrote:
>> Why two top tubes ?
>>
>> http://tinyurl.com/37sbwo
>
> They must have given up on the "laterally stiff but vertically
> compliant" nonsense.
>
English roadsters 24.5" frames "for the taller gent" were built with
double top tubes. Tradition? IMHO they wanted to make stiffier frame...

C.

[Coaster]

Coaster wrote:
> unforgiven99@juno.com wrote:
>> On Oct 25, 6:18 am, Rik O'Shea <rikos...@yahoo.com> wrote:
>>> Why two top tubes ?
>>>
>>> http://tinyurl.com/37sbwo
>>
>> They must have given up on the "laterally stiff but vertically
>> compliant" nonsense.
>>
> English roadsters 24.5" frames "for the taller gent" were built with
> double top tubes. Tradition? IMHO they wanted to make stiffier frame...
>
> C.
NIce bike with double TT:
http://www.uscoles.com/bikepix/073stpashleyl.jpg

C.

[A Muzi]

>> On Oct 25, 6:18 am, Rik O'Shea <rikos...@yahoo.com> wrote:
>>> Why two top tubes ?
>>> http://tinyurl.com/37sbwo

> unforgiven99@juno.com wrote:
>> They must have given up on the "laterally stiff but vertically
>> compliant" nonsense.

Coaster wrote:
> English roadsters 24.5" frames "for the taller gent" were built with
> double top tubes. Tradition? IMHO they wanted to make stiffier frame...

Raleighs were built both with single and with double top tubes, the dual
top tube version not sold in USA. I tried to add some to a container of
bikes. They declined even though they were shipping dual tube models to
selected 3d world markets at the time. Raleigh's official statement,
"It's fashion".
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

[* * Chas]

"Coaster" <manypeny@mac.com> wrote in message
news:ffq29a$1bfg$2@news2.ipartners.pl...
> Coaster wrote:
> > unforgiven99@juno.com wrote:
> >> On Oct 25, 6:18 am, Rik O'Shea <rikos...@yahoo.com> wrote:
> >>> Why two top tubes ?
> >>>
> >>> http://tinyurl.com/37sbwo
> >>
> >> They must have given up on the "laterally stiff but vertically
> >> compliant" nonsense.
> >>
> > English roadsters 24.5" frames "for the taller gent" were built with
> > double top tubes. Tradition? IMHO they wanted to make stiffier
frame...
> >
> > C.
> NIce bike with double TT:
> http://www.uscoles.com/bikepix/073stpashleyl.jpg
>
> C.

If you ever need a smaller sized frame, just break out your handy
hacksaw....

Chas.

[unforgiven99@juno.com]

On Oct 25, 8:40 am, M-gineering <ikmotgeens...@m-gineering.nl> wrote:
> Rik O'Shea wrote:
> > Why two top tubes ?
>
> >http://tinyurl.com/37sbwo
>
> two tubes are twice as stiff as a single tube
> It's easy to build as you can use the same tubes and lugs (with a bit of
> grinding on the seatlugears)
>
> --
> /Marten
>
> info(apestaartje)m-gineering(punt)nl

Well, about 30% stiffer laterally, and way stiffer vertically
depending on the geometry. The question is, why double the top tube?
The down tube makes much more sense.

[* * Chas]

"M-gineering" <ikmotgeenspam@m-gineering.nl> wrote in message
news:ffq2t2$pf0$1@localhost.localdomain...
> Rik O'Shea wrote:
> > Why two top tubes ?
> >
> > http://tinyurl.com/37sbwo
> >
>
> two tubes are twice as stiff as a single tube
> It's easy to build as you can use the same tubes and lugs (with a bit of
> grinding on the seatlugears)
>
>
> --
> /Marten

If more is better then......

http://www.classicrendezvous.com/Rarest/prison_bike.htm

Chas.

[Michael Press]

In article
<1193332196.834434.99760@o80g2000hse.googlegroups.c om>,
unforgiven99@juno.com wrote:

> On Oct 25, 8:40 am, M-gineering <ikmotgeens...@m-gineering.nl> wrote:
> > Rik O'Shea wrote:
> > > Why two top tubes ?
> >
> > >http://tinyurl.com/37sbwo
> >
> > two tubes are twice as stiff as a single tube
> > It's easy to build as you can use the same tubes and lugs (with a bit of
> > grinding on the seatlugears)
> >
> > --
> > /Marten
> >
> > info(apestaartje)m-gineering(punt)nl
>
> Well, about 30% stiffer laterally, and way stiffer vertically
> depending on the geometry. The question is, why double the top tube?
> The down tube makes much more sense.

