Rotor System Question

On 11 May 2004 13:37:22 -0700, [email hidden] (n crowley)

Quoted message said:

Using two bikes with rear wheels of identical size and with identical gearing,
one bike fitted with rotor cranks and the other with normal cranks, set the
upper crank of both bikes to that forward position of the upper rotor crank
when its lower crank is at 6 o'clock. Now measuring the exact distance that
each bike will travel as its upper crank is moved from that forward position
to the 3 o'clock mark, how will the distances compare ?

Dear N.,

I think that both bikes will move the same distance if you push one
pedal through 3/4ths of a revolution from top dead center.

That is, view a bicycle from its left side with 12 o'clock as top dead
center, 9 o'clock as level and toward the front wheel, 6 o'clock as
bottom dead center, and 3 o'clock as level and toward the rear wheel.

I may be wrong, but I have a vague notion that the pedal arms of a
rotor crank turn somewhat independently, the idea being to train the
rider to pull his idle foot up on its own instead of being pushed up
at least partly by the downward force of the active foot.

If so, forcing one pedal through 3/4ths of a revolution will produce
the same effect on both normal and rotor cranks.

I don't think that any gearing advantage or change is claimed, just a
pair of pedal arms that require each foot to pull its own weight on
the back half of the pedal circle. Whether such training has any
practical effect is regularly debated here on rec.bicycles.tech.

I'm not sure how much independence the rotor cranks offer. If they're
completely independent, both could hang straight down at the same
time. If they offer only a few degrees of independence, then one might
be able to trail the other by twenty degrees, or some similar figure.

Carl Fogel

[email hidden] wrote in
news:[email hidden]:

Quoted message said:

On 11 May 2004 13:37:22 -0700, [email hidden] (n

crowley) said:

Using two bikes with rear wheels of identical size and with
identical gearing,
one bike fitted with rotor cranks and the other with
normal cranks, set the upper crank of both bikes to that
forward position of the upper rotor crank when its lower
crank is at 6 o'clock. Now measuring the exact distance
that each bike will travel as its upper crank is moved
from that forward position to the 3 o'clock mark, how will
the distances compare ?

I don't think we really know how far it is from the upper
position to 3:00. Or how much leverage you gain with the Rotor
cranks. As a guess, I'd say the rotor crank would move not
quite as far. Because you're not moving the crank arm as much.
Probably it catches up by 6:00, though.

<snip stuff>

Quoted message said:

I may be wrong, but I have a vague notion that the pedal
arms of a rotor crank turn somewhat independently, the idea
being to train the rider to pull his idle foot up on its
own instead of being pushed up at least partly by the
downward force of the active foot.

If so, forcing one pedal through 3/4ths of a revolution
will produce the same effect on both normal and rotor
cranks.

I don't think that any gearing advantage or change is
claimed, just a pair of pedal arms that require each foot
to pull its own weight on the back half of the pedal
circle. Whether such training has any practical effect is
regularly debated here on rec.bicycles.tech.

I'm not sure how much independence the rotor cranks offer.
If they're completely independent, both could hang straight
down at the same time. If they offer only a few degrees of
independence, then one might be able to trail the other by
twenty degrees, or some similar figure.

Actually, that's PowerCranks:
www.powercranks.com
Both crank arms are completely independent, and they can indeed
both hang straight down.

Rotorcranks move the foot up more quickly on the up-stroke, so
that when the lower foot is at 6:00, the other foot is at 1:30
or so. Claimed to increase leverage, lower threshold heart
rate, and make you go faster.
http://www.rotorcranksusa.com/

Owen

Owen Pope said:

[email hidden] wrote in
news:[email hidden]:

Quoted message said:

On 11 May 2004 13:37:22 -0700, [email hidden] (n

crowley) said:

Using two bikes with rear wheels of identical size and with
identical gearing,
one bike fitted with rotor cranks and the other with
normal cranks, set the upper crank of both bikes to that
forward position of the upper rotor crank when its lower
crank is at 6 o'clock. Now measuring the exact distance
that each bike will travel as its upper crank is moved
from that forward position to the 3 o'clock mark, how will
the distances compare ?

I don't think we really know how far it is from the upper
position to 3:00. Or how much leverage you gain with the Rotor
cranks. As a guess, I'd say the rotor crank would move not
quite as far. Because you're not moving the crank arm as much.
Probably it catches up by 6:00, though.

<snip stuff>

Quoted message said:

I may be wrong, but I have a vague notion that the pedal
arms of a rotor crank turn somewhat independently, the idea
being to train the rider to pull his idle foot up on its
own instead of being pushed up at least partly by the
downward force of the active foot.

If so, forcing one pedal through 3/4ths of a revolution
will produce the same effect on both normal and rotor
cranks.

I don't think that any gearing advantage or change is
claimed, just a pair of pedal arms that require each foot
to pull its own weight on the back half of the pedal
circle. Whether such training has any practical effect is
regularly debated here on rec.bicycles.tech.

I'm not sure how much independence the rotor cranks offer.
If they're completely independent, both could hang straight
down at the same time. If they offer only a few degrees of
independence, then one might be able to trail the other by
twenty degrees, or some similar figure.

Actually, that's PowerCranks:
www.powercranks.com
Both crank arms are completely independent, and they can indeed
both hang straight down.

Rotorcranks move the foot up more quickly on the up-stroke, so
that when the lower foot is at 6:00, the other foot is at 1:30
or so. Claimed to increase leverage, lower threshold heart
rate, and make you go faster.
http://www.rotorcranksusa.com/

Owen

Dear Owen,

You're right and I'm wrong (as private email also pointed out).

