published helmet research - not troll

"Tom Kunich" writes:

"Steven L. Sheffield" wrote in message
...
On 10/19/2004 11:54 PM, in article ,
"Bill
Z." wrote:
These bozos are posting far more on the topic than I am. Blame
them.

And because they post you have to respond? You have this need to get the
last word in? Isn't that a bit irrational?

Expecting rationality from Zaumen is like expecting cake in a can of beans.

Well, Steve, it is interesting that you are blaming me when these other
guys are posting nothing but a string of baseless personal attacks. And
that doesn't show anything very complimentary about you. I've every
justification in telling these guys off given their continued behavior.

--
My real name backwards: nemuaZ lliB

Frank Krygowski writes:

Bill Z. wrote:
A V1 Pro has vents. Mine does too, plus having a more aerodyanmic
shape.

I know of no ordinary, off-the-shelf helmet that's been shown to have
a "more aerodynamic shape" than a V1 Pro, and I'm sure I've got more
experience measuring aerodynamic drag than you have.

THen you haven't looked very hard. A V1 Pro was first sold in 1983.
See http://www.bellbikehelmets.com/main/about/timeline.html, which
BTW has a picture of it. Modern helmets have an assymetric design,
which fills in the area behind the head. A Bell V1 Pro is
symmetric or very close - not at all "teardrop" shaped.

And I doubt if you've measured much of anything - otherwise you'd have
said what.

You could prove me wrong, of course. Just tell us the make and model
of your helmet, the one you're making these claims for. And point us
to the drag measurements that you're using to make your conclusion.

If you won't, it makes it clear that you're just trying to avoid
proving yourself a liar.

Unsuccessfully, of course!

Typical of Krygowski's dishonesty - the particular helmet I have is
a standard design with nothing particularly unique about it, so it
is not relevant to the discussion. I picked the particular model
because (a) the shop had it and (b) it fit my head well. There were
lots of other ones with similar shapes and a similar number of
vents.

--
My real name backwards: nemuaZ lliB

"Tom Kunich" writes:

"Bill Z." wrote in message
...
"Tom Kunich" writes:
And yet the most extreme design without vents wasn't as aerodynamic as a
bald head. Explain how your helmet with vents can be more aerodynamic
than a
V1 Pro.

A V1 Pro has vents. Mine does too, plus having a more aerodyanmic
shape. Is that *really* so hard for you to understand? And a bald
head is not relevant when you are not going to shave your head in
any case.

1) You haven't a clue what "more aerodynamic" means unless your helmet was
tested in a wind tunnel. Aerodymanics of low speed laminar flow shapes
cannot be estimated unless you have hundreds of hours in wind tunnel
research.

I have 10's of hours. What about you?

Given the number of careers you've claimed to have, Tommy, I really
don't believe you.

In case you've missed it, short hair is in. Short hair has a great deal less
aerodynamic drag than a modern helmet. Modern helmets don't meet the Snell
Foundation crash standards and perhaps HALF of them do not meet the
'voluntary' ANSI standards because they are self-certified.

Perhaps you'd care to explain Section 21212(c) of the California
Vehicle Code which says, "No person shall sell, or offer for sale, for
use by an operator or passenger of a bicycle, nonmotorized scooter,
skateboard, or in-line or roller skates any safety helmet which is not
of a type meeting requirements established by this section." That
section refers to standards set by the ASTM or the U.S. CPSC. Both
supercede the ANSI standard which expired in 1994. If you check
http://www.bhsi.org/stdcomp.htm, you'll find that "In May, 1995, the
ANSI Z90.4 committee voted to adopt the ASTM standard as its own to
replace the 1984 version, reflecting the movement of active standards
development to ASTM." http://www.bhsi.org/cpscfinl.htm has the CPSC
standard.

You can rant all you want, but any helmet sold in California (and I imagine
most other states) for use on a bicycle has to meet specific standards.