And putting gussets on the bottom bracket shell even more sense
but it is not done. Any frame makers here to comment?

--
Michael Press

[jim beam]

unforgiven99@juno.com wrote:
> On Oct 25, 8:40 am, M-gineering <ikmotgeens...@m-gineering.nl> wrote:
>> Rik O'Shea wrote:
>>> Why two top tubes ?
>>> http://tinyurl.com/37sbwo
>> two tubes are twice as stiff as a single tube
>> It's easy to build as you can use the same tubes and lugs (with a bit of
>> grinding on the seatlugears)
>>
>> --
>> /Marten
>>
>> info(apestaartje)m-gineering(punt)nl
>
> Well, about 30% stiffer laterally, and way stiffer vertically
> depending on the geometry.

10 points.

> The question is, why double the top tube?
> The down tube makes much more sense.

a bigger diameter down tube and a triangulating [as opposed to parallel]
second top tube makes more sense still.

[* * Chas]

<carlfogel@comcast.net> wrote in message
news:ubk1i35hteqictbsfmdd1mf2nnildmubn4@4ax.com...
> On Thu, 25 Oct 2007 10:18:15 -0000, Rik O'Shea <rikoshea@yahoo.com>
> wrote:
>
> >
> >Why two top tubes ?
> >
> >http://tinyurl.com/37sbwo
>
> Dear Rik,
>
> Partly for style, since double top tubes were popular around 1910:
>
> http://www.fixedgeargallery.com/morley/04.jpg
>
> http://www.fixedgeargallery.com/morley/06.jpg
>
> Partly for strength for carrying loads slung across the top tube, a
> popular habit in what the caption refers to as developing countries,
> where riders may sling 200-300 pounds of cargo across the top tube and
> trundle down a bumpy dirt road.
>
> Cheers,
>
> Carl Fogel

I remember reading that the dual top tube bikes were called "Policeman's
Models" throughout the UK and her former Empire.

Chas.

[Michael Press]

In article <ffqoos$gg1$1@cascade.cs.ubc.ca>,
gillies@cs.ubc.ca (Donald Gillies) wrote:

> Rik O'Shea <rikoshea@yahoo.com> writes:
>
> >Why two top tubes ?
>
> >http://tinyurl.com/37sbwo
>
> On this particular bike, i think it's a mistake, as the frame seems to
> be a 23" (58.5cm) c-t frame. The top tube is the least-stressed tube
> on the bicycle, because it's under compression. The downtube is the
> most-stressed tube.

It seems to me that tubes do not fail, typically.
Joints fail.
* down tube -- head tube.
* down tube -- braze on.
* any tube -- bottom bracket.
* chain stay -- drop out
* chain stay -- brake bridge
* seat stay -- seat tube

--
Michael Press

[A Muzi]

>>> Rik O'Shea wrote:
>>>> Why two top tubes ?
>>>> http://tinyurl.com/37sbwo

>> M-gineering <ikmotgeens...@m-gineering.nl> wrote:
>>> two tubes are twice as stiff as a single tube
>>> It's easy to build as you can use the same tubes and lugs (with a bit of
>>> grinding on the seatlugears)
>>> info(apestaartje)m-gineering(punt)nl

> unforgiven99@juno.com wrote:
>> Well, about 30% stiffer laterally, and way stiffer vertically
>> depending on the geometry. The question is, why double the top tube?
>> The down tube makes much more sense.

Michael Press wrote:
> And putting gussets on the bottom bracket shell even more sense
> but it is not done. Any frame makers here to comment?

The examples I can think of (3Rensho, Zunow) with cast gussets didn't
sell well. I believe you may yet have a frame made with the 3Rensho
flanged-sides BB casting from Jackson-Hetchins.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

[still me]

On Thu, 25 Oct 2007 12:10:09 -0700, Michael Press <rubrum@pacbell.net>
wrote:

>And putting gussets on the bottom bracket shell even more sense
>but it is not done. Any frame makers here to comment?

There's a couple guys who know a _lot_ about metallurgy who I'm sure
can comment!

