Powercranks

[Frank Day]

Tom Sherman <[email protected]> wrote in message news:<[email protected]>...
> Frank Day wrote:
>
> > ... There is another thing the rider can do to minimize this loss that doesn't involve weights
> > or varying pedal speed. That is to mount their cranks at 90 degrees to each other. In this
> > configuration one thigh is accelerating when the other is decelerating so the energy could be
> > transferred from one to the other through the BB. While these accelerations and decelerations
> > are not perfectly timed, they are close enough that it should get these losses much smaller.
> > Unfortunately, in order to do this one must be able to actually pedal in a complete circle
> > because one can't help the other leg over the top by pushing down as at some point both feet are
> > coming up at the same time. While this does require some external energy to increase the
> > potential energy of the legs during this portion of the stroke it is all recovered on the down
> > stroke so doesn't require any net energy....
>
> So why should I pay a lot of money for PowerCranks when I can pull one crank and reinstall it 90-
> degrees out of phase [1] for no cost other than my time (since I already own a crank puller)?

The only reason I can think of is one won't be able to pedal efficiently or well in this manner
unless one can pedal well in a complete circle. The problem is in learning how to do this and
learning how to do it efficiently. This pattern also won't be more efficient unless the rider can
learn how to appropriately relax the muscles, etc. to allow the necessary energy transfer. It is not
clear to me this will be easy to do. Try it and let us know how it goes.
>
> [1] I would probably do this on my trike, as it would eliminate balance issues when starting out.

I don't think it would be that hard but the trikee would work fine for the experiment. Don't forget,
there will only be a significant advantage at high cadences.

 

[Frank Day]

"Phil Holman" <[email protected]> wrote in message news:<[email protected]>...
> "Andrew Bradley" <[email protected]> wrote in message
> news:9DOYb.7688$Y%[email protected]...
> > Phil Holman <[email protected]> wrote in message
> > news:[email protected]...
> > > >
> > > Just to keep the thread going, take a look at what was done in this study.........
> > > http://tinyurl.com/24sph
> > >
> >
> > This study confirms what i mentioned earlier - Frank's calculation
> doesn't
> > set a precedent. Although he doesn't seem to realise it plenty of researchers have gone through
> > the "internal work" calculation, choosing to define "internal work" as the variation in
> > mechanical energy no matter what real life energy
> loss
> > mechanisms (such as viscosity and soft tissue oscillation) are or are
> not
> > present.
> >
> > I mean, do you understand what they call "mechanical efficiency" in
> the
> > study you cite (http://tinyurl.com/24sph)? All the costs of pedalling are already accounted for
> > in the gross
> efficiency
> > value. Why did they feel justified in adding in "internal work" to derive another "efficiency"
> > figure? Surely if "internal work" were a meaningful measure of cost (it isn't) it will already
> > have been accounted for. IOW, they make higher cadences sound more efficient via a fudge, no?
> >
> > As the later (1997) study i mentioned says: "the internal work method
> is
> > theoretically flawed". (However, even as late as 2001, a study cites "internal work" as a
> > _possible_ factor in the cost of pedalling (separate from viscosity
> etc)
> > but notes that the concept of internal work is "controversial in
> cycling".)
> >
> > So what do you think of the paper, Phil?
>
> I guess my final comments were only implicit and didn't quite do it, so.......it's a piece of
> doodoo. It's like knowing the answer to a math problem and then fudging the calculations to get
> there.You know the rate of energy input and the useful power output to the pedals. KE and PE
> changes net to zero over exactly one revolution at constant pedal speed. What's left are a number
> of buckets to put all the remaining losses. Into one, viscoelastic is kind of a catch all as AC
> pointed out. Into another, by subtracting the useful power output from all muscle activity, you
> have the energy required to stabilize the system. How do you model this? Integrating all of the
> lower limb segment inertia loads over one pedal revolution and balancing these with forces from
> the appropriate muscles, ligaments etc? How do you assign energy spent on lateral stability? Using
> athletes with good muscle tone and low body fat will minimize soft tissue oscillations (no masters
> fatties). Whole body losses over and above basic metabolic rate need to be accounted (heart, lungs
> etc). Somewhere in here the inefficiency of converting chemical into mechanical energy has to be
> factored. Did I miss anything? If you hire someone to model this setup, expect it to be late with
> significant budget overrun. I can hear it now.....we're having a problem running the model but I
> think if we tweak it just one more time (the umpteenth) we'll be done.

This is my "problem" with this "discussion". I think it is pretty clear that everyone will agree
that there is a optimum cadence for any particular rider to pedal at any particular power. Above
that or below that and efficiency drops. The experimental data is pretty clear about this. If one
is going to come up with a "model" for pedaling then one needs to be able to explain the
experimental data.

Further, models don't need to be perfect but good enough to help people solve everyday problems. The
models at analytical cycling are an example. They are not perfect and don't consider the persons
pedaling style or a whole host of other variables yet are still useful to understand what makes one
go faster or slower and the relative importance of aerodynamics, rolling resistance, and power under
various conditions. They ignore how one gets the power to the wheel, what one must do to get in an
aero position and what that does to power, etc.

In this discussion we have data that shows there is a cost to pedaling which is also the personal
experience of most as most do not like to ride around at a cadence or 120 when looking for sustained
power. Yet, attempts by some to analyze this data are derided as theoretically flawed, goes against
some model that doesn't reproduce the real life pedaling motion, etc. and because these "models" are
flawed it is presented that there is no cost to pedaling, which ignores the data.

