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On Sun, 5 Jan 2025 05:35:29 -0500, zen cycle
<funkmasterxx@hotmail.com> wrote:
On 1/3/2025 11:46 PM, Jeff Liebermann wrote:
In my never humble opinion,
IMNHO....Nice...The Interwebs newest intialism.....
I think you mean initialism.
<https://www.merriam-webster.com/dictionary/initialism>
I've been using "in my never humble opinion" in its fully expanded
form for probably 50 years. I typically the phrase only once per
posting, so there's no need for acronymization.
On 1/2/2025 11:06 AM, AMuzi wrote:
On 1/2/2025 9:42 AM, bp@www.zefox.net wrote:
But one can observe that in the case of smooth pavement,
suspension losses vanish, while hysteresis losses persist.
I think that would be true only if the smooth pavement were
as smooth as a linoleum floor. Or a wooden track. IIRC, what
got Jan Heine started on investigations of rolling
resistance vs. tire width was coast-down tests on a Soapbox
Derby track. I suspect that was quite smooth. Soapbox cars
have hard tires and no suspension, AFAIK.
In the end a bike is an overdamped resonator excited by the
pavement and damped by hysteresis, separately in the tire
and
suspenesion. In that limit, suspension would be faster if
used
with very hard tires on very smooth surfaces. In the
limit of
hard tires and no suspension, the dissipative element
becomes
the rider whose elastic properties are apt to be poor,
perhaps
accounting for the apparent slowness of solid tires.
Use of a rumble strip for testing is equivalent to selecting
a particular excitation spectrum. Choice of spectrum will
affect
dissipation depending on internal resonances of the bike/
rider
system. A real road likely corresponds to a 1/f spectrum,
but
a rumble strip will likely be something else. How much
difference
that makes isn't clear but it could be estimated using a
mechanical
analogy equivalent circuit of the kind used to model
loudspeakers.
A pair of series RLC circuits (one for the road-tire
interface
and a second for the suspension-rider interface) would be
a good
start. I'm not skilled enough to do the calculations, but
others
on this group likely are.
I _may_ have been able to do such calculations 50 years ago,
but I'm not sure. I certainly can't do them now.
The hardest part is apt to be finding
an equivalent circuit for the rider, who isn't a rigid
mass but
rather a dissipative blob....8-)
I actually think physically modeling that dissipative blob
might be valuable for the tire industry. Using such a blob
to apply weight during a rolling drum test might give better
information than what those tests give now.
Clever.
I take from that, you think the actual impact/height
change/velocity change etc from various irregular surfaces
can be quantified for any given random gravel (or road)
experience and used to compare efficiency for other
iterations.
I hadn't thought of that, but if that's true then the
rumble strip test isn't necessary for comparison. Which
assumes sensors have adequate sensitivity across whatever
range and that software for that data truly derives actual
impedimenta values.
There are ways of quantifying roughness, with varying
scales, varying tools. I'm most familiar with roughness
measurement of machined parts, with tools varying from
sample cards for "fingernail" test comparisons, to RMS
readers akin to phonograph needles or laser scattering devices.
https://en.wikipedia.org/wiki/Surface_roughness
ISTR reading about systems for evaluating pavement fairly
crudely, as in whether it should be repaved or not. I don't
know of a system actually used for measuring pavement
roughness at a scale affecting bike tire choice.
On 1/5/2025 4:39 PM, Jeff Liebermann wrote:
On Sun, 5 Jan 2025 05:35:29 -0500, zen cycle
<funkmasterxx@hotmail.com> wrote:
On 1/3/2025 11:46 PM, Jeff Liebermann wrote:
In my never humble opinion,
IMNHO....Nice...The Interwebs newest intialism.....
I think you mean initialism.
Indeed I did. It was a typo.
<https://www.merriam-webster.com/dictionary/initialism>
I've been using "in my never humble opinion" in its fully expanded
form for probably 50 years. I typically the phrase only once per
posting, so there's no need for acronymization.
I think you mean _an_ acronymization. :)
Good article from Jan Heine on benefits of wider, softer tires for
absorbing vibration and lessening suspension losses:
https://www.renehersecycles.com/the-missing-link-suspension-losses/
At the time the rumble strip test was published, I expressed some
skepticism because its roughness is fundamentally different than the
random roughness of either a rough road or a gravel road. In particular,
the rumble strip is all "negative," cut into the smooth surface, while
rough or gravel roads have both "negative" holes plus "positive" patches
or rocks that protrude above the surface. One practical difference is
that when dealing with only "negative" roughness, higher speeds reduce losses. The opposite is true with "positive" roughness.
But I suppose for demonstrating the fundamental effect, the consistency
of the rumbles is useful. And the measurements seem valid as long as the
test speed is also consistent.
