Elliptical Chainrings

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On Sunday, July 21, 2013 6:20:50 PM UTC-4, Sir Gregory Hall, Esq� wrote:
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On Sunday, July 21, 2013 1:11:28 PM UTC-4, Sir Gregory Hall, Esq? wrote:

"Steve Freides" wrote in message



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Mower Man wrote:



On 21/07/2013 4:35 PM, Steve Freides wrote:



Mower Man wrote:







Wrong. It does. And it's so obvious as to beggar belief. The slack



in the chain is utterly irrelevant, too.







Let us consider what's happening at a point in the rotation of the



chainrings where it's clearly not round. Are you suggesting there



is a different amount of pedal travel in order to advance the chain



at the rear wheel by one link? That's the crux of the issue - you



are arguing, I believe, that the amount of pedal travel varies



throughout a pedaling circle as the shape of the chainring changes -



because if it doesn't, then there is no difference.







What really could make a difference is if the shape of the chainring



effectively changed the gear ratio during a single pedal revolution.



If that happened, then we'd be talking about something tangible, the



reduction of force required by a lower gear at the point the rider's



legs were weakest. Now that sounds like it could be truly useful.







It is. At TDC and BDC it does.







How?







Assuming the proverbial 53-tooth chainring, doesn't one full revolution
of



the pedals have to move 53 links of chain? Yes, of course it does.







But the more relevant question to this discussion is: Doesn't _any_ 1/53

of



a revolution of the pedals have to move 1 link of chain?















BINGO!!!!!!!!!!!! And then there's this: Advocates talk about a leverage



advantage due to the major axis of the ellipse being, in effect, a longer



lever arm. But, I maintain leverage is accounted for at the pedal and



is a result of crank arm length. Until and unless the elliptical sprocket



becomes larger along its major axis than the length of the crank arm



then no additional leverage can result from it.



I think that the idea was to change whre/how the leverage was applied. Just

like when applying force to a stuck nut or bolt, the amount of leverage that

can be applied by the body using the wrench increases or decreases depending

where the leverage arm is located. Think of the bolt/nut as being in the

center of a clock face. Depending on the hour number the handle of the lever

is pointing towards can make a big difference in how much pressure one can

exert on that lever. The lever length doesn't change nor does the diameter
of

the turning circle of that lever but the amount of leverage that can be

applied does change because more force can be applied.



Cheers







=====================[reply]===========================



That's all well and good but let's place an 11 tooth sprocket on the bolt or

nut. Then let's place a 53-tooth chainring on the wrench and connect them
with

a chain. Then let's spin the wrench. The force applied to the wrench is

directly applied to the 53-tooth chainring and transferred via the chain to

the 11-tooth sprocket on the bolt or nut.



It is the gear ratio alone that and applies X amount of torque. It doesn't

matter one iota if the 53-tooth chainring is elliptical in shape as long as

the wrench is longer than the major axis of the elliptical chainring. The

false illusion of a different gear ration due to the placement of the

elliptical chainring belies the fact that it is still only the gear ratio
that

affects the torque value.



Cheerio!

A lot of times when trying to loosen a tight nut or bolt, if you place the
handle of the wrench lower than 12 o'clock you can exert more pressure onto
the handle but *NOTHING* else has changed. That's what the eliptical chainring
does. It allows more force to be applied at the former deadzones of TDC and
BDC. The gear size (effective diameter of a direct drive wheel) doesn't change
nor does the length of tthe lever - just the amount of force that can be
applied to that lever.

Cheers



===================[reply]======================

I understand what you're claiming but I reject it outright.
Why? Because what one may gain one place on the
ellipses one necessarily loses it in another and the
inefficiencies inherent in the system (such as the derailleur
tensioner spring being unwound and wound to take
up erratic chain slack) compound the loss. With a
circular chainring such inefficiencies and losses are
minimized.

As for being able to apply more force to a lever in
a certain optimal position that would be great provided
the lever always maintained that optimal position. It
does not and the loss becomes greater in the
less optimal positions. You end up with net loss in
power transfer over the more efficient circular
shape.

