Objective effects of bike on performance [Archive]

John Forrest Tomlinson

01-04-1970, 11:33 AM

Lou Holtman

01-04-1970, 11:33 AM

"Lou D'Amelio" <ldamelio@patmedia.net> wrote in message
news:9852ccad-3989-4a82-bfa3-b7ee4a14b14b@m45g2000hsb.googlegroups.com...
> Hi - looking for group thoughts on objective effects of equipment
> choices in road racing. I'm a 45+ mid-pack masters racer. Given my
> work/life situation, let's say for the sake of discussion that my
> fitness and weight are optimized. I'm train and race on an 17.5 - 18
> lb, subjectively somewhat flexible road bike (titanium). My fit and
> comfort are good, riding a 1500 g mid-profile wheelset (Campy Eurus).
> Other than maybe 150 grams in stem/brakeset, no rational place to lose
> weight with components without going 'stupid-light.' Most of my races
> are flat to moderately hilly and in the 25 -60 mile range. How much
> objective performance am I giving up by foregoing a current
> generation 14 lb super-stiff carbon uber-bike ? For a comparator,
> lets say we're looking at things like a Cervelo Soloist carbon, which
> would be about 3 lb lighter and somewhat stiffer and more aero than my
> current ride (2001 Litespeed Tuscany) Thanks in advance for any
> replies. Anyone heading down the 'it's the rider, not the bike' road,
> I already acknowledge that - hold the flames.
>
> TIA for replies...............Lou D'Amelio

Anything more aero.

Lou

landotter

01-04-1970, 11:33 AM

On Jun 6, 5:37 am, "Lou D'Amelio" <ldame...@patmedia.net> wrote:
> Hi - looking for group thoughts on objective effects of equipment
> choices in road racing.

One of the underappreciated places to invest a bit of attention
according to a few veteran posters on r.b.t that I respect is your
pedal/shoe system. You might be quite happy with the status quo--but
it's a place where adding efficiency and shaving a hundred grams is
fairly inexpensive relatively speaking compared to purchasing a new
carbon frame. Worth a think, anyway.

dustoyevsky@mac.com

01-04-1970, 11:33 AM

On Jun 6, 5:37*am, "Lou D'Amelio" <ldame...@patmedia.net> wrote:
> Hi - looking for group thoughts on objective effects of equipment
> choices in road racing. I'm a 45+ mid-pack masters racer. Given my
> work/life situation, let's say for the sake of discussion that my
> fitness and weight are optimized. I'm train and race on an 17.5 - 18
> lb, subjectively somewhat flexible road bike (titanium). My fit and
> comfort are good, riding a 1500 g mid-profile wheelset (Campy Eurus).
> Other than maybe 150 grams in stem/brakeset, no rational place to lose
> weight with components without going 'stupid-light.' Most of my races
> are flat to moderately hilly and in the 25 -60 mile range. How much
> objective performance am I giving up by foregoing a current
> generation *14 lb super-stiff carbon uber-bike ? For a comparator,
> lets say we're looking at things like a Cervelo Soloist carbon, which
> would be about 3 lb lighter and somewhat stiffer and more aero than my
> current ride (2001 Litespeed Tuscany) Thanks in advance for any
> replies. Anyone heading down the 'it's the rider, not the bike' road,
> I already acknowledge that - hold the flames.

Somewhat flexible is good for people older than 17. Little-if-any
energy is lost and (within reason) "spring" is better for bumpy
corners, etc.

Somewhere, maybe you can still read the Davis Phinney piece where he
talked about his favorite bike, the one he won at least one of his TdF
stages on. "Springy". Davis raced here (Austin area) in the old Tour
of Texas series (1980's); we all wish we could ride our bikes as well
as he did, FWIW/IMHO, and that's aside from the finishing sprint (ka-
ching).

Not flaming to suggest that, aero wheels aside, a real performance
improvement is available via losing that "last x (or xx <g>) pounds",
and getting real strict about what comprises the food/beverage intake,
optimizing sleep patterns, etc. The guys who are beating you, that's
probably their real advantage.

(more IMHO): Nuttin' wrong with a fancy new bike as long as it fits
the same as what you like, and you weigh it on the same scale on the
same day as your old reliable, which is a mighty fine bike. I have an
old Catalyst, which I bought cheap and lightly ridden, it's great. --
D-y

Tom Kunich

01-04-1970, 11:33 AM

andresmuro@aol.com

01-04-1970, 11:33 AM

On Jun 6, 4:37 am, "Lou D'Amelio" <ldame...@patmedia.net> wrote:
> Hi - looking for group thoughts on objective effects of equipment
> choices in road racing. I'm a 45+ mid-pack masters racer. Given my
> work/life situation, let's say for the sake of discussion that my
> fitness and weight are optimized. I'm train and race on an 17.5 - 18
> lb, subjectively somewhat flexible road bike (titanium). My fit and
> comfort are good, riding a 1500 g mid-profile wheelset (Campy Eurus).
> Other than maybe 150 grams in stem/brakeset, no rational place to lose
> weight with components without going 'stupid-light.' Most of my races
> are flat to moderately hilly and in the 25 -60 mile range. How much
> objective performance am I giving up by foregoing a current
> generation 14 lb super-stiff carbon uber-bike ? For a comparator,
> lets say we're looking at things like a Cervelo Soloist carbon, which
> would be about 3 lb lighter and somewhat stiffer and more aero than my
> current ride (2001 Litespeed Tuscany) Thanks in advance for any
> replies. Anyone heading down the 'it's the rider, not the bike' road,
> I already acknowledge that - hold the flames.
>
> TIA for replies...............Lou D'Amelio

I found out, after years of riding that a 75 to 76 degree seattube and
a 170 crankset were ideal for me. I used to get lower back pain after
more than two hours on the saddle. Now, I can easily ride five or six
hours with no pain. I can even ride on aerobars forever w/o pain.

I think that a bike that fits your anatomy, flexibility and riding
style can considerably improve your performance. If riding for a while
brings some discomfort a different position, angle can make you more
efficient. If you like to sprint, may be you can get a bike that
gives you a better feel for the sprint. OTOH, if you like to break
away and get low an aero for a long time, you need a bike that
enhances this.

If you have a well fitted road bike and you are in good shape, minor
weigh changes and minor tweaking will not make much difference.
However, being in a bike that you like to ride and makes you feel
comfortable on it, will get you to ride more. I would suggest that you
work on ultimate comfort. This may be a saddle, a wider/narrower
aerobars, steeper/slacker angles, etc.

There are places where you can spend a weekend getting fitted, etc.

Andres

Andres

carlfogel@comcast.net

01-04-1970, 11:33 AM

On Fri, 6 Jun 2008 03:37:56 -0700 (PDT), "Lou D'Amelio"
<ldamelio@patmedia.net> wrote:

>Hi - looking for group thoughts on objective effects of equipment
>choices in road racing. I'm a 45+ mid-pack masters racer. Given my
>work/life situation, let's say for the sake of discussion that my
>fitness and weight are optimized. I'm train and race on an 17.5 - 18
>lb, subjectively somewhat flexible road bike (titanium). My fit and
>comfort are good, riding a 1500 g mid-profile wheelset (Campy Eurus).
>Other than maybe 150 grams in stem/brakeset, no rational place to lose
>weight with components without going 'stupid-light.' Most of my races
>are flat to moderately hilly and in the 25 -60 mile range. How much
>objective performance am I giving up by foregoing a current
>generation 14 lb super-stiff carbon uber-bike ? For a comparator,
>lets say we're looking at things like a Cervelo Soloist carbon, which
>would be about 3 lb lighter and somewhat stiffer and more aero than my
>current ride (2001 Litespeed Tuscany) Thanks in advance for any
>replies. Anyone heading down the 'it's the rider, not the bike' road,
>I already acknowledge that - hold the flames.
>
>TIA for replies...............Lou D'Amelio

Dear Lou,

A stiffer frame probably means nothing in terms of effective power,
since a metal frame turns out to act as a very efficient spring.

Aerodynamics are far more important than weight. Change the
aerodynamics on the calculators below, and the predicted speeds change
more than they do with a 2 kg lighter bike.

A bike two kg lighter than normal has a small advantage.

Analytic Cycling has a side-by-side calculator offering several
courses:
http://www.analyticcycling.com/DiffEqWindCourse_Page.html

Set both wheelsets to the same generic 36 spoke values (you have to
check that the details are the same).

You can pick other wheelsets and several courses.

The predicted time improvement on the for losing 2 kg on the bike is
less than 1% for the example courses:

seconds
course 6kg / 8kg
----- ------
Generic TT 463.51 / 466.98 99.257%
Sydney 2000 1596.80 / 1602.28 99.658%
generic point-to-point 477.39 / 478.25 99.820%
3 mile point-to-point 574.75 / 575.77 99.823%
Florida 2002 State TT 3876.72 / 3882.99 99.839%
US Dist 20 TT 2002 3738.94 / 3749.89 99.708%
Ironman Hawaii alas, system times out

(Aero improves speed much more. The default generic TT course compares
generic 36-spoke wheels that take 466.98 seconds to an aero
combination that takes 454.23 seconds, 97.270% and over ten seconds
faster in 4000 meters.)

As a cross-check, use a different side-by-side calculator and add up
times for 15 km flat, 15 km 5% uphill, 15 km 5% downhill, taking 2 kg
off the default bike:
http://bikecalculator.com/veloMetricNum.html

Raise the power to 300 watts and drop the bike weight from 9 to 7 kg.

7kg 9kg
----- -----
15km flat 23.76 23.79 99.874% (heavier increases rolling drag)
15km 5% up 42.73 43.46 98.329% (heavier is slower uphill)
15km 5% down 15.90 15.78 100.760% (heavier is faster downhill)
----- ----- -------
total 82.39 83.03 99.229%

Cheers,

Carl Fogel

peter

01-04-1970, 11:33 AM

On Jun 6, 3:37 am, "Lou D'Amelio" <ldame...@patmedia.net> wrote:
> ... I'm train and race on an 17.5 - 18
> lb, subjectively somewhat flexible road bike (titanium). My fit and
> comfort are good, riding a 1500 g mid-profile wheelset (Campy Eurus).
> Other than maybe 150 grams in stem/brakeset, no rational place to lose
> weight with components without going 'stupid-light.'
....
> For a comparator,
> lets say we're looking at things like a Cervelo Soloist carbon, which
> would be about 3 lb lighter and somewhat stiffer and more aero than my
> current ride (2001 Litespeed Tuscany).

If your current components are already as light as you feel is
'rational' without going to 'stupid-light' then how is a bike with a
different frame going to save you 3 pounds? A typical Ti frame only
weighs about 3 - 3.5 lbs. and I don't think Cervelo has a weightless
frame. So either there's not a real 3 lb. difference or much of it is
coming from lighter components.

Since your rides are flat to moderate hilliness it seems like
concentrating on aerodynamics would be the first concern. Both in
your choice of wheelset (even if slightly heavier) and in terms of
your position on the bike.