--
My real name backwards: nemuaZ lliB

Bill Z. wrote:

Frank Krygowski writes:

[regarding Bill Zaumen's claim that _his_ helmet is more streamlined than a bare head:]

I know of no ordinary, off-the-shelf helmet that's been shown to have
a "more aerodynamic shape" than a V1 Pro, and I'm sure I've got more
experience measuring aerodynamic drag than you have.


THen you haven't looked very hard. A V1 Pro was first sold in 1983.
See http://www.bellbikehelmets.com/main/about/timeline.html, which
BTW has a picture of it. Modern helmets have an assymetric design,
which fills in the area behind the head.

If you think the shape of a typical bike helmet allows the airflow to
smoothly converge behind the helmet, you must know very, very little
about practical aerodynamics.

Look again at time trial head fairings or time trial helmets. Those
shapes are quite extreme - quite long and gently tapered. Why? Because
that's what it takes to get the airflow to follow the helmet contours to
a reasonable degree. If the rear of the helmet (or other object) tapers
too quickly, the boundary layer separates completely and heavy
turbulence results.

Modern bike helmets are even worse in this regard. The surface is
nowhere near smooth, due to the presence of the vents necessary for
cooling. The air gets stirred up, to the point it wouldn't follow even
a gentle taper.

FWIW, I've never seen mention of wind tunnel work aiming to streamline a
conventional helmet. I assume this is because the designers know such a
thing is practically impossible.

But if you want to understand the principles involved, examine the
fairings used on Human Powered Vehicles - i.e. streamlined bicycles.
Successful ones are very smooth, long and tapered, and as small as
possible in frontal area. You won't find one that's shaped like a
typical bike helmet, which is very rough, _not_ gently tapered, and
larger than a bare head.

You could prove me wrong, of course. Just tell us the make and model
of your helmet, the one you're making these claims for. And point us
to the drag measurements that you're using to make your conclusion.

If you won't, it makes it clear that you're just trying to avoid
proving yourself a liar.

Unsuccessfully, of course!


Typical of Krygowski's dishonesty - the particular helmet I have is
a standard design with nothing particularly unique about it, so it
is not relevant to the discussion.

If you say _your_ helmet causes less drag than a bare head, I think it's
relevant to ask what helmet you're talking about!


--
Frank Krygowski [To reply, remove rodent and vegetable dot com.
Substitute cc dot ysu dot
edu]

Frank Krygowski writes:

Bill Z. wrote:

Frank Krygowski writes:
[regarding Bill Zaumen's claim that _his_ helmet is more streamlined
than a bare head:]

I know of no ordinary, off-the-shelf helmet that's been shown to have
a "more aerodynamic shape" than a V1 Pro, and I'm sure I've got more
experience measuring aerodynamic drag than you have.
THen you haven't looked very hard. A V1 Pro was first sold in 1983.
See http://www.bellbikehelmets.com/main/about/timeline.html, which
BTW has a picture of it. Modern helmets have an assymetric design,
which fills in the area behind the head.

If you think the shape of a typical bike helmet allows the airflow to
smoothly converge behind the helmet, you must know very, very little
about practical aerodynamics.

It has to reduce drag relative to a completely symmetric helmet, and
not by very much. BTW, it is well known that you will speed up if
someone is drafting you - you'll put out more effort than the person
behind but you'll still go faster than if you were riding alone.
Filling in the are behind the cyclist (or behind the head) helps.

Look again at time trial head fairings or time trial helmets. Those
shapes are quite extreme - quite long and gently tapered. Why?

Because they are *optimized* for the lowest achievable drag. rest
of red herring snipped

If you won't, it makes it clear that you're just trying to avoid
proving yourself a liar.

Unsuccessfully, of course!
Typical of Krygowski's dishonesty - the particular helmet I have is
a standard design with nothing particularly unique about it, so it
is not relevant to the discussion.

If you say _your_ helmet causes less drag than a bare head, I think
it's relevant to ask what helmet you're talking about!


No it isn't. We were talking about reducing drag relative to a bare
head for someone with a full head of hair when a Bell V1 Pro causes
only a very tiny increase in drag over that case. It simply doesn't
require much of an improvement to get a tiny reduction in drag. The
particular model I have is not relevant - there's nothing special
about it.