My simple analysis tried to look at one aspect of this connundrum and I determned that the cost of
this one aspect varied with the cube of the cadence. My analysis didn't care what the masses are or
how these losses come about, only that they are there. It seems to be reasonable in view of the
experimental data and would explain the drop in effiiciency at high cadences but doesn't explain the
drop at low cadences.

To insist that one doesn't like the way I (or these other researchers) did things in our little
attempts to explain this problem so, because fault can be found with the analysis, I and others
should come around to the views of the "right thinkers" who seemingly ignore real world data by
insisting the cost of constant velocity pedaling is "nada" and if we could eliminate resistance
and viscoelastic losses this could be a perpetual motion machine. This argument is not going to
win me over.

To deride others for trying to explain what is going on here (and not trying yourself) doesn't show
much scientific integrity. So, Andrew and AC, where is your model that actually explains the
experimental data? Your current model (instantaneous pedal cadence must vary between 70 and 115
twice during each revolution to work) isn't even cycling! The king really isn't wearing any clothes.
Phil is right, if I understand him, that this problem is has so many variables, that it may not be
possible to come up with a good model that explains everyting. So, we may be left with these
inadequate attempts that look at a part of the problem at a time.

Frank

 

[Dvt]

Frank Day wrote:
> I think it is pretty clear that everyone will agree that there is a optimum cadence for any
> particular rider to pedal at any particular power. Above that or below that and efficiency drops.
> The experimental data is pretty clear about this.

Huh? I don't think that is a widely held opinion. See, for example, Robert Chung's web page: http://mywebpage.netscape.com/rechung/wattage/cadence/cadence-
plots.html. That page has been hit-and-miss in my attempts to view it over the past few weeks, so
try it again if it doesn't work the first time.

Dave dvt at psu dot edu

 

[Andrew Bradley]

[email protected] (Frank Day) wrote in message news:<[email protected]>...

>As with most physical systems there are more than one way to analyze the system so I am not sure I
>understand why "the internal work method is theoretically flawed". Is this because it comes up with
>a different result?

It comes up with poor predictions as studies have shown.

> Exactly what is the fatal flaw?

"Internal work" is pretty meaningless when applied to cycling. Indeed 3 years after the funny rings
paper two of the researchers invoved published a paper finding that "internal work" _doesn't_
correspond to the energy required to move the limbs in cycling, with the implication that their
rings weren't going to work after all.

As the French say "only imbeciles don't change their minds" Do you want to be 10 years
behind on this?

Andrew Bradley

 

[Frank Day]

dvt <[email protected]> wrote in message news:<[email protected]>...
> Frank Day wrote:
> > I think it is pretty
> > clear that everyone will agree that there is a optimum cadence for any particular rider to pedal
> > at any particular power. Above that or below that and efficiency drops. The experimental data is
> > pretty clear about this.
>
> Huh? I don't think that is a widely held opinion. See, for example, Robert Chung's web page: http://mywebpage.netscape.com/rechung/wattage/cadence/cadence-
> plots.html. That page has been hit-and-miss in my attempts to view it over the past few weeks, so
> try it again if it doesn't work the first time.
>
> Dave dvt at psu dot edu

I couldn't get the page up but I believe I have seen it before. Isn't it a plot of ride data showing
a wide spread? The problem with that is it doesn't take into account effort if I remember correctly.
Even if it did, HR on a ride, frequently lags effort such that, unless power is sustained for a long
period, such data is pretty useless in drawing conclusions. Most studies that have looked at cadence
and power/efficiency have shown an optimum cadence for any power. This "optimum" has varied between
studies but the conclusion that there is an "optimum" seems consistent.

 

[Frank Day]

[email protected] (Andrew Bradley) wrote in message news:<[email protected]>...
> [email protected] (Frank Day) wrote in message
> news:<[email protected]>...
>
> >As with most physical systems there are more than one way to analyze the system so I am not sure
> >I understand why "the internal work method is theoretically flawed". Is this because it comes up
> >with a different result?
>
> It comes up with poor predictions as studies have shown.
>
> > Exactly what is the fatal flaw?
>
> "Internal work" is pretty meaningless when applied to cycling. Indeed 3 years after the funny
> rings paper two of the researchers invoved published a paper finding that "internal work"
> _doesn't_ correspond to the energy required to move the limbs in cycling, with the implication
> that their rings weren't going to work after all.
>
> As the French say "only imbeciles don't change their minds" Do you want to be 10 years behind
> on this?

I can't speak to the predictions of others in this regard as I don't know them. Nor, do I know all
of the data. However, my prediction of the energy cost of pedaling varying with the square of the
cadence (and the power required varying with the cube) seems close to the data that has been
presented here in both Phil's little experiment showing changing HR (assuming HR correlates linearly
with power) with fixed power out and changing cadence, and the other experiment where they also
changed leg mass, showing it varying to the 4+ power. That prediction based upon and "internal work"
model, and, while, maybe not perfect, is clearly closer than a model that predicts no energy cost to
pedaling, which all the "right thinkers" here seem to be advocating. Or is there a better accepted
model that better predicts these outcomes that no one has mentioned yet?

Frank

 

[Frank Day]

"Andrew Bradley" <[email protected]> wrote in message news:<9DOYb.7688$Y%[email protected]>...
> Phil Holman <[email protected]> wrote in message
> news:[email protected]...
> > >
> > Just to keep the thread going, take a look at what was done in this study.........
> > http://tinyurl.com/24sph
> >
>
> This study confirms what i mentioned earlier - Frank's calculation doesn't set a precedent.
> Although he doesn't seem to realise it plenty of researchers have gone through the "internal work"
> calculation, choosing to define "internal work" as the variation in mechanical energy no matter
> what real life energy loss mechanisms (such as viscosity and soft tissue oscillation) are or are
> not present.

