rotor cranks

wrote:

On this point in isolation you can see the possibility of (small)
benefit in a max power situation at least, no?

No. A rider's power output is limited by cardiovascular capacity,
not by any modification of foot position timing, especially one
that attempts to have both feet push downward at the same time, as
this one does.

You must have misread the question. Anyway at first glance there
does seem to be the possibility of a little more max power but this
could be outweighed by complicating factors like those you outline
below.

I don't believe I missed anything. Work is work, regardless whether
it is done with one foot at a time or both in some other
configuration.

I'll highlight the words I think you might miss. I said _max_ power.
I'm not saying that you will in practice get more _an_aerobic power
with Rotor over any useful period of time and am still a Rotor skeptic
but "work is work" isn't a good enough argument against these cranks.


It's not physics at all, but rather a misunderstanding of what
physical exertion is and how it is applied to the propulsion of a
bicycle. All the work done by a rider (minus frictional losses) goes
to propelling the bicycle. Changing pedal timing cannot create more
work/unit-time (power) than the rider's cardiovascular system can
support.

This is the central point and the rotor people will presumably have to
argue that it _is_ possible to coax (a little) more power out of the
cardio vascular system via a longer duty cycle. If the physiologists
can indeed give a definitive "no" on this then things look bad for
Rotor - although I note that the experiment claimed greater efficiency
....


It means, however small, the imbalance requires muscular effort to
achieve that which requires none, using conventional fixed 180
degree opposed cranks.

But using muscular effort to get from one leg configuration to
another is known as pedaling. Are you saying that muscular effort
would be wasted with Rotor?

That's not what I meant. Removing the chain is only a clear way to
see that with other then 180 degree crank positions, holding the
cranks still at various other positions requires muscular force and if
rotating, this demands work. Therefore, right at the start, this
device is inferior to regular cranks.

Sounds woolly to me. You say elsewhere that all the riders work (minus
friction etc) goes to the drivetrain.

Yes. Next time you ride, note that you can stop pedaling at any
point of rotation without your feet tending toward a preferred
position such as occurs with cranks that are not diametrically
opposite.

Struck by the elegance of this concept and thinking the mechanics
must be neat I was going to draw a diagram and stuff, but as
touchy-feely is OK I jump on the bike , chain off, feet at twenty to
two, relax-muscles (except calves) and after a bit of oscillation
the legs end up at about ten to four, this presumably being a lower
potential energy state.

I'm not clear on what you performed the test. Was it a rotor crank or
a conventional one? From what you report, it must have been rotor
cranks because conventional cranks have no preferred position unless
the rider has problems with knee articulation.

Conventional cranks!

If your legs just hang in any configuration you may have knee problems
or need to sign up for relaxation classes.


Now there is another peer-reviewed and published system which balances
out the mechanical energy content of the legs - via an elliptical!

If "balance" is where it's at, what more could you want?

It's not balance. It's the extra effort it takes to move the cranks
around a revolution even when there is no load.

But these rings were designed precisely with a view to eliminating the
"extra effort" involved in simply moving the legs around at constant
pedal speed. They were working on the (false) assumption that the work
required to move the leg segments between configurations is wasted and
i wonder if you are doing the same.

Andrew Bradley

Carl- Of course, Jobst Brandt might have ethical qualms
about accepting for free what the rest of us expect
to pay $640 for: BRBR

Donno, I think as a tester of extraordinary knowledge and skill, his input
would be very useful.

We didn't pay $640 for ours BTW-

Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl St.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
"Ruote convenzionali costruite eccezionalmente bene"

Carl Fogel wrote:
snip

Dear Jeff,

Thanks for explaining an odd scheme that I wish
that I'd heard of earlier. Am I wrong in assuming
that these fire-all-cylinders-at-once monsters are
now safely dead, or do they still rumble among us?

Nice to meet a fellow Kevin Cameron fan. I still miss
Gordon Jennings.