BTW, Jobst Brandt is mentioned in the article. I recall that in
discussing rolling resistance here, he insisted that "rolling
resistance" should be defined _only_ as the losses generated by tire
rubber's hysteresis. I disagreed, because that implied that solid rubber tires a la 1880, or near infinite tire pressure, or even metal rims with
no tire, would be best. Anyone who has ridden an antique solid tire
"safety" bike knows how slow those tires were.
Frank Krygowski <frkrygow@sbcglobal.net> wrote:
Good article from Jan Heine on benefits of wider, softer tires for
absorbing vibration and lessening suspension losses:
https://www.renehersecycles.com/the-missing-link-suspension-losses/
At the time the rumble strip test was published, I expressed some
skepticism because its roughness is fundamentally different than the
random roughness of either a rough road or a gravel road. In particular,
the rumble strip is all "negative," cut into the smooth surface, while
rough or gravel roads have both "negative" holes plus "positive" patches
or rocks that protrude above the surface. One practical difference is
that when dealing with only "negative" roughness, higher speeds reduce
losses. The opposite is true with "positive" roughness.
But I suppose for demonstrating the fundamental effect, the consistency
of the rumbles is useful. And the measurements seem valid as long as the
test speed is also consistent.
Not that convinced to be honest, for a starters folks aren’t going to be riding rumble strips but by mistake!
And if you’re going to be real world testing, testing on dirt roads with all of the inconsistencies that brings is what gravel riders do. With the dips as well as the bumps, plus ruts etc.
Rumble strip testing seems somewhat misleading ie it’s not that controlled nor what riders do.
As ever claims that they influence pro athletes etc and started the wider tire use, IMO it along with disks was adapted by consumers/commuters with
pro racers lagging behind with adoption and haven’t gone quite as wide, ie stopped at 28 for the Pros where as 30/32 are fairly common among club riders.
BTW, Jobst Brandt is mentioned in the article. I recall that in
discussing rolling resistance here, he insisted that "rolling
resistance" should be defined _only_ as the losses generated by tire
rubber's hysteresis. I disagreed, because that implied that solid rubber
tires a la 1880, or near infinite tire pressure, or even metal rims with
no tire, would be best. Anyone who has ridden an antique solid tire
"safety" bike knows how slow those tires were.
As ever is a what you want as well, on the old school road bike, I commute on, 28mm felt on the twitchy side 32mm much more planted, the speed difference I’m less concerned about, though at that level maybe wider is faster? What is faster would depend on road/bike/rider.
Roger Merriman
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
But one can observe that in the case of smooth pavement,
suspension losses vanish, while hysteresis losses persist.
In the end a bike is an overdamped resonator excited by the
pavement and damped by hysteresis, separately in the tire and
suspenesion. In that limit, suspension would be faster if used
with very hard tires on very smooth surfaces. In the limit of
hard tires and no suspension, the dissipative element becomes
the rider whose elastic properties are apt to be poor, perhaps
accounting for the apparent slowness of solid tires.
Use of a rumble strip for testing is equivalent to selecting
a particular excitation spectrum. Choice of spectrum will affect
dissipation depending on internal resonances of the bike/rider
system. A real road likely corresponds to a 1/f spectrum, but
a rumble strip will likely be something else. How much difference
that makes isn't clear but it could be estimated using a mechanical
analogy equivalent circuit of the kind used to model loudspeakers.
A pair of series RLC circuits (one for the road-tire interface
and a second for the suspension-rider interface) would be a good
start. I'm not skilled enough to do the calculations, but others
on this group likely are. The hardest part is apt to be finding
an equivalent circuit for the rider, who isn't a rigid mass but
rather a dissipative blob....8-)
Thanks for reading,
bob prohaska
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
I take from that, you think the actual impact/height
change/velocity change etc from various irregular surfaces
can be quantified for any given random gravel (or road)
experience and used to compare efficiency for other iterations.
I hadn't thought of that, but if that's true then the rumble
strip test isn't necessary for comparison. Which assumes
sensors have adequate sensitivity across whatever range and
that software for that data truly derives actual impedimenta
values.
On 1/2/2025 11:06 AM, AMuzi wrote:
On 1/2/2025 9:42 AM, bp@www.zefox.net wrote:
But one can observe that in the case of smooth pavement,
suspension losses vanish, while hysteresis losses persist.
I think that would be true only if the smooth pavement were
as smooth as a linoleum floor. Or a wooden track. IIRC, what
got Jan Heine started on investigations of rolling
resistance vs. tire width was coast-down tests on a Soapbox
Derby track. I suspect that was quite smooth. Soapbox cars
have hard tires and no suspension, AFAIK.
In the end a bike is an overdamped resonator excited by the
pavement and damped by hysteresis, separately in the tire
and
suspenesion. In that limit, suspension would be faster if
used
with very hard tires on very smooth surfaces. In the
limit of
hard tires and no suspension, the dissipative element
becomes
the rider whose elastic properties are apt to be poor,
perhaps
accounting for the apparent slowness of solid tires.
