Elliptical Chainrings

On 19/07/2013 2:58 PM, Steve Freides wrote:
none (Yannick Tremblay) wrote:
In article ,
Steve Freides wrote:
Mower Man wrote:

Isn't it the point that elliptical chain rings actually vary the
gear ratio? Forget the number of teeth, they're only there 'cos a
chain is used. Think of diameter. Variable diameter. Honest. Think
drive belt? Big pulley vs small pulley?

But big pulley versus small pulley, first of all, means something
different for belt drive than for one with teeth. If one pedal
revolution gets you 39 teeth spaced evenly apart, what's the
difference what the shape is? For a belt driven system, a change in
shape could at least mean a change in circumference.

For 1 complete revolution, there is no difference. Absolutely
correct.

However what about 1/4 of a revolution or 1/8 of a revolution? Then
the diameter of the "big pulley" does differs.

Yan

You misread what I wrote. I don't assume that a change in circumference
matters, either - you could accomplish the same thing with a larger or
smaller, but still round, pulley.

The reason tests cannot confirm that this idea works is simple - it
doesn't. Neither the rear wheel nor your legs care about the shape of
the chainring. When you're pulling one tooth's worth of chain, that's
what you're doing, period.

-S-


I think you've failed to understand my post? Disregard the bloody chain,
it's totally irrelevant. Think of the diameter of the chainring. An
elliptical ring's diameter varies. It's that simple. If the chainring
was the diameter of it's smallest point, gearing would be lower.
Conversely, at it's largest point, higher.

The chain is just a way (one way) of joining two things in a non slip
way. Bet there's an internal combustion engine that uses this stuff to
vary camshaft timing. (Research on way?)

As for your remarks about "change in circumference", that's exactly what
an elliptical ring does. Changes gearing with every revolution.

--
Chris

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

(Oscar Wilde.)

On 19/07/2013 7:35 PM, Sir Gregory Hall, Esq· wrote:
"none (Yannick Tremblay)" yatremblay@bel1lin202. wrote in
message ...

On an ovoid chain rig however, this is not the case. While the ovoid
rotate 10 degree, its active diameter also changes.

Active diameter doesn't matter. Only the gear ratio matters and
that gear ration depends on number of teeth.

The change in
active diameter of the front can be observed by looking at the
derailler moving in an out as the front rig rotates. It is kind of
equivalent to the front rig dynamically changing between, say 35 and 37
teeth during a full rotation. (This is possible because only about
half of the front rig is touching the chain at any point in time and
there is slack in the chain).

Wrong! The gear ration doesn't change. Only the slack in the chain
changes depending upon the position of the shape of the chainring.
The derailleur pulleys are a chain tensioner so of course when the
chain becomes slack it takes up the slack. This doesn't mean the
gear ratio is changing. One could use a square or rectangular
chainring but if it had 53 teeth then the shape of it won't change
the gear ratio. It is gear ratio that determines mechanical advantage
not gear shape. Oddly shaped gears only result in reduced efficiency
compared to circular gears.



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

What is all this 53 tooth numbers stuff about? Old fashioned wrong
headed nonsense. The chain just is a convenient non slip way to drive
one rotating thing from another. If it was a Vee belt, what would you
then think? I assure you that the theory is the same, exactly the same.

Did you do "moments" in physics? You should have in the context of this
discussion. :-)

--
Chris

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

(Oscar Wilde.)

On 19/07/2013 7:09 PM, none Yannick Tremblay wrote:
In article ,
Sir Gregory Hall, Esq· åke wrote:
"none (Yannick Tremblay)" yatremblay@bel1lin202. wrote in message
...
In article ,
Steve Freides wrote:
Mower Man wrote:

Isn't it the point that elliptical chain rings actually vary the gear
ratio? Forget the number of teeth, they're only there 'cos a chain is
used. Think of diameter. Variable diameter. Honest. Think drive belt?
Big pulley vs small pulley?

But big pulley versus small pulley, first of all, means something
different for belt drive than for one with teeth. If one pedal
revolution gets you 39 teeth spaced evenly apart, what's the difference
what the shape is? For a belt driven system, a change in shape could at
least mean a change in circumference.

For 1 complete revolution, there is no difference. Absolutely correct.

However what about 1/4 of a revolution or 1/8 of a revolution? Then
the diameter of the "big pulley" does differs.


