rotor cranks



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[email protected] (Bill Franklin) wrote in message
news:<[email protected]>...
> Yeah Dave, like I really believe that myth. A USAF engineer "proved" that bees cannot fly using
> physics. Of course he was wrong- he used incorrect assumptions. Just like a few years ago when the
> Universe was "proven" by scientists to be 12B years old, yet the same scientists "determined"
> certain stars to be 14B years old. Of course that was eventually rectified. I am using simple
> metaphors because you guys can't seem to get it.
> Mr. Brandt is wrong in saying that it is about force times distance. That is work. We are
> interested in power. That's what wins races. He is a racer like me. We are not talking touring
> here. What he doesn't realize is that the Cam on the rotors slows down your power stroke's
> angular velocity in comparison to the bottom bracket a.v. (which is what is driving the
> chain). Thus the "time" of the power stoke has effectively increased. Also the time of the
> upsstoke (no power applied) has decreased. Look at an olympic swimmer closely, the arms don't
> move 180 degrees out of phase like windmills. They move more slowly on the power stroke and
> quickly on the recovery. It is wrong to say the rotors shift phases of the legs' strokes. They
> cause your legs to work like a swimmers arms. Why spend 50% of your time recovering? Another
> way to say it is the duty cycle has increased. JB says riding fast though is all about
> cardiovascular limitations. If this was true we could bike just as fast with our arms alone!
> Think about it.
>
> Of course you will not believe me. Of course my name is an alias--I want to keep winning races
> next year. While you morons are out spending $2500 on a frame, I bought a set of RCs and a Power
> tap and with my HRM I saw the difference for myself. I've participated in many threads in many
> forums regarding these devices. The reaction is always the same. "I know they don't work
> because..." Unless I get I job with RC Inc. this is the last you'll hear from me.
>
> --"Bill"
>
> PS- Rotor Cranks don't work. Please spread that around while you enjoy your fancy ass frame that
> makes you sooo much faster.

Dear "Bill,"

What aliases do you use in what other threads?

Is the real "Bill Franklin" a moron? Shouldn't you email him to let him know how you picked him?

Are your other aliases attached to equally convincing records of achievement?

Do you conceal your fabulous cranks by the simple ruse of letting most other riders pedal
ahead of you?

Or is this just the amusingly cranky response of someone sputtering in water rather over his head?

Carl Fogel
 
Simon Brooke <[email protected]> writes:

> Oh, granted - you only have to look at a biopace to see that its effect must be small; and indeed
> it may be _largely_
> psychological. But then one of the interesting things about having a human being as the motor is
> that psychological and even 'placebo' effects can actually work.

Well, it depends on how you are defining "work" in this case. These effects are commonly reported in
bicycling in that the rider *thinks* these things work, but when measured objectively no benefit is
seen. In short, the rider is fooled. There is a layman's belief that the placebo effect is
statistically significant, but in actuality it's only significant in subjective measurement.
Objective measurement shows that the effect size of the placebo effect approaches zero in nearly all
cases (there are some cases in psychology and medicine where the placebo effect has confounded
outcomes, but often this has been traced to bad experimental design).

Now, to a great extent I am not one to worry about this in many cases. I ride because it's an
enjoyable subjective experience, and since I no longer race objective performance is not all that
important. So if something makes the subjective experience better in some way, I am inclined to say
"it works" just like the next person. There are issues where objective performance is actually
important (e.g., braking, tire grip, rim durability, etc) and also issues where subjective
performance is the important issue (e.g., saddle comfort).

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. I would expect that the next
person would have the same experience as I using the salmon brake pads, but I wouldn't necessarily
expect that someone else would like my Brooks Pro.
 