My calculation ingnored viscosity losses and "soft tissue oscillations" (whatever those are). I
don't even know why you are referring to this as "internal work" as I see it as simply system
inefficiencies or losses. I have never claimed my examination was a precedent, in fact I would be
surprised to have found out that others had not done same. I have been making this "claim" for about
5 years and the only respons I have received on this and other forums is I am stupid because it is
obvious to the slowest cretin that energy is conserved and energy loss due to pedaling is "nada". No
one has ever supported me or provided any articles, until this thread, that support my opinion but
no one has ever given any data to refute it, only name calling. I have seen nothing in this thread
to change my opinion although I will concede that my analysis was done very amateurishly. I still
don't doubt the results, within reason.
>
> I mean, do you understand what they call "mechanical efficiency" in the study you cite
> (http://tinyurl.com/24sph)? All the costs of pedalling are already accounted for in the gross
> efficiency value. Why did they feel justified in adding in "internal work" to derive another
> "efficiency" figure?

Seems to me there are several separable inefficiencies to which they tried to see if they could
separate them. There is the conversion of chemical to mechanical energy in the muscle. There is the
cost of keeping the organism alive. There is the viscoelastic friction forces. And, there are the
"internal" work inefficiencies that come from pedaling this poorly balanced system at a constant
cadence. There are porbably others.

> Surely if "internal work" were a meaningful measure of cost (it isn't) it will already have been
> accounted for. IOW, they make higher cadences sound more efficient via a fudge, no?

Possibly, as I didn't understand from the abstract what they did there. Clearly, in my mind, there
is an optimum cadence. Biolgical systems cannot just keep uping the force as the cadence is
decreased as muscles are only opimally efficient in a certain range of forces and contraction rates.
>
> As the later (1997) study i mentioned says: "the internal work method is theoretically flawed".
> (However, even as late as 2001, a study cites "internal work" as a _possible_ factor in the cost
> of pedalling (separate from viscosity etc) but notes that the concept of internal work is
> "controversial in cycling".)

If it is controversial then it is only "flawed" in the minds of some, not all.

 

[Andrew Bradley]

Frank Day <[email protected]> wrote in message
news:[email protected]...
> "Andrew Bradley" <[email protected]> wrote in message
news:<9DOYb.7688$Y%[email protected]>...
> > Phil Holman <[email protected]> wrote in message
> > news:[email protected]...
> > > >
> > > Just to keep the thread going, take a look at what was done in this study.........
> > > http://tinyurl.com/24sph
> > >
> >
> > This study confirms what i mentioned earlier - Frank's calculation
doesn't
> > set a precedent. Although he doesn't seem to realise it plenty of researchers have gone through
> > the "internal work" calculation, choosing to define "internal work" as the variation in
> > mechanical energy no matter what real life energy
loss
> > mechanisms (such as viscosity and soft tissue oscillation) are or are
not
> > present.
>
> My calculation ingnored viscosity losses and "soft tissue oscillations" (whatever those are). I
> don't even know why you are referring to this as "internal work" as I see it as simply system
> inefficiencies or losses.

That's it, thats the problem - defining "internal work" with no regard for "internal energy loss"
which has to occur through loss producing mechanisms such as viscosity, soft tissue damping,
stabilising muscle work. You can't have ANY losses, (your heat production) without these things. The
theoretical flaw in the internal work method (and your calcs) really is that simple.

(Soft tissue oscillations are the jelly-wobble you get in leg-flesh, most noticeable when
pedalling fast)

>I have never claimed my examination was a precedent, in fact I would be surprised to have found out
>that others had not done same. I have been making this "claim" for about 5 years and the only
>respons I have received on this and other forums is I am stupid because it is obvious to the
>slowest cretin that energy is conserved and energy loss due to pedaling is "nada". No one has ever
>supported me or provided any articles, until this thread, that support my opinion but no one has
>ever given any data to refute it, only name calling. I have seen nothing in this thread to change
>my opinion although I will concede that my analysis was done very amateurishly. I still don't doubt
>the results, within reason.
> >
> > I mean, do you understand what they call "mechanical efficiency" in the study you cite
> > (http://tinyurl.com/24sph)? All the costs of pedalling are already accounted for in the gross
efficiency
> > value. Why did they feel justified in adding in "internal work" to derive another "efficiency"
> > figure?
>
> Seems to me there are several separable inefficiencies to which they tried to see if they could
> separate them. There is the conversion of chemical to mechanical energy in the muscle. There is
> the cost of keeping the organism alive. There is the viscoelastic friction forces. And, there are
> the "internal" work inefficiencies that come from pedaling this poorly balanced system at a
> constant cadence.

Loss due to the "poor balance" of the system is not the same as internal work. Internal work is
defined as the total (absolute) variation in mechanical leg energy -how does that relate to any of
the real world losses? All the real losses are accounted for in the gross efficiency figure and they
can't be separated out in this way.

> > Surely if "internal work" were a meaningful measure of cost (it isn't) it will already have been
> > accounted for. IOW, they make higher cadences sound more efficient via a fudge, no?
>
> Possibly, as I didn't understand from the abstract what they did there. Clearly, in my mind,
> there is an optimum cadence. Biolgical systems cannot just keep uping the force as the cadence
> is decreased as muscles are only opimally efficient in a certain range of forces and
> contraction rates.
> >
> > As the later (1997) study i mentioned says: "the internal work method is theoretically flawed".
> > (However, even as late as 2001, a study cites "internal work" as a _possible_ factor in the cost
> > of pedalling (separate from viscosity
etc)
> > but notes that the concept of internal work is "controversial in
cycling".)
>
> If it is controversial then it is only "flawed" in the minds of some, not all.

