curved seat stays, why?
~Von
car that was next to me at an intersection. It had seat stays that bowed in
towards the BB. Anyone know the purpose for this? Is it supposed to make
the ride smoother or just for looks. It appears that litespeed does this on
some of their bikes. DOes anyone else?
Pete Biggs
"~Von" <reidr...@yahoo.com> wrote in message
news:OLup6.1170$8O3.1...@dfiatx1-snr1.gtei.net...
I've got "s-bend" seat stays & chain stays on my Dawes cromo frame. Apart
from looking niiiiiiiiiiice, they're aero (I think!).
- Pete Biggs
BB
bumps, I would think. Same thing I would think for the seat stays......
BB
ken...@nojunk.rahul.net-
> I've got "s-bend" seat stays & chain stays on my Dawes cromo frame. Apart
> from looking niiiiiiiiiiice, they're aero (I think!).
Do they improve ankle clearance when pedaling? If so, that could also
reduce your Q-factor, which some riders like. I don't buy the aero
argument since your legs are much bigger than the chainstays.
--
Ken Lee, http://www.rahul.net/kenton/
Dave Chen
news:3AA685BC...@attglobal.net...
> Think straight forks vs. raked forks - raked can soften the compression
> bumps, I would think. Same thing I would think for the seat stays......
>
> BB
Oh boy...here we go....
Straight and raked forks have no discernable differences in
"compression"...so probably same thing for seat stays. Can you say,
"marketing gimmick"?
Dave
Pete Biggs
<ken...@nojunk.rahul.net-> wrote in message
news:9861va$h08$1...@samba.rahul.net...
> Pete Biggs wrote:
> > I've got "s-bend" seat stays & chain stays on my Dawes cromo frame.
Apart
> > from looking niiiiiiiiiiice, they're aero (I think!).
>
> Do they improve ankle clearance when pedaling? If so, that could also
> reduce your Q-factor, which some riders like.
Yes, I understand that is a reason why some bikes incorporate s-bend stays.
> I don't buy the aero
> argument since your legs are much bigger than the chainstays.
I tend to agree but the Dawes catalogue describes the stays as "aero". (The
tubes aren't really squashed, btw). The bike looks v sexy from behind
though!
~PB
Pete Biggs
<ken...@nojunk.rahul.net-> wrote in message
news:9861va$h08$1...@samba.rahul.net...
> > I've got "s-bend" seat stays & chain stays on my Dawes cromo frame.
Apart
> > from looking niiiiiiiiiiice, they're aero (I think!).
>
> Do they improve ankle clearance when pedaling? If so, that could also
I forgot to mention the bike has a triple chainset. The stays do provide
plenty of clearance.
~PB
Frank Krygowski
Digging deep into my memory ... I thought I recalled that decades ago,
there were strict rules against having manufacturer's names on bike in
English racing (which was almost entirely time trialing, IIRC). So, to
make their frames easily identifiable, some manufacturers came up with
weird bends in the tubes. Thus, even if there was no label,
afficianados could look at a photo and say "Hey, he won on a curly-stay
Hetchins" or something similar.
Of course, they probably marketed it based on some other rationale, like
(almost certainly non-existent) shock absorption.
That's a classic Usenet semi-informed guess, BTW. I'd be interested if
anybody can confirm or deny it.
--
Frank Krygowski frkr...@cc.ysu.edu
Peter Hilton
Hi there,
Take a look at:-
http://www.cyclesdeoro.com/Hetchins.htm
Some very beautiful curly-framed machines.
cheers
pete
--
pete hilton
sar...@transmeta.com
(408)-919-6976
Suzy Jackson
They're there specifically to make the bike stand out in the crowd, as
being different. Newer Cannondales also use curved seatstays, for much
the same reason.
Cheers,
Suzy
--
-----------------------------------------------------------
Suzy Jackson http://www.suzyj.net su...@suzyj.net
-----------------------------------------------------------
Joshua_Putnam
>Think straight forks vs. raked forks - raked can soften the compression
>bumps, I would think. Same thing I would think for the seat stays......
As with straight vs. curved fork blades, the difference is
primarily fashion, not function. Curved seat stays, like
straight fork blades, harken back to the days of
pennyfarthings, when the fork blades were straight and the
frame curved gracefully down to the rear hub. But if your
non-suspension bike has any noticeable vertical compliance
in the rear triangle when going over bumps, it's probably
broken.
--
Jo...@WolfeNet.com
"My other bike is a car."
http://www.wolfenet.com/~josh/
Greg R
wrote:
Curved stays allow the rear triangle to flex. Some think that it is a
good idea....imagine that...
G
Pete Biggs
"Peter Hilton" <sar...@transmeta.com> wrote in message
news:yzsae6x...@saruman-linux.transmeta.com...
> Take a look at:-
> http://www.cyclesdeoro.com/Hetchins.htm
> Some very beautiful curly-framed machines.
The bendy stays on my (modern) Dawes ('99 Giro 500) are much more subtle
(and attractive *to me*) -- curved in the horizontal plane only. It never
ceases to amaze me how radical some of the past designs were. More:
http://www.flashq.de/HETCH16.HTM.
~PB
Pete Biggs
"Suzy Jackson" <su...@suzyj.net> wrote in message
news:3AA6A340...@suzyj.net...
> They're there specifically to make the bike stand out in the crowd, as
> being different. Newer Cannondales also use curved seatstays, for much
> the same reason.
Are they steel or al?
~PB
Alex Rodriguez
says...
Fashion, of course.
--
-----------------
Alex __O
_-\<,_
(_)/ (_)
Suzy Jackson
Having never in my life seen a steel Cannondale, I'd hazard a guess at
aluminium.
John Carrier
have slightly more flexibility from the additional length compared to a
straight stay of identical tubing. I don't think this would be remotely
noticeable, even to the pea detecting princess.
Curved chain stays have a function in that they can provide ankle clearance
while still flaring sufficiently to take a 130mm rear axle.
OTOH, minor cosmetic changes have a very real effect on making last year's
bike look so out of date. My favorite is the tube with a decagonal
(10-sided) cross section ... and that is superior to a round tube because???
R / John
"~Von" <reidr...@yahoo.com> wrote in message
news:OLup6.1170$8O3.1...@dfiatx1-snr1.gtei.net...
Jobst Brandt
> Think straight forks vs. raked forks - raked can soften the
> compression bumps, I would think. Same thing I would think for the
> seat stays......
You might think so but it doesn't. You could test this by tying a
string (thin wire) between the fork crown and protruding axle (or QR)
and notice whether you can make it go slack by loading the bars, or
just riding off a curb. It doesn't take a large stroke to cause slack,
slack that won't occur.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
> It appears that litespeed does this on some of their bikes. Does
> anyone else?
Run a string or wire from the axle to the seat lug and load the
saddle. I think you won't find slack occurring even with heavy loads.
Hence, this is a design gimmick like the one that Hetchins did 50
years ago. Were they thin enough to flex perceptibly, the chainstays
would soon break out of the BB. What else is new?
Jobst Brandt <jbr...@hpl.hp.com>
Scott Hendricks
designs don't actually allow for rear wheel movement, because if they did
the
chainstays would break???
