The difference tube diameter makes

On Tuesday, August 12, 2014 4:00:20 AM UTC+1, James wrote:
I had a bit of road rubbish flick up and dent the underside of the down

tube on my new road bike. (It's only done 45,000km).

Sorry to hear your "new" bike was dented at "only 45,000km".

You really get value out of your bikes.

Andre Jute

On 13/08/14 01:22, Frank Krygowski wrote:
On 8/11/2014 11:00 PM, James wrote:
I had a bit of road rubbish flick up and dent the underside of the down
tube on my new road bike. (It's only done 45,000km). The dent was
probably 2-3mm deep, and had damaged the paint. There were a few other
scratches here and there, so I gave it a birthday, and had the dent
pulled out and the frame resprayed.

I'm curious about getting the dent pulled out. How did they do that?


The frame builder said he silver soldered a wire on and used a slide hammer.

It's a pretty good job. Hard to detect there was a dent there, unless
you know it was there and go looking for evidence.



In the down time, I completed building a training bike I'd started a
year ago. A 20 year old custom 853 lugged racing frame, with the same
wheels as my new bike.

The major difference is the frame tube diameter. The old frame having
the customary 1" tubes, where as the new bike frame has 1 1/8" and 1
1/4" oversize tubes.

I rode 166km on Saturday on the old bike, and then last night, 60km on
the new bike.

The difference in the way they ride is very obvious. The old bike feels
like a soft spring when I stand on the pedals, and I can watch the chain
rings wobble around while I pedal hard, even seated.

The new bike feels crisp and zippy underneath me. It feels like every
ounce of effort going into the pedals gets translated to the back wheel
and on to the road....

I prefer a stiff frame, too. But I note that Jan Heine, who (almost
single-handedly) publishes _Bicycle Quarterly_, likes a certain amount
of flex. He claims the flex somehow allows the bike to synchronize with
his pedal strokes (or something). He calls the action "planing," as
when certain types of power boats skim the surface, rather than floating.

Hard to tell if it's imaginary or not. His magazine has some
interesting tests and data from time to time, but his road tests greatly
emphasize how a bike feels to him - as is usually the case with road tests.


How the bike feels is all in the eyes of the tester, and I agree many
get carried away. I guess in the magazines that's what they're paid for
- advertising bull****, mostly.

I note my old frame has a steeper head tube angle, and will shimmy
easily, where as the new frame is more relaxed and longer and gives a
very stable ride. I asked for more clearance so I could fit larger
tyres easily.

You really only experience the effects of frame stiffness when you jump
for a sprint, or need to stand on the pedals up a steep hill. If the
whole thing contorts underneath you, it's very disconcerting. It
doesn't inspire confidence. In a race, you probably won't do as well as
a result - even if it is only in your mind.

I think people have been sold on shorter wheel base as giving a more
lively ride. Well, it might make the steering more twitchy, but I don't
think it necessarily helps in a sprint - especially today with modern
engineered materials and processes, frames that can be made as stiff as
you like without noticeable weight penalty or need for shortening the tubes.

--
JS

On 8/12/2014 6:18 PM, James wrote:


You really only experience the effects of frame stiffness when you jump
for a sprint, or need to stand on the pedals up a steep hill. If the
whole thing contorts underneath you, it's very disconcerting. It
doesn't inspire confidence. In a race, you probably won't do as well as
a result - even if it is only in your mind.

I think people have been sold on shorter wheel base as giving a more
lively ride. Well, it might make the steering more twitchy, but I don't
think it necessarily helps in a sprint - especially today with modern
engineered materials and processes, frames that can be made as stiff as
you like without noticeable weight penalty or need for shortening the
tubes.

I agree, sprinting or climbing is when I appreciate a bottom bracket
that stays in place.

But thinking about twitchiness: I've never understood why twitchy
steering is supposed to be an advantage in a race. I'd think it would
be tiring during a long race, and make the bike less controllable in a
sprint, so be disconcerting in the same way you describe frame flex to be.