Simon Brooke <[email protected]> wrote in message
news:<[email protected]>...
> [email protected] (Carl Fogel) writes:
>
> > Simon Brooke <[email protected]> wrote in message
> > news:<[email protected]>...
> > > The problem is not quite like this. Imagine you have a single cylinder engine that runs at
> > > between 120 and 200 RPM. When the power stroke happens there's quite a surge of power through
> > > the drive train which tends to break traction at the rear wheel. In between power strokes the
> > > tyre is able to grip, but as there's only the flywheel keeping the engine turning you don't
> > > get very far.
> > >
> > > A 'masher' on a hill bike is in this situation, particularly on mud or gravel slopes. This is
> > > why sitting down and spinning is better if you can do it. Obviously as the gradient steepens
> > > you may reach the point where you can no longer remain in the saddle without the bike tipping
> > > backwards and you have to get out of the saddle and mash... at which point if you're on bare
> > > rock with appropriate tyres you may make it, but if the going is either soft or loose you
> > > probably won't.
> >
> > I expect that you have far more bicycling experience (and know far more about physics), so I'm
> > inclined to believe you. I agree that it would be nice if there were some way to buffer the
> > power impulses, as you aptly describe it, but I have a vague suspicion that the actual
> > "buffering" in Biopace and rotor and other systems (there was one that was Biopace offset 90
> > degrees, but I can't think of its name) turns out to be much smaller when calculated than riders
> > think.
>
> Oh, granted - you only have to look at a biopace to see that its effect must be small; and indeed
> it may be _largely_
> psychological. But then one of the interesting things about having a human being as the motor is
> that psychological and even 'placebo' effects can actually work.

Don't know if it was all in the head but i felt that Biopace was _reducing_ traction during my brief
spell with them (i turned them round after a while).

The mechanical energy they may "buffer" in the leg mass (does anybody have the calcs?) has to be
weighed in against Biopace's longer "dead spot" transitions and shorter power stroke. And there's
reportedly a tendency for riders to use bigger gears.

Andrew Bradley
 
Tim McNamara <[email protected]> wrote in message
news:<[email protected]>...
> "Hugh Fenton" <[email protected]> writes:
>
> > Now I'm getting confused - I seem to remember from watching motorcycle racing in the 1980's that
> > people like Honda and Laverda (Jota) purposely modified their engines to fire all cylinders as
> > simultaneously as possible on some theory that the tyre gripped better when all the torque came
> > at once, then the tyre had a chance to regain traction.
>
> That's a theory that was severely confused, and would have ended up dumping riders all over the
> pavement in the first wet corner. Are you sure you have that right?

No, Hugh's got it mostly right. The "Big Bang" engines gave their riders *more warning* that they
were approaching the limits of traction while turning and accelerating, particularly on dry tracks.
The rider could feel the tire beginning to slip with the torque peaks and still have time to react
and back out of the throttle. With smooth torque increases, the tire would break loose, the engine
would continue to rev, and the rider (and motorcycle) goes sliding.

So, the reason behind those engines wasn't that the ti(y)re didn't grip better, is was that the
riders were more able to manage the available grip.

Motorcycle engine and suspension tuning is apparently a black art- one of the reasons I enjoy
reading Kevin Cameron's columns in Cycle World
(U.S. motorcycle magazine).

Jeff
 
[email protected] (Jeff Wills) wrote in message
news:<[email protected]>...
> Tim McNamara <[email protected]> wrote in message
> news:<[email protected]>...
> > "Hugh Fenton" <[email protected]> writes:
> >
> > > Now I'm getting confused - I seem to remember from watching motorcycle racing in the 1980's
> > > that people like Honda and Laverda (Jota) purposely modified their engines to fire all
> > > cylinders as simultaneously as possible on some theory that the tyre gripped better when all
> > > the torque came at once, then the tyre had a chance to regain traction.
> >
> > That's a theory that was severely confused, and would have ended up dumping riders all over the
> > pavement in the first wet corner. Are you sure you have that right?
>
> No, Hugh's got it mostly right. The "Big Bang" engines gave their riders *more warning* that they
> were approaching the limits of traction while turning and accelerating, particularly on dry
> tracks. The rider could feel the tire beginning to slip with the torque peaks and still have time
> to react and back out of the throttle. With smooth torque increases, the tire would break loose,
> the engine would continue to rev, and the rider (and motorcycle) goes sliding.
>
> So, the reason behind those engines wasn't that the ti(y)re didn't grip better, is was that the
> riders were more able to manage the available grip.
>
> Motorcycle engine and suspension tuning is apparently a black art- one of the reasons I enjoy
> reading Kevin Cameron's columns in Cycle World
> (U.S. motorcycle magazine).
>
> Jeff

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
 
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
 
<[email protected]> wrote in message news:[email protected]...

> 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
 
[email protected] 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
 
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