>===== Original Message From jbr...@hpl.hp.com (Jobst Brandt) =====
------------------------------------------------------------
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KevinM23
>(10-sided) cross section ... and that is superior to a round tube because???
I'm holding out for the 11-sided tube. Why? It's one better, of course.
-Nigel Tufnel
Rob Mauhar
<jbr...@hpl.hp.com> wrote:
Riding behind a Moots Vamoots YBB (which has seat stays that telescope
freely and no pivots on the chain stays), I saw the seat stays
telescope in and out up to at least 1/2 inch (to my uncalibrated eye)
continually during the 5 hour ride. The chain stays had to be bending
in order for this to happen and, at the end of the ride, they seemed to
be still firmly attached to the BB.
Rob
alex wetmore
news:9861va$h08$1...@samba.rahul.net...
> > I've got "s-bend" seat stays & chain stays on my Dawes cromo frame.
Apart
> > from looking niiiiiiiiiiice, they're aero (I think!).
>
> Do they improve ankle clearance when pedaling? If so, that could also
> reduce your Q-factor, which some riders like. I don't buy the aero
> argument since your legs are much bigger than the chainstays.
Some chainstays are curved in the other direction to provide additional
tire clearance (the chainstays on my Bridgestone XO-1 bow outwards so
that it can fit 2" tires).
This bike still fits Ritchey cranks with a 119mm bottom bracket, giving
me a Q-factor of about 150mm.
alex
Tho X. Bui
Rob Mauhar wrote:
>
> In article <986bd4$kpk$2...@hplms2.hpl.hp.com>, Jobst Brandt
> <jbr...@hpl.hp.com> wrote:
>
> Run a string or wire from the axle to the seat lug and load the
> > saddle. I think you won't find slack occurring even with heavy loads.
> > Hence, this is a design gimmick like the one that Hetchins did 50
> > years ago. Were they thin enough to flex perceptibly, the chainstays
> > would soon break out of the BB. What else is new?
> Riding behind a Moots Vamoots YBB (which has seat stays that telescope
> freely and no pivots on the chain stays), I saw the seat stays
> telescope in and out up to at least 1/2 inch (to my uncalibrated eye)
> continually during the 5 hour ride. The chain stays had to be bending
> in order for this to happen and, at the end of the ride, they seemed to
> be still firmly attached to the BB.
It is a very simple calculation to measure the force required to cause a
1/2 inch compression of a 1/2 diameter, 1/32" thick walled aluminum or
steel tube that's about 18 inch long. You will find that it is very,
very, very high.
Since such seat stays will not compress, the chain stays cannot move
upward. It is false analogy to compare the very high rigidity of a
rigid rear triangle to that of a suspension rear triangle.
Beware the strength of the tetrahedron....
Tho
Tho X. Bui
BB wrote:
>
> Think straight forks vs. raked forks - raked can soften the compression
> bumps, I would think. Same thing I would think for the seat stays......
Neither rake forks nor curved seat stays would absorb shocks or soften bumps.
Tho
G.T.
>
> Rob Mauhar wrote:
> >
> > In article <986bd4$kpk$2...@hplms2.hpl.hp.com>, Jobst Brandt
> > <jbr...@hpl.hp.com> wrote:
> >
> > Run a string or wire from the axle to the seat lug and load the
> > > saddle. I think you won't find slack occurring even with heavy loads.
> > > Hence, this is a design gimmick like the one that Hetchins did 50
> > > years ago. Were they thin enough to flex perceptibly, the chainstays
> > > would soon break out of the BB. What else is new?
>
> > Riding behind a Moots Vamoots YBB (which has seat stays that telescope
> > freely and no pivots on the chain stays), I saw the seat stays
> > telescope in and out up to at least 1/2 inch (to my uncalibrated eye)
> > continually during the 5 hour ride. The chain stays had to be bending
> > in order for this to happen and, at the end of the ride, they seemed to
> > be still firmly attached to the BB.
>
> It is a very simple calculation to measure the force required to cause a
> 1/2 inch compression of a 1/2 diameter, 1/32" thick walled aluminum or
> steel tube that's about 18 inch long. You will find that it is very,
> very, very high.
>
> Since such seat stays will not compress,
What if they bend? Seatstays bend quite a bit under heavy sprinting,
why wouldn't they when hitting a bump?
Greg
John Thompson
>I saw a road frame (appeared to be steel, tho I didn't catch the mfgr) on a
>car that was next to me at an intersection. It had seat stays that bowed in
>towards the BB. Anyone know the purpose for this? Is it supposed to make
>the ride smoother or just for looks. It appears that litespeed does this on
>some of their bikes. DOes anyone else?
I suspect it is merely cosmetic. Basso used to have their stays bow in
toward the brake bridge, which became sort of a signature for their
frames. I think it also allowed them to use the same size brake bridge
for all their frames... :-)
--
-John (John.T...@attglobal.net)
Rob Mauhar
<bl...@prodigy.net> wrote:
You miss the point Tho, Brandt said that if the chainstays are "thin
enough to flex perceptibly, the chainstays would soon break out of the
BB." In this Moots case, with telescoping seat stays and no pivot at
the chainstays, the chainstays are obviously thin enough to flex
(because they do) and do not break out of the BB.
Rob
Jobst Brandt
> Riding behind a Moots Vamoots YBB (which has seat stays that
> telescope freely and no pivots on the chain stays), I saw the seat
> stays telescope in and out up to at least 1/2 inch (to my
> uncalibrated eye) continually during the 5 hour ride. The chain
> stays had to be bending in order for this to happen and, at the end
> of the ride, they seemed to be still firmly attached to the BB.
I haven't seen these but if it hasn't got a hinge, these will break.
A hinge could be a reduced cross section to less than 10mm height.
Even then these things tend to break as was tested by Ritchey on several
frames.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
> What if they bend? Seatstays bend quite a bit under heavy sprinting,
> why wouldn't they when hitting a bump?
On a conventional bicycle the rear triangle (actually a tetrahedron)
does not bend. That is why it can be made of small diamter tubes
because it supports only tension and compression. Please explain what
you believe deforms while sprinting or for that matter riding at all.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
> Are you suggesting that Moots YBB's and other 'pivotless' rear
> suspension designs don't actually allow for rear wheel movement,
> because if they did the chainstays would break???
If it doesn't have a hinge, it will break.
Jobst Brandt <jbr...@hpl.hp.com>
Mark Hickey
Heh heh heh... it would be interesting to see how much weight you'd
have to load on a firmly-braced curved-stay frame to get it to flex
5mm. If you loaded it on the top tube, it would probably bend and/or
tear off the seat tube before the back end flexed 5mm (1/4") (if this
was done on a full bike, the rear tire would have been thoroughly
flattened, and the rim bent beyond repair).
Still, companies advertize it, folks spend big buck for it, and the
folklore grows and grows... unfortunately it won't ever be true, and
those who bought the design for its "compliance" got fleeced - but I
suppose if they don't know that they'll "feel the difference".
So, for those of you who have bikes with curved stays, I was only
kidding. Stop reading now.