Granted, there must be a such a thing as too much stability (I remember
being astonished at the super-stability in a 1970s low-end Schwinn I was
tuning for a neighbor), but modern racing bikes are nowhere near
excessively stable.


--
- Frank Krygowski

On Tue, 12 Aug 2014 11:22:03 -0400, Frank Krygowski
wrote:

On 8/11/2014 11:00 PM, James wrote:
I had a bit of road rubbish flick up and dent the underside of the down
tube on my new road bike. (It's only done 45,000km). The dent was
probably 2-3mm deep, and had damaged the paint. There were a few other
scratches here and there, so I gave it a birthday, and had the dent
pulled out and the frame resprayed.

I'm curious about getting the dent pulled out. How did they do that?



In the down time, I completed building a training bike I'd started a
year ago. A 20 year old custom 853 lugged racing frame, with the same
wheels as my new bike.

The major difference is the frame tube diameter. The old frame having
the customary 1" tubes, where as the new bike frame has 1 1/8" and 1
1/4" oversize tubes.

I rode 166km on Saturday on the old bike, and then last night, 60km on
the new bike.

The difference in the way they ride is very obvious. The old bike feels
like a soft spring when I stand on the pedals, and I can watch the chain
rings wobble around while I pedal hard, even seated.

The new bike feels crisp and zippy underneath me. It feels like every
ounce of effort going into the pedals gets translated to the back wheel
and on to the road....

I prefer a stiff frame, too. But I note that Jan Heine, who (almost
single-handedly) publishes _Bicycle Quarterly_, likes a certain amount
of flex. He claims the flex somehow allows the bike to synchronize with
his pedal strokes (or something). He calls the action "planing," as
when certain types of power boats skim the surface, rather than floating.

Hard to tell if it's imaginary or not. His magazine has some
interesting tests and data from time to time, but his road tests greatly
emphasize how a bike feels to him - as is usually the case with road tests.

I would say that his choice of words is incorrect. A boat doesn't
plane due to a flexible frame. Quite the opposite perhaps :-)

But as the frame of a bicycle flexes under load and than returns to
its original position when the load is reduced it might be referred to
as "Springing". Which does sound sort of "cool". "I was just springing
along on my bike", "I shall just hop on my bicycle and spring away"
:-)
--
Cheers,

John B.

On 13/08/14 12:38, John B. Slocomb wrote:
On Tue, 12 Aug 2014 11:22:03 -0400, Frank Krygowski
wrote:

On 8/11/2014 11:00 PM, James wrote:
I had a bit of road rubbish flick up and dent the underside of the down
tube on my new road bike. (It's only done 45,000km). The dent was
probably 2-3mm deep, and had damaged the paint. There were a few other
scratches here and there, so I gave it a birthday, and had the dent
pulled out and the frame resprayed.

I'm curious about getting the dent pulled out. How did they do that?



In the down time, I completed building a training bike I'd started a
year ago. A 20 year old custom 853 lugged racing frame, with the same
wheels as my new bike.

The major difference is the frame tube diameter. The old frame having
the customary 1" tubes, where as the new bike frame has 1 1/8" and 1
1/4" oversize tubes.

I rode 166km on Saturday on the old bike, and then last night, 60km on
the new bike.

The difference in the way they ride is very obvious. The old bike feels
like a soft spring when I stand on the pedals, and I can watch the chain
rings wobble around while I pedal hard, even seated.

The new bike feels crisp and zippy underneath me. It feels like every
ounce of effort going into the pedals gets translated to the back wheel
and on to the road....

I prefer a stiff frame, too. But I note that Jan Heine, who (almost
single-handedly) publishes _Bicycle Quarterly_, likes a certain amount
of flex. He claims the flex somehow allows the bike to synchronize with
his pedal strokes (or something). He calls the action "planing," as
when certain types of power boats skim the surface, rather than floating.

Hard to tell if it's imaginary or not. His magazine has some
interesting tests and data from time to time, but his road tests greatly
emphasize how a bike feels to him - as is usually the case with road tests.