Use of a rumble strip for testing is equivalent to selecting
a particular excitation spectrum. Choice of spectrum will
affect
dissipation depending on internal resonances of the bike/
rider
system. A real road likely corresponds to a 1/f spectrum,
but
a rumble strip will likely be something else. How much
difference
that makes isn't clear but it could be estimated using a
mechanical
analogy equivalent circuit of the kind used to model
loudspeakers.
A pair of series RLC circuits (one for the road-tire
interface
and a second for the suspension-rider interface) would be
a good
start. I'm not skilled enough to do the calculations, but
others
on this group likely are.
I _may_ have been able to do such calculations 50 years ago,
but I'm not sure. I certainly can't do them now.
The hardest part is apt to be finding
an equivalent circuit for the rider, who isn't a rigid
mass but
rather a dissipative blob....8-)
I actually think physically modeling that dissipative blob
might be valuable for the tire industry. Using such a blob
to apply weight during a rolling drum test might give better
information than what those tests give now.
Clever.
I take from that, you think the actual impact/height
change/velocity change etc from various irregular surfaces
can be quantified for any given random gravel (or road)
experience and used to compare efficiency for other
iterations.
I hadn't thought of that, but if that's true then the
rumble strip test isn't necessary for comparison. Which
assumes sensors have adequate sensitivity across whatever
range and that software for that data truly derives actual
impedimenta values.
There are ways of quantifying roughness, with varying
scales, varying tools. I'm most familiar with roughness
measurement of machined parts, with tools varying from
sample cards for "fingernail" test comparisons, to RMS
readers akin to phonograph needles or laser scattering devices.
https://en.wikipedia.org/wiki/Surface_roughness
ISTR reading about systems for evaluating pavement fairly
crudely, as in whether it should be repaved or not. I don't
know of a system actually used for measuring pavement
roughness at a scale affecting bike tire choice.
On 1/2/2025 12:06 PM, bp@www.zefox.net wrote:
AMuzi <am@yellowjersey.org> wrote:
To a decent approximation, yes. Any surface profile can be represented
I take from that, you think the actual impact/height
change/velocity change etc from various irregular surfaces
can be quantified for any given random gravel (or road)
experience and used to compare efficiency for other iterations.
by a spectrum. Music is usually represented by "pink" noise, thermal
noise is white (uniform) and most real systems have noise proportional
to 1/f (imagine turn-on transients as singularities). A real road would
likely be some combination with the radius of the tire serving as a high
frequency filter.
I hadn't thought of that, but if that's true then the rumble
strip test isn't necessary for comparison. Which assumes
sensors have adequate sensitivity across whatever range and
that software for that data truly derives actual impedimenta
values.
One would have to measure the force/deflection curves for both tires
and suspension elements, along with the masses of the sprung and unsprung
elements. Since losses are rate dependent, especially for suspensions
with hydraulic damping, a range of speeds/frequencies would have to be
measured. I think an accurate model would get fairly complicated, especially >> if the rider were included. Each compliance (tire, suspension spring, seat >> spring and rider body part that deflects) would have to be accounted for.
There are potentially four coupled resonators: Tires, swingarm/forks and
finally rider (divided into arms/torso sections probably). Overall, tests
on a rumble strip or drum with some kind of ergometer might be simpler.
Very likely the motor racing industry already has software that can do the >> analysis. Most of the interest in that market is controlling resonances,
not minimizing losses, but otherwise the problems are very similar.
One further thought: If we accept (as I do) that jiggling the human
pedaler does cause loss in energy and speed, why aren't we all using
saddles with some sort of damped springing?
I know suspension seatposts exist, but even those are not popular on
road bikes.
ISTM that if more "suspension" is valuable via wider tires, it might
also be valuable via sprung saddles, if done right.
My wife used to ride a Brooks B72. Its four curly support wires gives
just a bit of spring action. It's now on my about-town 3 speed. That
bike never goes far, but I don't detect any detriments to the slight springiness.
One further thought: If we accept (as I do) that jiggling the human
pedaler does cause loss in energy and speed, why aren't we all using
saddles with some sort of damped springing?
I know suspension seatposts exist, but even those are not popular on
road bikes.
On 1/2/2025 11:06 AM, AMuzi wrote:
On 1/2/2025 9:42 AM, bp@www.zefox.net wrote:
But one can observe that in the case of smooth pavement,
suspension losses vanish, while hysteresis losses persist.
I think that would be true only if the smooth pavement were as smooth as
a linoleum floor.
Yes, I'm familiar with surface finish (roughness) numbers in
machining, but an offroad bicycle, for example on a gravel
path (bianca strada) or babyheads (much of Paris Roubaix)
would be a series of variable impedimenta in some chaotic
non-order for height & frequency. The principle is the same
but the amount of data is staggering.