Frank Krygowski

01-04-1970, 11:33 AM

On Jun 6, 6:37 am, "Lou D'Amelio" <ldame...@patmedia.net> wrote:
> Hi - looking for group thoughts on objective effects of equipment
> choices in road racing. I'm a 45+ mid-pack masters racer. Given my
> work/life situation, let's say for the sake of discussion that my
> fitness and weight are optimized. I'm train and race on an 17.5 - 18
> lb, subjectively somewhat flexible road bike (titanium). My fit and
> comfort are good, riding a 1500 g mid-profile wheelset (Campy Eurus).
> Other than maybe 150 grams in stem/brakeset, no rational place to lose
> weight with components without going 'stupid-light.' Most of my races
> are flat to moderately hilly and in the 25 -60 mile range. How much
> objective performance am I giving up by foregoing a current
> generation 14 lb super-stiff carbon uber-bike ? For a comparator,
> lets say we're looking at things like a Cervelo Soloist carbon, which
> would be about 3 lb lighter and somewhat stiffer and more aero than my
> current ride (2001 Litespeed Tuscany) Thanks in advance for any
> replies. Anyone heading down the 'it's the rider, not the bike' road,
> I already acknowledge that - hold the flames.

You've gotten lots of replies, and I've chimed in on the "stiffness"
question. But let me suggest some alternatives.

First, sad to say, I doubt any conventional approach will be a magic
bullet for you. For purposes of climbing or accelerating, any
practical weight (or mass) reductions will be a negligible percentage
of your total. If you weigh 150 pounds and your bike weighs 18
pounds, even a three pound difference is just a couple percent. It
may very slightly increase your odds of gaining one place or two at
the finish line, but it certainly won't make you win.

The same is probably true for most hardware changes. If you feel you
must buy something, I'd consider nothing other than a nice set of
wheels. As everyone at Buycycling magazine knows, the more
unrepairable they are, the faster they'll make you. ;-)

I say wheels because aero is almost always more important than weight;
but a mid-pack guy is rarely fighting the air on his own, so body &
bike aero matters less to you. However, even in a zero-wind
environment (like riding rollers) the spokes chop the air and stir it
up. (Try cranking a spoke wheel and a disk wheel on inverted bikes.)
So even drafting five giants, you get some aero benefit from boutique
wheels. Plus you get that psychological boost, which is not
negligible.

But again, the practical gains are small. So what might be bigger?
Here are two longshots.

One is to pay for a professional bike fit session. I've got no real
data, but I've heard claims and testimonials about one shop's fitting
sessions, where some racers claimed very measurable power gains (using
power meters) after extended, detailed fitting sessions. And those
were guys who had ridden and raced for year.

Another is to go iconoclast, and try wider tires. One r.b.tech
controversy involved Bicycle Quarterly's coast-down tire tests.
Supposedly, those demonstrated that wider tires might actually save
energy - sacrificing a bit of energy in flexing rubber, to save a lot
of energy in jostling the rider less. BQ claimed it showed up in
coasting speeds - not to mention in rider comfort.

There were the usual enthusiastic disagreements here. But ISTM it
might be worth experimenting, at least for longer races. Especially
for a guy past his twenties, a few hours of more comfort & less
fatigue will allow for greater power output in the sprint.

Finally, like I said in the other post, consider a "magic
decal" (something visible as you ride your bike) coupled with a
hypnosis session. Psychology is important!

- Frank Krygowski

Sandy

01-04-1970, 11:33 AM

Dans le message de
news:861c3913-42e6-4fc2-a2a2-bb4a1aed75da@d1g2000hsg.googlegroups.com,
dustoyevsky@mac.com <dustoyevsky@mac.com> a réfléchi, et puis a déclaré :
>
> Not flaming to suggest that, aero wheels aside, a real performance
> improvement is available via losing that "last x (or xx <g>) pounds",
> and getting real strict about what comprises the food/beverage intake,
> optimizing sleep patterns, etc. The guys who are beating you, that's
> probably their real advantage.

Well, a shiny new toy is sooooooooo much nicer than being monastic with your
diet. Really, for a masters' racer, who probably can't steal time from
family, a winning gimmick (the analog of a new putter in golf) can make a
real difference in results, even if it's all in the mind. Frankly, I'd go
with a Honda twin disguised as oversized waterbottles - screw the weight.
--
Sandy
Verneuil-sur-Seine FR

"Le Vin est la plus saine et la plus hygiénique des boissons."
- Louis Pasteur

Andre Jute

01-04-1970, 11:33 AM

On Jun 6, 2:37*pm, "dustoyev...@mac.com" <dustoyev...@mac.com> wrote:
> On Jun 6, 5:37*am, "Lou D'Amelio" <ldame...@patmedia.net> wrote:
>
>
>
> > Hi - looking for group thoughts on objective effects of equipment
> > choices in road racing. I'm a 45+ mid-pack masters racer. Given my
> > work/life situation, let's say for the sake of discussion that my
> > fitness and weight are optimized.

Snip a description of a fit, thin cyclist riding well-suited
equipment.

Just want to highlight this bit here in dusto's reply:

******
> optimizing sleep patterns, etc. The guys who are beating you, that's
> probably their real advantage.
*****

Nothing costs as much performance as not being well-rested. It's like
being permanently uptight, over-focussed, tensed up.

While I'm on the subject of being tensed up by your head. Know a guy
you consider a clown who always finishes ahead of his natural athletic
endowment? You can bet he sleeps well, and he doesn't let excess
adrenaline interfere with his performance. Nothing shakes out
adrenaline like laughter. Too many cyclists are held back by their
grim ambition; the minute they relax, accept that perhaps they are in
their natural place, suddenly they pick up a place or two from guys
who were in front of them not by athletic prowess per se but by having
a more relaxed attitude and thereby, paradoxically, becoming more
efficient. Laughter is a good tool for tuning the man/machine
engineering interface at its invisible control centre inside your
head.

Andre Jute
http://members.lycos.co.uk/fiultra/BICYCLE%20%26%20CYCLING.html

rick b

01-04-1970, 11:33 AM

Um...I beg to differ from some posters in this thread. I have a 2000
model Litespeed Tuscany. It's a fine, comfortable bike but I consider
it a rather poor choice for racing. It was probably designed for long-
distance riding. On the other hand, I also have a 2005 model Litespeed
Ultimate frame which is better more suited for racing. The frame is
stiffer, although I think it is just an ounce or two lighter. IMHO I
can go slightly faster on the Ultimate than the Tuscany...although I
don't race. So Lou, you have my blessing to find a bike better
suited for your goals.

r.b.

Camilo

01-04-1970, 11:33 AM

On Jun 6, 5:44 am, "Tom Kunich" <cyclintom@yahoo. com> wrote:
> "Lou D'Amelio" <ldame...@patmedia.net> wrote in message
>
> news:9852ccad-3989-4a82-bfa3-b7ee4a14b14b@m45g2000hsb.googlegroups.com...
>
> > Hi - looking for group thoughts on objective effects of equipment
> > choices in road racing. I'm a 45+ mid-pack masters racer. Given my
> > work/life situation, let's say for the sake of discussion that my
> > fitness and weight are optimized. I'm train and race on an 17.5 - 18
> > lb, subjectively somewhat flexible road bike (titanium). My fit and
> > comfort are good, riding a 1500 g mid-profile wheelset (Campy Eurus).
>
> Lou, you are giving up almost nothing at all. In your class fitness is far
> more important than a 2% difference in bike weight or stiffness.
>
> After you've optimized your training regime then you can start to think
> about changing your equipment.

That's exactly what he was asking us to assume - that his fitness and
weight were optimized.

Tim McNamara

01-04-1970, 11:33 AM

In article <484956b8$0$4276$4c368faf@roadrunner.com>,
"Sandy" <leurrre@free.fr> wrote:

> Well, a shiny new toy is sooooooooo much nicer than being monastic
> with your diet.

LOL! Ain't that the truth!

Ryan Cousineau

01-04-1970, 11:33 AM

In article <484956b8$0$4276$4c368faf@roadrunner.com>,
"Sandy" <leurrre@free.fr> wrote:

> Dans le message de
> news:861c3913-42e6-4fc2-a2a2-bb4a1aed75da@d1g2000hsg.googlegroups.com,
> dustoyevsky@mac.com <dustoyevsky@mac.com> a réfléchi, et puis a déclaré :
> >
> > Not flaming to suggest that, aero wheels aside, a real performance
> > improvement is available via losing that "last x (or xx <g>) pounds",
> > and getting real strict about what comprises the food/beverage intake,
> > optimizing sleep patterns, etc. The guys who are beating you, that's
> > probably their real advantage.
>
> Well, a shiny new toy is sooooooooo much nicer than being monastic with your
> diet. Really, for a masters' racer, who probably can't steal time from
> family, a winning gimmick (the analog of a new putter in golf) can make a
> real difference in results, even if it's all in the mind. Frankly, I'd go
> with a Honda twin disguised as oversized waterbottles - screw the weight.

Surely the new hotness is an electric hub disguised as a power meter,
and batteries slid into the frame.

Just don't let anyone lift your bike,

--
Ryan Cousineau rcousine@gmail.com 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

zencycle

01-04-1970, 11:34 AM

On Jun 6, 2:21 pm, rick b <blue_...@yahoo.com> wrote:
> Um...I beg to differ from some posters in this thread. I have a 2000
> model Litespeed Tuscany. It's a fine, comfortable bike but I consider
> it a rather poor choice for racing.

I have to agree with rick. While it certainly is the case that fitness
and biomechanical efficiency are the highest contributing factors, I
notice a huge difference in performance of my Giant TCR over my merlin
road (not an extralight).

It snaps under acceleration out of corners and uphills, and the power
transfer makes the difference in closing the gaps, especially when you
hit it chasing an attack up a steep hill. The biggest difference will
come in tight crits, where you need to keep re-accelerating out of
corners. You probably won't have any _overall_ difference in speed,
but keeping up with the pack will have become noticably easier.

Go for the cervelo - you won't be sorry.

It was probably designed for long-
> distance riding. On the other hand, I also have a 2005 model Litespeed
> Ultimate frame which is better more suited for racing. The frame is
> stiffer, although I think it is just an ounce or two lighter. IMHO I
> can go slightly faster on the Ultimate than the Tuscany...although I
> don't race. So Lou, you have my blessing to find a bike better
> suited for your goals.
>
> r.b.

dustoyevsky@mac.com

01-04-1970, 11:34 AM

On Jun 6, 1:21*pm, rick b <blue_...@yahoo.com> wrote:
> Um...I beg to differ from some posters in this thread. *I have a 2000
> model Litespeed Tuscany. *It's a fine, comfortable bike but I consider
> it a rather poor choice for racing. It was probably designed for long-
> distance riding. On the other hand, I also have a 2005 model Litespeed
> Ultimate frame which is better more suited for racing. *The frame is
> stiffer, although I think it is just an ounce or two lighter. * IMHO I
> can go slightly faster on the Ultimate than the Tuscany...although I
> don't race. * So Lou, you have my blessing to find a bike better
> suited for your goals.

Well... OK, I'll go along with this. Back in the day, I had a "road"
bike and a "crit" bike. Crit bike was stiffer, carved smooth crit-
style corners quite a bit better, as far as just diving in and going
around, where the road bike would go just as fast but had a little
resistance to the process. The cirt bike also had a higher BB. So, in
all, it worked better for crits. But I had crit wins and places on
both bikes. Each was a better tool for certain conditions than the
other-- I rode the crit bike on the 100+ mile dirt road extravaganzas
of old. It never spit me off or anything, but the rear wheel's
traction when going hard in the rough stuff was not as good as the
road bike, it didn't corner as well in the dirt and rocks as the road
bike did, once out of its natural, smooth-pavement-please element, and
it sure didn't ride as smooth over the long haul, either.