Carl Fogel

The "big bang" bikes I remember were some of the 500cc
2-stroke GP bikes in the 90's, and I think they were
around until Moto GP became a 990cc 4-stroke class in the
last couple of seasons. In particular, Honda built their
500cc V-4 2-stroke GP engines in at least two different
firing configurations, a more-even firing and a less-even
firing version. The big-bang version did not fire all 4 at
once, but produced less smooth power than the earlier
version. Quite a few riders liked it better, some didn't.
I don't remember if Yamaha or others tried this. You might
check some of Cameron's columns from the era.

Dave Lehnen

Tim McNamara wrote:
So when I say that Kool-Stop salmon (a.k.a. Scott/Mathauser) brake
pads work better, it's because there's objective data to that effect
(formal lab testing) combined with subjective experience. When I say
that Brooks Pro saddles work better, that's purely subjective.

But unless you actually experience numbness in the nether regions, the
effect of a saddle is inherently purely subjective - how does your bottom
feel?
--
David Damerell Kill the tomato!

Andrew Bradley writes:

I'll highlight the words I think you might miss. I said _max_ power.
I'm not saying that you will in practice get more _an_aerobic power
with Rotor over any useful period of time and am still a Rotor
skeptic but "work is work" isn't a good enough argument against
these cranks.

It's not physics at all, but rather a misunderstanding of what
physical exertion is and how it is applied to the propulsion of a
bicycle. All the work done by a rider (minus frictional losses) goes
to propelling the bicycle. Changing pedal timing cannot create more
work/unit-time (power) than the rider's cardiovascular system can
support.

This is the central point and the rotor people will presumably have
to argue that it _is_ possible to coax (a little) more power out of
the cardiovascular system via a longer duty cycle. If the
physiologists can indeed give a definitive "no" on this then things
look bad for Rotor - although I note that the experiment claimed
greater efficiency ...

Duty cycle can be changed by selecting an appropriate gear. No
special crank is required for that.

It means, however small, the imbalance requires muscular effort
to achieve that which requires none, using conventional fixed 180
degree opposed cranks.

But using muscular effort to get from one leg configuration to
another is known as pedaling. Are you saying that muscular effort
would be wasted with Rotor?

That's not what I meant. Removing the chain is only a clear way to
see that with other then 180 degree crank positions, holding the
cranks still at various other positions requires muscular force and
if rotating, this demands work. Therefore, right at the start,
this device is inferior to regular cranks.

Sounds woolly to me. You say elsewhere that all the riders work
(minus friction etc) goes to the drivetrain.

Not with the rotor crank as I took time to explain.

Yes. Next time you ride, note that you can stop pedaling at any
point of rotation without your feet tending toward a preferred
position such as occurs with cranks that are not diametrically
opposite.

Struck by the elegance of this concept and thinking the mechanics
must be neat I was going to draw a diagram and stuff, but as
touchy-feely is OK I jump on the bike , chain off, feet at twenty
to two, relax-muscles (except calves) and after a bit of
oscillation the legs end up at about ten to four, this presumably
being a lower potential energy state.

I'm not clear on what you performed the test. Was it a rotor crank
or a conventional one? From what you report, it must have been
rotor cranks because conventional cranks have no preferred position
unless the rider has problems with knee articulation.

Conventional cranks!

If your legs just hang in any configuration you may have knee problems
or need to sign up for relaxation classes.

What do you believe causes a preferred position on conventional cranks
when both legs are relaxed? My legs are very nearly the same weight and
balance at any position of crank rotation. You say there is a favored
position. Have you compared that to rotor cranks?

Now there is another peer-reviewed and published system which
balances out the mechanical energy content of the legs - via an
elliptical!

If "balance" is where it's at, what more could you want?

It's not balance. It's the extra effort it takes to move the
cranks around a revolution even when there is no load.

But these rings were designed precisely with a view to eliminating
the "extra effort" involved in simply moving the legs around at
constant pedal speed. They were working on the (false) assumption
that the work required to move the leg segments between
configurations is wasted and I wonder if you are doing the same.