Cheerio

On Sunday, July 21, 2013 6:53:30 PM UTC-4, Sir Gregory Hall, Esq· wrote:
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On Sunday, July 21, 2013 6:20:50 PM UTC-4, Sir Gregory Hall, Esq� wrote:

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On Sunday, July 21, 2013 1:11:28 PM UTC-4, Sir Gregory Hall, Esq? wrote:



"Steve Freides" wrote in message







...







Mower Man wrote:







On 21/07/2013 4:35 PM, Steve Freides wrote:







Mower Man wrote:















Wrong. It does. And it's so obvious as to beggar belief. The slack







in the chain is utterly irrelevant, too.















Let us consider what's happening at a point in the rotation of the







chainrings where it's clearly not round. Are you suggesting there







is a different amount of pedal travel in order to advance the chain







at the rear wheel by one link? That's the crux of the issue - you







are arguing, I believe, that the amount of pedal travel varies







throughout a pedaling circle as the shape of the chainring changes -







because if it doesn't, then there is no difference.















What really could make a difference is if the shape of the chainring







effectively changed the gear ratio during a single pedal revolution.







If that happened, then we'd be talking about something tangible, the







reduction of force required by a lower gear at the point the rider's







legs were weakest. Now that sounds like it could be truly useful..















It is. At TDC and BDC it does.















How?















Assuming the proverbial 53-tooth chainring, doesn't one full revolution

of







the pedals have to move 53 links of chain? Yes, of course it does.















But the more relevant question to this discussion is: Doesn't _any_ 1/53



of







a revolution of the pedals have to move 1 link of chain?































BINGO!!!!!!!!!!!! And then there's this: Advocates talk about a leverage







advantage due to the major axis of the ellipse being, in effect, a longer







lever arm. But, I maintain leverage is accounted for at the pedal and







is a result of crank arm length. Until and unless the elliptical sprocket







becomes larger along its major axis than the length of the crank arm







then no additional leverage can result from it.







I think that the idea was to change whre/how the leverage was applied. Just



like when applying force to a stuck nut or bolt, the amount of leverage that



can be applied by the body using the wrench increases or decreases depending



where the leverage arm is located. Think of the bolt/nut as being in the



center of a clock face. Depending on the hour number the handle of the lever



is pointing towards can make a big difference in how much pressure one can



exert on that lever. The lever length doesn't change nor does the diameter

of



the turning circle of that lever but the amount of leverage that can be



applied does change because more force can be applied.







Cheers















=====================[reply]===========================







That's all well and good but let's place an 11 tooth sprocket on the bolt or



nut. Then let's place a 53-tooth chainring on the wrench and connect them

with



a chain. Then let's spin the wrench. The force applied to the wrench is



directly applied to the 53-tooth chainring and transferred via the chain to



the 11-tooth sprocket on the bolt or nut.







It is the gear ratio alone that and applies X amount of torque. It doesn't



matter one iota if the 53-tooth chainring is elliptical in shape as long as



the wrench is longer than the major axis of the elliptical chainring. The



false illusion of a different gear ration due to the placement of the



elliptical chainring belies the fact that it is still only the gear ratio

that



affects the torque value.







Cheerio!



A lot of times when trying to loosen a tight nut or bolt, if you place the

handle of the wrench lower than 12 o'clock you can exert more pressure onto

the handle but *NOTHING* else has changed. That's what the eliptical chainring

does. It allows more force to be applied at the former deadzones of TDC and

BDC. The gear size (effective diameter of a direct drive wheel) doesn't change

nor does the length of tthe lever - just the amount of force that can be

applied to that lever.



Cheers







===================[reply]======================



I understand what you're claiming but I reject it outright.

Why? Because what one may gain one place on the

ellipses one necessarily loses it in another and the

inefficiencies inherent in the system (such as the derailleur

tensioner spring being unwound and wound to take

up erratic chain slack) compound the loss. With a

circular chainring such inefficiencies and losses are

minimized.



As for being able to apply more force to a lever in

a certain optimal position that would be great provided

the lever always maintained that optimal position. It

does not and the loss becomes greater in the

less optimal positions. You end up with net loss in

power transfer over the more efficient circular

shape.



Cheerio

No, I don't think you lose it elsewhere because elsewhere the chainring is back to be more nearlt the normal circular ring.

I also think that the friction loss in the derailleur is minimal and that the added apploed force at the crankset is far greater than those losses.