Minor, maybe important differences I guess, and if you can afford
"something better", and/or have bikes tailored for certain uses, then
by all means, "worked for me" <g>.

However, racing results come from being able to go fast at the right
time.

Offering the example of Tom Finklea winning local Austin races on his
old steel bike with downtube shifters and brake wires hanging out all
over the place, way too many spokes in his wheels, etc. etc.,
probably ten years after everyone else had gone "modern". Of course,
if he'd been on that Cervelo, lighter (pounds lighter), and no doubt
stiffer while being more compliant (sorry, couldn't resist), with
brifter shifting, it would likely have been even more embarrassing to
the defeated, but for a different reason. --D-y

John Forrest Tomlinson

01-04-1970, 11:34 AM

On Fri, 6 Jun 2008 12:52:05 -0700 (PDT), zencycle
<zencycle@bikerider.com> wrote:

>On Jun 6, 2:21 pm, rick b <blue_...@yahoo.com> wrote:
>> Um...I beg to differ from some posters in this thread. I have a 2000
>> model Litespeed Tuscany. It's a fine, comfortable bike but I consider
>> it a rather poor choice for racing.
>
>I have to agree with rick. While it certainly is the case that fitness
>and biomechanical efficiency are the highest contributing factors, I
>notice a huge difference in performance of my Giant TCR over my merlin
>road (not an extralight).
>
>It snaps under acceleration out of corners and uphills, and the power
>transfer makes the difference in closing the gaps, especially when you
>hit it chasing an attack up a steep hill. The biggest difference will
>come in tight crits, where you need to keep re-accelerating out of
>corners. You probably won't have any _overall_ difference in speed,
>but keeping up with the pack will have become noticably easier.

I'm not familiar with the Tuscany, but had a cheaper Litespeed (a
Catalyst) a bit older than the bike in question. I raced it a couple
of years and it was OK, but it wasn't great in the sort of conditions
you descibe. Also did not feel secure in sharp high-speed turns. My
next bike was, I think, quite a bit siffer, and felt better in those
situations.

zencycle

01-04-1970, 11:34 AM

On Jun 6, 4:11 pm, carlfo...@comcast.net wrote:
>
> A stiffer frame probably means nothing in terms of effective power,
> since a metal frame turns out to act as a very efficient spring.

But a softer frame does has a damping effect on the immediate transfer
of power. We refer to this as 'snap'. Ti or Steel frames don't have
the snap that aluminum or carbon frames do. I'm speaking from many
years of experience here. Certainly one would be able to develop that
same effective and peak power regardless of the frame material, but
when you accelerate out of a corner trying to stay on the wheel in
front of you, a frame that needs to take the time to 'regenerate' the
energy is much more dificult to accelerate than one that doesn't have
that characteristic.

Besides that, Lou is talking about pack racing, and is an admitted
'middle of the pack' racer (I hear ya lou, I'm one of those cat3
masters myself). Aerodynamic positioning is a significantly smaller
factor in a pack than riding solo. In that situation, the weight of
the bike is more of a factor as it relates to accelerating to stay on
the wheel in front of you and again the immediate power transfer is of
a significant benefit. Granted, a more aerodynamic wheelset will
result in less drag for the same work, but again, the benefit of an
aero wheel is significantly less when riding in a pack as opposed to
time trialing.

Ben C

01-04-1970, 11:34 AM

On 2008-06-06, carlfogel@comcast.net <carlfogel@comcast.net> wrote:
[...]
> A stiffer frame probably means nothing in terms of effective power,
> since a metal frame turns out to act as a very efficient spring.

Does that really work though? Does the springing back somehow help drive
the cranks?

The energy can't go back into your legs, as this chap points out:

http://hea-www.harvard.edu/~fine/opinions/stiffframe.html

The stiffness of a bike frame has a significant effect on the way a
bike rides. One fact is hard to argue with: most people with a lot
of cycling experience like a good stiff frame. Further, many people
claim that a stiff frame is actually more energy efficient.

Armchair physicists are quick to point out that this is nonsense,
because a steel frame is a nearly ideal spring, and it will return
any energy you put into it. They will point out that you can put a
frame on a work bench, and flex it 10,000 times, and have almost no
heat buildup in the frame. This "proves" that there's no energy loss
from pedaling on a flexible frame.

Armchair physicists tend to miss the bigger picture. (Except for me
of course).

What they got wrong is that the energy loss isn't absorbed by the
frame. Instead it is absorbed by your leg muscles. While a frame is
an ideal spring, your legs aren't. If you push with your legs, you
use energy. If something else pushes back on your legs, you still
lose energy. This happens because of the way your muscles work
internally. The short answer is that there is no way for your
muscles to turn mechanical energy into glucose (or any chemical that
provides fuel to your muscles).

John Forrest Tomlinson

01-04-1970, 11:34 AM

On Fri, 06 Jun 2008 14:11:48 -0600, carlfogel@comcast.net wrote:

>A stiffer frame probably means nothing in terms of effective power,
>since a metal frame turns out to act as a very efficient spring.

A stiffer frame feels more solid in hard cornering. In criteriums
that's important.

Michael Press

01-04-1970, 11:34 AM

In article <743j44hb8kh4o7e2hv19d7pd8j5a73gquc@4ax.com>,
carlfogel@comcast.net wrote:

> A stiffer frame probably means nothing in terms of effective power,
> since a metal frame turns out to act as a very efficient spring.

Nobody here has ever presented a persuasive argument or
a pointer to a persuasive argument showing that energy
expended flexing the frame is not totally dissipated.
Less flex means less power going into flexing the frame.

--
Michael Press

carlfogel@comcast.net

01-04-1970, 11:34 AM

On Fri, 6 Jun 2008 13:53:34 -0700 (PDT), zencycle
<zencycle@bikerider.com> wrote:

>On Jun 6, 4:11 pm, carlfo...@comcast.net wrote:
>>
>> A stiffer frame probably means nothing in terms of effective power,
>> since a metal frame turns out to act as a very efficient spring.
>
>But a softer frame does has a damping effect on the immediate transfer
>of power. We refer to this as 'snap'. Ti or Steel frames don't have
>the snap that aluminum or carbon frames do. I'm speaking from many
>years of experience here. Certainly one would be able to develop that
>same effective and peak power regardless of the frame material, but
>when you accelerate out of a corner trying to stay on the wheel in
>front of you, a frame that needs to take the time to 'regenerate' the
>energy is much more dificult to accelerate than one that doesn't have
>that characteristic.

Dear Z,

Do you know of any actual tests that show bicycles accelerating
differently according to whether the frames are made of steel,
aluminum, carbon, or titanium?

Cheers,

Carl Fogel

Tom Kunich

01-04-1970, 11:34 AM

"Ben C" <spamspam@spam.eggs> wrote in message
news:slrng4j9l4.eh5.spamspam@bowser.marioworld...
> One fact is hard to argue with: most people with a lot
> of cycling experience like a good stiff frame. Further, many people
> claim that a stiff frame is actually more energy efficient.

Unless you've actually ridden such a machine. I've had several aluminum
bikes famed for their stiffness as well as an older Colnago Master which
originally belonged to Axel Merckx and was WAY stiffer than those AL bikes.
And the problem was that you couldn't keep the wheels on the road to deliver
all that power that was supposedly otherwise lost in wobble in the frame.

> Armchair physicists are quick to point out that this is nonsense,
> because a steel frame is a nearly ideal spring, and it will return
> any energy you put into it.

Not to put too fine a point on it but the frame wobbles back and forth
misaligning the front wheel which drag absorbs the TINY amount of energy
that goes into "flex".

Tim McNamara

01-04-1970, 11:34 AM

In article <slrng4j9l4.eh5.spamspam@bowser.marioworld>,
Ben C <spamspam@spam.eggs> wrote:

> On 2008-06-06, carlfogel@comcast.net <carlfogel@comcast.net> wrote:
> [...]
> > A stiffer frame probably means nothing in terms of effective power,
> > since a metal frame turns out to act as a very efficient spring.
>
> Does that really work though? Does the springing back somehow help
> drive the cranks?
>
> The energy can't go back into your legs, as this chap points out:
>
> http://hea-www.harvard.edu/~fine/opinions/stiffframe.html
>
>The stiffness of a bike frame has a significant effect on the way a
>bike rides. One fact is hard to argue with: most people with a lot of
>cycling experience like a good stiff frame. Further, many people claim
>that a stiff frame is actually more energy efficient.

Without a way to isolate and test this, it's just a hunch.

sergio

01-04-1970, 11:34 AM

On 6 Giu, 23:05, Ben C <spams...@spam.eggs> wrote:

> * * Armchair physicists are quick to point out that this is nonsense,
> * * because a steel frame is a nearly ideal spring, and it will return
> * * any energy you put into it.

'Nearly', except for dispersion relations.

>
> * * Armchair physicists tend to miss the bigger picture. (Except for me
> * * of course).
> * * What they got wrong is that the energy loss isn't absorbed by the
> * * frame. Instead it is absorbed by your leg muscles.

Whether you are a physicist or not, you invariably absorb a lot by
damping with your arms, legs, neck and torso too.
To a measure, it is preferable that the frame absorbs a bit (smooth
v.s harsh ride) but at large we got to do it ourselves working as
shock absorbers on rough terrain or while going downhill. To be able
to control the machine much in the same way as skiers do.
So, I would second Jobst's remark that it is mainly a control problem.

Sergio
Pisa

andresmuro@aol.com

01-04-1970, 11:34 AM

On Jun 6, 3:19 pm, John Forrest Tomlinson <usenetrem...@jt10000.com>
wrote:
> On Fri, 06 Jun 2008 14:11:48 -0600, carlfo...@comcast.net wrote:
> >A stiffer frame probably means nothing in terms of effective power,
> >since a metal frame turns out to act as a very efficient spring.
>
> A stiffer frame feels more solid in hard cornering. In criteriums
> that's important.

I've ridden ti, al and steel frames. Haven't tried carbon. Regarding
the feeling of responsiveness and jumping forward in a sprint, my
favorite frame was a Basso Ascott MS steel. When I rode that frame, I
loved the feeling that I got when I stood up and accelerated. I don't
know if I was accelerating any faster than with any of my other bikes,
but I certainly got this really nice feeling that the frame was
propelling me forward. That frame was totaled by a car. I've had other
frames since, but none gave me that nice feeling. I had to learn to
accelerate at first with this frame. Otherwise, I would always lift
the rear wheel. I don't know if it was stiffness or geometry that made
that frame so nice. However, I could definitely see the crankset
moving and rubbing the front deraullier when I stomped on the pedals,
more so than with other bikes. The bike had very little clearance
between the rear wheel and the seat tube and the head tube angle was
pretty tight.