I would say that his choice of words is incorrect. A boat doesn't
plane due to a flexible frame. Quite the opposite perhaps :-)

But as the frame of a bicycle flexes under load and than returns to
its original position when the load is reduced it might be referred to
as "Springing". Which does sound sort of "cool". "I was just springing
along on my bike", "I shall just hop on my bicycle and spring away"
:-)



Sounds cool, but I don't think it helps. If you use muscle to bend a
spring and let it return by reducing the effort back to zero, a perfect
spring will return the energy put into it, but the returned energy
doesn't end up as calories in your muscles again. Instead your body
consumes energy as you bend and release the spring. I think similarly
when you flex a bicycle frame, the energy that went into flexing it
doesn't find it's way to increasing your kinetic energy forward on the
bike (some might, but certainly not all). More likely it is wasted
while your body deals with it.

The only good thing that comes from spring in a bike frame is suspension
- but then slightly fatter tyres and less air pressure can achieve the
same effect on bitumen - better in fact, because it doesn't bounce the
whole think around. It's only when the bumps get really big that we
need to resort to shock absorbers, etc.

--
JS

On Wed, 13 Aug 2014 13:19:36 +1000, James
wrote:

On 13/08/14 12:38, John B. Slocomb wrote:
On Tue, 12 Aug 2014 11:22:03 -0400, Frank Krygowski
wrote:

On 8/11/2014 11:00 PM, James wrote:
I had a bit of road rubbish flick up and dent the underside of the down
tube on my new road bike. (It's only done 45,000km). The dent was
probably 2-3mm deep, and had damaged the paint. There were a few other
scratches here and there, so I gave it a birthday, and had the dent
pulled out and the frame resprayed.

I'm curious about getting the dent pulled out. How did they do that?



In the down time, I completed building a training bike I'd started a
year ago. A 20 year old custom 853 lugged racing frame, with the same
wheels as my new bike.

The major difference is the frame tube diameter. The old frame having
the customary 1" tubes, where as the new bike frame has 1 1/8" and 1
1/4" oversize tubes.

I rode 166km on Saturday on the old bike, and then last night, 60km on
the new bike.

The difference in the way they ride is very obvious. The old bike feels
like a soft spring when I stand on the pedals, and I can watch the chain
rings wobble around while I pedal hard, even seated.

The new bike feels crisp and zippy underneath me. It feels like every
ounce of effort going into the pedals gets translated to the back wheel
and on to the road....

I prefer a stiff frame, too. But I note that Jan Heine, who (almost
single-handedly) publishes _Bicycle Quarterly_, likes a certain amount
of flex. He claims the flex somehow allows the bike to synchronize with
his pedal strokes (or something). He calls the action "planing," as
when certain types of power boats skim the surface, rather than floating.

Hard to tell if it's imaginary or not. His magazine has some
interesting tests and data from time to time, but his road tests greatly
emphasize how a bike feels to him - as is usually the case with road tests.

I would say that his choice of words is incorrect. A boat doesn't
plane due to a flexible frame. Quite the opposite perhaps :-)

But as the frame of a bicycle flexes under load and than returns to
its original position when the load is reduced it might be referred to
as "Springing". Which does sound sort of "cool". "I was just springing
along on my bike", "I shall just hop on my bicycle and spring away"
:-)



Sounds cool, but I don't think it helps. If you use muscle to bend a
spring and let it return by reducing the effort back to zero, a perfect
spring will return the energy put into it, but the returned energy
doesn't end up as calories in your muscles again. Instead your body
consumes energy as you bend and release the spring. I think similarly
when you flex a bicycle frame, the energy that went into flexing it
doesn't find it's way to increasing your kinetic energy forward on the
bike (some might, but certainly not all). More likely it is wasted
while your body deals with it.


No, a cyclist loads the spring but then the takes all the weight off
the pedal and the spring doesn't do any work on the "return stroke".