Someplace where I really noticed the Bio Pace benefit was seated hill climbing.

Cheers

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[big trim]


No, I don't think you lose it elsewhere because elsewhere the
chainring is back to be more nearlt the normal circular ring.

I also think that the friction loss in the derailleur is minimal and
that the added apploed force at the crankset is far greater than
those losses.

Someplace where I really noticed the Bio Pace benefit was
seated hill climbing.

This is all to say if you cut off six inches from one end of a
blanket and sew it on the other end you will end up with a
longer blanket.

Simply not so!

On 21/07/2013 5:30 PM, Steve Freides wrote:
Mower Man wrote:
On 21/07/2013 4:35 PM, Steve Freides wrote:
Mower Man wrote:

Wrong. It does. And it's so obvious as to beggar belief. The slack
in the chain is utterly irrelevant, too.

Let us consider what's happening at a point in the rotation of the
chainrings where it's clearly not round. Are you suggesting there
is a different amount of pedal travel in order to advance the chain
at the rear wheel by one link? That's the crux of the issue - you
are arguing, I believe, that the amount of pedal travel varies
throughout a pedaling circle as the shape of the chainring changes -
because if it doesn't, then there is no difference.

What really could make a difference is if the shape of the chainring
effectively changed the gear ratio during a single pedal revolution.
If that happened, then we'd be talking about something tangible, the
reduction of force required by a lower gear at the point the rider's
legs were weakest. Now that sounds like it could be truly useful.

-S-

It is. At TDC and BDC it does.

How?

Assuming the proverbial 53-tooth chainring, doesn't one full revolution
of the pedals have to move 53 links of chain? Yes, of course it does.

But the more relevant question to this discussion is: Doesn't _any_ 1/53
of a revolution of the pedals have to move 1 link of chain?

-S-


You need to abandon the idea that the number of links is the thing. It's
not. It's the effective diameter of the chainwheel.

--
Chris

'Fashion is a form of ugliness so intolerable that we have to alter it
every six months.'

(Oscar Wilde.)

On 21/07/2013 10:40 PM, wrote:
On Sunday, July 21, 2013 11:43:58 AM UTC-4, Mower Man wrote:
On 21/07/2013 4:35 PM, Steve Freides wrote:

Mower Man wrote:



Wrong. It does. And it's so obvious as to beggar belief. The slack in

the chain is utterly irrelevant, too.



Let us consider what's happening at a point in the rotation of the

chainrings where it's clearly not round. Are you suggesting there is a

different amount of pedal travel in order to advance the chain at the

rear wheel by one link? That's the crux of the issue - you are arguing,

I believe, that the amount of pedal travel varies throughout a pedaling

circle as the shape of the chainring changes - because if it doesn't,

then there is no difference.



What really could make a difference is if the shape of the chainring

effectively changed the gear ratio during a single pedal revolution. If

that happened, then we'd be talking about something tangible, the

reduction of force required by a lower gear at the point the rider's

legs were weakest. Now that sounds like it could be truly useful.



-S-



It is. At TDC and BDC it does.



--

Chris



'Fashion is a form of ugliness so intolerable that we have to alter it

every six months.'



(Oscar Wilde.)

I remember Shimano saying that Bio Pace was designed to eliminate the dead zone at TDC and BDC. In other words

BP allowed tthe bicyclist to maintain the same pressure on the crank
arms throughout the entire revolution.

The design of the eliptical rings was such that in effect there was no
longer a real TDC or BDC.

Cheers


Kind of, yes!

--
Chris

'Fashion is a form of ugliness so intolerable that we have to alter it
every six months.'

(Oscar Wilde.)

Assuming the proverbial 53-tooth chainring, doesn't one full revolution
of the pedals have to move 53 links of chain? Yes, of course it does.

But the more relevant question to this discussion is: Doesn't _any_ 1/53
of a revolution of the pedals have to move 1 link of chain?

No, that's the key. The angle the crank moves is equal to the chain spacing
(1/2 inch) divided by what I'll call the "effective radius" of the
chainring - the distance from the center of the crank to the point where the
chainring contacts the chain (exerts force on the chain), at the top. When
Froome's crank arms are horizontal, the contact point of the chain is far
from the center, so a smaller change in crank angle pulls one link of chain,
corresponding to a higher gear.