Andres

zencycle

01-04-1970, 11:35 AM

On Jun 6, 6:25 pm, carlfo...@comcast.net wrote:>
> Do you know of any actual tests that show bicycles accelerating
> differently according to whether the frames are made of steel,
> aluminum, carbon, or titanium?
>

Carl, are you really that old? There's no question that the design of
the frame is of the paramount consideration, but given two identical
frame designs, the inherent stiffness (modulus of elasticity) of
carbon or aluminum translates into less damping of the power to the
wheel.

Besides that, do you think that if there were no advantage, people
wouldn't still be racing steel frames?

zencycle

01-04-1970, 11:35 AM

On Jun 6, 6:25 pm, carlfo...@comcast.net wrote:
>
> Do you know of any actual tests that show bicycles accelerating
> differently according to whether the frames are made of steel,
> aluminum, carbon, or titanium?

One last point, while I don't any studies that conform to the
scientific method at my fingertips (not that there aren't any, I just
don't know of them, and trust me, I'll look), I have the anecdotal and
experiential evidence of the 100s of local racers I know that race on
carbon and aluminum. Would a super fit athlete be able to wipe the
pavement with me on an old steel schwinn paramount? sure. But if that
were the case, why do these really good former cat 1's who now have a
jobwifehomecarkid and limited expendable income race almost
exclusively on carbon? Face it, a competitve athlete will use the
equipment that will help him win. That isn't to say that a competent
frame builder cannot build build a steel frame that has the same
'snap' that an aluminum or carbon frame has, but for a much smaller
investment, you can get a carbon or aluminum frame that's as
responsive as the highest end steel frame available.

Michael Press

01-04-1970, 11:35 AM

In article <95ej44pcoitj8jqmmg8pi5r42t5k2mn38l@4ax.com>,
carlfogel@comcast.net wrote:

> On Fri, 6 Jun 2008 13:53:34 -0700 (PDT), zencycle
> <zencycle@bikerider.com> wrote:
>
> >On Jun 6, 4:11 pm, carlfo...@comcast.net wrote:
> >>
> >> A stiffer frame probably means nothing in terms of effective power,
> >> since a metal frame turns out to act as a very efficient spring.
> >
> >But a softer frame does has a damping effect on the immediate transfer
> >of power. We refer to this as 'snap'. Ti or Steel frames don't have
> >the snap that aluminum or carbon frames do. I'm speaking from many
> >years of experience here. Certainly one would be able to develop that
> >same effective and peak power regardless of the frame material, but
> >when you accelerate out of a corner trying to stay on the wheel in
> >front of you, a frame that needs to take the time to 'regenerate' the
> >energy is much more dificult to accelerate than one that doesn't have
> >that characteristic.
>
> Do you know of any actual tests that show bicycles accelerating
> differently according to whether the frames are made of steel,
> aluminum, carbon, or titanium?

Carl, do you know of any actual tests showing that energy
going into frame flex is returned in such a way as to
propel the bicycle?

--
Michael Press

Tom Kunich

01-04-1970, 11:35 AM

"Camilo" <campascual@yahoo.com> wrote in message
news:b1b5e761-9150-4c8e-9a5a-c7a0903611da@q27g2000prf.googlegroups.com...
>
> That's exactly what he was asking us to assume - that his fitness and
> weight were optimized.

Sure, and so is yours.

Camilo

01-04-1970, 11:35 AM

On Jun 6, 4:49 pm, "Tom Kunich" <cyclintom@yahoo. com> wrote:
> "Camilo" <campasc...@yahoo.com> wrote in message
>
> news:b1b5e761-9150-4c8e-9a5a-c7a0903611da@q27g2000prf.googlegroups.com...
>
>
>
> > That's exactly what he was asking us to assume - that his fitness and
> > weight were optimized.
>
> Sure, and so is yours.

Hey, I'm not saying it's true, just that it is the mental exercise he
asked us to participate in. I appreciate your wise insight though,
it's very original to discuss fitness and personal weight when asked
about equipment upgrades.

jobst.brandt@stanfordalumni.org

01-04-1970, 11:36 AM

Michael Press wrote:

>> A stiffer frame probably means nothing in terms of effective power,
>> since a metal frame turns out to act as a very efficient spring.

> Nobody here has ever presented a persuasive argument or a pointer to
> a persuasive argument showing that energy expended flexing the frame
> is not totally dissipated. Less flex means less power going into
> flexing the frame.

Much more important is that no one has shown where elastic deformation
absorbs energy (power) or that frame flex which is almost entirely
lateral from off center pedal force, causes plastic deformation, the
only mode where energy might be dissipated. Of course, such
deformation would cause frame rapid failure.

The old "frame-flex" bugaboo has been with us too long to feed it
further here on "tech". Frame flex is a control problem, not power
loss. Shimmy fits that definition as well. In automobiles, vertical
suspension travel has such poor energy absorption that hydraulic
"shock absorbers" are used to absorb energy to control the vehicle.

Jobst Brandt

peter

01-04-1970, 11:36 AM

On Jun 6, 9:11 pm, Michael Press <rub...@pacbell.net> wrote:
> In article <743j44hb8kh4o7e2hv19d7pd8j5a73g...@4ax.com>,
>
> carlfo...@comcast.net wrote:
> > A stiffer frame probably means nothing in terms of effective power,
> > since a metal frame turns out to act as a very efficient spring.
>
> Nobody here has ever presented a persuasive argument or
> a pointer to a persuasive argument showing that energy
> expended flexing the frame is not totally dissipated.

As the rider begins a pedal stroke, most of the foot motion is
translated into rotation of the crank, but a small portion is instead
used to flex the frame from its normal shape. But toward the end of
the pedal stroke the foot pressure on the pedal gradually decreases
and the frame returns to its normal shape. At that point the crank
will be turned a bit more than the actual foot motion would indicate
and at least some of the energy stored in the frame at the beginning
of the stroke is returned to provide useful propulsion.

Frank Krygowski

01-04-1970, 11:36 AM

On Jun 7, 12:11 am, Michael Press <rub...@pacbell.net> wrote:
> In article <743j44hb8kh4o7e2hv19d7pd8j5a73g...@4ax.com>,
>
> carlfo...@comcast.net wrote:
> > A stiffer frame probably means nothing in terms of effective power,
> > since a metal frame turns out to act as a very efficient spring.
>
> Nobody here has ever presented a persuasive argument or
> a pointer to a persuasive argument showing that energy
> expended flexing the frame is not totally dissipated.

Well, "persuasive" is in the eye of the beholder. And it's very hard
to persuade most people that what they've posted is wrong!

> Less flex means less power going into flexing the frame.

Let me try some alternative explanations.

First, if frame flex absorbs leg power, it can only be because your
leg does more work on the downstroke - that is, applies force through
a greater distance in the same direction as the force. Now, how much
greater is that distance? IOW, how much further downward does the
pedal move with a flexible frame? Probably no more than 3 mm, I'd
guess. That's a very minor portion of the 350 mm your foot moves down
in the power stroke.

BUT even that energy is not lost. Remember that cyclists don't pull
up on the backstroke, despite some claims to the contrary. Your leg
is lifted on the backstroke at least partly by the front leg's power
stroke.

So the energy that comes from more downward motion on the forward
stroke causes more upward motion for the backstroke. It's at least
partly (maybe entirely) captured by raising the back leg.

Finally, as people have pointed out before, if energy is dissipated by
frame flex, it should be detectable in temperature rise of the frame
material. AFAIK, this has never been detected. (People have used
thermal imaging to "see" friction loss in chain drives, so the
temperature rise wouldn't need to be huge to be seen.)

If there's a benefit to a stiff frame, it may be psychological. Which
is not to say it's negligible! Sports has a huge psych component.

But instead of spending for a frame, it may be as effective, and much
cheaper, to spend for a new "magic" frame decal, plus a hypnosis
session. ;-)

- Frank Krygowski

carlfogel@comcast.net

01-04-1970, 11:36 AM

On Fri, 6 Jun 2008 22:16:03 -0700 (PDT), zencycle
<zencycle@bikerider.com> wrote:

>On Jun 6, 6:25 pm, carlfo...@comcast.net wrote:>
>> Do you know of any actual tests that show bicycles accelerating
>> differently according to whether the frames are made of steel,
>> aluminum, carbon, or titanium?
>>
>
>Carl, are you really that old? There's no question that the design of
>the frame is of the paramount consideration, but given two identical
>frame designs, the inherent stiffness (modulus of elasticity) of
>carbon or aluminum translates into less damping of the power to the
>wheel.
>
>Besides that, do you think that if there were no advantage, people
>wouldn't still be racing steel frames?

Dear Z,

I take it that you don't know of any actual tests that show bicycles
accelerating faster with frames made of one material rather than
another.

Cheers,

Carl Fogel

Ben C

01-04-1970, 11:36 AM

On 2008-06-07, zencycle <zencycle@bikerider.com> wrote:
> On Jun 6, 6:25 pm, carlfo...@comcast.net wrote:>
>> Do you know of any actual tests that show bicycles accelerating
>> differently according to whether the frames are made of steel,
>> aluminum, carbon, or titanium?
>>
>
> Carl, are you really that old? There's no question that the design of
> the frame is of the paramount consideration, but given two identical
> frame designs, the inherent stiffness (modulus of elasticity) of
> carbon or aluminum translates into less damping of the power to the
> wheel.
>
> Besides that, do you think that if there were no advantage, people
> wouldn't still be racing steel frames?

Aluminium has a much _lower_ modulus of elasticity than steel. But an
aluminium frame may or may not be stiffer than a steel one, because it
depends on a lot of things like how thick/fat you make the tubes.

I found this an interesting read: http://www.bobbrowncycles.com/eng.htm
(thanks to Tim for a link to bobbrowncycles the other day).

See also: http://www.sheldonbrown.com/frame-materials.html
and: http://sheldonbrown.com/rinard_frametest.html

Damping is distinct from stiffness. Carbon fibre may provide some
damping that you don't get in metal frames.

A Muzi

01-04-1970, 11:36 AM

> carlfo...@comcast.net wrote:
>> Do you know of any actual tests that show bicycles accelerating
>> differently according to whether the frames are made of steel,
>> aluminum, carbon, or titanium?

zencycle wrote:
> One last point, while I don't any studies that conform to the
> scientific method at my fingertips (not that there aren't any, I just
> don't know of them, and trust me, I'll look), I have the anecdotal and
> experiential evidence of the 100s of local racers I know that race on
> carbon and aluminum. Would a super fit athlete be able to wipe the
> pavement with me on an old steel schwinn paramount? sure. But if that
> were the case, why do these really good former cat 1's who now have a
> jobwifehomecarkid and limited expendable income race almost
> exclusively on carbon? Face it, a competitve athlete will use the
> equipment that will help him win. That isn't to say that a competent
> frame builder cannot build build a steel frame that has the same
> 'snap' that an aluminum or carbon frame has, but for a much smaller
> investment, you can get a carbon or aluminum frame that's as
> responsive as the highest end steel frame available.

Your argument could easily apply to oval chainrings or centerpull
brakes, each of which were de rigeur for the trendy race bikes of their
respective eras. 'Popular' is not proof of anything but sales.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

Tom Kunich

01-04-1970, 11:36 AM

<jobst.brandt@stanfordalumni.org> wrote in message
news:484a237d$0$17199$742ec2ed@news.sonic.net...
>
> The old "frame-flex" bugaboo has been with us too long to feed it
> further here on "tech". Frame flex is a control problem, not power
> loss. Shimmy fits that definition as well. In automobiles, vertical
> suspension travel has such poor energy absorption that hydraulic
> "shock absorbers" are used to absorb energy to control the vehicle.