Yes, the right thinkers Believe it or not, i threw this background info in so the ng could see
that other intelligent people have been down the same road as you, so you aren't necessarily the
"cretin" you seem to think everybody thinks you are. I haven't called you any names yet, so bearing
in mind this is supposed to be a technical discussion on a technical ng rather than a chat about
Frank Day's plight, could you try and stay on topic?

Andrew Bradley

 

[Frank Day]

"Andrew Bradley" <[email protected]> wrote in message news:<[email protected]>...
> Frank Day <[email protected]> wrote in message
> news:[email protected]...
> > "Andrew Bradley" <[email protected]> wrote in message
> news:<9DOYb.7688$Y%[email protected]>...
> > > Phil Holman <[email protected]> wrote in message
> > > news:[email protected]...
> > > > >
> > > > Just to keep the thread going, take a look at what was done in this study.........
> > > > http://tinyurl.com/24sph
> > > >
> > >
> > > This study confirms what i mentioned earlier - Frank's calculation
> doesn't
> > > set a precedent. Although he doesn't seem to realise it plenty of researchers have gone
> > > through the "internal work" calculation, choosing to define "internal work" as the variation
> > > in mechanical energy no matter what real life energy
> loss
> > > mechanisms (such as viscosity and soft tissue oscillation) are or are
> not
> > > present.
> >
> > My calculation ingnored viscosity losses and "soft tissue oscillations" (whatever those are). I
> > don't even know why you are referring to this as "internal work" as I see it as simply system
> > inefficiencies or losses.
>
> That's it, thats the problem - defining "internal work" with no regard for "internal energy loss"
> which has to occur through loss producing mechanisms such as viscosity, soft tissue damping,
> stabilising muscle work. You can't have ANY losses, (your heat production) without these things.
> The theoretical flaw in the internal work method (and your calcs) really is that simple.

I don't understand the "problem" here in looking at just one aspect of the problem (internal work)
and ignoring others (internal viscosity, damping, and stabilization, etc, some of which would
qualify as work and some wouldn't). Work is force exerted through a distance. Work is done whenever
a mass is accelerated (that includes deceleration also) as it requires a force exerted through a
distance. If the acceleration is radial (the pedals) and balanced then it can be shown that the
"work" requires no net energy. It is when the motions are not circular or symmetrical that it starts
to take external energy to maintain the motion. It is this simple energy analysis that I looked at
which you are calling internal work (which I would agree is a valid descriptive term). Perhaps this
method of analysis has been discredited (at least in the minds of some) but I certainly haven't seen
any arguments here that justify the discrediting.
>
> (Soft tissue oscillations are the jelly-wobble you get in leg-flesh, most noticeable when
> pedalling fast)

(or when riding over cobbles?)
>
> >I have never claimed my examination was a precedent, in fact I would be surprised to have found
> >out that others had not done same. I have been making this "claim" for about 5 years and the only
> >respons I have received on this and other forums is I am stupid because it is obvious to the
> >slowest cretin that energy is conserved and energy loss due to pedaling is "nada". No one has
> >ever supported me or provided any articles, until this thread, that support my opinion but no one
> >has ever given any data to refute it, only name calling. I have seen nothing in this thread to
> >change my opinion although I will concede that my analysis was done very amateurishly. I still
> >don't doubt the results, within reason.
> > >
> > > I mean, do you understand what they call "mechanical efficiency" in the study you cite
> > > (http://tinyurl.com/24sph)? All the costs of pedalling are already accounted for in the gross
> efficiency
> > > value. Why did they feel justified in adding in "internal work" to derive another "efficiency"
> > > figure?
> >
> > Seems to me there are several separable inefficiencies to which they tried to see if they could
> > separate them. There is the conversion of chemical to mechanical energy in the muscle. There is
> > the cost of keeping the organism alive. There is the viscoelastic friction forces. And, there
> > are the "internal" work inefficiencies that come from pedaling this poorly balanced system at a
> > constant cadence.
>
> Loss due to the "poor balance" of the system is not the same as internal work. Internal work is
> defined as the total (absolute) variation in mechanical leg energy -how does that relate to any of
> the real world losses? All the real losses are accounted for in the gross efficiency figure and
> they can't be separated out in this way.

I agree. So how do you account for the difference between muscle contraction gross efficiency
(around 40% and the typical cyclists gross efficiency, around 20%). Where are the losses?

>
> > > Surely if "internal work" were a meaningful measure of cost (it isn't) it will already have
> > > been accounted for. IOW, they make higher cadences sound more efficient via a fudge, no?
> >
> > Possibly, as I didn't understand from the abstract what they did there. Clearly, in my mind,
> > there is an optimum cadence. Biolgical systems cannot just keep uping the force as the cadence
> > is decreased as muscles are only opimally efficient in a certain range of forces and contraction
> > rates.
> > >
> > > As the later (1997) study i mentioned says: "the internal work method is theoretically
> > > flawed". (However, even as late as 2001, a study cites "internal work" as a _possible_ factor
> > > in the cost of pedalling (separate from viscosity
> etc)
> > > but notes that the concept of internal work is "controversial in
> cycling".)
> >
> > If it is controversial then it is only "flawed" in the minds of some, not all.
>
> Yes, the right thinkers Believe it or not, i threw this background info in so the ng could see
> that other intelligent people have been down the same road as you, so you aren't necessarily the
> "cretin" you seem to think everybody thinks you are. I haven't called you any names yet, so
> bearing in mind this is supposed to be a technical discussion on a technical ng rather than a chat
> about Frank Day's plight, could you try and stay on topic?

Oh, I don't think everyone on this newsgroup thinks me a cretin. I think there are a couple
though. Just to let everyone know I don't take such name calling too seriously. If I believed it I
would go away.