On 1/2/2025 8:45 PM, bp@www.zefox.net wrote:
Frank Krygowski <frkrygow@sbcglobal.net> wrote:
One further thought: If we accept (as I do) that jiggling
the human
pedaler does cause loss in energy and speed, why aren't
we all using
saddles with some sort of damped springing?
I know suspension seatposts exist, but even those are not
popular on
road bikes.
I'm using a suspension seatpost now, removed from a town
bike. It's
slightly more comfortable. No idea if it's more efficient.
Certainly
heavier, probably lossy unless I balance pedal effort to
keep pressure
on the saddle constant. That difference is small at most.
FWIW, when coasting - especially on rough downhills - my
habit is to take some of my weight off the saddle, hoping
the "suspension" offered by my legs causes less jiggling of
my body mass, so less energy loss.
On 1/2/2025 8:45 PM, bp@www.zefox.net wrote:
Frank Krygowski <frkrygow@sbcglobal.net> wrote:
I'm using a suspension seatpost now, removed from a town bike. It's
One further thought: If we accept (as I do) that jiggling the human
pedaler does cause loss in energy and speed, why aren't we all using
saddles with some sort of damped springing?
I know suspension seatposts exist, but even those are not popular on
road bikes.
slightly more comfortable. No idea if it's more efficient. Certainly
heavier, probably lossy unless I balance pedal effort to keep pressure
on the saddle constant. That difference is small at most.
FWIW, when coasting - especially on rough downhills - my habit is to
take some of my weight off the saddle, hoping the "suspension" offered
by my legs causes less jiggling of my body mass, so less energy loss.
On 1/2/2025 9:42 AM, bp@www.zefox.net wrote:
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
But one can observe that in the case of smooth pavement,
suspension losses vanish, while hysteresis losses persist.
In the end a bike is an overdamped resonator excited by the
pavement and damped by hysteresis, separately in the tire and
suspenesion. In that limit, suspension would be faster if used
with very hard tires on very smooth surfaces. In the limit of
hard tires and no suspension, the dissipative element becomes
the rider whose elastic properties are apt to be poor, perhaps
accounting for the apparent slowness of solid tires.
Use of a rumble strip for testing is equivalent to selecting
a particular excitation spectrum. Choice of spectrum will affect
dissipation depending on internal resonances of the bike/rider
system. A real road likely corresponds to a 1/f spectrum, but
a rumble strip will likely be something else. How much difference
that makes isn't clear but it could be estimated using a mechanical
analogy equivalent circuit of the kind used to model loudspeakers.
A pair of series RLC circuits (one for the road-tire interface
and a second for the suspension-rider interface) would be a good
start. I'm not skilled enough to do the calculations, but others
on this group likely are. The hardest part is apt to be finding
an equivalent circuit for the rider, who isn't a rigid mass but
rather a dissipative blob....8-)
Thanks for reading,
bob prohaska
Clever.
I take from that, you think the actual impact/height change/velocity
change etc from various irregular surfaces can be quantified for any
given random gravel (or road) experience and used to compare efficiency
for other iterations.
I hadn't thought of that, but if that's true then the rumble strip test
isn't necessary for comparison. Which assumes sensors have adequate sensitivity across whatever range and that software for that data truly derives actual impedimenta values.
On 1/2/2025 11:06 AM, AMuzi wrote:
On 1/2/2025 9:42 AM, bp@www.zefox.net wrote:
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given
rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given
rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
But one can observe that in the case of smooth pavement,
suspension losses vanish, while hysteresis losses persist.
In the end a bike is an overdamped resonator excited by the
pavement and damped by hysteresis, separately in the tire
and
suspenesion. In that limit, suspension would be faster if
used
with very hard tires on very smooth surfaces. In the
limit of
hard tires and no suspension, the dissipative element
becomes
the rider whose elastic properties are apt to be poor,
perhaps
accounting for the apparent slowness of solid tires.
Use of a rumble strip for testing is equivalent to selecting
a particular excitation spectrum. Choice of spectrum will
affect
dissipation depending on internal resonances of the bike/
rider
system. A real road likely corresponds to a 1/f spectrum,
but
a rumble strip will likely be something else. How much
difference
that makes isn't clear but it could be estimated using a
mechanical
analogy equivalent circuit of the kind used to model
loudspeakers.
This is a great analysis and reveals a highly problematic
aspect of the "rumble strip" test. As Bob notes, it's
essentially limiting the noise input into the system to a
somewhat narrow spectral component (though the 1/f
assumption for real-world is way to broad)
The idea of using the rumble strip test seems adequate at
first, but is prone to misleading results. Since the rumble
strip sets up a regular frequency component, there's a
possibility that a resonance or cancellation effect can
occur which can dramatically skew the results.
In the world of environmental testing, physical vibration
analysis is typically broken up into three different stimuli
- swept frequency, noise*, and environmental specific
(usually a combination of noise with higher energy
components around certain frequencies).
