wind tunnel

http://www.nyvelocity.com/content.php?id=1300
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John Forrest Tomlinson said:

http://www.nyvelocity.com/content.php?id=1300

It's remarkably cool what some guys will go through to avoid doing a little
math.

Robert Chung said:

John Forrest Tomlinson said:

http://www.nyvelocity.com/content.php?id=1300

It's remarkably cool what some guys will go through to avoid doing a little
math.

Ya know for some people out here when you run out of fingers and toes
the answer becomes "Many" or "A whole bunch.".
Bill C

John Forrest Tomlinson said:

http://www.nyvelocity.com/content.php?id=1300

Where can I order one?

Robert Chung said:

John Forrest Tomlinson said:

http://www.nyvelocity.com/content.php?id=1300

It's remarkably cool what some guys will go through to avoid doing a little
math.

Fluids calculations that have any resolution whatsoever for a
relatively complicated setup such as a bike/rider is more than a
little math.

Kurgan Gringioni said:

Robert Chung said:

John Forrest Tomlinson said:

http://www.nyvelocity.com/content.php?id=1300

It's remarkably cool what some guys will go through to avoid doing a
little math.

Fluids calculations that have any resolution whatsoever for a
relatively complicated setup such as a bike/rider is more than a
little math.

Right, but the cross-section of that tunnel is so small that he can't hope
to get an absolute value for CdA; the most he can hope for is an estimate of
relative CdA. In that case, he can get the same level of (im)precision from
an on-bike power meter, which he appears to have.

Robert Chung said:

Right, but the cross-section of that tunnel is so small that he can't hope
to get an absolute value for CdA; the most he can hope for is an estimate of
relative CdA. In that case, he can get the same level of (im)precision from
an on-bike power meter, which he appears to have.

I think he claims to have precision -- it's accuracy he lacks.

Dan

Dan Connelly said:

I think he claims to have precision -- it's accuracy he lacks.

I'd be surprised if he had much precision. Not only is he going to get
turbulence off the walls, but I'm guessing the vanes aren't tuned.

Robert Chung said:

Dan Connelly said:

I think he claims to have precision -- it's accuracy he lacks.

I'd be surprised if he had much precision. Not only is he going to get
turbulence off the walls, but I'm guessing the vanes aren't tuned.

A trivial demonstration is theory says the wind resistance on a 3'3" radius sphere should have around the same drag as a 1'7.5" radius sphere at twice the wind speed.

But I still wonder...

A decent wind resistance test, which I saw first mentioned by Robin Horowitz, should be to run a powertap in conjunction with an iBike. If Crr is right, the single fitting parameter to get agreement is CdA, assuming negligible cross-winds.

Dan

Dan Connelly said:

A decent wind resistance test, which I saw first mentioned by Robin
Horowitz, should be to run a powertap in conjunction with an iBike. If Crr
is right, the single fitting parameter to get agreement is
CdA, assuming negligible cross-winds.

I think Coggan talked about doing something like that in the past. IIRC, he
seemed to think the precision was poor.

Robert Chung said:

Dan Connelly said:

A decent wind resistance test, which I saw first mentioned by Robin
Horowitz, should be to run a powertap in conjunction with an iBike. If Crr
is right, the single fitting parameter to get agreement is
CdA, assuming negligible cross-winds.

I think Coggan talked about doing something like that in the past. IIRC, he
seemed to think the precision was poor.

Allen & Coggan is pre-IBike, but discusses using power for aerodynamics without a wind gauge: just after dawn, to minimize wind, ride a route in each direction, and do a regression of power/v versus v, with intercept Crr, and slope CdA/2, with power measured with a PowerTap to avoid drivetrain losses.

Dan

Dan Connelly said:

Quoted message said:

I think Coggan talked about doing something like that in the past.
IIRC, he seemed to think the precision was poor.

Allen & Coggan is pre-IBike, but discusses using power for
aerodynamics without a wind gauge: just after dawn, to minimize wind,
ride a route in each direction, and do a regression of power/v versus
v, with intercept Crr, and slope CdA/2, with power measured with a
PowerTap to avoid drivetrain losses.

Yeah, and I have my doubts about that method. Windless is important, but I
think you'll get poor precision unless you take into account accelerations.

However, I was referring to something else: Andy wrote somewhere or other
that when the iBike came out it reminded him of an experiment he'd done with
an on-bike wind gauge and on-bike power meter sometime before in an attempt
to estimate CdA.

On 31 Mar 2007 08:20:10 -0700, "Bill C" <[email hidden]>

Quoted message said:

Ya know for some people out here when you run out of fingers and toes
the answer becomes "Many" or "A whole bunch.".
Bill C

And some make up a number and then argue to the death defending it.

Curtis L. Russell
Odenton, MD (USA)
Just someone on two wheels...

Curtis L. Russell said:

On 31 Mar 2007 08:20:10 -0700, "Bill C" <[email hidden]>

Quoted message said:

Ya know for some people out here when you run out of fingers and toes
the answer becomes "Many" or "A whole bunch.".
Bill C

And some make up a number and then argue to the death defending it.

Curtis L. Russell
Odenton, MD (USA)
Just someone on two wheels...

Is that why we don't see more pictures of Bush with his shoes off??
(Joke! Alert for theHumor impaired )
Bill C

Bill C said:

Quoted message said:

And some make up a number and then argue to the death defending it.

Is that why we don't see more pictures of Bush with his shoes off??

Here he is trying to count to 21:

http://static.crooksandliars.com/2007/03/bush-carrot.jpg

Robert Chung said:

Dan Connelly said:

Quoted message said:

I think Coggan talked about doing something like that in the past.
IIRC, he seemed to think the precision was poor.

Quoted message said:

Allen & Coggan is pre-IBike, but discusses using power for
aerodynamics without a wind gauge: just after dawn, to minimize wind,
ride a route in each direction, and do a regression of power/v versus
v, with intercept Crr, and slope CdA/2, with power measured with a
PowerTap to avoid drivetrain losses.

Yeah, and I have my doubts about that method. Windless is important, but I
think you'll get poor precision unless you take into account accelerations.

That point is discussed in the book (as is the need to start and end
each run on a banked track on the straight and not in the turn).

Quoted message said:

However, I was referring to something else: Andy wrote somewhere or other
that when the iBike came out it reminded him of an experiment he'd done with
an on-bike wind gauge and on-bike power meter sometime before in an attempt
to estimate CdA.

We never got our device working well enough to ascertain the
"workability" of the approach itself.

Andy Coggan

In article <[email hidden]>,

Curtis L. Russell said:

On 31 Mar 2007 08:20:10 -0700, "Bill C" <[email hidden]>

Quoted message said:

Ya know for some people out here when you run out of fingers and toes
the answer becomes "Many" or "A whole bunch.".
Bill C

And some make up a number and then argue to the death defending it.

Could there also be a bit of "accusing everyone else of being stupid / fools /
suckers / Liberals" involved here?

--
tanx,
Howard

Never take a tenant with a monkey.

remove YOUR SHOES to reply, ok?