Just give me a model that accounts for all of the energy losses. Let us see, we have to account for
as much energy as we get to the wheel at power (40% to 20% so we are at a 50% overall net efficiency
for this problem). Of the 100% loss you have to account for I will accept a 5% loss for drive train
friction. If we can't have any "internal work" losses due to pedaling, that leaves you with only 95%
left to go. Where does it go?

Frank

 

[Dvt]

Frank Day wrote:
> dvt <[email protected]> wrote in message news:<[email protected]>...
>>Frank Day wrote:
>>> I think it is pretty clear that everyone will agree that there is a optimum cadence for any
>>> particular rider to pedal at any particular power. Above that or below that and efficiency
>>> drops. The experimental data is pretty clear about this.

>>I don't think that is a widely held opinion. See, for example, Robert Chung's web page: http://mywebpage.netscape.com/rechung/wattage/cadence/cadence-
>>plots.html. That page has been hit-and-miss in my attempts to view it over the past few weeks, so
>>try it again if it doesn't work the first time.

> I couldn't get the page up but I believe I have seen it before. Isn't it a plot of ride data
> showing a wide spread?

I guess your description vaguely describes the page.

> The problem with that is it doesn't take into account effort if I remember correctly. Even if it
> did, HR on a ride, frequently lags effort such that, unless power is sustained for a long period,
> such data is pretty useless in drawing conclusions.

He doesn't chart HR on the page to which I refer. The important chart is power vs. cadence, which
shows data points all over the map (r=0.03 for a linear fit). By contrast, when he plots power vs.
torque, there appears to be a relationship (r=0.9).

Note that the charts I describe are found on the second page of the analysis; I gave the link to the
first page.

> Most studies that have looked at cadence and power/efficiency have shown an optimum cadence for
> any power. This "optimum" has varied between studies but the conclusion that there is an "optimum"
> seems consistent.

I don't think I've seen those studies. Mind you, I'm not an exercise physiologist so my exposure is
limited to stuff linked from r.b.tech and a little bit of reading on my own. I have seen the study
that shows maximum efficiency for most riders at low (60ish) rpm, but I can't produce the reference
immediately. As stated earlier in this thread, efficiency is probably not the primary quantity of
interest in racing. Are there studies that disagree with Robert's analysis?

Dave dvt at psu dot edu

 

[andrewbradley]

Originally posted by Frank Day
I don't understand the "problem" here in looking at just one aspect of the problem (internal work)
and ignoring others (internal viscosity, damping, and stabilization, etc, some of which would
qualify as work and some wouldn't).

At long last I (think I) understand why you don't see the need for a specific mechanism for energy loss and this could unlock the circular debate we are in:

Work is done whenever a mass is accelerated (that includes deceleration also) as it requires a force exerted through a
distance.

Accelerating a mass does indeed require work BUT decelerating a mass requires NO WORK to be done on that mass! The mass does work on the retarding mechanism (although should this be via the excentric contraction of a muscle there will be some metabolic cost).

Assuming a freewheel, the muscles will have to do work to "accelerate the thighs" but the thigh deceleration you talk about will do work on the drivetrain and in the process drive the bike. No work is required to decelerate that thigh!

Just give me a model that accounts for all of the energy losses. Let us see, we have to account for
as much energy as we get to the wheel at power (40% to 20% so we are at a 50% overall net efficiency
for this problem). Of the 100% loss you have to account for I will accept a 5% loss for drive train
friction. If we can't have any "internal work" losses due to pedaling, that leaves you with only 95%
left to go. Where does it go?.

Most of the loss mechanisms have been previously mentioned, but
sorry Frank, it's far too complicated for me to model

Andrew Bradley

 

[N Crowley]

[email protected] (Frank Day) wrote in message news:<[email protected]>...
> andrewbradley <[email protected]> wrote in message
> news:<UH2Xb.323$%[email protected]>...
> > Frank Day wrote:
> > > > > Even if pedal speed were allowed to vary and internal resistance were zero, this would
> > > > > not become a peretual motion machine because it requires external energy to keep it
> > > > > going.
> > > >
> > > > Eh? How much energy? The amount you have calculated or an unspecified amount? Please
> > > > explain the mysterious mechanism of heat production in your model?
> > > the rate of energy loss depends upon the length of the cranks, the mass of the various leg
> > > components, and the cadence (and varies with the square of the cadence). I can't give you a
> > > number. The mysterous mechanism of heat production is simply the muscular energy required to
> > > make the muscles contract that is required to keep the pedaling motion going. It ain't
> > > rocket science, although you would think so by how many don't get it

How much extra power has the most experienced PC'er produced by pulling up?
> >
> >
> >
> > You hit the nail on the head. It ain't rocket science, since rocket science uses the established
> > laws of physics.
> >
> > Your method seems to stem from Winter 1979: A new definition of mechanical work done in human
> > movement. For it to have a hope, you need to be able to assume that no useful work is transfered
> > to the environment, which is clearly not the case on a bike where the environment is the pedal.
> > In running it is the ground an thus the concept is plausible.
>
> HUH?