I confused RotorCranks and PowerCranks--d'oh!

Homer Simpson

Originally posted by Owen Pope
[email hidden] wrote in
news:[email hidden]:news:[email hidden]:

Quoted message said:

On 11 May 2004 13:37:22 -0700, [email hidden] (n

crowley) said:

Using two bikes with rear wheels of identical size and with identical
gearing, one bike fitted with rotor cranks and the other with normal
cranks, set the upper crank of both bikes to that forward position of
the upper rotor crank when its lower crank is at 6 o'clock. Now
measuring the exact distance that each bike will travel as its upper
crank is moved from that forward position to the 3 o'clock mark, how
will the distances compare ?

I don't think we really know how far it is from the upper position to
3:00. Or how much leverage you gain with the Rotor cranks. As a guess,
I'd say the rotor crank would move not quite as far. Because you're not
moving the crank arm as much. Probably it catches up by 6:00, though.

<snip stuff>

Quoted message said:

I may be wrong, but I have a vague notion that the pedal arms of a
rotor crank turn somewhat independently, the idea being to train the
rider to pull his idle foot up on its own instead of being pushed up
at least partly by the downward force of the active foot.

If so, forcing one pedal through 3/4ths of a revolution will produce
the same effect on both normal and rotor cranks.

I don't think that any gearing advantage or change is claimed, just a
pair of pedal arms that require each foot to pull its own weight on
the back half of the pedal circle. Whether such training has any
practical effect is regularly debated here on rec.bicycles.tech.

I'm not sure how much independence the rotor cranks offer. If they're
completely independent, both could hang straight down at the same
time. If they offer only a few degrees of independence, then one might
be able to trail the other by twenty degrees, or some similar figure.

Actually, that's PowerCranks: www.powercranks.com Both crank arms are
completely independent, and they can indeed both hang straight down.

Rotorcranks move the foot up more quickly on the up-stroke, so that when
the lower foot is at 6:00, the other foot is at
1:30 or so. Claimed to increase leverage, lower threshold heart rate,
and make you go faster.

Just testing to find out how many understand the objective. The Rotor
cranked bike would go further, it would travel the same distance that
the normal cranked bike would have travelled if its upper crank had
started form the 12 o'clock position. With the normal crank starting
from that forward position, it would be impossible for that bike to
equal the distance of the Rotor cranked bike. If you were now to
measure the distance that the normal cranked bike would travel as its
upper crank moved from 11 to 1 o'clock, you have the value of the dead
spot area.

increase in distance of RC bike / dead spot area value X 100

equals in percentage terms how much of the dead spot area that Rotor
cranks can attempt to compensate for.

--

n crowley said:

Actually, that's PowerCranks: www.powercranks.com Both crank arms are
completely independent, and they can indeed both hang straight down.

You are correct about the Powercranks

Quoted message said:

Rotorcranks move the foot up more quickly on the up-stroke, so that

But here you are misinformed. It is over TDC ( Top Dead Center ) where the
foot moves quicker. The downstroke and upstroke are perfectly normal, where
you for instance can let your upstroke leg be lifted up by the downstroke
leg. When the upstroke gets close to TDC it is speeded through so that you
can begin mashing down sooner. I can't remember if the pedal pointing down
at this moment is then speeded through BDC ( Bottom Dead Center ) I would
imagine so.

Quoted message said:

when the lower foot is at 6:00, the other foot is at
1:30 or so. Claimed to increase leverage, lower threshold heart rate,

Now you're caught up again 😉

Quoted message said:

and make you go faster.

I tried them out shortly at a bikeshow, but they evidently hadn't expected
anybody to put any power on them so the crankarms started slipping and came
out of position. They had to stop the demo for the rest of that day.
Evidently they need some attention getting set up right.
From what I experienced they felt perfectly normal in the sense that I could
just start pedaling away as opposed to the Powercranks that take some
getting used to.

--
Perre

You have to be smarter than a robot to reply.

Originally posted by Per ElmsäTer

n crowley said:

Actually, that's PowerCranks: www.powercranks.com Both crank arms are
completely independent, and they can indeed both hang straight down.

You are correct about the Powercranks

Quoted message said:

Rotorcranks move the foot up more quickly on the up- stroke, so that

But here you are misinformed. It is over TDC ( Top Dead Center ) where
the foot moves quicker. The downstroke and upstroke are perfectly
normal, where you for instance can let your upstroke leg be lifted up by
the downstroke leg. When the upstroke gets close to TDC it is speeded
through so that you can begin mashing down sooner. I can't remember if
the pedal pointing down at this moment is then speeded through BDC (
Bottom Dead Center ) I would imagine so.

Quoted message said:

when the lower foot is at 6:00, the other foot is at
1:30 or so. Claimed to increase leverage, lower threshold heart rate,

Now you're caught up again 😉

Quoted message said:

and make you go faster.

==============================================

Sorry that is not part of my post. My reply started with " just testing
to find out etc. " Rotor cranks act as normal cranks between 3 and 9
o'clock, from 9 the rising crank speeds up until it get to about the 3
or 4 minute mark past 12 o'clock, it then has to slow down in order to
have both cranks back in alignment in the 3 - 9 o'clock positions.
Allowing the rising crank to push your idling foot up and through the
dead spot area is one sure way of losing any benefit that RC's have to
offer. As I see it, these cranks do have an advantage but there seems to
be a lot of difficulty in setting up the whole system and then there is
the friction aspect but to get any real advantage you have to know what
the objective is and adjust your pedaling to suit this. Even at that you
are only attempting to compensate for less than a third of the dead spot
area so at best your gains are very limited and they are expensive.

--