It's nearly impossible to simulate all the possible real-
world conditions, which is why the testing regimen includes
a sweep - the intent being to see any resonances. I've
personally witnessed an electronic assembly quite nearly
disintegrate with the right frequency and energy input. The
task then was to redesign the piece such that the resonance
was damped.
It's easy to see how this can translate to the rumble strip
test. Under the right conditions, one might actually see a
speed _increase_ as a result of a sympathetic resonance.
A pair of series RLC circuits (one for the road-tire
interface
and a second for the suspension-rider interface) would be
a good
start. I'm not skilled enough to do the calculations, but
others
on this group likely are. The hardest part is apt to be
finding
an equivalent circuit for the rider, who isn't a rigid
mass but
rather a dissipative blob....8-)
In the old days, we had to do reiterative tests on massive
vibration tables. These days, FEA software removes the vast
amount of guesswork. The last few times I've had to conduct
these tests I only had to do one test twice, and the problem
turned out to be an assembly specification error rather than
inherent design.
Thanks for reading,
bob prohaska
Clever.
I take from that, you think the actual impact/height
change/velocity change etc from various irregular surfaces
can be quantified for any given random gravel (or road)
experience and used to compare efficiency for other
iterations.
"Real-world" would simulate a more stochastic environment
with larger "impact" events rather than a regular
"sinusoidal" spectrum like a rumble strip. Currently, for
example, we use this for our truck-mounted electronics:
https://cvgstrategy.com/wp-content/uploads/2019/08/MIL- STD-810H-Method-514.8-Vibration.pdf
Refer to page 514.8C-5 (Page 58 in the PDF).
I hadn't thought of that, but if that's true then the
rumble strip test isn't necessary for comparison. Which
assumes sensors have adequate sensitivity across whatever
range and that software for that data truly derives actual
impedimenta values.
Even low-cost accelerometers have incredible accuracy,
sensitivity, and repeatability across spectrum they're
designed to operate these days. We have two 3-axis units
accurate to .01G that we paid like $25 each for - coupled to
a mid-range oscilloscope they give more than adequate
results for our "warm fuzzy" testing before we send of to a
testing lab for 3rd party analysis.
*"Noise" being a broad term meaning quasi-random frequency
and amplitude components within limits.
On 1/2/2025 5:45 AM, Roger Merriman wrote:
Frank Krygowski <frkrygow@sbcglobal.net> wrote:
Good article from Jan Heine on benefits of wider, softer tires for
absorbing vibration and lessening suspension losses:
https://www.renehersecycles.com/the-missing-link-suspension-losses/
At the time the rumble strip test was published, I expressed some
skepticism because its roughness is fundamentally different than the
random roughness of either a rough road or a gravel road. In particular, >>> the rumble strip is all "negative," cut into the smooth surface, while
rough or gravel roads have both "negative" holes plus "positive" patches >>> or rocks that protrude above the surface. One practical difference is
that when dealing with only "negative" roughness, higher speeds reduce
losses. The opposite is true with "positive" roughness.
But I suppose for demonstrating the fundamental effect, the consistency
of the rumbles is useful. And the measurements seem valid as long as the >>> test speed is also consistent.
Not that convinced to be honest, for a starters folks aren’t going to be >> riding rumble strips but by mistake!
And if you’re going to be real world testing, testing on dirt roads with >> all of the inconsistencies that brings is what gravel riders do. With the
dips as well as the bumps, plus ruts etc.
Rumble strip testing seems somewhat misleading ie it’s not that controlled >> nor what riders do.
As ever claims that they influence pro athletes etc and started the wider
tire use, IMO it along with disks was adapted by consumers/commuters with
pro racers lagging behind with adoption and haven’t gone quite as wide, ie >> stopped at 28 for the Pros where as 30/32 are fairly common among club
riders.
BTW, Jobst Brandt is mentioned in the article. I recall that in
discussing rolling resistance here, he insisted that "rolling
resistance" should be defined _only_ as the losses generated by tire
rubber's hysteresis. I disagreed, because that implied that solid rubber >>> tires a la 1880, or near infinite tire pressure, or even metal rims with >>> no tire, would be best. Anyone who has ridden an antique solid tire
"safety" bike knows how slow those tires were.
As ever is a what you want as well, on the old school road bike, I commute >> on, 28mm felt on the twitchy side 32mm much more planted, the speed
difference I’m less concerned about, though at that level maybe wider is >> faster? What is faster would depend on road/bike/rider.
Roger Merriman
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
In short you make an interesting point but it's not
measurable for comparative purposes.
On 1/3/2025 10:46 AM, Radey Shouman wrote:
Frank Krygowski <frkrygow@sbcglobal.net> writes:
On 1/2/2025 8:45 PM, bp@www.zefox.net wrote:
Frank Krygowski <frkrygow@sbcglobal.net> wrote:
I'm using a suspension seatpost now, removed from a town bike. It's
One further thought: If we accept (as I do) that jiggling the human
pedaler does cause loss in energy and speed, why aren't we all using >>>>> saddles with some sort of damped springing?