For the rest of you, I wasn't kidding - they got fleeced. ;-)
Mark Hickey
Habanero Cycles
www.habcycles.com
Home of the $695 ti frame
G.T.
I have see time lapse photos from behind the bike during a sprint. This
was in the early 80s with typical lightweight steel road frames of the
day. The seatstays clearly bow to the left and right with each pedal
stroke.
Greg
--
"Why does a man with nothing to say, he always seems to talk?" - Marc
Riley
Steve
OTOH, I used to train on an old Turbo trainer where the BB was supported,
not the rear axle. During hard in the saddle sprints I could see the rear
triangle moving laterally perhaps 1/2 to 3/4 inch.
G.T. <eth...@pacificnet.net> wrote in message
news:3AA6EEE5...@pacificnet.net...
Theresa Ell
>
> Theoretically the curved stay is slightly (perhaps 1-2%) longer and could
> have slightly more flexibility from the additional length compared to a
> straight stay of identical tubing. I don't think this would be remotely
> noticeable, even to the pea detecting princess.
>
> Curved chain stays have a function in that they can provide ankle clearance
> while still flaring sufficiently to take a 130mm rear axle.
>
> OTOH, minor cosmetic changes have a very real effect on making last year's
> bike look so out of date. My favorite is the tube with a decagonal
> (10-sided) cross section ... and that is superior to a round tube because???
>
> R / John
> "~Von" <reidr...@yahoo.com> wrote in message
> news:OLup6.1170$8O3.1...@dfiatx1-snr1.gtei.net..
> a
> > car that was next to me at an intersection. It had seat stays that bowed
> in
> > towards the BB. Anyone know the purpose for this? Is it supposed to make
> > the ride smoother or just for looks. It appears that litespeed does this
> on
> > some of their bikes. DOes anyone else?
> >
a sense it artificially lengthens your frame top tube overall. on
off-road bikes this creates a different leverage on the rear suspension
pivot point this all takes into account you have to have your butt on
the seat.
Chris Z. ~The Wheelman~
"Digging deep into my memory ... I thought I recalled that decades ago,
there were strict rules against having manufacturer's names on bike in
English racing (which was almost entirely time trialing, IIRC). So, to
make their frames easily identifiable, some manufacturers came up with
weird bends in the tubes. Thus, even if there was no label, afficianados
could look at a photo and say "Hey, he won on a curly-stay Hetchins" or
something similar."
I heard that story too, many times. I don't think there is any real
purpose to the bent stays either except, as some have pointed out, for
looks or to be distinctive in some way.
However, the chainstays that "flair" outward from the BB to the axle, DO
have a purpose. Thay allow for crankarm clearence needed for shorter
stays and wider (10 (& 9?) speed) axles.
May you have the wind at your back.
And a really low gear for the hills!
Chris
Chris'Z Corner
"The Website for the Common Bicyclist":
http://www.geocities.com/czcorner
Chris Z. ~The Wheelman~
machine on the road. Bar none.
Now THAT is fine craftsmanship!
David Balfoort
distribution? Income distribution, yes. But weight distribution? I
don't think so.
David
G.T.
>
> As I remember those photos, there was alot of flex from the wheels.
> OTOH, I used to train on an old Turbo trainer where the BB was supported,
> not the rear axle. During hard in the saddle sprints I could see the rear
> triangle moving laterally perhaps 1/2 to 3/4 inch.
Yes, but the stays quite clearly bowed to the left, and then bowed to
the right. If they bend left and right, then why couldn't curved stays
ala the Ritchey and Hetchins bend upwards?
Greg
--
See http://www.2fortheroad.net for ugly bikes and stale music.
Chris Z. ~The Wheelman~
"Are you suggesting that Moots YBB's and other 'pivotless' rear
suspension designs don't actually allow for rear wheel movement, because
if they did the
chainstays would break???"
I saw a design like that a couple of weeks ago. I don't remember if it
was a Mott's or not, but I do remember the frame was carbon fiber. Just
why aren't the chainstays pivoted anyway? I would think the carbon fiber
would suffer a lot from fatigue.
Would it have to do with PIS (pedal-induced-suspensioning)? I thought
they fixed that problem by repositioning the pivot...
Stephen D. Cohen
>Scott Hendricks writes:
>
>> Are you suggesting that Moots YBB's and other 'pivotless' rear
>> suspension designs don't actually allow for rear wheel movement,
>> because if they did the chainstays would break???
>
>If it doesn't have a hinge, it will break.
Hmmm... They are Ti frames if that matters. The pictures on
the web page do not show any thin portions for "hinges", so they
appear to be depending on bending in the chain stays. They do have
shock absorbers at the seat bridge to soften the blow.
Didn't Ibis pioneer this concept with their first rear
suspension mountain bike (also in Ti)?
Steve
David L. Johnson
Hetchins, I believe, that had seriously curved seat stays as well as
chainstays. It also had unbelieveable lugwork. Story was at the time that
they were softer, but I'm sure there will be considerable disagreement over
this.
Pretty bikes, though.
--
David L. Johnson
__o | As far as the laws of mathematics refer to reality, they are not
_`\(,_ | certain, and as far as they are certain, they do not refer to
(_)/ (_) | reality. -- Albert Einstein
Tho X. Bui
Rob, I'm not too sure I missed the point. We are discussing frame
flexing and shock absorption on a rigid frame with bent stay. The
comparison of that to a specifically designed suspension frame, even if
it is pivotless, is neither here nor there, IMO. As JBrandt indicated,
the typical rear triangle approximates rigid tetrahedron. It can flex
to some degree left or right because the axle, which forms a leg of the
tetrahedron, is relatively short. However, such lateral flexing from
sprinting is still not proper comparison to the issue at hand, which is
shock absortion from riding over rough road. Such flexing would have
mainly vertical components. It is pretty well established from
measurements that the vertical deflection of a bike frame is too small
to absorb shock.
Typical frame failures that you can see at most shops are around the bb
area, which is highly stressed. It is not uncommon to see fatigue
cracks on the stays (as well as the down tube). It is not really a
stretch to claim that more deflection would result in more failure at
the stays--again, on a typical frame, not one designed specifically to
combat that mode of failure, e.g., the Moots.
Tho
John Carrier
"David Balfoort" <dsba...@library.syr.edu> wrote in message
news:3AA6FBF6...@library.syr.edu...
I think she's talking about a seat tube.
R / John
KevinM23
>a sense it artificially lengthens your frame top tube overall. on
>off-road bikes this creates a different leverage on the rear suspension
>pivot point this all takes into account you have to have your butt on
>the seat.
Huh?
rec.bicycle.alchemy
-Kevin Munday
Jon Isaacs
>was a Mott's or not, but I do remember the frame was carbon fiber. Just
>why aren't the chainstays pivoted anyway? I would think the carbon fiber
>would suffer a lot from fatigue.
I think this design is what MTBers call a Soft Tail as opposed to a Hard Tail
or FS bike.
The idea I think is to avoid using a pivot and all its complex geometry and
rather just allow a small amount of vertical flex into the rear triangle.
There obviously has to be something more than just the chainstay acting as a
spring but I would guess, not having done the calcs, that it would be possible
to design a BB and chainstay that could allow a certain amount of spring
action.