Why is it so difficult to understand that flexing a frame misaligns the
wheels which scrub off a tiny portion of the input power?

Michael Press

01-04-1970, 11:36 AM

In article <484a237d$0$17199$742ec2ed@news.sonic.net>,
jobst.brandt@stanfordalumni.org wrote:

> Michael Press wrote:
>
> >> A stiffer frame probably means nothing in terms of effective power,
> >> since a metal frame turns out to act as a very efficient spring.
>
> > Nobody here has ever presented a persuasive argument or a pointer to
> > a persuasive argument showing that energy expended flexing the frame
> > is not totally dissipated. Less flex means less power going into
> > flexing the frame.
>
> Much more important is that no one has shown where elastic deformation
> absorbs energy (power) or that frame flex which is almost entirely
> lateral from off center pedal force, causes plastic deformation, the
> only mode where energy might be dissipated. Of course, such
> deformation would cause frame rapid failure.

I am not quantifying. I hold that energy going into flexing
the frame is lost to propelling the bicycle forward.

--
Michael Press

almost_fast@yahoo.com

01-04-1970, 11:37 AM

On Jun 7, 2:35*am, carlfo...@comcast.net wrote:

> Dear Z,
>
> I take it that you don't know of any actual tests that show bicycles
> accelerating faster with frames made of one material rather than
> another.
>
> Cheers,
>
> Carl Fogel

I'm not Z, but here's a study from MIT that addresses energy to
maintain speed (not acceleration). Here's one quote:
"The aluminum bicycle required less energy to maintain the testing
speed for a short duration ride."

Abstract below. Quote:
=================
The Engineering of Sport 5 Vol. 2
619
Measuring the effect of transmitted road vibration on
cycling performance
A. Z. Hastings, K. B. Blair, and K. F. Culligan
Center for Sports Innovation, Massachusetts Institute of Technology,
Cambridge, MA, USA
D. M. Pober
Department of Exercise Science, University of Massachusetts,
Amherst, MA, USA
ABSTRACT: In the cycling industry, the qualitative term “ride quality”
is used to describe
the effect of transmitted road vibrations on the cyclist. While
bicycle frames are made from a
range of materials, each purported to deliver a comfortable yet
efficient ride, the relationship
between road vibration and rider performance has not been
quantitatively determined. The
objectives of this study were to develop a system to characterize the
effect of transmitted road
vibration on rider performance for road racing bicycles and to
demonstrate the ability of the
test method to quantify the differences between three different
bicycle frames, each
constructed of a different material. We have developed a treadmill
based instrumentation
system to induce simulated road vibrations and measure both the
dynamic response of the
bicycle as well as the power output and steady-state-oxygen
consumption of the athlete. This
data provides a quantitative measure of the efficiency of a bicycle
subject to known vibrations
representative of those produced in road cycling. Using three
bicycles, identical except for
frame material (steel, aluminum and carbon fiber), we found that
different frame materials
damp road vibrations in different ways. The carbon fiber bike
transmits a broader spectrum of
frequency than the others with somewhat lower peak value. The aluminum
bicycle was found
to impart the largest acceleration values measured at the seat post.
The aluminum bicycle
required less energy to maintain the testing speed for a short
duration ride. These results
indicate the need for a quantitative measure that includes several
frequency components, and
occurs over different time scales in order to characterize the
vibration effects of road bicycle
performance.
========================
end quote

jobst.brandt@stanfordalumni.org

01-04-1970, 11:37 AM

Ben C? wrote:

>>> Do you know of any actual tests that show bicycles accelerating
>>> differently according to whether the frames are made of steel,
>>> aluminum, carbon, or titanium?

>> Carl, are you really that old? There's no question that the design
>> of the frame is of the paramount consideration, but given two
>> identical frame designs, the inherent stiffness (modulus of
>> elasticity) of carbon or aluminum translates into less damping of
>> the power to the wheel.

>> Besides that, do you think that if there were no advantage, people
>> wouldn't still be racing steel frames?

> Aluminium has a much _lower_ modulus of elasticity than steel. But
> an aluminium frame may or may not be stiffer than a steel one,
> because it depends on a lot of things like how thick/fat you make
> the tubes.

> I found this an interesting read:

http://www.bobbrowncycles.com/eng.htm

> (thanks to Tim for a link to bobbrowncycles the other day).

> See also:

http://www.sheldonbrown.com/frame-materials.html
> and:

http://sheldonbrown.com/rinard_frametest.html

> Damping is distinct from stiffness. Carbon fibre may provide some
> damping that you don't get in metal frames.

Hold the phone! Energy absorption must be in the frequency of input
forces, of which human input is far from the acoustic range, the one
so obviously not transmitted by materials as soft as plastics, of
which the mass of carbon fiber frames are. Their strength is
longitudinally with the fibers but not laterally, the direction of
vibration of frame elements.

This is a mishmash of half truths and out of context assessments.
Frame flex does not absorb rider input work for the reasons stated.

Jobst Brandt

jobst.brandt@stanfordalumni.org

01-04-1970, 11:37 AM

Tom Kunich wrote:

>> The old "frame-flex" bugaboo has been with us too long to feed it
>> further here on "tech". Frame flex is a control problem, not power
>> loss. Shimmy fits that definition as well. In automobiles,
>> vertical suspension travel has such poor energy absorption that
>> hydraulic "shock absorbers" are used to absorb energy to control
>> the vehicle.

> Why is it so difficult to understand that flexing a frame misaligns
> the wheels which scrub off a tiny portion of the input power?

Tire scrub has been accused of all sorts of ills, none of which exist,
especially from frame flex. If that were so, you ought to try this on
a freshly concreted street where the road is still white. Tire scrub
would be shockingly obvious. My experience is that just mild smooth
cornering will leave a faint track. Pedaling hard (in a straight line)
should leave a darker track with lateral waves.

Do it!

Jobst Brandt

John Forrest Tomlinson

01-04-1970, 11:38 AM

On Sat, 07 Jun 2008 09:45:52 -0500, A Muzi <am@yellowjersey.org>
wrote:

>Your argument could easily apply to oval chainrings or centerpull
>brakes, each of which were de rigeur for the trendy race bikes of their
>respective eras.

Centerpull was the best for a long time. Non-round rings never caught
on that much -- they were specced on a lot of bikes and removed on a
lot of bikes.

Michael Press

01-04-1970, 11:38 AM

In article
<7c71e4cc-83a0-462e-87ea-d5712d978a9b@i76g2000hsf.googlegroups.com>,
Frank Krygowski <frkrygow@gmail.com> wrote:

> On Jun 7, 12:11 am, Michael Press <rub...@pacbell.net> wrote:
> > In article <743j44hb8kh4o7e2hv19d7pd8j5a73g...@4ax.com>,
> >
> > carlfo...@comcast.net wrote:
> > > A stiffer frame probably means nothing in terms of effective power,
> > > since a metal frame turns out to act as a very efficient spring.
> >
> > Nobody here has ever presented a persuasive argument or
> > a pointer to a persuasive argument showing that energy
> > expended flexing the frame is not totally dissipated.
>
> Well, "persuasive" is in the eye of the beholder. And it's very hard
> to persuade most people that what they've posted is wrong!
>
> > Less flex means less power going into flexing the frame.
>
> Let me try some alternative explanations.
>
> First, if frame flex absorbs leg power, it can only be because your
> leg does more work on the downstroke - that is, applies force through
> a greater distance in the same direction as the force. Now, how much
> greater is that distance? IOW, how much further downward does the
> pedal move with a flexible frame? Probably no more than 3 mm, I'd
> guess. That's a very minor portion of the 350 mm your foot moves down
> in the power stroke.
>
> BUT even that energy is not lost. Remember that cyclists don't pull
> up on the backstroke, despite some claims to the contrary. Your leg
> is lifted on the backstroke at least partly by the front leg's power
> stroke.
>
> So the energy that comes from more downward motion on the forward
> stroke causes more upward motion for the backstroke. It's at least
> partly (maybe entirely) captured by raising the back leg.

You make the conventional plausible argument.
It is not persuasive. Persuasive is an enormous
simulation taking into account everything or an
elaborate measuring project.

> Finally, as people have pointed out before, if energy is dissipated by
> frame flex, it should be detectable in temperature rise of the frame
> material. AFAIK, this has never been detected. (People have used
> thermal imaging to "see" friction loss in chain drives, so the
> temperature rise wouldn't need to be huge to be seen.)

As Tom mentions, flexing the frame makes the tires scrub,
and this dissipates energy.

> If there's a benefit to a stiff frame, it may be psychological. Which
> is not to say it's negligible! Sports has a huge psych component.
>
> But instead of spending for a frame, it may be as effective, and much
> cheaper, to spend for a new "magic" frame decal, plus a hypnosis
> session. ;-)

A new bicycle is a Good Thing.

--
Michael Press

carlfogel@comcast.net

01-04-1970, 11:38 AM

On Sat, 7 Jun 2008 08:24:03 -0700 (PDT), Frank Krygowski
<frkrygow@gmail.com> wrote:

>On Jun 7, 12:11 am, Michael Press <rub...@pacbell.net> wrote:
>> In article <743j44hb8kh4o7e2hv19d7pd8j5a73g...@4ax.com>,
>>
>> carlfo...@comcast.net wrote:
>> > A stiffer frame probably means nothing in terms of effective power,
>> > since a metal frame turns out to act as a very efficient spring.
>>
>> Nobody here has ever presented a persuasive argument or
>> a pointer to a persuasive argument showing that energy
>> expended flexing the frame is not totally dissipated.
>
>Well, "persuasive" is in the eye of the beholder. And it's very hard
>to persuade most people that what they've posted is wrong!
>
>> Less flex means less power going into flexing the frame.
>
>Let me try some alternative explanations.
>
>First, if frame flex absorbs leg power, it can only be because your
>leg does more work on the downstroke - that is, applies force through
>a greater distance in the same direction as the force. Now, how much
>greater is that distance? IOW, how much further downward does the
>pedal move with a flexible frame? Probably no more than 3 mm, I'd
>guess. That's a very minor portion of the 350 mm your foot moves down
>in the power stroke.
>
>BUT even that energy is not lost. Remember that cyclists don't pull
>up on the backstroke, despite some claims to the contrary. Your leg
>is lifted on the backstroke at least partly by the front leg's power
>stroke.
>
>So the energy that comes from more downward motion on the forward
>stroke causes more upward motion for the backstroke. It's at least
>partly (maybe entirely) captured by raising the back leg.
>
>Finally, as people have pointed out before, if energy is dissipated by
>frame flex, it should be detectable in temperature rise of the frame
>material. AFAIK, this has never been detected. (People have used
>thermal imaging to "see" friction loss in chain drives, so the
>temperature rise wouldn't need to be huge to be seen.)
>
>If there's a benefit to a stiff frame, it may be psychological. Which
>is not to say it's negligible! Sports has a huge psych component.
>
>But instead of spending for a frame, it may be as effective, and much
>cheaper, to spend for a new "magic" frame decal, plus a hypnosis
>session. ;-)
>
>- Frank Krygowski

Dear Frank,

Damon Rinard measured frame flex for a variety of models, sizes, and
materials:
http://www.sheldonbrown.com/rinard/rinard_frametest.html

He noted that larger frames flex more than smaller frames:

"All frame builders know that smaller frames are inherently stiffer
and larger frames are inherently more flexible. What I found in my
testing is that this effect is greater than I thought. Even the
lightest tube sets, when made into a small frame, end up nearly the
same stiffness as the heaviest tube sets, when made into a large
frame! And many frame models, since the model's identity is often
defined by a certain tube set, do not make use of the lighter tubes in
the small sizes, nor the heavier tubes in the large sizes. This
problem is compounded by the fact that quite often it is the larger
frame sizes which carry the most powerful riders, and are thus in
greatest need of the heavier tube sets. In fact, with the exception of
oversize welded aluminum frames, even the stiffest tubing used for
large frames did not always make up for the increase in flexibility
caused by the larger frame size. In the very large sizes (above 61
cm), the frames are almost never stiff enough to satisfy powerful
riders. It is a challenge to the designer to make the small frames as
light as possible and large frames stiff enough."