True, but *overall* diameter doesn't change as the number
of teeth remains the same. So, the gear ratio remains the
same. And, as long as the chainring radius is no greater than
that of the crank arm there isn't even any leverage difference
as if often the (erroneous) claim, due to the fact that it's
the length of the crank arms that determines the lever arm.

Please, this is pure mathematics and mechanics.

The "active" "current" diameter of the front rig changes dynamically
during a rotation which means that the current amount of rotation
of the pedal that is needs to achieve some specific rotation of
the rear wheel with the pedal-crank-rig-chain-cog-wheel assembly
changes dynamically. In average over 360 degree it is the same but
instantaneously it differs.

The problem and complexity occurs when you start introducing a bloody
human in the equation and these pesky things are pretty much impossible
to model mathematically and are notoriously irregular between
individuals.

Serously, by all mean disagree that it has any benefits to humans (I
am certainly not convinced either) but lets not disagree on
mathematics.

Yan


Congratulations. "Instantaneously". Very nearly the right word.

"Progressively" and "variably" would have been even better.

I think that there are benefits as we humans a

a) good at stamping down

b) not too bad at pulling up on the cleats

c) not very good at pushing over TDC or BDC.

d) ...er, that's it.

--
Chris

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

(Oscar Wilde.)

Sir Gregory Hall, Esq· wrote:

Froome mostly sits because any energy used moving the body
up and down when standing is energy wasted compared to
not lifting the body and staying seated.

Froome's height is 6 feet, 13 inches. History tells us that smaller
racers like to stand more often. Froome, who looks like Lurch, sits -
follows past precedent. The little Columbian guy, however, often
stands.

Whether it's mass or height, I couldn't say, but clearly here, size does
matter.

-S-

"Steve Freides" writes:

Sir Gregory Hall, Esq· wrote:

Froome mostly sits because any energy used moving the body
up and down when standing is energy wasted compared to
not lifting the body and staying seated.

Froome's height is 6 feet, 13 inches.

Maybe he isn't quite that tall.

"Steve Freides" wrote in message
...
Sir Gregory Hall, Esq· wrote:

Froome mostly sits because any energy used moving the body
up and down when standing is energy wasted compared to
not lifting the body and staying seated.

Froome's height is 6 feet, 13 inches. History tells us that smaller racers
like to stand more often. Froome, who looks like Lurch, sits - follows past
precedent. The little Columbian guy, however, often stands.

Whether it's mass or height, I couldn't say, but clearly here, size does
matter.



The little Colombian climber would be better off if he would
stay in the saddle and develop his spin technique to put
forth max power with fewer calories burned. Probably he looks
at the power meter and comes to the conclusion that he creates
more power standing.

Should this be the case, then he needs to consider calories
burned vs. power output. The human body is a machine that
runs best when it stays within certain parameters. Standing
and pedaling uses more calories even if it should, for a time,
create higher wattage. Standing is probably the best thing
in a short sprint whereas over the long-haul, climbing included,
staying in the saddle will allow greater overall speeds for the
long-haul due to energy conserved. It's a fact that the human
body is able to burn calories faster than they can be replaced.

This is what bonking is all about. So, it would behoove a wise
pro cyclist to not ride so close to the ragged edge. Sitting
when climbing can develop just as much power as standing
if one develops the right technique and with that power comes
with a greater efficiency. That's called win-win in a grand classic.

--
Sir Gregory

On 19/07/2013 11:49 PM, Steve Freides wrote:
Sir Gregory Hall, Esq· wrote:

Froome mostly sits because any energy used moving the body
up and down when standing is energy wasted compared to
not lifting the body and staying seated.

Froome's height is 6 feet, 13 inches. History tells us that smaller
racers like to stand more often. Froome, who looks like Lurch, sits -
follows past precedent. The little Columbian guy, however, often
stands.

Whether it's mass or height, I couldn't say, but clearly here, size does
matter.

-S-




Hold on - how many inches are there in a foot?

Answer -

a) Over 12 inches
b) fewer (note - NOT less) than 12 inches
c) 12

OMG.


--
Chris

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

(Oscar Wilde.)

On 20/07/2013 12:07 AM, Doug Anderson wrote:
"Steve Freides" writes:

Sir Gregory Hall, Esq· wrote:

Froome mostly sits because any energy used moving the body
up and down when standing is energy wasted compared to
not lifting the body and staying seated.

Froome's height is 6 feet, 13 inches.