As an added note, Carbon Fiber reinforced composites are very good in fatigue.
Apparently the matrix material may crack but the CF bridges the cranks
preventing their growth.
jon isaacs
Jon Isaacs
>have a purpose. Thay allow for crankarm clearence needed for shorter
>stays and wider (10 (& 9?) speed) axles.
I have one such bike with radically curved chainstays, at the BB they are
parallel and run essentially straight back until they curve towards the hub.
The problem with these is that my feet still hit the axle/RD with narrow cranks
so their main advantage is in limiting the size of tire that can be used. Not
a problem on a 650C bike.
jon isaacs
Joel Solomon
Joel Solomon
Jim Edgar
sco...@tampabay.rr.com wrote on 3/7/01 9:00 PM:
> Hmmm... They are Ti frames if that matters. The pictures on
> the web page do not show any thin portions for "hinges", so they
> appear to be depending on bending in the chain stays. They do have
> shock absorbers at the seat bridge to soften the blow.
>
> Didn't Ibis pioneer this concept with their first rear
> suspension mountain bike (also in Ti)?
No, I believe this was a Moots concept (that is a pivotless design using the
flex of titanium with a spring at the top of the seat stay/seat tube). I
recall some articles that they didn't patent it, which is why several
manufacturers now use it.
The Ibis FS bikes that I've seen were the "Bow-ti", which uses the URT
design of their "Szazbo" with the single pivot replaced by an "X" joint of
titanium. There's also their "Silk Ti" which uses flattened seat stays of
titanium to flex a sprung rear Moot's-type triangle.
There are others like this, (Trek STPro in carbon, for example), but they
are quite different beasts than the type of frame originally described in
this post.
Alex Rodriguez
says...
> Didn't Ibis pioneer this concept with their first rear
>suspension mountain bike (also in Ti)?
I believe you are refering to the Ibis Bow-Ti .
--
-----------------
Alex __O
_-\<,_
(_)/ (_)
Jim Adney
>Digging deep into my memory ... I thought I recalled that decades ago,
>there were strict rules against having manufacturer's names on bike in
>English racing (which was almost entirely time trialing, IIRC). So, to
>make their frames easily identifiable, some manufacturers came up with
>weird bends in the tubes. Thus, even if there was no label,
>afficianados could look at a photo and say "Hey, he won on a curly-stay
>Hetchins" or something similar.
Exactly right, except that I think it was longer ago than that. 40s, I
think. And yes, it was Hetchins who did this first.
Just a way to make their frames recognizable without a maker's name
visible on the frame.
-
-----------------------------------------------
Jim Adney jad...@vwtype3.org
Madison,Wisconsin USA
-----------------------------------------------
Jobst Brandt
>>> What if they bend? Seatstays bend quite a bit under heavy
>>> sprinting, why wouldn't they when hitting a bump?
>> On a conventional bicycle the rear triangle (actually a
>> tetrahedron) does not bend. That is why it can be made of small
>> diameter tubes because it supports only tension and compression.
>> Please explain what you believe deforms while sprinting or for that
>> matter riding at all.
> I have see time lapse photos from behind the bike during a sprint.
> This was in the early 80s with typical lightweight steel road frames
> of the day. The seatstays clearly bow to the left and right with
> each pedal stroke.
It was a long time ago, therefore, irrefutable and what are "time
lapse photos." Do you mean motion pictures, and if so, how did you
determine what was bending? Can you explain what forces might bow
seat stays. I assume this was a standing sprint in which the bicycle
usually moves from side to side. In this mode, torque is applied to
skew the head tube with respect to the seat tube putting the top and
down tubes into torsion and the seat tube into bending near the BB.
The "rear triangle" is still in a tension and compression mode. Where
does your seat stay bend come from?
> "Why does a man with nothing to say, he always seems to talk?"
> - Marc Riley
That's a screwy sentence if ever there was one. Who is Marc Riley?
Jobst Brandt <jbr...@hpl.hp.com>
G.T.
>
> Greg T. who? writes:
>
> >>> What if they bend? Seatstays bend quite a bit under heavy
> >>> sprinting, why wouldn't they when hitting a bump?
>
> >> On a conventional bicycle the rear triangle (actually a
> >> tetrahedron) does not bend. That is why it can be made of small
> >> diameter tubes because it supports only tension and compression.
> >> Please explain what you believe deforms while sprinting or for that
> >> matter riding at all.
>
> > I have see time lapse photos from behind the bike during a sprint.
> > This was in the early 80s with typical lightweight steel road frames
> > of the day. The seatstays clearly bow to the left and right with
> > each pedal stroke.
>
> It was a long time ago, therefore, irrefutable and what are "time
> lapse photos."
Oops, we were talking about time lapse photography at work right before
I sent this. I realized the error shortly after hitting send. 16 years
ago isn't all that long ago.
> Do you mean motion pictures, and if so, how did you
> determine what was bending?
Yes, motion pictures. The seatstays clearly weren't straight, they were
bent left and right.
> Can you explain what forces might bow
> seat stays. I assume this was a standing sprint in which the bicycle
> usually moves from side to side. In this mode, torque is applied to
> skew the head tube with respect to the seat tube putting the top and
> down tubes into torsion and the seat tube into bending near the BB.
If the seat tube is bending why wouldn't the seatsay bend?
> The "rear triangle" is still in a tension and compression mode. Where
> does your seat stay bend come from?
>
> > "Why does a man with nothing to say, he always seems to talk?"
> > - Marc Riley
>
> That's a screwy sentence if ever there was one. Who is Marc Riley?
>
A crazy Brit from Manchester. It's a lyric, mostly applicable to Tom
Kunich's posts.
Greg
Jobst Brandt
>> Do you mean motion pictures, and if so, how did you determine what
>> was bending?
> Yes, motion pictures. The seatstays clearly weren't straight, they
> were bent left and right.
Again, how can you see this when the whole frame of reference is
moving laterally as it does in standing sprinting? Are you saying you
could sight down the normally straight seat stays (and I don't know
how you could do this) and see that they were curving under load?
>> Can you explain what forces might bow seat stays. I assume this
>> was a standing sprint in which the bicycle usually moves from side
>> to side. In this mode, torque is applied to skew the head tube
>> with respect to the seat tube putting the top and down tubes into
>> torsion and the seat tube into bending near the BB.
> If the seat tube is bending why wouldn't the seatstay bend?
The seat tube does not bend sufficiently to be visibly bent,
especially because it is a large diameter tube to resist bending, in
contrast to seat and chainstays. The seat tube receives a
considerable bending load at the BB and that is why it is large
diameter and why steel frames have traditionally failed there at
times. Again, what forces do you believe could cause what you think
you saw and how did you determine that the tubes were curving?
Jobst Brandt <jbr...@hpl.hp.com>
Pete Biggs
"Jobst Brandt" <jbr...@hpl.hp.com> wrote in message
news:988dqe$ldg$2...@hplms2.hpl.hp.com...
> > "Why does a man with nothing to say, he always seems to talk?"
> > - Marc Riley
>
> That's a screwy sentence if ever there was one. Who is Marc Riley?