The table of results by frame sizes often shows carbon frames flexing
as much or more as steel and titanium frames of the same size.

Oversize aluminum tubes are often stiffer.

Front and rear triangle stiffness varied even in the same frame--that
is, a frame with a very stiff rear triangle may have a front triangle
that bends easily, and vice-versa.

Other than Damon Rinard's testing for flex, I know of no place to find
any numbers or testing for the familiar claim that bicycles of roughly
similar weight accelerate so differently due to frame material that a
rider should be able to feel the improvement.

I'd love to see such tests or even someone working through some
numbers in search of a theoretical result.

Cheers,

Carl Fogel

carlfogel@comcast.net

01-04-1970, 11:38 AM

On Sat, 07 Jun 2008 15:38:31 GMT, John Forrest Tomlinson
<usenetremove@jt10000.com> wrote:

>On Sat, 07 Jun 2008 09:45:52 -0500, A Muzi <am@yellowjersey.org>
>wrote:
>
>>Your argument could easily apply to oval chainrings or centerpull
>>brakes, each of which were de rigeur for the trendy race bikes of their
>>respective eras.
>
>Centerpull was the best for a long time. Non-round rings never caught
>on that much -- they were specced on a lot of bikes and removed on a
>lot of bikes.

Dear John,

Speaking of popularity and non-round rings . . .

A few weeks ago, an experienced, successful, and enthusiastic rider
and bicycle collector showed me a few "PowerCam" cranks, which he
swears by.

Embarrassingly, I'd never heard of "PowerCam" and couldn't figure out
how the hell the contraption worked, even when he showed me one still
sitting in its box.

A "PowerCam" is supposed to feel very different from a normal crank
and requires a 60-tooth front sprocket. The only drawback, according
to the owner, was that it had to be lubricated daily.

I looked "PowerCam" up, but I still can't figure it out. I have a
vague suspicion that the whole crank slides back and forth slightly
instead of staying fixed in the bottom bracket, turning the circular
pedal cycle into a flattened oval.

Here's a page with pictures of a "PowerCam":

http://www.velobase.com/ViewSingleComponent.aspx?ID=EA56395B-A2BF-4EA7-BF4E-3BB0449EFF8B&Enum=115&AbsPos=0

The mysterious entrails on the inside of a "PowerCam":

http://www.velobase.com/CompImages/Crankset/B1977919-CB29-46DA-92B2-9FA1DB6F8556.jpeg

The directions on that page are almost unreadable, but they seem to
explain how to install the "PowerCam" and warn about not shifting
during some part of the pedal cycle.

If nothing else, hunting for "PowerCam" led me to this nice site for
looking up old equipment:
http://www.velobase.com/SearchComponent.aspx

"PowerCam" from Houdille was not considered a breakthrough on RBT:

http://groups.google.com/group/rec.bicycles.tech/search?group=rec.bicycles.tech&q=powercam

Cheers,

Carl Fogel

Frank Krygowski

01-04-1970, 11:38 AM

On Jun 7, 3:12 pm, carlfo...@comcast.net wrote:
>
> Dear John,
>
> Speaking of popularity and non-round rings . . .
>
> A few weeks ago, an experienced, successful, and enthusiastic rider
> and bicycle collector showed me a few "PowerCam" cranks, which he
> swears by.
>
> Embarrassingly, I'd never heard of "PowerCam" and couldn't figure out
> how the hell the contraption worked, even when he showed me one still
> sitting in its box.
>
> A "PowerCam" is supposed to feel very different from a normal crank
> and requires a 60-tooth front sprocket. The only drawback, according
> to the owner, was that it had to be lubricated daily.
>
> I looked "PowerCam" up, but I still can't figure it out. I have a
> vague suspicion that the whole crank slides back and forth slightly
> instead of staying fixed in the bottom bracket, turning the circular
> pedal cycle into a flattened oval.

The Powercam device caused the chainring to change phase angle with
respect to the crank. IOW, if you turned the crank at constant
angular velocity, the chainring would speed up and slow down (twice)
as you made your way through each revolution.

The effect was to give a higher gear ratio in one part of the pedal
stroke, and a lower gear ratio in a different part of the stroke.
Your feet still moved in circles. The effect was similar to what
results from elliptical or Biopace chainrings do, but with more
mechanical complication. I imagine the effective profiles are
different with Powercam, too. ISTR the overall gear ratio was
extremely high.

It was yet another invention claimed to Transform Bicycling As We Know
It. And IIRC, Lon Haldeman used it with some success in endurance
racing - which probably means it at least didn't break down
mechanically.

But Bicycling As We Know It remains much the same - except for the
modern addition of "unrepairability."

- Frank Krygowski

carlfogel@comcast.net

01-04-1970, 11:39 AM

On Sat, 07 Jun 2008 14:10:11 -0600, carlfogel@comcast.net wrote:

>On Sat, 7 Jun 2008 08:24:03 -0700 (PDT), Frank Krygowski
><frkrygow@gmail.com> wrote:
>
>>On Jun 7, 12:11 am, Michael Press <rub...@pacbell.net> wrote:
>>> In article <743j44hb8kh4o7e2hv19d7pd8j5a73g...@4ax.com>,
>>>
>>> carlfo...@comcast.net wrote:
>>> > A stiffer frame probably means nothing in terms of effective power,
>>> > since a metal frame turns out to act as a very efficient spring.
>>>
>>> Nobody here has ever presented a persuasive argument or
>>> a pointer to a persuasive argument showing that energy
>>> expended flexing the frame is not totally dissipated.
>>
>>Well, "persuasive" is in the eye of the beholder. And it's very hard
>>to persuade most people that what they've posted is wrong!
>>
>>> Less flex means less power going into flexing the frame.
>>
>>Let me try some alternative explanations.
>>
>>First, if frame flex absorbs leg power, it can only be because your
>>leg does more work on the downstroke - that is, applies force through
>>a greater distance in the same direction as the force. Now, how much
>>greater is that distance? IOW, how much further downward does the
>>pedal move with a flexible frame? Probably no more than 3 mm, I'd
>>guess. That's a very minor portion of the 350 mm your foot moves down
>>in the power stroke.
>>
>>BUT even that energy is not lost. Remember that cyclists don't pull
>>up on the backstroke, despite some claims to the contrary. Your leg
>>is lifted on the backstroke at least partly by the front leg's power
>>stroke.
>>
>>So the energy that comes from more downward motion on the forward
>>stroke causes more upward motion for the backstroke. It's at least
>>partly (maybe entirely) captured by raising the back leg.
>>
>>Finally, as people have pointed out before, if energy is dissipated by
>>frame flex, it should be detectable in temperature rise of the frame
>>material. AFAIK, this has never been detected. (People have used
>>thermal imaging to "see" friction loss in chain drives, so the
>>temperature rise wouldn't need to be huge to be seen.)
>>
>>If there's a benefit to a stiff frame, it may be psychological. Which
>>is not to say it's negligible! Sports has a huge psych component.
>>
>>But instead of spending for a frame, it may be as effective, and much
>>cheaper, to spend for a new "magic" frame decal, plus a hypnosis
>>session. ;-)
>>
>>- Frank Krygowski
>
>Dear Frank,
>
>Damon Rinard measured frame flex for a variety of models, sizes, and
>materials:
> http://www.sheldonbrown.com/rinard/rinard_frametest.html
>
>He noted that larger frames flex more than smaller frames:
>
>"All frame builders know that smaller frames are inherently stiffer
>and larger frames are inherently more flexible. What I found in my
>testing is that this effect is greater than I thought. Even the
>lightest tube sets, when made into a small frame, end up nearly the
>same stiffness as the heaviest tube sets, when made into a large
>frame! And many frame models, since the model's identity is often
>defined by a certain tube set, do not make use of the lighter tubes in
>the small sizes, nor the heavier tubes in the large sizes. This
>problem is compounded by the fact that quite often it is the larger
>frame sizes which carry the most powerful riders, and are thus in
>greatest need of the heavier tube sets. In fact, with the exception of
>oversize welded aluminum frames, even the stiffest tubing used for
>large frames did not always make up for the increase in flexibility
>caused by the larger frame size. In the very large sizes (above 61
>cm), the frames are almost never stiff enough to satisfy powerful
>riders. It is a challenge to the designer to make the small frames as
>light as possible and large frames stiff enough."
>
>The table of results by frame sizes often shows carbon frames flexing
>as much or more as steel and titanium frames of the same size.
>
>Oversize aluminum tubes are often stiffer.
>
>Front and rear triangle stiffness varied even in the same frame--that
>is, a frame with a very stiff rear triangle may have a front triangle
>that bends easily, and vice-versa.
>
>Other than Damon Rinard's testing for flex, I know of no place to find
>any numbers or testing for the familiar claim that bicycles of roughly
>similar weight accelerate so differently due to frame material that a
>rider should be able to feel the improvement.
>
>I'd love to see such tests or even someone working through some
>numbers in search of a theoretical result.
>
>Cheers,
>
>Carl Fogel

I should have added that Damon Rinard has a long FEA page about strain
energy and how it's stored in frames:
http://www.sheldonbrown.com/rinard/fea.htm

A few passages of interest . . .

"The true intent of a stiff frame is to transfer energy efficiently
from the cyclist to the rear wheel. This implies that the designer
should minimize the amount of energy that goes into flexing
(straining) the frame. Some of this strain energy might be recoverable
(i.e., released in such a way as to add power to the rear wheel). But
we know of no measurements that show how much is recovered. Thus, we
assume that the best policy is to minimize strain energy absorption in
the frame."

[That is, how much of the energy is recovered is unknown.]

"First, note that the start-up (or hill-climbing) load generates the
highest level of energy storage. The energy stored here (79.5 in-lb)
represents about 4.0 percent of the rider's total energy output under
typical hill-climbing conditions. This might sound like a small
percentage, but in racing situations, even a slight reduction in this
percentage would be noticed."

[That is, hill-climbing and start-up would be where things might be
noticed, not the familiar case of "snap" out of corners. And frame
differences will be trying to change a maximum loss of 4% of the
rider's effort--meaning that a frame twice as efficient could save a
maximum 6 watts at 300 watts, and less than that if any energy is
recovered.]