I know suspension seatposts exist, but even those are not popular on >>>>> road bikes.
slightly more comfortable. No idea if it's more efficient. Certainly
heavier, probably lossy unless I balance pedal effort to keep pressure >>>> on the saddle constant. That difference is small at most.
FWIW, when coasting - especially on rough downhills - my habit is to
take some of my weight off the saddle, hoping the "suspension" offered
by my legs causes less jiggling of my body mass, so less energy loss.
To get back to the question of how this might be modeled, it's really
complicated. Sometimes all your weight is probably off the saddle,
meaning that any computation would have to figure out when there was
contact, and the forces generated by that contact.
You can read a whole book about it online, if you're ambitious:
https://www.yastrebov.fr/LECTURES/Yastrebov_NMCM_Wiley_ISTE.pdf
Not to mention that there is a poorly understood nonlinear control
mechanism involved, somewhat different for each individual.
Wow. Yes, it's probably good to remind ourselves that whatever topic we
tyros discuss here has probably been the life's work of some true expert.
On 1/3/2025 11:12 AM, cyclintom wrote:
Coming out of Niles Canyon, you have to ride at around 20 mph Because of
traffic I was forced to cross a rumble strip with my 28 mm tires and
came damned close to losing control but it did allow me to let 5 cars
moving at 45 mph + get past before a constriction. While you're talking
about taking the lane why don't you come here and try taking the lane?
You would soon discover, if you're lucky, from a hospital bed that
California deivers don't like your ideas.
Ah. We haven't had a "Bicycling is really dangerous _HERE_!" post in
quite a while.
So you judged that nearly losing control in front of a 45 mph car was
safer than legally taking the lane? Yes, my choice would have been
different, and I've made that choice in <gasp!> California; but
admittedly not in your super-dangerous neighborhood. When I do that, motorists wait until its safe to pass. Exceptions are vanishingly rare.
As I often ask, what do you do when riding in a ten foot lane with no shoulder, when an 8.5 foot wide truck approaches from behind? Do you
jump off the bike and humbly bow?
On 1/3/2025 10:41 AM, Zen Cycle wrote:
On 1/2/2025 11:06 AM, AMuzi wrote:
On 1/2/2025 9:42 AM, bp@www.zefox.net wrote:
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
But one can observe that in the case of smooth pavement,
suspension losses vanish, while hysteresis losses persist.
In the end a bike is an overdamped resonator excited by the
pavement and damped by hysteresis, separately in the tire and
suspenesion. In that limit, suspension would be faster if used
with very hard tires on very smooth surfaces. In the limit of
hard tires and no suspension, the dissipative element becomes
the rider whose elastic properties are apt to be poor, perhaps
accounting for the apparent slowness of solid tires.
Use of a rumble strip for testing is equivalent to selecting
a particular excitation spectrum. Choice of spectrum will affect
dissipation depending on internal resonances of the bike/rider
system. A real road likely corresponds to a 1/f spectrum, but
a rumble strip will likely be something else. How much difference
that makes isn't clear but it could be estimated using a mechanical
analogy equivalent circuit of the kind used to model loudspeakers.
This is a great analysis and reveals a highly problematic aspect of
the "rumble strip" test. As Bob notes, it's essentially limiting the
noise input into the system to a somewhat narrow spectral component
(though the 1/f assumption for real-world is way to broad)
The idea of using the rumble strip test seems adequate at first, but
is prone to misleading results. Since the rumble strip sets up a
regular frequency component, there's a possibility that a resonance or
cancellation effect can occur which can dramatically skew the results.
In the world of environmental testing, physical vibration analysis is
typically broken up into three different stimuli - swept frequency,
noise*, and environmental specific (usually a combination of noise
with higher energy components around certain frequencies).
It's nearly impossible to simulate all the possible real-world
conditions, which is why the testing regimen includes a sweep - the
intent being to see any resonances.
Interesting. I suppose the rumble strip test could do a "sweep" by
riding repeatedly at a wide range of speeds.
On 1/3/2025 9:41 AM, Zen Cycle wrote:
On 1/2/2025 11:06 AM, AMuzi wrote:
On 1/2/2025 9:42 AM, bp@www.zefox.net wrote:
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
But one can observe that in the case of smooth pavement,
suspension losses vanish, while hysteresis losses persist.
In the end a bike is an overdamped resonator excited by the
pavement and damped by hysteresis, separately in the tire and
suspenesion. In that limit, suspension would be faster if used
with very hard tires on very smooth surfaces. In the limit of
hard tires and no suspension, the dissipative element becomes
the rider whose elastic properties are apt to be poor, perhaps
accounting for the apparent slowness of solid tires.