Otherwise known as "Lard", he was in The Fall and now is a co-presenter on
BBC Radio One.
~PB
www.topica.com/lists/cycle-hware
www.topica.com/lists/chw-news
sar...@transmeta.com
What a great site ... so why doesn't the US site have all this
great documentation?
cheers
pete
--
pete hilton
sar...@transmeta.com
(408)-919-6976
sar...@transmeta.com
Whoops ... right response, wrong article!
I was commenting about the European Shimano site
http://shimano-europe.com/cycling
which has pdf files of exploded diagrams/maintenance instructions
for lots of their products ... information that I cannot find on
the USA Shimano site
G.T.
>
> Greg T. who? writes:
>
> >> Do you mean motion pictures, and if so, how did you determine what
> >> was bending?
>
> > Yes, motion pictures. The seatstays clearly weren't straight, they
> > were bent left and right.
>
> Again, how can you see this when the whole frame of reference is
> moving laterally as it does in standing sprinting? Are you saying you
> could sight down the normally straight seat stays (and I don't know
> how you could do this) and see that they were curving under load?
>
How difficult is it to see a significant bend in a straight line? The
photos were taken from directly behind the bike, the seatsays very
obviously bowed to the left and right.
Greg T. who?
--
See http://www.2fortheroad.net for ugly bikes and stale music.
Mark Hickey
>A curved seat stay puts your wieght further back over the rear tire in
>a sense it artificially lengthens your frame top tube overall. on
>off-road bikes this creates a different leverage on the rear suspension
>pivot point this all takes into account you have to have your butt on
>the seat.
I think you misunderstand the fixed and variable bits here...
Picture two bikes, one with straight seat stays and one with curved
seat stays. Imagine both top and bottom are in exactly the same place
relative to the dropouts and seat tube (and in the real world, this is
the case). No difference in weight distribution.
The only thing that will change the weight distribution over the rear
tire is the saddle to rear axle relationship - entirely determined by
the horizontal relationship between the bottom bracket and rear axle
(since your saddle is s'pozed to be in only the "perfect" relationship
to the bottom bracket, no matter how tortured the method of getting it
there happens to be).
Mark Hickey
Habanero Cycles
www.habcycles.com
Home of the $695 ti frame
Mark Hickey
>Jobst Brandt wrote:
>>
>> G.T. writes:
>>
>> > What if they bend? Seatstays bend quite a bit under heavy sprinting,
>> > why wouldn't they when hitting a bump?
>>
>> On a conventional bicycle the rear triangle (actually a tetrahedron)
>> does not bend. That is why it can be made of small diamter tubes
>> because it supports only tension and compression. Please explain what
>> you believe deforms while sprinting or for that matter riding at all.
>>
>
>I have see time lapse photos from behind the bike during a sprint. This
>was in the early 80s with typical lightweight steel road frames of the
>day. The seatstays clearly bow to the left and right with each pedal
>stroke.
Jobst was talking about compression of the seat stays (i.e. the
mythical vertical compliance). In this, he is virtually correct
(there ain't none). Sure, lateral movement is possible (determined by
the beefiness of the stays and the dropouts, and the dropout-to-axle
interface to a degree), but that doesn't do beans for ride quality
(the original assumption as to the reasons for curved seat stays).
Just TRY to compress ANY rear triangle vertically. If you can do it,
I won't disagree with you (but only because you're strong enough to
tie a gorilla in a knot).
G.T.
I completely and thoroughly understand that the stays don't compress.
But how do you know they don't bow outward or inward or forward or
backward? The Jobsts and the Thos never address this.
Tho X. Bui
Don't know about the other Thos, but this Tho did mention on a previous
post that lateral flexing of the rear triangle is at least theoretically
possible because the axle is a shortest arm of the tetrahedron. This
Tho also added that this has nuthing to do with shock absorbtion in
riding, because shock absorption implies vertical deflection and not
lateral--unless you have a very strange riding technique.
Tho (one of many).
ERust3
There are certain people I trust, as a given, on this newsgroup. Jobst, you
were one of them. The assumption that a pivot is needed to have travel is
absurd, and you know it as well as I do. Granted, the tubes might break after
time, a lot of time. Come on, lets be fair.
Ed
Qui si parla Campagnolo
were one of them. The assumption that a pivot is needed to have travel is
absurd, and you know it as well as I do. >>
Doubt Jobst has even seen a YBB-let alone ride one or talk to MOOTS to see if
any have broken-
Peter Chisholm
"Vecchio's" Bicicletteria
1833 Pearl ST.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
G.T.
But you're still not addressing my question. On, say, a Hetchins can
the seatstays bow forward and downward as the axle is forced upwards?
Greg
Chris Breen
joni...@aol.com (Jon Isaacs) wrote:
>>I saw a design like that a couple of weeks ago. I don't remember if it
>>was a Mott's or not, but I do remember the frame was carbon fiber. Just
>>why aren't the chainstays pivoted anyway? I would think the carbon fiber
>>would suffer a lot from fatigue.
>
>I think this design is what MTBers call a Soft Tail as opposed to a Hard Tail
>or FS bike.
>
>The idea I think is to avoid using a pivot and all its complex geometry and
>rather just allow a small amount of vertical flex into the rear triangle.
>There obviously has to be something more than just the chainstay acting as a
>spring but I would guess, not having done the calcs, that it would be possible
>to design a BB and chainstay that could allow a certain amount of spring
>action.
>jon isaacs
Litespeed also makes one,
http://www.litespeed.com/html/off_road/tsali_img/tsali_frame_close.jpg
--
Chris Breen
Matt Bushore
>
> << . Jobst, you
> were one of them. The assumption that a pivot is needed to have travel is
> absurd, and you know it as well as I do. >>
>
> Doubt Jobst has even seen a YBB-let alone ride one or talk to MOOTS to see if
> any have broken-
I never saw a broken YBB either them I went to Moots. Probably not a
scientific sample I realize. I'd also never heard one mentioned, which
leads me
to think it's pretty rare.
I have a frame that broke on the underside of the drive side chainstay.
The crack started on the bottom, and worked it's way towards the top.
The implication
from the geometry was that the bottoms of the chainstays were under
stress, as if
they were bending upwards under load.
No material defects in the stay. No scratches or cuts. Just the crimp
for
chainring clearance. I'm fairly certain the crimp was the problem, but
still, I'd
think the stays had to have been deforming under load.
How probable is my hypothesis? If it's unprobably, what are other
possible
explanations for the crack location and geometry?
I figured it was marginally related to bent stays since the frame is a
bit
unconventional.
http://www.monty.es/hidra.html (I didn't realize a picutre could be
that fuzzy. yikes!)
Jay Beattie
G.T. wrote in message
<3AA8FA2A...@pacificnet.net>...
No, unless you own the very rare Eames leatherette
Hetchins made in the early '50s. -- Jay Beattie.
Jobst Brandt
>> Again, how can you see this when the whole frame of reference is
>> moving laterally as it does in standing sprinting? Are you saying
>> you could sight down the normally straight seat stays (and I don't
>> know how you could do this) and see that they were curving under
>> load?