"The down tube is always the greatest energy absorber. It stores
between 38% and 49% of the total. Of this, between 58% and 66% is due
to torsion. The remainder is due to out-of-plane bending. In-plane
bending and axial loading are insignificant."

[In other words, the slight barber-pole twisting of the down-tube is
where most of the action is, not the bending that's often noticed when
the chain rubs the front derailleur.]

Cheers,

Carl Fogel

Frank Krygowski

01-04-1970, 11:39 AM

On Jun 7, 4:28 pm, carlfo...@comcast.net wrote:
>
> I should have added that Damon Rinard has a long FEA page about strain
> energy and how it's stored in frames:
> http://www.sheldonbrown.com/rinard/fea.htm
>
> A few passages of interest . . .
>
> "The true intent of a stiff frame is to transfer energy efficiently
> from the cyclist to the rear wheel. This implies that the designer
> should minimize the amount of energy that goes into flexing
> (straining) the frame. Some of this strain energy might be recoverable
> (i.e., released in such a way as to add power to the rear wheel). But
> we know of no measurements that show how much is recovered. Thus, we
> assume that the best policy is to minimize strain energy absorption in
> the frame."
>
> [That is, how much of the energy is recovered is unknown.]
>
> "First, note that the start-up (or hill-climbing) load generates the
> highest level of energy storage. The energy stored here (79.5 in-lb)
> represents about 4.0 percent of the rider's total energy output under
> typical hill-climbing conditions. This might sound like a small
> percentage, but in racing situations, even a slight reduction in this
> percentage would be noticed."
>
> [That is, hill-climbing and start-up would be where things might be
> noticed, not the familiar case of "snap" out of corners. And frame
> differences will be trying to change a maximum loss of 4% of the
> rider's effort--meaning that a frame twice as efficient could save a
> maximum 6 watts at 300 watts, and less than that if any energy is
> recovered.]

ISTM that there is evidence that either much of the strain energy is
recovered, or at least that down tube strain energy does not
significantly sap acceleration.

My thought processes went like this:

One could build some racing bikes with absurdly stiff down tubes, and
race them in competition with more normal bikes. If the absurdly
stiff frames didn't strongly dominate, that would be evidence that
down tube energy absorption wasn't a strong effect.

Then I thought: Oh yeah. That's been done. By Cannondale.

Cannondale was successful enough with their early '90s (was it?)
frames, with downtubes that looked like cannons. But they weren't so
successful that everybody else jumped on the absolutely-massive-
downtube wagon. They weren't seen as magic bullets - just another
good, trendy bike for those who liked them.

BTW, there is a completely opposite viewpoint out there. Jan Heine,
in his "Bicycle Quarterly" magazine, compliments many frames for their
mysterious "planing" action. It's a word he uses for some mystical
synchronizing between frame flex and rider input. He maintains that
if a frame doesn't have the so-far-unexplained flex, the rider never
"gets on top of the gear" and is significantly slower. He's
absolutely against super-rigid bikes, from what I can tell.

I get the impression that, as in lots of bike technology, there's lots
of "magic" at work. Some of the incantations involve ill-defined
words and indescribable feelings. Other incantations involve
inscrutable numerology. ;-)

- Frank Krygowski

Ben C

01-04-1970, 11:41 AM

On 2008-06-08, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
> Ben C? wrote:
>
>>>> Do you know of any actual tests that show bicycles accelerating
>>>> differently according to whether the frames are made of steel,
>>>> aluminum, carbon, or titanium?
>
>>> Carl, are you really that old? There's no question that the design
>>> of the frame is of the paramount consideration, but given two
>>> identical frame designs, the inherent stiffness (modulus of
>>> elasticity) of carbon or aluminum translates into less damping of
>>> the power to the wheel.
>
>>> Besides that, do you think that if there were no advantage, people
>>> wouldn't still be racing steel frames?
>
>> Aluminium has a much _lower_ modulus of elasticity than steel. But
>> an aluminium frame may or may not be stiffer than a steel one,
>> because it depends on a lot of things like how thick/fat you make
>> the tubes.
>
>> I found this an interesting read:
>
> http://www.bobbrowncycles.com/eng.htm
>
>> (thanks to Tim for a link to bobbrowncycles the other day).
>
>> See also:
>
> http://www.sheldonbrown.com/frame-materials.html
>> and:
>
> http://sheldonbrown.com/rinard_frametest.html
>
>> Damping is distinct from stiffness. Carbon fibre may provide some
>> damping that you don't get in metal frames.
>
> Hold the phone! Energy absorption must be in the frequency of input
> forces, of which human input is far from the acoustic range, the one
> so obviously not transmitted by materials as soft as plastics, of
> which the mass of carbon fiber frames are. Their strength is
> longitudinally with the fibers but not laterally, the direction of
> vibration of frame elements.

While I don't really think the damping effects of CF result in any
inefficiency (I'm still not convinced that on a springy but undamped
frame you get any of the energy back anyway), you raise an interesting
point.

How does the damping of a tube of CF vary with the frequency at which it
is oscillating (as opposed to the frequency at which it is driven, so as
to eliminate the consideration of resonance)?

It depends how we measure damping-- if it's a power then it probably is
at least proportional to the frequency and amplitude.

Tom Kunich

01-04-1970, 11:41 AM

<jobst.brandt@stanfordalumni.org> wrote in message
news:484b355f$0$17235$742ec2ed@news.sonic.net...
> Tom Kunich wrote:
>> Why is it so difficult to understand that flexing a frame misaligns
>> the wheels which scrub off a tiny portion of the input power?
>
> Tire scrub has been accused of all sorts of ills, none of which exist,
> especially from frame flex. If that were so, you ought to try this on
> a freshly concreted street where the road is still white. Tire scrub
> would be shockingly obvious. My experience is that just mild smooth
> cornering will leave a faint track. Pedaling hard (in a straight line)
> should leave a darker track with lateral waves.
>
> Do it!

Come on Jobst! The amount of wear is microscopic and you well know it. The
amount of energy a flexy frame "absorbs" vs. a stiffer frame is minute to
begin with.

sergio

01-04-1970, 11:42 AM

On 8 Giu, 12:18, Ben C <spams...@spam.eggs> wrote:
> On 2008-06-08, jobst.bra...@stanfordalumni.org <jobst.bra...@stanfordalumni.org> wrote:

> > Hold the phone! Energy absorption must be in the frequency of input
> > forces,

In the linear range that is mainly so, though not exactly. In fact,
there is absoption also away from the proper frequency.

> > of which human input is far from the
acoustic range,

... and, in this regard, human flesh is highly non linear, absorbing
just about anything (a punch in the nose just as well as the
vibrations of a violin string).

Unless you pedal essentially in phase with the vibrations,, an
impossible feat, you won't get any benefit from them; instead, you are
just bound to jump around and provide some absoption.

Sergio
Pisa

Tom Kunich

01-04-1970, 11:43 AM

"Frank Krygowski" <frkrygow@gmail.com> wrote in message
news:eddadd62-a6cb-46eb-a9da-e1d3cae8cb51@d1g2000hsg.googlegroups.com...
>
> But Bicycling As We Know It remains much the same - except for the
> modern addition of "unrepairability."

Ahh, yes, Frank you seem to jump right to the heart of the matter. Carbon
fiber bicycles are so superior to steel. For instance, my foot went into the
front spokes a couple of weeks ago and the carbon fiber fork broke so
rapidly and cleanly that it didn't put a single scratch on my toes! Of
course trying to ride a bike without a front wheel had some grave
consequences but I'll recover soon.....

Tom Kunich

01-04-1970, 11:43 AM

"Frank Krygowski" <frkrygow@gmail.com> wrote in message
news:2c966c9c-f205-4be0-a467-0bb7d9d2b330@s50g2000hsb.googlegroups.com...
>
> One could build some racing bikes with absurdly stiff down tubes, and
> race them in competition with more normal bikes. If the absurdly
> stiff frames didn't strongly dominate, that would be evidence that
> down tube energy absorption wasn't a strong effect.
>
> Then I thought: Oh yeah. That's been done. By Cannondale.
>
> Cannondale was successful enough with their early '90s (was it?)
> frames, with downtubes that looked like cannons. But they weren't so
> successful that everybody else jumped on the absolutely-massive-
> downtube wagon. They weren't seen as magic bullets - just another
> good, trendy bike for those who liked them.

I've had just about every kind of bike and to tell you the truth the
difference in input power vs. speed is essentially identical. The bike I'm
riding a great deal lately is my Look KG 241 which is a quite soft carbon
fiber frame. I don't seem to have any problems with it. My Time VX carbon
frame rides slightly faster. My Colnago C40 slightly faster still and
corners MUCH better because the frame is super stiff.

And they when you start thinking about it - the compliance of the tires is
perhaps 100 times as great as the compliance of the frame. How would you
ever tell between frames?

Jay Beattie

01-04-1970, 11:43 AM

On Jun 8, 8:05*am, Frank Krygowski <frkry...@gmail.com> wrote:
> On Jun 7, 4:28 pm, carlfo...@comcast.net wrote:
>
>
>
>
>
>
>
> > I should have added that Damon Rinard has a long FEA page about strain
> > energy and how it's stored in frames:
> > *http://www.sheldonbrown.com/rinard/fea.htm
>
> > A few passages of interest . . .
>
> > "The true intent of a stiff frame is to transfer energy efficiently
> > from the cyclist to the rear wheel. This implies that the designer
> > should minimize the amount of energy that goes into flexing
> > (straining) the frame. Some of this strain energy might be recoverable
> > (i.e., released in such a way as to add power to the rear wheel). But
> > we know of no measurements that show how much is recovered. Thus, we
> > assume that the best policy is to minimize strain energy absorption in
> > the frame."
>
> > [That is, how much of the energy is recovered is unknown.]
>
> > "First, note that the start-up (or hill-climbing) load generates the
> > highest level of energy storage. The energy stored here (79.5 in-lb)
> > represents about 4.0 percent of the rider's total energy output under
> > typical hill-climbing conditions. This might sound like a small
> > percentage, but in racing situations, even a slight reduction in this
> > percentage would be noticed."
>
> > [That is, hill-climbing and start-up would be where things might be
> > noticed, not the familiar case of "snap" out of corners. And frame
> > differences will be trying to change a maximum loss of 4% of the
> > rider's effort--meaning that a frame twice as efficient could save a
> > maximum 6 watts at 300 watts, and less than that if any energy is
> > recovered.]
>
> ISTM that there is evidence that either much of the strain energy is
> recovered, or at least that down tube strain energy does not
> significantly sap acceleration.
>
> My thought processes went like this:
>
> One could build some racing bikes with absurdly stiff down tubes, and
> race them in competition with more normal bikes. *If the absurdly
> stiff frames didn't strongly dominate, that would be evidence that
> down tube energy absorption wasn't a strong effect.
>
> Then I thought: *Oh yeah. *That's been done. *By Cannondale.
>
> Cannondale was successful enough with their early '90s (was it?)
> frames, with downtubes that looked like cannons. *But they weren't so
> successful that everybody else jumped on the absolutely-massive-
> downtube wagon. *They weren't seen as magic bullets - just another
> good, trendy bike for those who liked them.
>

These weren't magically stiff frames. In fact, they were a lot less
stiff than the original 6061 straight gauge design. They were
lighter, though. The 2.8 was actually too soft in the head tube/top
tube, and the aluminum fork was spongy. The current budget frame
(which I ride) is quite nice --- and less harsh riding than the
original Cannondale frame or even my 70/80s Columbus SP frames.