Use of a rumble strip for testing is equivalent to selecting
a particular excitation spectrum. Choice of spectrum will affect
dissipation depending on internal resonances of the bike/ rider
system. A real road likely corresponds to a 1/f spectrum, but
a rumble strip will likely be something else. How much difference
that makes isn't clear but it could be estimated using a mechanical
analogy equivalent circuit of the kind used to model loudspeakers.
This is a great analysis and reveals a highly problematic aspect of
the "rumble strip" test. As Bob notes, it's essentially limiting the
noise input into the system to a somewhat narrow spectral component
(though the 1/f assumption for real-world is way to broad)
The idea of using the rumble strip test seems adequate at first, but
is prone to misleading results. Since the rumble strip sets up a
regular frequency component, there's a possibility that a resonance or
cancellation effect can occur which can dramatically skew the results.
In the world of environmental testing, physical vibration analysis is
typically broken up into three different stimuli - swept frequency,
noise*, and environmental specific (usually a combination of noise
with higher energy components around certain frequencies).
It's nearly impossible to simulate all the possible real- world
conditions, which is why the testing regimen includes a sweep - the
intent being to see any resonances. I've personally witnessed an
electronic assembly quite nearly disintegrate with the right frequency
and energy input. The task then was to redesign the piece such that
the resonance was damped.
It's easy to see how this can translate to the rumble strip test.
Under the right conditions, one might actually see a speed _increase_
as a result of a sympathetic resonance.
A pair of series RLC circuits (one for the road-tire interface
and a second for the suspension-rider interface) would be a good
start. I'm not skilled enough to do the calculations, but others
on this group likely are. The hardest part is apt to be finding
an equivalent circuit for the rider, who isn't a rigid mass but
rather a dissipative blob....8-)
In the old days, we had to do reiterative tests on massive vibration
tables. These days, FEA software removes the vast amount of guesswork.
The last few times I've had to conduct these tests I only had to do
one test twice, and the problem turned out to be an assembly
specification error rather than inherent design.
Thanks for reading,
bob prohaska
Clever.
I take from that, you think the actual impact/height change/velocity
change etc from various irregular surfaces can be quantified for any
given random gravel (or road) experience and used to compare
efficiency for other iterations.
"Real-world" would simulate a more stochastic environment with larger
"impact" events rather than a regular "sinusoidal" spectrum like a
rumble strip. Currently, for example, we use this for our truck-
mounted electronics:
https://cvgstrategy.com/wp-content/uploads/2019/08/MIL- STD-810H-
Method-514.8-Vibration.pdf
Refer to page 514.8C-5 (Page 58 in the PDF).
I hadn't thought of that, but if that's true then the rumble strip
test isn't necessary for comparison. Which assumes sensors have
adequate sensitivity across whatever range and that software for that
data truly derives actual impedimenta values.
Even low-cost accelerometers have incredible accuracy, sensitivity,
and repeatability across spectrum they're designed to operate these
days. We have two 3-axis units accurate to .01G that we paid like $25
each for - coupled to a mid-range oscilloscope they give more than
adequate results for our "warm fuzzy" testing before we send of to a
testing lab for 3rd party analysis.
*"Noise" being a broad term meaning quasi-random frequency and
amplitude components within limits.
Thanks I knew nothing about this before our discussion.
On 1/2/2025 11:06 AM, AMuzi wrote:
On 1/2/2025 9:42 AM, bp@www.zefox.net wrote:
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
But one can observe that in the case of smooth pavement,
suspension losses vanish, while hysteresis losses persist.
In the end a bike is an overdamped resonator excited by the
pavement and damped by hysteresis, separately in the tire and
suspenesion. In that limit, suspension would be faster if used
with very hard tires on very smooth surfaces. In the limit of
hard tires and no suspension, the dissipative element becomes
the rider whose elastic properties are apt to be poor, perhaps
accounting for the apparent slowness of solid tires.
Use of a rumble strip for testing is equivalent to selecting
a particular excitation spectrum. Choice of spectrum will affect
dissipation depending on internal resonances of the bike/rider
system. A real road likely corresponds to a 1/f spectrum, but
a rumble strip will likely be something else. How much difference
that makes isn't clear but it could be estimated using a mechanical
analogy equivalent circuit of the kind used to model loudspeakers.
This is a great analysis and reveals a highly problematic aspect of the "rumble strip" test. As Bob notes, it's essentially limiting the noise
input into the system to a somewhat narrow spectral component (though
the 1/f assumption for real-world is way to broad)
The idea of using the rumble strip test seems adequate at first, but is
prone to misleading results. Since the rumble strip sets up a regular frequency component, there's a possibility that a resonance or
cancellation effect can occur which can dramatically skew the results.
In the world of environmental testing, physical vibration analysis is typically broken up into three different stimuli - swept frequency,
noise*, and environmental specific (usually a combination of noise with higher energy components around certain frequencies).