> How difficult is it to see a significant bend in a straight line?
More difficult than you think.
> The photos were taken from directly behind the bike, the seatstays
> very obviously bowed to the left and right.
OK. Take a steel tube 3/4 inch in diameter and see how far you can
bend it without it taking a set. You'll see that as you get visible
deflection, the tube will remain bent. The way you describe what you
saw, the bicycle is made of plastic tubing. Steel, in cross sections
the size of frame tubes, does not deflect visibly from a straight line
without yielding. This is more evident if you stand next to a bicycle
and press inward on the downward pedal. The pedal deflects noticeably
but you cannot see any curved tubes as a result, not even if you hold
a straight edge against them... and you say you saw tubes curving
elastically.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
You have an odd way of presenting your perception of frame
deflections. The preamble takes on a message of its own. How about
saying what it is you believe about frame tube flexing and how large
it is? You'll notice that conventional chainstays are largest in
diameter at the BB and become more slender toward the dropout, a
typical design for an element that is to resist bending at its root.
So let's be fair and get to the facts, not the implications and
allusions.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
>> Jobst, you were one of them. The assumption that a pivot is needed
>> to have travel is absurd, and you know it as well as I do.
I didn't say a pivot but rather a hinge. A hinge can be a flexure
that is designed to operate in the elastic range of the material, like
the top tube to seat tube of a Slingshot bicycle. THe MOOTS frame
pictures on their web page gloss over what the seat stay thickness at
the BB is but it seems they are a lot thinner than conventional frams
have.
> Doubt Jobst has even seen a YBB-let alone ride one or talk to MOOTS
> to see if any have broken.
That's hard to say. Manufacturers seldom reveal such information,
usually only word of mouth from users reveals this in an imprecise
way. I guess we'll have to wait and see. I am aware of tests with
other frame that caused failures with this approach.
The claim:
"It will mercilessly savage any other
bike on the market, suspension or no,
when it comes to climbing."
Sounds like a lot of puff to me.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
> But you're still not addressing my question. On, say, a Hetchins
> can the seatstays bow forward and downward as the axle is forced
> upwards?
No. Not to any effect. You'll notice that no spring design uses this
layout because it is inherently unstable in the event of actual
deflection because it is in its most rigid position when straightest
and is progressively more compressible if any deflection occurs. An
analogy is coming up behind someone and pushing his knees forward as
he stands by pushing your knees into his. The buckling effect is
sudden. Column buckling typically follows this mode of failure.
Easily overlooked is that, chain tension is the greatest load on the
chainstays and that it occurs when climbing or sprinting. It is
greater than any suspension loads and, applied statically, can be
observed to cause effectively zero deflection. Chain tension is
easily 3X pedal pressure with small chainwheels, pedal force being as
much as 300 lbs combining force from both pedals. I take that from
having ridden up Filbert St in San Francisco at 33% grade in a 47-21
gear on a road bicycle. With my weight it takes that much force just
to stand still on a 33% grade.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
>> The idea I think is to avoid using a pivot and all its complex
>> geometry and rather just allow a small amount of vertical flex into
>> the rear triangle. There obviously has to be something more than
>> just the chainstay acting as a spring but I would guess, not having
>> done the calcs, that it would be possible to design a BB and
>> chainstay that could allow a certain amount of spring action.
Flexures are used in many applications where bearing slop and
compliance are not acceptable ot the environment precludes moving
joints. However, in such applications, the hinge is designed as a
localized flexing element that has spring like characteristics, not
tubing, that is classically designed to give greatest rigidity for its
weight.
> Litespeed also makes one,
> http://www.litespeed.com/html/off_road/tsali_img/tsali_frame_close.jpg
This web site typifies the failure prone design of using constant
diameter tubing as a flexing element. Because bending moment is
highest at the root of the tube, which is also the weakest point from
having been welded, this is a bad design that is being copied by many
builders. Durable flexures have been in use for a long time and this
is an obvious application for them, but it's not happening yet.
You'll notice that all these frames have tiny stroke in the "spring"
element. Certainly not something that one might call effective
suspension.
Jobst Brandt <jbr...@hpl.hp.com>
Ron
since '93, and I've had one since '94. Her's broke at the top of the
seat tube. A horizontal crack that ran from the stress relief hole at
the bottom of the split tube in the seatpost clamping area. That area
was beefed up on later models.
Kent (the builder) fixed it and claimed at the time to have not had
any failures in the chainstays.
Ron
----------------------------------
remove "nospam" to reply directly
Jay Beattie
Jobst Brandt wrote in message
<98b267$7co$1...@hplms2.hpl.hp.com>...
Idiot question: when you press down on the pedal
and noticeably deflect the bottom bracket on a
long-wheelbase, limber steel frame, what is
flexing?-- Jay Beattie.
Jobst Brandt
> My wife broke her Moots!...but not at the chainstay. She's had a YBB
> since '93, and I've had one since '94. Her's broke at the top of the
> seat tube. A horizontal crack that ran from the stress relief hole at
> the bottom of the split tube in the seatpost clamping area. That area
> was beefed up on later models.
What is the travel of this suspension, measured at the shock absorber?
Jobst Brandt <jbr...@hpl.hp.com>
G.T.
Approx 1".
Greg
Ron
Jobst:
When our bikes were made they claimed 1 1/8 inches of travel. There
is steel coil spring and elastomer mounted above the wishbone seat
stays. I have not measured the travel personally.
Their website www.moots.com now claims 1 inch of "rear wheel travel"
and has an air shock instead of the spring/elastomer.
The frame has a lifetime warranty. (so called "superlight" models
with thinner tubing have a 5 year warranty.) The YBB has been in
production since 1987.
Ron
----------------------------------
Chris Z. ~The Wheelman~
was, was "suspended" in a way, There was a shock absorber at the point
where the seat stays would attach to the seat cluster. It looked like it
was capable of about 2"of travel.
The concept, to me, looked like a sound one. Any movement of the rear
wheel would tend to be vertical, so it would make sense to place the
direction of suspension in line with that movement.
Also, since a vertical direction is more perpendicular to the direction
of pedaling force, I would think that said force would have less effect
on the suspension.
It would be lighter too, simply because the whole set up is less
complex. Give it a longer movement of the shock, and a pivot at the BB
cluster to allow for the greater movement, and it looks like it would
make for a nice FS design.
But then, I'm no engineer...
May you have the wind at your back.
And a really low gear for the hills!
Chris
Chris'Z Corner
"The Website for the Common Bicyclist":
http://www.geocities.com/czcorner
Eric Salathe
> Idiot question: when you press down on the pedal
> and noticeably deflect the bottom bracket on a
> long-wheelbase, limber steel frame, what is
> flexing?-- Jay Beattie.
Depending on what your are doing, probably the tires. That's what
happens in the bike against the wall trick.
Eric Salathe
Eric Salathe
> How difficult is it to see a significant bend in a straight line?
Impossible in something that is moving. That's the old grammar school
pencil trick. Hold a pencil by the end and wiggle it; it certainly
looks bent to me.
The only way to cause deflections in a bike frame (due to elastic
deformation) is to amplify a small deformation across a long
distance. So a small torsional deflection in the downtube can move the
FD so you get chain-rub when standing.
