Power to Weight Chart?

In a nutshell, on steep climbs your speed will be a little less than
proportional to power to weight ratio. In other words increasing P/W
(that is total weight) by 10% will get you maybe 8-9% faster speed. On
the flat, weight hardly matters... P/CdA being the more important
consideration.

gkaton said:

Does anyone know of a chart that shows how much additional speed can be
expected upon a given reduction in weight, assuming power and other
variables remain constant? I seem to recall hearing about Johan
Bruyneel running such numbers pre-1999 on Lance's power to determine
how much weight he'd need to lose to win the Tour. There would be some
imprecision based upon the reality that body drag is likely to decrease
from weight loss, but there should be some good approximation. Anyone?

I seem to recall Lafferty's Italian friend has a theory using a term
called VAM to measure climbing speed improvement vs weight. Its probably
on 53x12.com (but the secret subscription site 55x11.com might also have
some orange juice on sale).

"Ron Ruff" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In a nutshell, on steep climbs your speed will be a little less than
proportional to power to weight ratio. In other words increasing P/W
(that is total weight) by 10% will get you maybe 8-9% faster speed. On
the flat, weight hardly matters... P/CdA being the more important
consideration.

Yes, but there is a general correlation between weight and CdA. In
theory, surface area will increase to the 2/3 power of weight increase.
For a 10% weight change, the drag will change by approx 7% and the speed
by 3.5% for the same power output.

Phil H

Phil Holman said:

Yes, but there is a general correlation between weight and CdA. In
theory, surface area will increase to the 2/3 power of weight increase.
For a 10% weight change, the drag will change by approx 7% and the speed
by 3.5% for the same power output.

2/3 would be true only if BMI was proportional to height^3. Since height
tends to scale more rapidly than mass^(1/3), the actual power is more than
(2/3). From the paper I read, it's closer to 0.75.

Dan

"Dan Connelly" <d_j_c_o_n_n_e_l@i_e_e_e.o_r_g> wrote in message
news:[email hidden]...

Quoted message said:

Phil Holman said:

Yes, but there is a general correlation between weight and CdA. In
theory, surface area will increase to the 2/3 power of weight
increase. For a 10% weight change, the drag will change by approx 7%
and the speed by 3.5% for the same power output.

2/3 would be true only if BMI was proportional to height^3. Since
height
tends to scale more rapidly than mass^(1/3), the actual power is more
than
(2/3). From the paper I read, it's closer to 0.75.

Dan

Let's think about this some more. When people gain weight, their height
doesn't change :-)

Phil H

Phil Holman said:

Yes, but there is a general correlation between weight and CdA. In
theory, surface area will increase to the 2/3 power of weight increase.
For a 10% weight change, the drag will change by approx 7% and the speed
by 3.5% for the same power output.

I can't agree that "A" is proportional to .7*W. Surface area is not the
"A" in CdA... it is frontal area. True, this is correlated somewhat
with weight... but probably less than height. An even bigger factor is
the shape of the rider's body.

"Ron Ruff" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Phil Holman said:

Yes, but there is a general correlation between weight and CdA. In
theory, surface area will increase to the 2/3 power of weight
increase.
For a 10% weight change, the drag will change by approx 7% and the
speed
by 3.5% for the same power output.

I can't agree that "A" is proportional to .7*W. Surface area is not
the
"A" in CdA... it is frontal area.

Cross sectional area and surface area increase in the same proportion.
It's the effect of a volume change on area. As Dan pointed out, not all
dimensions scale equally so the effect does not fit exactly.

Quoted message said:

True, this is correlated somewhat
with weight... but probably less than height. An even bigger factor is
the shape of the rider's body.

Duh! Especially if that extra weight can be sculpted into a NACA
symmetric profile :-)

Phil H

Phil Holman said:

Duh! Especially if that extra weight can be sculpted into a NACA
symmetric profile :-)

I think the lower legs could really benefit from this... imagine
squashing the calves into an airfoil shape...?

Having a wide butt wouldn't be good... that trailing edge needs to
taper as much as possible.

"Ron Ruff" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Phil Holman said:

Duh! Especially if that extra weight can be sculpted into a NACA
symmetric profile :-)

I think the lower legs could really benefit from this... imagine
squashing the calves into an airfoil shape...?

About 30+ years ago Jerry Ash was a pretty fair sprinter and a tandem
partner with Leigh Barczewski. Somehow a rumor got passed to the Soviets
that Ash had gotten deer tendons grafted onto his legs to improve his
sprinting ability. Obviously not true, but good for a laugh.

Quoted message said:

Having a wide butt wouldn't be good... that trailing edge needs to
taper as much as possible.

Didn't seem to hurt Felicia Ballanger.

In article <Fq6Tf.56529$Dh.38459@dukeread04>,

Carl Sundquist said:

"Ron Ruff" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Phil Holman said:

Duh! Especially if that extra weight can be sculpted into a NACA
symmetric profile :-)

I think the lower legs could really benefit from this... imagine
squashing the calves into an airfoil shape...?

About 30+ years ago Jerry Ash was a pretty fair sprinter and a tandem
partner with Leigh Barczewski. Somehow a rumor got passed to the Soviets
that Ash had gotten deer tendons grafted onto his legs to improve his
sprinting ability. Obviously not true, but good for a laugh.

Quoted message said:

Having a wide butt wouldn't be good... that trailing edge needs to
taper as much as possible.

Didn't seem to hurt Felicia Ballanger.

<http://slam.canoe.ca/2000GamesGallerySep20/cycling3.html>

--
Michael Press