 

[Phil Holman]

"Frank Day" <[email protected]> wrote in message
news:[email protected]...
> "Andrew Bradley" <[email protected]> wrote in message
news:<[email protected]>...
> > Frank Day <[email protected]> wrote in message
> > news:[email protected]...
> > > "Andrew Bradley" <[email protected]> wrote in message
> > news:<9DOYb.7688$Y%[email protected]>...
> > > > Phil Holman <[email protected]> wrote in message
> > > > news:[email protected]...
> > > > > >
> > > > > Just to keep the thread going, take a look at what was done in
this
> > > > > study......... http://tinyurl.com/24sph
> > > > >
> > > >
> > > > This study confirms what i mentioned earlier - Frank's
calculation
> > doesn't
> > > > set a precedent. Although he doesn't seem to realise it plenty
of
> > > > researchers have gone through the "internal work" calculation, choosing to
define
> > > > "internal work" as the variation in mechanical energy no matter what real life
energy
> > loss
> > > > mechanisms (such as viscosity and soft tissue oscillation) are
or are
> > not
> > > > present.
> > >
> > > My calculation ingnored viscosity losses and "soft tissue oscillations" (whatever those are).
> > > I don't even know why you are referring to this as "internal work" as I see it as simply
> > > system inefficiencies or losses.
> >
> > That's it, thats the problem - defining "internal work" with no
regard for
> > "internal energy loss" which has to occur through loss producing mechanisms such as viscosity,
> > soft tissue damping, stabilising
muscle work.
> > You can't have ANY losses, (your heat production) without these
things.
> > The theoretical flaw in the internal work method (and your calcs)
really is
> > that simple.
>
> I don't understand the "problem" here in looking at just one aspect of the problem (internal work)
> and ignoring others (internal viscosity, damping, and stabilization, etc, some of which would
> qualify as work and some wouldn't). Work is force exerted through a distance. Work is done
> whenever a mass is accelerated (that includes deceleration also) as it requires a force exerted
> through a distance. If the acceleration is radial (the pedals) and balanced then it can be shown
> that the "work" requires no net energy. It is when the motions are not circular or symmetrical
> that it starts to take external energy to maintain the motion. It is this simple energy analysis
> that I looked at which you are calling internal work (which I would agree is a valid descriptive
> term). Perhaps this method of analysis has been discredited (at least in the minds of some) but I
> certainly haven't seen any arguments here that justify the discrediting.

Lets take a frictionless, infinitely stiff mechanism simulating a single leg without an ankle joint
or any lateral freedom in a vacuum. If allowed to fall under gravity from TDC, the crank would
rotate exactly one revolution and return to its starting position. There are no non-conservative
forces or movement acting on the system to rob it of energy. A pendulum accelerates and decelerates
but without friction or air resistance (both non-conservative) it would keep oscillating forever.

> >
> > (Soft tissue oscillations are the jelly-wobble you get in leg-flesh,
most
> > noticeable when pedaling fast)
>
> (or when riding over cobbles?)
> >
> > >I have never claimed my examination was a precedent, in fact I would be surprised to have found
> > >out that
others
> > > had not done same. I have been making this "claim" for about 5
years
> > > and the only response I have received on this and other forums is
I am
> > > stupid because it is obvious to the slowest cretin that energy is conserved and energy loss
> > > due to pedaling is "nada". No one has
ever
> > > supported me or provided any articles, until this thread, that
support
> > > my opinion but no one has ever given any data to refute it, only
name
> > > calling. I have seen nothing in this thread to change my opinion although I will concede that
> > > my analysis was done very
amateurishly. I
> > > still don't doubt the results, within reason.
> > > >
> > > > I mean, do you understand what they call "mechanical efficiency"
in the
> > > > study you cite (http://tinyurl.com/24sph)? All the costs of pedaling are already accounted
> > > > for in the gross
> > efficiency
> > > > value. Why did they feel justified in adding in "internal work"
to
> > > > derive another "efficiency" figure?
> > >
> > > Seems to me there are several separable inefficiencies to which
they
> > > tried to see if they could separate them. There is the conversion
of
> > > chemical to mechanical energy in the muscle. There is the cost of keeping the organism alive.
> > > There is the viscoelastic friction
forces.
> > > And, there are the "internal" work inefficiencies that come from pedaling this poorly balanced
> > > system at a constant cadence.
> >
> > Loss due to the "poor balance" of the system is not the same as
internal
> > work. Internal work is defined as the total (absolute) variation in mechanical leg energy -how
> > does that relate to any of the real world losses? All the real losses are accounted for in the
> > gross efficiency figure and they can't be separated out in this
way.
>
> I agree. So how do you account for the difference between muscle contraction gross efficiency
> (around 40% and the typical cyclists gross efficiency, around 20%). Where are the losses?
>
> >
> > > > Surely if "internal work" were a meaningful measure of cost (it
isn't)
> > > > it will already have been accounted for. IOW, they make higher cadences sound more efficient
> > > > via a fudge,
no?
> > >
> > > Possibly, as I didn't understand from the abstract what they did there. Clearly, in my mind,
> > > there is an optimum cadence.
Biological
> > > systems cannot just keep upping the force as the cadence is
decreased
> > > as muscles are only optimally efficient in a certain range of
forces
> > > and contraction rates.
> > > >
> > > > As the later (1997) study I mentioned says: "the internal work
method is
> > > > theoretically flawed". (However, even as late as 2001, a study
cites
> > > > "internal work" as a _possible_ factor in the cost of pedaling (separate from
viscosity
> > etc)
> > > > but notes that the concept of internal work is "controversial in
> > cycling".)
> > >
> > > If it is controversial then it is only "flawed" in the minds of
some,
> > > not all.
> >
> > Yes, the right thinkers Believe it or not, I threw this background info in so the ng could
see that
> > other intelligent people have been down the same road as you, so you
aren't
> > necessarily the "cretin" you seem to think everybody thinks you are. I haven't
called you
> > any names yet, so bearing in mind this is supposed to be a
technical
> > discussion on a technical ng rather than a chat about Frank Day's
plight,
> > could you try and stay on topic?
>
> Oh, I don't think everyone on this newsgroup thinks me a cretin. I think there are a couple
> though. Just to let everyone know I don't take such name calling too seriously. If I believed it I
> would go away.