But, the standard trick of leaning your buddies new bike with saddle
against the wall and pushing on the pedal so that it deflects
horrifyingly is just an optical illusion. Small tire deflections are
amplified to a large displacement of the crank, even though there is
no flexation in the frame.
Eric Salathe
G.T.
>
> G.T. <eth...@pacificnet.net> wrote:
> > How difficult is it to see a significant bend in a straight line?
>
> Impossible in something that is moving.
It's not moving. It's a photo.
Greg
Jobst Brandt
> Their website www.moots.com now claims 1 inch of "rear wheel travel"
> and has an air shock instead of the spring/elastomer.
That comes out to be less than 2 degrees of bending in the chainstay,
something that may last a while but not ideally because that still
stresses a tube of that diameter fairly high. An air shock is also a
flaky device for this application because it can leak down and has no
center position. Suspension normally at the top of the stroke is
about as bad as at the bottom of the stroke. Besides, depending on
the weight of the rider and position, where does this one inch reside?
I suspect it is harder than a rock so it doesn't much matter.
> The frame has a lifetime warranty. (so called "superlight" models
> with thinner tubing have a 5 year warranty.) The YBB has been in
> production since 1987.
So have a lot of oddball devices. They take a while to die, like the
Two-wheel drive bicycles:
http://www.spicercycles.com/2wd.html
and Slingshot:
http://www.slingshotbikes.com/
and many more.
We've heard people give the facts about these products that strongly
contrast to the clains in the literature... and they're still here.
Even Alenax, one of the wackiest mechanisms with real CVT is still
hovering in the wings:
http://www.trbsystems.com/media&press/newsrelease.html
Just because it was in print somewhere doesn't make it a fact and just
because someone sells such devices doesn't mean they are worthwhile or
reliable. Not everyone puts these things to the test, in fact few
people do.
Jobst Brandt <jbr...@hpl.hp.com>
Ron
>Ron ? writes:
My full name is right there in my address. What more were you looking
for?
>
>I suspect it is harder than a rock so it doesn't much matter.
What does this mean? If you mean the suspension is as hard as a rock,
no, it's less hard than a rock.
>
>So have a lot of oddball devices. They take a while to die, like the
>Two-wheel drive bicycles:
>http://www.spicercycles.com/2wd.html
>and Slingshot:
>http://www.slingshotbikes.com/
>and many more.
>We've heard people give the facts about these products that strongly
>contrast to the clains in the literature... and they're still here.
>
>Even Alenax, one of the wackiest mechanisms with real CVT is still
>hovering in the wings:
>
>http://www.trbsystems.com/media&press/newsrelease.html
>
>Just because it was in print somewhere doesn't make it a fact and just
>because someone sells such devices doesn't mean they are worthwhile or
>reliable.
I never said it was a fact. I said I was quoting from the web site
and brochure. I also didn't say they were reliable or worthwhile. I
said mine didn't break at the chainstay and I answered your question
regarding (claimed) suspension travel.
> Not everyone puts these things to the test, in fact few
>people do.
No doubt.
Ron
Jobst Brandt
Greg T. ? writes:
>>> How difficult is it to see a significant bend in a straight line?
>> Impossible in something that is moving.
> It's not moving. It's a photo.
Make up your mind, is it time lapse motion pictures or still shots.
You keep changing the parameters and "it was 16 years ago" covers a
lot of ground. You said you could see it swing from side to side.
That doesn't sound like sitll shots.
# I have see time lapse photos from behind the bike during a sprint.
# This was in the early 80s with typical lightweight steel road frames
# of the day. The seatstays clearly bow to the left and right with
# each pedal stroke.
You still haven't explained what would make seat stays visibly bend
and how you could see that they were curved without sighting down them
lengthwise. You must realize that as you pursue this line with no
credible explanation, you are painting yourself into the incredible
corner.
Jobst Brandt <jbr...@hpl.hp.com>
Eric Salathe
A) I thought it was a movie, not a photo.
2) If it is a photo, what is the exposure rate? What effect does lens
aberation have on perceived lines?
This is no way to ascertain whether there is any flexation.
Eric Salathe
Jon Isaacs
>It would be lighter too, simply because the whole set up is less
>complex. Give it a longer movement of the shock, and a pivot at the BB
>cluster to allow for the greater movement, and it looks like it would
>make for a nice FS design.
>But then, I'm no engineer...
I think one of Jobsts points is that a tube is a poor design for a flexure, a
tube is optimal in stiffness and strength but in this design this is not what
is optimal. That combined with the fact that the highest moments occur at the
point where the chainstay joins the BB is foreboding.
As with all designs this is a compromise so with appropriate measures it is
probably workable, though fatigue may be a problem.
It would be interesting to know how the chainstays are designed and where the
bending occurs.
jon isaacs
Ron
slingshot bicycles mentions a 2 year warranty. Offering a lifetime
warranty doesn't mean the product is good, or that it won't break, or
that most riders will ride enough to test it's limits. "Lifetime"
still seems more confident than "2 year" or "no apparent warranty".
Maybe it's just a calculated risk on their part to sell more bikes.
Ron
On 9 Mar 2001 23:59:04 GMT, jbr...@hpl.hp.com (Jobst Brandt) wrote:
>
>> The frame has a lifetime warranty. (so called "superlight" models
>> with thinner tubing have a 5 year warranty.) The YBB has been in
>> production since 1987.
>
>So have a lot of oddball devices. They take a while to die, like the
>Two-wheel drive bicycles:
>http://www.spicercycles.com/2wd.html
>and Slingshot:
>http://www.slingshotbikes.com/
>and many more.
>
>
>
G.T.
>
> G.T. writes:
>
> Greg T. ? writes:
>
> >>> How difficult is it to see a significant bend in a straight line?
>
> >> Impossible in something that is moving.
>
> > It's not moving. It's a photo.
>
> Make up your mind, is it time lapse motion pictures or still shots.
> You keep changing the parameters and "it was 16 years ago" covers a
> lot of ground. You said you could see it swing from side to side.
> That doesn't sound like sitll shots.
>
There was a sequence of 6 still shots. I didn't say I saw them "swing
side to side". The photos were pre-sprint, 4 during the sprint, and one
after.
> # I have see time lapse photos from behind the bike during a sprint.
> # This was in the early 80s with typical lightweight steel road frames
> # of the day. The seatstays clearly bow to the left and right with
> # each pedal stroke.
>
> You still haven't explained what would make seat stays visibly bend
> and how you could see that they were curved without sighting down them
> lengthwise. You must realize that as you pursue this line with no
> credible explanation, you are painting yourself into the incredible
> corner.
>
You state that the seat tube unnoticeably bends during sprinting, it
doesn't take a stretch of the mind to consider that the smaller diameter
seatstays could bend noticeably from the same twisting of the frame.
Greg
Jobst Brandt
> It would be interesting to know how the chainstays are designed and where the
> bending occurs.
In the picture they are uniform diameter so all bending takes place
at the BB attachment, the bending moment being greatest there. That's
pretty simple for the Lightspeed and the Moots that look very much
alike.