The only good thing that comes from spring in a bike frame is suspension
- but then slightly fatter tyres and less air pressure can achieve the
same effect on bitumen - better in fact, because it doesn't bounce the
whole think around. It's only when the bumps get really big that we
need to resort to shock absorbers, etc.

One wonders why skinny tube racing bikes were used for so long a
period. It is certainly not because engineers didn't know that a thin
large diameter tube is stiffer then a thin small diameter tube.
--
Cheers,

John B.

Am 13.08.2014 12:54, schrieb John B. Slocomb:

One wonders why skinny tube racing bikes were used for so long a
period. It is certainly not because engineers didn't know that a thin
large diameter tube is stiffer then a thin small diameter tube.

the most important aspect has always been minimal weight. For a given
minimal thickness of tubing, a small diameter tube is lighter than a
large diameter tube.

Large diameter tubes only started coming up when technology reached the
stage that the minimum thickness of tube that could be produced and
welded became significantly thinner than the minimum thickness necessary
for structural stability (I believe this was reached for aluminium
frames in the 1980s and for steel frames a lot later).

Rolf Mantel

John B. Slocomb wrote:
On Wed, 13 Aug 2014 13:19:36 +1000, James
wrote:

On 13/08/14 12:38, John B. Slocomb wrote:
On Tue, 12 Aug 2014 11:22:03 -0400, Frank Krygowski
wrote:

On 8/11/2014 11:00 PM, James wrote:
I had a bit of road rubbish flick up and dent the underside of the down
tube on my new road bike. (It's only done 45,000km). The dent was
probably 2-3mm deep, and had damaged the paint. There were a few other
scratches here and there, so I gave it a birthday, and had the dent
pulled out and the frame resprayed.

I'm curious about getting the dent pulled out. How did they do that?



In the down time, I completed building a training bike I'd started a
year ago. A 20 year old custom 853 lugged racing frame, with the same
wheels as my new bike.

The major difference is the frame tube diameter. The old frame having
the customary 1" tubes, where as the new bike frame has 1 1/8" and 1
1/4" oversize tubes.

I rode 166km on Saturday on the old bike, and then last night, 60km on
the new bike.

The difference in the way they ride is very obvious. The old bike feels
like a soft spring when I stand on the pedals, and I can watch the chain
rings wobble around while I pedal hard, even seated.

The new bike feels crisp and zippy underneath me. It feels like every
ounce of effort going into the pedals gets translated to the back wheel
and on to the road....

I prefer a stiff frame, too. But I note that Jan Heine, who (almost
single-handedly) publishes _Bicycle Quarterly_, likes a certain amount
of flex. He claims the flex somehow allows the bike to synchronize with
his pedal strokes (or something). He calls the action "planing," as
when certain types of power boats skim the surface, rather than floating.

Hard to tell if it's imaginary or not. His magazine has some
interesting tests and data from time to time, but his road tests greatly
emphasize how a bike feels to him - as is usually the case with road tests.

I would say that his choice of words is incorrect. A boat doesn't
plane due to a flexible frame. Quite the opposite perhaps :-)

But as the frame of a bicycle flexes under load and than returns to
its original position when the load is reduced it might be referred to
as "Springing". Which does sound sort of "cool". "I was just springing
along on my bike", "I shall just hop on my bicycle and spring away"
:-)



Sounds cool, but I don't think it helps. If you use muscle to bend a
spring and let it return by reducing the effort back to zero, a perfect
spring will return the energy put into it, but the returned energy
doesn't end up as calories in your muscles again. Instead your body
consumes energy as you bend and release the spring. I think similarly
when you flex a bicycle frame, the energy that went into flexing it
doesn't find it's way to increasing your kinetic energy forward on the
bike (some might, but certainly not all). More likely it is wasted
while your body deals with it.


No, a cyclist loads the spring but then the takes all the weight off
the pedal and the spring doesn't do any work on the "return stroke".