Its a flawed argument of discrediting the inventor to discredit the device. Whether it works or not
has nothing to do with the mental capacity of the person who came up with this particular idea.

>
> Just give me a model that accounts for all of the energy losses. Let us see, we have to account
> for as much energy as we get to the wheel at power (40% to 20% so we are at a 50% overall net
> efficiency for this problem). Of the 100% loss you have to account for I will accept a 5% loss for
> drive train friction. If we can't have any "internal work" losses due to pedaling, that leaves you
> with only 95% left to go. Where does it go?

Non-conservative forces. I think I listed most of them previously but missed out joint friction and
possibly some other minor ones.

Phil Holman

 

[Frank Day]

andrewbradley <[email protected]> wrote in message news:<[email protected]>...
> Frank Day wrote:
> > I don't understand the "problem" here in looking at just one aspect of the problem (internal
> > work) and ignoring others (internal viscosity, damping, and stabilization, etc, some of which
> > would qualify as work and some wouldn't). At long last I (think I) understand why you don't
> > see the need for a specific mechanism for energy loss and this could unlock the circular
> > debate we are in: Work is done whenever a mass is accelerated (that includes deceleration
> > also) as it requires a force exerted through a distance. Accelerating a mass does indeed
> > require work BUT decelerating a mass requires NO WORK to be done on that mass! The mass does
> > work on the retarding mechanism (although should this be via the excentric contraction of a
> > muscle there will be some metabolic cost). Assuming a freewheel, the muscles will have to do
> > work to "accelerate the thighs" but the thigh deceleration you talk about will do work on the
> > drivetrain and in the process drive the bike. No work is required to decelerate that thigh!
> > Just give me a model that accounts for all of the energy losses. Let us see, we have to
> > account for as much energy as we get to the wheel at power (40% to 20% so we are at a 50%
> > overall net efficiency for this problem). Of the 100% loss you have to account for I will
> > accept a 5% loss for drive train friction. If we can't have any "internal work" losses due to
> > pedaling, that leaves you with only 95% left to go. Where does it go?.

First, I would like to point out that I did not say all of the above. I think I may have actually
said the first two paragraphs and th last.

So, you are saying it takes no work to decelerate the space shuttle for reentry? Whether work is
done or not by the pusher or the pushee depends upon the frame of reference as to which or what is
the pusher or pushee.
>
>
> Most of the loss mechanisms have been previously mentioned, but sorry Frank, it's far too
> complicated for me to model

Most of the mechanisms have previously been mentioned? In this thread? Then it should be easy to
give me how much each one accounts for the remaining 95% that must be accounted for. If you can't
account for the bulk of these losses then you don't understand it. If you don't understand it then
shouldn't be critical of those of us who are making at least a token effort to do so.

I would like to point out that if one doesn't understand where all the losses are then one cannot
understand where improvements may or may not be made. I think I understand at least some of these
losses and the results of the users of my product, which is designed to address some of them, would
support that.

Frank

 

[Frank Day]

dvt <[email protected]> wrote in message news:<[email protected]>...
> Frank Day wrote:
> > dvt <[email protected]> wrote in message news:<[email protected]>...
> >>Frank Day wrote:
> >>> I think it is pretty clear that everyone will agree that there is a optimum cadence for any
> >>> particular rider to pedal at any particular power. Above that or below that and efficiency
> >>> drops. The experimental data is pretty clear about this.
>
> >>I don't think that is a widely held opinion. See, for example, Robert Chung's web page: http://mywebpage.netscape.com/rechung/wattage/cadence/cadence-
> >>plots.html. That page has been hit-and-miss in my attempts to view it over the past few weeks,
> >>so try it again if it doesn't work the first time.
>
> > I couldn't get the page up but I believe I have seen it before. Isn't it a plot of ride data
> > showing a wide spread?
>
> I guess your description vaguely describes the page.
>
> > The problem with that is it doesn't take into account effort if I remember correctly. Even if it
> > did, HR on a ride, frequently lags effort such that, unless power is sustained for a long
> > period, such data is pretty useless in drawing conclusions.
>
> He doesn't chart HR on the page to which I refer. The important chart is power vs. cadence, which
> shows data points all over the map (r=0.03 for a linear fit). By contrast, when he plots power vs.
> torque, there appears to be a relationship (r=0.9).

The problem with power vs cadence is cadence can easily be high with low power depending on gearing
and terrain while cadence can be high with high power if one is sprinting with high effort. That
spread is to be expected and is pretty worthless. However, it is hard to have high torque without a
high effort. Hence, the relationship.
>
> Note that the charts I describe are found on the second page of the analysis; I gave the link to
> the first page.
>
> > Most studies that have looked at cadence and power/efficiency have shown an optimum cadence for
> > any power. This "optimum" has varied between studies but the conclusion that there is an
> > "optimum" seems consistent.
>
> I don't think I've seen those studies. Mind you, I'm not an exercise physiologist so my exposure
> is limited to stuff linked from r.b.tech and a little bit of reading on my own. I have seen the
> study that shows maximum efficiency for most riders at low (60ish) rpm, but I can't produce the
> reference immediately. As stated earlier in this thread, efficiency is probably not the primary
> quantity of interest in racing. Are there studies that disagree with Robert's analysis?

An easy reference that goes to many of these issues is the book Bicycling Science, by whitt and
wilson. It is available in paperback so is not too expensive. I understand they may discuss
PowerCranks in the next edition due to come out "soon" so I am told.