Jobst Brandt <jbr...@hpl.hp.com>
John Miller
news:98brej$p6i$2...@hplms2.hpl.hp.com...
> Make up your mind, is it time lapse motion pictures or still shots.
> You keep changing the parameters and "it was 16 years ago" covers a
> lot of ground. You said you could see it swing from side to side.
> That doesn't sound like sitll shots.
Time-lapse motion picture *are* still shots, Jobst. It's just that they're
in a sequence. By definition, time between shots can vary between
milliseconds and minutes.
--
John Miller, who made his living behind the camera before he made it in
front of it.
Jobst Brandt
>> You still haven't explained what would make seat stays visibly bend
>> and how you could see that they were curved without sighting down
>> them lengthwise. You must realize that as you pursue this line
>> with no credible explanation, you are painting yourself into the
>> incredible corner.
> You state that the seat tube unnoticeably bends during sprinting, it
> doesn't take a stretch of the mind to consider that the smaller
> diameter seatstays could bend noticeably from the same twisting of
> the frame.
If you had spread rear dropouts from 120 to 135mm you would know that
this is preposterous, You can't even see the bend when you cold set
the frame unless you look lengthwise down the tube. Not only that,
but you can't see the misalignment between the seat stay from seat
tube to brake bridge and from brake bridge to dropout, that is now no
longer a straight line.
The paint in your corner is closing in. I don't believe it!
So how come you don't know how to automatically append a Sig to your
messages? It's easy and gets ride of anonymity that may be in order
for your tall tales.
Jobst Brandt <jbr...@hpl.hp.com>
Tom Nakashima
G.T.
>
> Greg T. ? writes:
>
> >> You still haven't explained what would make seat stays visibly bend
> >> and how you could see that they were curved without sighting down
> >> them lengthwise. You must realize that as you pursue this line
> >> with no credible explanation, you are painting yourself into the
> >> incredible corner.
>
> > You state that the seat tube unnoticeably bends during sprinting, it
> > doesn't take a stretch of the mind to consider that the smaller
> > diameter seatstays could bend noticeably from the same twisting of
> > the frame.
>
> If you had spread rear dropouts from 120 to 135mm you would know that
> this is preposterous, You can't even see the bend when you cold set
> the frame unless you look lengthwise down the tube. Not only that,
> but you can't see the misalignment between the seat stay from seat
> tube to brake bridge and from brake bridge to dropout, that is now no
> longer a straight line.
>
> The paint in your corner is closing in. I don't believe it!
>
I'm just raising issues from all perspectives. I find that engineers
quite often look at a problem from only one perspective. With all the
questions I've asked you've pretty much convinced me that my memory has
failed me.
> So how come you don't know how to automatically append a Sig to your
> messages? It's easy and gets ride of anonymity that may be in order
> for your tall tales.
>
Making fun of me for not always providing my sig? That's pretty low and
considering that I know how to automatically append my sig it's quite
inappropriate!
Greg "with sig" T. who?
--
See http://www.2fortheroad.net for ugly bikes and stale music.
"Why does a man with nothing to say, he always seems to talk?" - Marc
Riley
Tim McNamara
"~Von" <reidr...@yahoo.com> wrote:
> I saw a road frame (appeared to be steel, tho I didn't catch the mfgr) on a
> car that was next to me at an intersection. It had seat stays that bowed in
> towards the BB. Anyone know the purpose for this? Is it supposed to make
> the ride smoother or just for looks. It appears that litespeed does this on
> some of their bikes. DOes anyone else?
Lots of bike makers. Lightspeed and Ritchey, for examples in titanium
and steel respectively. Bianchi, Cannondale and lots of makers using fat
aluminum tubes.
It's comsetic and does nothing in terms of stiffness or flexibility, ride
quality etc. Don't believe the hype. Just read the reviews: one
reviwer proclaims that the bends make the bike "more compliant" and
another that the bends make the bike "stiffer." These are mutually
exclusive qualities and they are illusory, anyway.
On aluminum frames with fat chainstays and seatstays it may help with
clearance issues- making room for chainrings, hee;s and tires without
crimping tubes.
Tim McNamara
Rob Mauhar <bu...@san.rr.com> wrote:
> Riding behind a Moots Vamoots YBB (which has seat stays that telescope
> freely and no pivots on the chain stays), I saw the seat stays
> telescope in and out up to at least 1/2 inch (to my uncalibrated eye)
> continually during the 5 hour ride. The chain stays had to be bending
> in order for this to happen and, at the end of the ride, they seemed to
> be still firmly attached to the BB.
The Moots has a shock absorber built into the seatstays, which eliminates
the triangulation in regards to vertical loading of the frame. The
chainstays *will* break eventually from this flexing, even though
titanium has good fatigue characteristics.
Tim McNamara
"G.T." <eth...@pacificnet.net> wrote:
> "Tho X. Bui" wrote:
> > Since such seat stays will not compress,
>
> What if they bend? Seatstays bend quite a bit under heavy sprinting,
> why wouldn't they when hitting a bump?
They do? You have measured this?
Tim McNamara
"G.T." <eth...@pacificnet.net> wrote:
> You state that the seat tube unnoticeably bends during sprinting, it
> doesn't take a stretch of the mind to consider that the smaller diameter
> seatstays could bend noticeably from the same twisting of the frame.
I've been able to make the rear triangle appear to flex slightly, by
holding the bike upright by the saddle and handlebars and shoving against
the crank arm at the BB axle bolt with my foot. I can move the BB
sideways about an inch without too much difficulty. Problem is that it's
hard to tell *what* is flexing without careful measurements.
Theresa Ell
>
> Theresa Ell <t....@cableregina.com> wrote:
>
> >A curved seat stay puts your wieght further back over the rear tire in
> >a sense it artificially lengthens your frame top tube overall. on
> >off-road bikes this creates a different leverage on the rear suspension
> >pivot point this all takes into account you have to have your butt on
> >the seat.
>
> I think you misunderstand the fixed and variable bits here...
>
> Picture two bikes, one with straight seat stays and one with curved
> seat stays. Imagine both top and bottom are in exactly the same place
> relative to the dropouts and seat tube (and in the real world, this is
> the case). No difference in weight distribution.
>
> The only thing that will change the weight distribution over the rear
> tire is the saddle to rear axle relationship - entirely determined by
> the horizontal relationship between the bottom bracket and rear axle
> (since your saddle is s'pozed to be in only the "perfect" relationship
> to the bottom bracket, no matter how tortured the method of getting it
> there happens to be).
>
> Mark Hickey
> Habanero Cycles
> www.habcycles.com
> Home of the $695 ti frameYes a misunderstanding what I ment to say was if I look at my CCM Legacy
it clearly has different shape of seat stays than those of my Bianchi 10
speed and the shape has a great deal to do with how physical forces are
applied in the design.
Qui si parla Campagnolo
bike on the market, suspension or no,
when it comes to climbing."
Sounds like a lot of puff to me. >>
Me too-I'll bet tho, that the really nice people at Moots would love to talk to
you about the whys and where-fors of their design.
Peter Chisholm
"Vecchio's" Bicicletteria
1833 Pearl ST.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com