The only good thing that comes from spring in a bike frame is suspension
- but then slightly fatter tyres and less air pressure can achieve the
same effect on bitumen - better in fact, because it doesn't bounce the
whole think around. It's only when the bumps get really big that we
need to resort to shock absorbers, etc.

One wonders why skinny tube racing bikes were used for so long a
period. It is certainly not because engineers didn't know that a thin
large diameter tube is stiffer then a thin small diameter tube.

Contact patch. Weight. Rotational torque.
Also look better with those purple shorts.

--
duane

On 8/12/2014 11:19 PM, James wrote:


Sounds cool, but I don't think it helps. If you use muscle to bend a
spring and let it return by reducing the effort back to zero, a perfect
spring will return the energy put into it, but the returned energy
doesn't end up as calories in your muscles again. Instead your body
consumes energy as you bend and release the spring. I think similarly
when you flex a bicycle frame, the energy that went into flexing it
doesn't find it's way to increasing your kinetic energy forward on the
bike (some might, but certainly not all). More likely it is wasted
while your body deals with it.

Certainly, James is right, that energy can't be put back into the
muscles. If bottom bracket flexibility helps at all, I think it must be
a very subtle mechanism. Jan Heine never, IIRC, explains a plausible
mechanism. For a long time, he just said something like "this bike
planes for me" with no explanation of the word "planes". It took me a
while to deduce the word's etymology.

But here's a potentially analogous situation: Walking while carrying
two heavy loads balanced on the ends of a flexible pole.
http://www.talkvietnam.com/2014/04/t...amese-culture/
Of course, there's practicality in having a wide load spaced away from
one's body, so it doesn't bang against one's legs. But many seem to
think a flexible pole makes carrying easier, somehow reducing the work load.

This paper http://www.ncbi.nlm.nih.gov/pubmed/1757307 found no
reduction in oxygen consumption for a pole vs. a backpack. But it did
find less peak loads. Is there a chance that a certain amount of bottom
bracket flex would similarly reduce peak loads on the legs at the bottom
of the pedal stroke?

I have noticed that when I stand to climb a very steep hill, it feels
like my weight lands harshly on the pedals at the bottom of the pedal
stroke.

All the above is speculation. I don't claim to have this figured out.

--
- Frank Krygowski

On 8/13/2014 7:04 AM, Rolf Mantel wrote:
Am 13.08.2014 12:54, schrieb John B. Slocomb:

One wonders why skinny tube racing bikes were used for so long a
period. It is certainly not because engineers didn't know that a thin
large diameter tube is stiffer then a thin small diameter tube.

I think there's always been a tremendous amount of bike "engineering"
that was really tradition. And come to think of it, that's true of
other fields as well. Look at the 100 year history of auto design, for
example.

the most important aspect has always been minimal weight. For a given
minimal thickness of tubing, a small diameter tube is lighter than a
large diameter tube.

Large diameter tubes only started coming up when technology reached the
stage that the minimum thickness of tube that could be produced and
welded became significantly thinner than the minimum thickness necessary
for structural stability (I believe this was reached for aluminium
frames in the 1980s and for steel frames a lot later).

IIRC, the first I heard of a significant design choice based on
oversized tubes was in an article about Gary Klein. Supposedly, he was
an MIT engineering student who was excited to visit an exhibit of a
super-light bicycle; but was very disappointed to see that it had no
engineering innovation. They'd simply drilled and whittled conventional
parts down to stupid-light thicknesses.

He then started thinking about using aluminum frames, and it occurred to
him that aluminum's lower density would allow thicker (non-denting) tube
walls at larger diameters. So we got light & rigid Klein frames.
Cannondale and others copied the concept.

Tandem tubing has long been oversized. Our 1979 tandem is oversized
Reynolds 531. But the wall thickness is no less than standard, probably
to allow brazing by any guy with a torch. So back in those days, the
extra stiffness from oversized steel tubes came with a weight penalty.

Since then, there have been improvements in steel alloys and welding
techniques, so oversized steel works better than it once did.


--
- Frank Krygowski