wind tunnel
John Forrest Tomlinson
--
JT
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Bill C
wrote:
That's some really cool stuff. That's gotta be the ultimate cycling
gadget. I love it.
Bill C
Robert Chung
> http://www.nyvelocity.com/content.php?id=1300
It's remarkably cool what some guys will go through to avoid doing a little
math.
Bill C
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
Fred Fredburger
> http://www.nyvelocity.com/content.php?id=1300
Where can I order one?
Kurgan Gringioni
Fluids calculations that have any resolution whatsoever for a
relatively complicated setup such as a bike/rider is more than a
little math.
Robert Chung
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.
Dan Connelly
> 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
Robert Chung
> 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.
Dan Connelly
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
Robert Chung
> 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.
Dan Connelly
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
Robert Chung
>> 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.
Curtis L. Russell
wrote:
>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...
Bill C
> On 31 Mar 2007 08:20:10 -0700, "Bill C" <tritonri...@verizon.net>
> wrote:
>
> >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
Robert Chung
>> 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
Andy Coggan
> Dan Connelly wrote:
> >> 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.
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).
> 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
Howard Kveck
Curtis L. Russell <cur...@md-bicycling.org> wrote:
> On 31 Mar 2007 08:20:10 -0700, "Bill C" <trito...@verizon.net>
> wrote:
>
> >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?
Qui si parla Campagnolo
Most guys can only count to 20, 21 when naked.....
Kevin Tuttle
Did you guys ever hear of Photoshop? Why does the structure have to
be off the ground and can the supports really support it? Look a
little closer at the imagery.