:-)

[M-gineering]

Michael Press wrote:
> In article
> <1193332196.834434.99760@o80g2000hse.googlegroups.c om>,
> unforgiven99@juno.com wrote:
>
>> On Oct 25, 8:40 am, M-gineering <ikmotgeens...@m-gineering.nl> wrote:
>>> Rik O'Shea wrote:
>>>> Why two top tubes ?
>>>> http://tinyurl.com/37sbwo
>>> two tubes are twice as stiff as a single tube
>>> It's easy to build as you can use the same tubes and lugs (with a bit of
>>> grinding on the seatlugears)
>>>
>>> --
>>> /Marten
>>>
>>> info(apestaartje)m-gineering(punt)nl
>> Well, about 30% stiffer laterally, and way stiffer vertically
>> depending on the geometry. The question is, why double the top tube?
>> The down tube makes much more sense.
>
> And putting gussets on the bottom bracket shell even more sense
> but it is not done. Any frame makers here to comment?
>

Anything makes more sense than a double toptube, until you add the
constraint that you have to use existing parts only. And if it sells:
problem solved

--
/Marten

info(apestaartje)m-gineering(punt)nl

[* * Chas]

"still me" <wheeledBob@yahoo.com> wrote in message
news:sqt1i3db2933ip4larvi0cpqvl6i3tgll0@4ax.com...
> On Thu, 25 Oct 2007 12:10:09 -0700, Michael Press <rubrum@pacbell.net>
> wrote:
>
> >And putting gussets on the bottom bracket shell even more sense
> >but it is not done. Any frame makers here to comment?
>
> There's a couple guys who know a _lot_ about metallurgy who I'm sure
> can comment!
>
> :-)

Not me, no comment.... ;-)

Some of the larger 1 & 3 speed bikes in Japan came with double toptubes
but not many riders were tall enough to need a frame that big.

I believe that these style frames were referred to in the UK and
throughout the Empire as "Policeman's Models".

Chas.

[M-gineering]

Michael Press wrote:

>
> It seems to me that tubes do not fail, typically.
> Joints fail.
> * down tube -- head tube.
> * down tube -- braze on.
> * any tube -- bottom bracket.
> * chain stay -- drop out
> * chain stay -- brake bridge
> * seat stay -- seat tube
>

no tubes, no joints

--
/Marten

info(apestaartje)m-gineering(punt)nl

[Ryan Cousineau]

In article <rubrum-234EF3.23555325102007@newsclstr02.news.prodigy.com>,
Michael Press <rubrum@pacbell.net> wrote:

> In article <ffqoos$gg1$1@cascade.cs.ubc.ca>,
> gillies@cs.ubc.ca (Donald Gillies) wrote:
>
> > Rik O'Shea <rikoshea@yahoo.com> writes:
> >
> > >Why two top tubes ?
> >
> > >http://tinyurl.com/37sbwo
> >
> > On this particular bike, i think it's a mistake, as the frame seems to
> > be a 23" (58.5cm) c-t frame. The top tube is the least-stressed tube
> > on the bicycle, because it's under compression. The downtube is the
> > most-stressed tube.
>
> It seems to me that tubes do not fail, typically.
> Joints fail.
> * down tube -- head tube.
> * down tube -- braze on.
> * any tube -- bottom bracket.
> * chain stay -- drop out
> * chain stay -- brake bridge
> * seat stay -- seat tube

http://www.parktool.com/images_inc/repair_help/frame10.jpg
http://www.sandsmachine.com/p_crash.jpg
http://www.sandsmachine.com/a_swa_r1.htm
http://flickr.com/photos/78941945@N00/696417275/in/photostream/

--
Ryan Cousineau rcousine@sfu.ca http://www.wiredcola.com/
"My scenarios may give the impression I could be an excellent crook.
Not true - I am a talented lawyer." - Sandy in rec.bicycles.racing

[Tom Sherman]

M-gineering aka Marten Gerritsen wrote:
> Michael Press wrote:
>
>>
>> It seems to me that tubes do not fail, typically. Joints fail. * down
>> tube -- head tube.
>> * down tube -- braze on.
>> * any tube -- bottom bracket.
>> * chain stay -- drop out
>> * chain stay -- brake bridge
>> * seat stay -- seat tube
>>
>
> no tubes, no joints
>
Will the latest M-gineering bicycle frame be machined from a single
billet? ;)

--
Tom Sherman - Holstein-Friesland Bovinia
When did ignorance of biology become a "family value"?