Maybe he isn't quite that tall.

Another LOB. How - given that there are 12 inches to a foot (FFS why do
you lot not use the metric system? Sooooo much simpler) is 6 feet 13
inches really 7 feet one inch?

LOB = Met Police slang, "Load of ********".

--
Chris

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

(Oscar Wilde.)

Yannick Tremblay yatremblay@bel1lin202.(none) wrote:
In article ,
Friso wrote:
Yannick Tremblay yatremblay@bel1lin202.(none) wrote:
In article ,
Steve Freides wrote:
Mower Man wrote:

Isn't it the point that elliptical chain rings actually vary the gear
ratio? Forget the number of teeth, they're only there 'cos a chain is
used. Think of diameter. Variable diameter. Honest. Think drive belt?
Big pulley vs small pulley?

But big pulley versus small pulley, first of all, means something
different for belt drive than for one with teeth. If one pedal
revolution gets you 39 teeth spaced evenly apart, what's the difference
what the shape is? For a belt driven system, a change in shape could at
least mean a change in circumference.

For 1 complete revolution, there is no difference. Absolutely correct.

However what about 1/4 of a revolution or 1/8 of a revolution? Then
the diameter of the "big pulley" does differs.


I think that's the point of Biopace and this new system (has it got a
name yet?). The strength needed to rotate 1 cycle is equal, but with an
elliptical chainring this strength is supposed to be more equally
distributed.

The key is that the human ability to deliver power and generate torque
varies depending on the position of the pedals.

If you had a human with perfect spinning pedalling movement able to
generate the same amount of torque at every points over 360 degs then
these system would be useless. But they are an attempt to compensate
for the imperfect human engine (and pedals).

Given the way everything is shaking and non-smooth there must be an
effect. I would think this effect is negative, also given the silent
passing of Biopace, but given the performance of Froome that doesn't
make sense.

Why would you think that they have a negative effect?

First, thanks for your posts, they give a really good insight in why
this might (or might not) work.

The reason why I think it has a negative effect is non-scientific.
It doesn't look smooth, the chain is jumping, body is shaking. Part of
it is just Froome's style. Maybe the 'juming of the chain' is just the
effect of the low gears Froome is using. I mainly think that
not-smooth is not-100% effective.


Shimano, Rotors, and the like have made scientific studies on the
subject. We could dismiss some of it as marketing gimmick, other as
flawed science but I would not dismiss the Sky team and David
Brailsford.

The UK cycling team has achieved so much success in the Olympics and
WC in large part by preparing and training better, harder and more
scientifically than anyone else. Team Sky is most probably the most
scientifically trained and tested team. I would be incredibly
surprised if Chris Froome has not spent hundreds of hours on a
training bikes in the lab trying different setup including circular
chain rig and ovoid chain rig. The difference may have been only 0.5%
or even less but Brailsford believes in summing all these small minor
advantages and making it a winning difference.

I wouldn't even be surprised that the exact angle of the ovoid for
Froome differs between his mountain climbing bike and his time trial
bike and that they all differ from Wiggins ones all of that based on
labs measurement for the specific athlete under specific conditions.
Brailsford and his team are that anal with regards to details.

In act, the above probably highlight one of the problem with Biopace
in that it was one setup that may have been good for a certain type of
rider with a certain pedalling style but not for a different rider with
a different pedalling style.

That might very well be true. I would like to add another point to the
equation, which is the placebo effect. All this training and figuring
out the right ovoid might give Froome the idea that he is very ahead of
the rest, while strictly looking at the scientific facts he isn't. But
a it gives more 'morale' and therefore has a positive effect on his
perormance in the Tour.

I wonder: is it still possible to stand up on your pedals when you're
going uphill, or is this why Froome is almost always sitting?

Hmm, not sure. In theory "dancing on a bike" is not very good and a
waste of effort in the long term although climbers like to do it for
short efforts. I don't seem to recall someone like Indurain standing
up too often either. I'd put it down to riding style.

Yani

Sir Gregory Hall, Esq· wrote:

The little Colombian climber would be better off if he would
stay in the saddle and develop his spin technique to put
forth max power with fewer calories burned.

You are arguing with facts. I don't know _why_ little climbers like to
stand, but it's indisputable that they do. Speaking for myself, even
though I'm not that little, I do find standing sometimes just feels
right when climbing. (I weigh 68 kg or about 150 lbs.)

-S-