Bike weight and tire profile can make a huge difference. I do the
same climbs on my cross bike with 35mm tires and my racing bike with
23/25mm tires, and on the racing bike, I do the climb in a cog two or
three teeth smaller and quite a bit faster. Shoe sole stiffness can
make a big difference, too. -- Jay Beattie.

PS -- I just have to share this, I got back in to cleats on both feet
today almost five months after breaking my leg skiing (slow union). I
was riding in an orthopedic boot and using a platform pedal for a
couple months, and now I just have a little gel splint on my right
ankle. Having both feet clipped in makes a huge difference --
although my right leg is not contributing much at this point. There
were flocks of brightlly colored riders out today, and I rolled past a
group on the way up a climb -- a mix of racers and wannabes, and half
way up, three twenty-something racers on uber-bikes went around and
gapped me, except that one blew up before the top, and I passed him.
I felt like saying, dude, you're getting passed by a 51 year old with
a broken leg --- on a cheap Cannondale frame. Time to spend more
moneey on a lighter bike -- maybe Ti cogs or something.

andresmuro@aol.com

01-04-1970, 11:43 AM

On Jun 8, 9:05 am, Frank Krygowski <frkry...@gmail.com> wrote:
> On Jun 7, 4:28 pm, carlfo...@comcast.net wrote:
>
>
>
>
>
> > I should have added that Damon Rinard has a long FEA page about strain
> > energy and how it's stored in frames:
> > http://www.sheldonbrown.com/rinard/fea.htm
>
> > A few passages of interest . . .
>
> > "The true intent of a stiff frame is to transfer energy efficiently
> > from the cyclist to the rear wheel. This implies that the designer
> > should minimize the amount of energy that goes into flexing
> > (straining) the frame. Some of this strain energy might be recoverable
> > (i.e., released in such a way as to add power to the rear wheel). But
> > we know of no measurements that show how much is recovered. Thus, we
> > assume that the best policy is to minimize strain energy absorption in
> > the frame."
>
> > [That is, how much of the energy is recovered is unknown.]
>
> > "First, note that the start-up (or hill-climbing) load generates the
> > highest level of energy storage. The energy stored here (79.5 in-lb)
> > represents about 4.0 percent of the rider's total energy output under
> > typical hill-climbing conditions. This might sound like a small
> > percentage, but in racing situations, even a slight reduction in this
> > percentage would be noticed."
>
> > [That is, hill-climbing and start-up would be where things might be
> > noticed, not the familiar case of "snap" out of corners. And frame
> > differences will be trying to change a maximum loss of 4% of the
> > rider's effort--meaning that a frame twice as efficient could save a
> > maximum 6 watts at 300 watts, and less than that if any energy is
> > recovered.]
>
> ISTM that there is evidence that either much of the strain energy is
> recovered, or at least that down tube strain energy does not
> significantly sap acceleration.
>
> My thought processes went like this:
>
> One could build some racing bikes with absurdly stiff down tubes, and
> race them in competition with more normal bikes. If the absurdly
> stiff frames didn't strongly dominate, that would be evidence that
> down tube energy absorption wasn't a strong effect.
>
> Then I thought: Oh yeah. That's been done. By Cannondale.
>
> Cannondale was successful enough with their early '90s (was it?)
> frames, with downtubes that looked like cannons. But they weren't so
> successful that everybody else jumped on the absolutely-massive-
> downtube wagon. They weren't seen as magic bullets - just another
> good, trendy bike for those who liked them.
>
> BTW, there is a completely opposite viewpoint out there. Jan Heine,
> in his "Bicycle Quarterly" magazine, compliments many frames for their
> mysterious "planing" action. It's a word he uses for some mystical
> synchronizing between frame flex and rider input. He maintains that
> if a frame doesn't have the so-far-unexplained flex, the rider never
> "gets on top of the gear" and is significantly slower. He's
> absolutely against super-rigid bikes, from what I can tell.
>
> I get the impression that, as in lots of bike technology, there's lots
> of "magic" at work. Some of the incantations involve ill-defined
> words and indescribable feelings. Other incantations involve
> inscrutable numerology. ;-)
>
> - Frank Krygowski

In fact during the 80s and 90s most pros used to ride italian steel
frames or french aluminum frames. The french aluminum frames were
known for being very soft. Pros who rode the french vitus frames were
apparently not at any disadvantage over the stiffer columbus slx and
max tubed frames. If there was a proven advantage of stiff vs soft
frames everyone would ride the stiffer ones. In fact, many pros would
disguise the softer vitus frames as the stiff steel frames if their
sponsors required them to ride the italian stiff stuff.

This argument has been around at least since I started riding in the
early 80s. Magazines would always compliment stiffer frames and ads
would always pronounce the superiority of their stiffer frames.
However, I haven't read any article that proves that stiffer is better
and my own experience is that I don't get any faster with a stiffer or
softer frame.

Andres

jobst.brandt@stanfordalumni.org

01-04-1970, 11:45 AM

Michael Press wrote:

>>>> A stiffer frame probably means nothing in terms of effective
>>>> power, since a metal frame turns out to act as a very efficient
>>>> spring.

>>> Nobody here has ever presented a persuasive argument or a pointer
>>> to a persuasive argument showing that energy expended flexing the
>>> frame is not totally dissipated. Less flex means less power going
>>> into flexing the frame.

>> Much more important is that no one has shown where elastic
>> deformation absorbs energy (power) or that frame flex which is
>> almost entirely lateral from off center pedal force, causes plastic
>> deformation, the only mode where energy might be dissipated. Of
>> course, such deformation would cause frame rapid failure.

> I am not quantifying. I hold that energy going into flexing the
> frame is lost to propelling the bicycle forward.

Please consider where this energy is going and what occurs at the end
of the pedal stroke as downward force returns to zero. Let me suggest
that the frame does not remain flexed, but rather returns to its
original shape and in doing so returns the active foot to the position
it would have with an infinitely rigid frame. It is that elastic
return that restores the imagined loss to the input work.

From the discussions on this topic, one might imagine a frame that
gets progressively farther out of no-load geometry with each stroke
and absorbs work that must escape as heat. Neither of these occurs.

Jobst Brandt

Lawrence Doan

01-04-1970, 11:45 AM

jobst.brandt@stanfordalumni.org wrote:
> Michael Press wrote:
>
>>>>> A stiffer frame probably means nothing in terms of effective
>>>>> power, since a metal frame turns out to act as a very efficient
>>>>> spring.
>
>>>> Nobody here has ever presented a persuasive argument or a pointer
>>>> to a persuasive argument showing that energy expended flexing the
>>>> frame is not totally dissipated. Less flex means less power going
>>>> into flexing the frame.
>
>>> Much more important is that no one has shown where elastic
>>> deformation absorbs energy (power) or that frame flex which is
>>> almost entirely lateral from off center pedal force, causes plastic
>>> deformation, the only mode where energy might be dissipated. Of
>>> course, such deformation would cause frame rapid failure.
>
>> I am not quantifying. I hold that energy going into flexing the
>> frame is lost to propelling the bicycle forward.
>
> Please consider where this energy is going and what occurs at the end
> of the pedal stroke as downward force returns to zero. Let me suggest
> that the frame does not remain flexed, but rather returns to its
> original shape and in doing so returns the active foot to the position
> it would have with an infinitely rigid frame. It is that elastic
> return that restores the imagined loss to the input work.
>
> From the discussions on this topic, one might imagine a frame that
> gets progressively farther out of no-load geometry with each stroke
> and absorbs work that must escape as heat. Neither of these occurs.
>
> Jobst Brandt

Hm. Makes one wonder if perceived differences in performance with
frame stiffness have to do with harmonics. If the rider pedals at
the natural frequency of bottom bracket sway, for instance, that
would be expected to drive the frame oscillations to higher amplitudes
than a stiffer frame with a correspondingly higher natural frequency.

Might not driving the frame into resonance be perceived as 'whippy'?
In either case the frame isn't absorbing energy, but in the
large-amplitude/low stiffness case, the rider feeling the movement
could easily _seem_ like work not going into the wheels.

I can see bottom bracket sway when I sprint up a hill but only ride
the one bike so I have nothing to compare it to.

-Lawrence

Ben C

01-04-1970, 11:45 AM

On 2008-06-08, jobst.brandt@stanfordalumni.org <jobst.brandt@stanfordalumni.org> wrote:
[...]
>> I am not quantifying. I hold that energy going into flexing the
>> frame is lost to propelling the bicycle forward.
>
> Please consider where this energy is going and what occurs at the end
> of the pedal stroke as downward force returns to zero. Let me suggest
> that the frame does not remain flexed, but rather returns to its
> original shape and in doing so returns the active foot to the position
> it would have with an infinitely rigid frame. It is that elastic
> return that restores the imagined loss to the input work.

Yes this is the most convincing theory-- basically that the frame
springing back helps you lift your foot back up again.

> From the discussions on this topic, one might imagine a frame that
> gets progressively farther out of no-load geometry with each stroke
> and absorbs work that must escape as heat. Neither of these occurs.

There's no reason the energy has to be lost as plastic deformation of
the frame or heat. It could easily be absorbed by the big bag of water
perched on the seat and connected to the pedals by flexible rods.

Michael Press

01-04-1970, 11:45 AM

In article <484c62fc$0$17194$742ec2ed@news.sonic.net>,
jobst.brandt@stanfordalumni.org wrote:

> Michael Press wrote:
>
> >>>> A stiffer frame probably means nothing in terms of effective
> >>>> power, since a metal frame turns out to act as a very efficient
> >>>> spring.
>
> >>> Nobody here has ever presented a persuasive argument or a pointer
> >>> to a persuasive argument showing that energy expended flexing the
> >>> frame is not totally dissipated. Less flex means less power going
> >>> into flexing the frame.
>
> >> Much more important is that no one has shown where elastic
> >> deformation absorbs energy (power) or that frame flex which is
> >> almost entirely lateral from off center pedal force, causes plastic
> >> deformation, the only mode where energy might be dissipated. Of
> >> course, such deformation would cause frame rapid failure.
>
> > I am not quantifying. I hold that energy going into flexing the
> > frame is lost to propelling the bicycle forward.
>
> Please consider where this energy is going and what occurs at the end
> of the pedal stroke as downward force returns to zero. Let me suggest
> that the frame does not remain flexed, but rather returns to its
> original shape and in doing so returns the active foot to the position
> it would have with an infinitely rigid frame. It is that elastic
> return that restores the imagined loss to the input work.

Some of the return flex motion moves the pedal and foot
laterally. Dot product of force and displacement is zero.
No work done turning the crank.

> From the discussions on this topic, one might imagine a frame that
> gets progressively farther out of no-load geometry with each stroke
> and absorbs work that must escape as heat. Neither of these occurs.

But not by me. Nowhere have I advanced that notion.

--
Michael Press