[Jon_C]

On Oct 26, 9:16 am, jim beam <spamvor...@bad.example.net> wrote:
> unforgive...@juno.com wrote:
> > On Oct 25, 8:40 am, M-gineering <ikmotgeens...@m-gineering.nl> wrote:
> >> Rik O'Shea wrote:
> >>> Why two top tubes ?
> >>>http://tinyurl.com/37sbwo
> >> two tubes are twice as stiff as a single tube
> >> It's easy to build as you can use the same tubes and lugs (with a bit of
> >> grinding on the seatlugears)
>
> >> --
> >> /Marten
>
> >> info(apestaartje)m-gineering(punt)nl
>
> > Well, about 30% stiffer laterally, and way stiffer vertically
> > depending on the geometry.
>
> 10 points.
>
> > The question is, why double the top tube?
> > The down tube makes much more sense.
>
> a bigger diameter down tube and a triangulating [as opposed to parallel]
> second top tube makes more sense still.

Not really. There's nowhere to triangulate against. If you connected
it half way down the seat tube it'd tend to bend it. I think the idea
is to give more bracing to the headstock so it can resist torquing
from heavy loads on the handlebars.
Down tube is in tension so diameter isn't a factor (no tendency to
bend/buckle). I think fat down tubes are just to resist torque applied
to pedals/bars by rider but won't help with vertical loads from cargo.

[jim beam]

Jon_C wrote:
> On Oct 26, 9:16 am, jim beam <spamvor...@bad.example.net> wrote:
>> unforgive...@juno.com wrote:
>>> On Oct 25, 8:40 am, M-gineering <ikmotgeens...@m-gineering.nl> wrote:
>>>> Rik O'Shea wrote:
>>>>> Why two top tubes ?
>>>>> http://tinyurl.com/37sbwo
>>>> two tubes are twice as stiff as a single tube
>>>> It's easy to build as you can use the same tubes and lugs (with a bit of
>>>> grinding on the seatlugears)
>>>> --
>>>> /Marten
>>>> info(apestaartje)m-gineering(punt)nl
>>> Well, about 30% stiffer laterally, and way stiffer vertically
>>> depending on the geometry.
>> 10 points.
>>
>>> The question is, why double the top tube?
>>> The down tube makes much more sense.
>> a bigger diameter down tube and a triangulating [as opposed to parallel]
>> second top tube makes more sense still.
>
> Not really. There's nowhere to triangulate against.

yes there is - bottom of head tube to top of seat tube. not an issue on
frames for small people i guess, but for those of us with big frames,
it's a real deal.

> If you connected
> it half way down the seat tube it'd tend to bend it. I think the idea
> is to give more bracing to the headstock so it can resist torquing
> from heavy loads on the handlebars.
> Down tube is in tension so diameter isn't a factor (no tendency to
> bend/buckle). I think fat down tubes are just to resist torque

indeed - just like what was suggested as a benefit of a second top tube.

> applied
> to pedals/bars by rider but won't help with vertical loads from cargo.
>

[still me]

On Fri, 26 Oct 2007 22:52:09 -0700, "* * Chas"
<verktygjunk@aol.spamski.com> wrote:

>If more is better then......
>
>http://www.classicrendezvous.com/Rarest/prison_bike.htm
>
>Chas.

Wow... think of all the water bottles you could carry!

[M-gineering]

Tom Sherman wrote:
> M-gineering aka Marten Gerritsen wrote:
>> Michael Press wrote:
>>
>>>
>>> It seems to me that tubes do not fail, typically. Joints fail. *
>>> down tube -- head tube.
>>> * down tube -- braze on.
>>> * any tube -- bottom bracket.
>>> * chain stay -- drop out
>>> * chain stay -- brake bridge
>>> * seat stay -- seat tube
>>>
>>
>> no tubes, no joints
>>
> Will the latest M-gineering bicycle frame be machined from a single
> billet? ;)
>

I think that the failure rate of 11 tubes and a torch is acceptable ;)
And more fun for me than pushing a wheelbarrow to get rid of the
machining swarf!

--
/Marten

info(apestaartje)m-gineering(punt)nl