Frank

 

[Frank Day]

[email protected] (n crowley) wrote in message news:<[email protected]>...
> [email protected] (Frank Day) wrote in message
> news:<[email protected]>...
> > andrewbradley <[email protected]> wrote in message
> > news:<UH2Xb.323$%[email protected]>...
> > > Frank Day wrote:
> > > > > > Even if pedal speed were allowed to vary and internal resistance were zero, this would
> > > > > > not become a peretual motion machine because it requires external energy to keep it
> > > > > > going.
> > > > >
> > > > > Eh? How much energy? The amount you have calculated or an unspecified amount? Please
> > > > > explain the mysterious mechanism of heat production in your model?
> > > > the rate of energy loss depends upon the length of the cranks, the mass of the various leg
> > > > components, and the cadence (and varies with the square of the cadence). I can't give you
> > > > a number. The mysterous mechanism of heat production is simply the muscular energy
> > > > required to make the muscles contract that is required to keep the pedaling motion going.
> > > > It ain't rocket science, although you would think so by how many don't get it
>
>
>
>
>
> How much extra power has the most experienced PC'er produced by pulling up?

I can only tell you what I think the most dramatic power improvement I have heard of is after two
years on the cranks. I can't tell you how much of this power improvement came from pulling up as it
is not possible to know without before and after pedal force data.

Joe Skufka has reported increasing his average speed on a 12 mile TT loop he rides once a month as a
gauge of his fitness from 20 mph pre PowerCranks to over 25 mph in one year and over 27 mph after
two years on PowerCranks. This calculates to an increase in power of 146%. Such increases help me in
my claim that the average user can anticipate a power increase of only 40%

Frank

 

[Tom Sherman]

dvt wrote:

> ... He doesn't chart HR on the page to which I refer. The important chart is power vs. cadence,
> which shows data points all over the map (r=0.03 for a linear fit). By contrast, when he plots
> power vs. torque, there appears to be a relationship (r=0.9)....

I believe that there is an exact relationship between power and torque: rotational speed.

Tom Sherman - Quad Cities (Illinois Side)

 

[Dvt]

Tom Sherman wrote:
> dvt wrote:
>
>> ... He doesn't chart HR on the page to which I refer. The important chart is power vs. cadence,
>> which shows data points all over the map (r=0.03 for a linear fit). By contrast, when he plots
>> power vs. torque, there appears to be a relationship (r=0.9)....
>
>
> I believe that there is an exact relationship between power and torque: rotational speed.

Yeah, and there's another name for rotational speed: cadence.

Dave dvt at psu dot edu

 

[Dvt]

Frank Day wrote:
> The problem with power vs cadence is cadence can easily be high with low power depending on
> gearing and terrain while cadence can be high with high power if one is sprinting with high
> effort. That spread is to be expected and is pretty worthless. However, it is hard to have high
> torque without a high effort. Hence, the relationship.

So you can have high effort (and thus high power) at a wide range of cadences. How does this imply
an optimal cadence?

Did you see the charts of cadence vs power in the TT and the climbing ride? The TT data showed a
very broad power peak in the cadence vs. power curve, indicating that if there was an optimum
cadence, it was maybe 97 rpm. The hilly ride curve would seem to indicate that the optimum cadence
was much lower. The data seems to indicate that if there is an optimum cadence, it is at best condition-
dependent.

> An easy reference that goes to many of these issues is the book Bicycling Science, by whitt and
> wilson. It is available in paperback so is not too expensive. I understand they may discuss
> PowerCranks in the next edition due to come out "soon" so I am told.

Did that study look at efficiency as well? Or did they optimize cadence for max power? I just got
some good reading from my library to keep me busy, so I probably won't get around to reading that
one soon. Thanks for the tip.

Dave dvt at psu dot edu

 

[andrewbradley]

Originally posted by Frank Day
So, you are saying it takes no work to decelerate the space shuttle for reentry? Whether work is
done or not by the pusher or the pushee depends upon the frame of reference as to which or what is
the pusher or pushee.

The space shuttle looses energy, thats negative work done on it in my book which means there is energy for the taking if the retarding mechanism is capable of it. A giant spring would do the trick.
To what degree the energy is converted to heat or whether it requires energy to produce the force is a separate but important issue. The internal work method depends on it.

There are 3 distinct mechanisms for doing negative work on the legs during pedalling. The first is conservative - the drivetrain, the second is non conservative - viscoscity etc and the third is costly - excentric muscle contraction.

In running, if you assume that all leg-deceleration is via excentric muscle work, the method stands a chance, although assuming that a given amount of negative work has an equal metabolic cost is a fudge.

Most of the mechanisms have previously been mentioned? In this thread? Then it should be easy to
give me how much each one accounts for the remaining 95% that must be accounted for. If you can't
account for the bulk of these losses then you don't understand it. If you don't understand it then
shouldn't be critical of those of us who are making at least a token effort to do so.

I reckon I "understand" these losses as well as you do. I understand they can't easily be modelled.

As I said, this is a cadence question and has nothing to do with PCs. I asked you what your method was because the "establishment" hasn't cracked it yet and i wondered if you had (yes, I was sceptical). You put us (esp the powercrankers) in a tricky position with some of your mechanics.

I would like to point out that if one doesn't understand where all the losses are then one cannot
understand where improvements may or may not be made. I think I understand at least some of these
losses and the results of the users of my product, which is designed to address some of them, would
support that.

If Phil says he believes the PCs have worked for him then I sit up and listen and try to understand why they may have worked - as he seems to be doing himself.
Trying to spare the feelings of an inventor who comes in gung-ho just makes the debate awkward.

If PC's do work, we want to know precisely why. You certainly make a lot of claims so what's wrong with proceeding by a process of elimination?

Andrew Bradley