Not at all. They were designed to not be 180 degrees apart and
therefore have a preferred position with equal weight on both pedals.
If you've got these cranks, how about putting a bicycle show in each
pedal and see where they stop when allowed to rotate freely. I assume
your shoes are about equal weight but if they are not, I'm sure you
can stuff a sock in the light one or some such thing.

Jobst Brandt

wrote in message
...

Duty cycle can be changed by selecting an appropriate gear. No
special crank is required for that.

But whatever gear you always get more power stroke compared to recovery
stroke with Rotor. Of course if no extra fuel can be made available that's
no advantage.

Yes. Next time you ride, note that you can stop pedaling at any
point of rotation without your feet tending toward a preferred
position such as occurs with cranks that are not diametrically
opposite.

Struck by the elegance of this concept and thinking the mechanics
must be neat I was going to draw a diagram and stuff, but as
touchy-feely is OK I jump on the bike , chain off, feet at twenty
to two, relax-muscles (except calves) and after a bit of
oscillation the legs end up at about ten to four, this presumably
being a lower potential energy state.

I'm not clear on what you performed the test. Was it a rotor crank
or a conventional one? From what you report, it must have been
rotor cranks because conventional cranks have no preferred position
unless the rider has problems with knee articulation.

Conventional cranks!

If your legs just hang in any configuration you may have knee problems
or need to sign up for relaxation classes.

What do you believe causes a preferred position on conventional cranks
when both legs are relaxed?

The other positions don't have symmetry in leg weight distribution. I have
also seen a plot of the potential energy of the legs-cranks system and it
isn't flat.

My legs are very nearly the same weight and
balance at any position of crank rotation. You say there is a favored
position. Have you compared that to rotor cranks?

No and I wouldn't see much point (and I haven't got a set).
I agree that out-of-line cranks can be a problem around the dead centres (as
can ellipticals). Your tendency to backpedal with them was because you were
not in the habit of having to use much muscle power in that sector.
I'm not saying you ought to use muscle power in that sector, just that if
you did, the effort would not be wasted.

Now there is another peer-reviewed and published system which
balances out the mechanical energy content of the legs - via an
elliptical!

If "balance" is where it's at, what more could you want?

It's not balance. It's the extra effort it takes to move the
cranks around a revolution even when there is no load.

But these rings were designed precisely with a view to eliminating
the "extra effort" involved in simply moving the legs around at
constant pedal speed. They were working on the (false) assumption
that the work required to move the leg segments between
configurations is wasted and I wonder if you are doing the same.

Not at all. They were designed to not be 180 degrees apart and
therefore have a preferred position with equal weight on both pedals.
If you've got these cranks, how about putting a bicycle show in each
pedal and see where they stop when allowed to rotate freely. I assume
your shoes are about equal weight but if they are not, I'm sure you
can stuff a sock in the light one or some such thing.

Like it, but I wasn't talking about the Rotors here. I was talkng
about a non-circular chainring which was designed so that the mechanical
energy of the legs remained constant - never requiring any muscular work to
be done to maintain movement (friction neglected).

Sounded rather like what you see for the ordinary chainset.

Although it is strange they thought there was any advantage in such a system
there were some nice mechanical energy plots in the paper.


Andrew Bradley

writes:

Duty cycle can be changed by selecting an appropriate gear. No
special crank is required for that.

How so? Duty cycle, or Tpw/T, where Tpw is (crudely) the
duration of the power stroke and T the period, is more or less
fixed by design (or a crank).


Sounds woolly to me. You say elsewhere that all the riders work
(minus friction etc) goes to the drivetrain.

Not with the rotor crank as I took time to explain.

I'm not convinced. The work has to go into the drivetrain. Hmmm. The
real issue here is whether the changing velocity of the legs can be
effectively recovered. I don't believe that that can be answered by
just looking at the motion of the pedals. The legs have to be
considered.

Joe Riel