It's nearly impossible to simulate all the possible real-world
conditions, which is why the testing regimen includes a sweep - the
intent being to see any resonances. I've personally witnessed an
electronic assembly quite nearly disintegrate with the right frequency
and energy input. The task then was to redesign the piece such that the resonance was damped.
It's easy to see how this can translate to the rumble strip test. Under
the right conditions, one might actually see a speed _increase_ as a
result of a sympathetic resonance.
A pair of series RLC circuits (one for the road-tire interface
and a second for the suspension-rider interface) would be a good
start. I'm not skilled enough to do the calculations, but others
on this group likely are. The hardest part is apt to be finding
an equivalent circuit for the rider, who isn't a rigid mass but
rather a dissipative blob....8-)
In the old days, we had to do reiterative tests on massive vibration
tables. These days, FEA software removes the vast amount of guesswork.
The last few times I've had to conduct these tests I only had to do one
test twice, and the problem turned out to be an assembly specification
error rather than inherent design.
Thanks for reading,
bob prohaska
Clever.
I take from that, you think the actual impact/height change/velocity
change etc from various irregular surfaces can be quantified for any
given random gravel (or road) experience and used to compare efficiency
for other iterations.
"Real-world" would simulate a more stochastic environment with larger "impact" events rather than a regular "sinusoidal" spectrum like a
rumble strip. Currently, for example, we use this for our truck-mounted electronics:
https://cvgstrategy.com/wp-content/uploads/2019/08/MIL-STD-810H-Method-514.8-Vibration.pdf
Refer to page 514.8C-5 (Page 58 in the PDF).
I hadn't thought of that, but if that's true then the rumble strip test
isn't necessary for comparison. Which assumes sensors have adequate
sensitivity across whatever range and that software for that data truly
derives actual impedimenta values.
Even low-cost accelerometers have incredible accuracy, sensitivity, and repeatability across spectrum they're designed to operate these days. We
have two 3-axis units accurate to .01G that we paid like $25 each for - coupled to a mid-range oscilloscope they give more than adequate results
for our "warm fuzzy" testing before we send of to a testing lab for 3rd
party analysis.
*"Noise" being a broad term meaning quasi-random frequency and amplitude components within limits.
On 1/3/2025 10:41 AM, Zen Cycle wrote:
On 1/2/2025 11:06 AM, AMuzi wrote:
On 1/2/2025 9:42 AM, bp@www.zefox.net wrote:This is a great analysis and reveals a highly problematic aspect of
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
AMuzi <am@yellowjersey.org> wrote:
I don't have a coherent argument either way but a rumble
strip test introduces a repeatable experience so that
various data may be compared. Each rider on a dirt or
gravel path, and each ride experience by any given rider, is
an unique set of impedimenta such that data cannot be as
readily compared.
But one can observe that in the case of smooth pavement,
suspension losses vanish, while hysteresis losses persist.
In the end a bike is an overdamped resonator excited by the
pavement and damped by hysteresis, separately in the tire and
suspenesion. In that limit, suspension would be faster if used
with very hard tires on very smooth surfaces. In the limit of
hard tires and no suspension, the dissipative element becomes
the rider whose elastic properties are apt to be poor, perhaps
accounting for the apparent slowness of solid tires.
Use of a rumble strip for testing is equivalent to selecting
a particular excitation spectrum. Choice of spectrum will affect
dissipation depending on internal resonances of the bike/rider
system. A real road likely corresponds to a 1/f spectrum, but
a rumble strip will likely be something else. How much difference
that makes isn't clear but it could be estimated using a mechanical
analogy equivalent circuit of the kind used to model loudspeakers.
the "rumble strip" test. As Bob notes, it's essentially limiting the
noise input into the system to a somewhat narrow spectral component
(though the 1/f assumption for real-world is way to broad)
The idea of using the rumble strip test seems adequate at first, but
is prone to misleading results. Since the rumble strip sets up a
regular frequency component, there's a possibility that a resonance
or cancellation effect can occur which can dramatically skew the
results.
In the world of environmental testing, physical vibration analysis
is typically broken up into three different stimuli - swept
frequency, noise*, and environmental specific (usually a combination
of noise with higher energy components around certain frequencies).
It's nearly impossible to simulate all the possible real-world
conditions, which is why the testing regimen includes a sweep - the
intent being to see any resonances.
Interesting. I suppose the rumble strip test could do a "sweep" by
riding repeatedly at a wide range of speeds.
I take from that, you think the actual impact/height
change/velocity change etc from various irregular surfaces
can be quantified for any given random gravel (or road)
experience and used to compare efficiency for other iterations.
A pair of series RLC circuits (one for the road-tire interface
and a second for the suspension-rider interface) would be a good
start. I'm not skilled enough to do the calculations, but others
on this group likely are.
I _may_ have been able to do such calculations 50 years ago, but I'm not >sure. I certainly can't do them now.
The hardest part is apt to be finding
an equivalent circuit for the rider, who isn't a rigid mass but
rather a dissipative blob....8-)