On 22/07/2013 12:28, Bertrand wrote:
Assuming the proverbial 53-tooth chainring, doesn't one full revolution
of the pedals have to move 53 links of chain? Yes, of course it does.

But the more relevant question to this discussion is: Doesn't _any_ 1/53
of a revolution of the pedals have to move 1 link of chain?

No, that's the key. The angle the crank moves is equal to the chain
spacing (1/2 inch) divided by what I'll call the "effective radius" of
the chainring - the distance from the center of the crank to the point
where the chainring contacts the chain (exerts force on the chain), at
the top. When Froome's crank arms are horizontal, the contact point of
the chain is far from the center, so a smaller change in crank angle
pulls one link of chain, corresponding to a higher gear.


Correct and nicely explained.

On Monday, July 22, 2013 4:57:33 AM UTC-7, atriage wrote:
On 22/07/2013 12:28, Bertrand wrote:

Assuming the proverbial 53-tooth chainring, doesn't one full revolution

of the pedals have to move 53 links of chain? Yes, of course it does.



But the more relevant question to this discussion is: Doesn't _any_ 1/53

of a revolution of the pedals have to move 1 link of chain?



No, that's the key. The angle the crank moves is equal to the chain

spacing (1/2 inch) divided by what I'll call the "effective radius" of

the chainring - the distance from the center of the crank to the point

where the chainring contacts the chain (exerts force on the chain), at

the top. When Froome's crank arms are horizontal, the contact point of

the chain is far from the center, so a smaller change in crank angle

pulls one link of chain, corresponding to a higher gear.





Correct and nicely explained.

The teeth are not really relevant in gearing except to provide a method of calculating the geat ratios. All they do really is prevent the drive belt (chain) from slipping on the gears. It is the effective diameters of the gears and chain rings that provide the gear ratios and with an eliptical chain ring, because the radius varies then so does the instantaneous effective gear ratio. Although an eliptical and a round chain ring can have the same number of teeth, that just means the average ratio for both is the same over one revolution. The eliptical will have postitions where the ratio is both higher and lower making the average ratio the same over one revolution. In reality, and this is why I don't think they work, the foot speed varies over one revolution of the crank even though the rider speed stays almost constant. This constant accelerating and decelerating of the feet and pedals can't be efficient. My 2 cents FWIW.

[snip]

This constant accelerating and decelerating of the feet and pedals can't be efficient. My 2 cents FWIW.

I suspect that whether or not that matters comes down to how it feels to
the rider. These guys report that it felt jerky at first but that they
got used to it quite quickly. I'm vaguely thinking of getting one since
they hardly break the bank. What concerns me most about them is the
chain whip they produce which I instinctively don't like.


http://www.artscyclery.com/reviews/R...QRSreview.html


"The difference in feel was immediately noticeable and my pedal stroke
felt uneven at first, but not in a jarring way. On my first ride I
noticed I was able to engage my hamstring muscles more effectively near
the bottom of the pedal stoke. By the third ride, I was spinning faster
than before and any feelings of unevenness were gone. My pedal stroke is
now as smooth as ever, and I don’t notice the rotor rings at all. It
genuinely feels like the power producing area of my pedal stroke is
larger than with normal rings."

On 22/07/2013 12:57 PM, atriage wrote:
On 22/07/2013 12:28, Bertrand wrote:
Assuming the proverbial 53-tooth chainring, doesn't one full revolution
of the pedals have to move 53 links of chain? Yes, of course it does.

But the more relevant question to this discussion is: Doesn't _any_ 1/53
of a revolution of the pedals have to move 1 link of chain?

No, that's the key. The angle the crank moves is equal to the chain
spacing (1/2 inch) divided by what I'll call the "effective radius" of
the chainring - the distance from the center of the crank to the point
where the chainring contacts the chain (exerts force on the chain), at
the top. When Froome's crank arms are horizontal, the contact point of
the chain is far from the center, so a smaller change in crank angle
pulls one link of chain, corresponding to a higher gear.


Correct and nicely explained.

+1

--
Chris

'Fashion is a form of ugliness so intolerable that we have to alter it
every six months.'

(Oscar Wilde.)