--
My real name backwards: nemuaZ lliB

Bill Z. wrote:

Frank Krygowski writes:


If you think the shape of a typical bike helmet allows the airflow to
smoothly converge behind the helmet, you must know very, very little
about practical aerodynamics.


It has to reduce drag relative to a completely symmetric helmet, and
not by very much. BTW, it is well known that you will speed up if
someone is drafting you - you'll put out more effort than the person
behind but you'll still go faster than if you were riding alone.
Filling in the are behind the cyclist (or behind the head) helps.

:-)

Yes, you've just proven conclusively how little you know about practical
aerodynamics.

Carry on, Bill. You're fun to watch!

--
--------------------+
Frank Krygowski [To reply, remove rodent and vegetable dot com,
replace with cc.ysu dot edu]

Frank Krygowski writes:

Bill Z. wrote:

Frank Krygowski writes:


If you think the shape of a typical bike helmet allows the airflow to
smoothly converge behind the helmet, you must know very, very little
about practical aerodynamics.
It has to reduce drag relative to a completely symmetric helmet, and
not by very much. BTW, it is well known that you will speed up if
someone is drafting you - you'll put out more effort than the person
behind but you'll still go faster than if you were riding alone.
Filling in the are behind the cyclist (or behind the head) helps.

Yes, you've just proven conclusively how little you know about
practical aerodynamics.

As opposed to the real thing, I presume. BTW, you might read
_Bicycle Science_ for a short introduction.

Carry on, Bill. You're fun to watch!

You've proven once again that you'll resort to mindless rhetoric,
which seems to be all you are capable of. Where you perchance fool
enough to vote for Bush?

--
My real name backwards: nemuaZ lliB

"Bill Z." wrote in message
...
Frank Krygowski writes:

Bill Z. wrote:
A V1 Pro has vents. Mine does too, plus having a more aerodyanmic
shape.

I know of no ordinary, off-the-shelf helmet that's been shown to have
a "more aerodynamic shape" than a V1 Pro, and I'm sure I've got more
experience measuring aerodynamic drag than you have.

THen you haven't looked very hard. A V1 Pro was first sold in 1983.
See http://www.bellbikehelmets.com/main/about/timeline.html, which
BTW has a picture of it. Modern helmets have an assymetric design,
which fills in the area behind the head. A Bell V1 Pro is
symmetric or very close - not at all "teardrop" shaped.

Let me guess - you have one of those genetic diseases that cause you to
forget anything before the last posting?

It is humorous though to watch someone as ignorant as yourself tell us that
you can determine areodynamics by having some crude ideas gotten by magazine
articles on the subject but those with actual wind tunnel experience in the
speed regimes pertinent have to somehow have published papers on precisely
the helmet that you're wearing before their opinions are valid. And of
course you won't actually SAY what your helmet is.

Is it true that you say "wascuwy wabbit"?

Typical of Krygowski's dishonesty - the particular helmet I have is
a standard design with nothing particularly unique about it, so it
is not relevant to the discussion.

You're the one claiming that your helmet somehow is more aerodynamic than a
Bell X1 Pro. We're the one's laughing in your face since you don't have a
clue what you're talking about. "Teardrop" shaped indeed!

You real name backwards is "tihs pid"

"Bill Z." wrote in message
...
Frank Krygowski writes:

If you think the shape of a typical bike helmet allows the airflow to
smoothly converge behind the helmet, you must know very, very little
about practical aerodynamics.

It has to reduce drag relative to a completely symmetric helmet, and
not by very much.

Bill, you really are a nutcase aren't you? You haven't even a rudimentary
understanding of linear flow aerodynamics and every word from your brain
makes that more apparent.

If you say _your_ helmet causes less drag than a bare head, I think
it's relevant to ask what helmet you're talking about!


No it isn't.

Yes it is.

Your real name backwards is "ssakcaJ"

"Bill Z." wrote in message
...
Frank Krygowski writes:
Yes, you've just proven conclusively how little you know about
practical aerodynamics.

As opposed to the real thing, I presume. BTW, you might read
_Bicycle Science_ for a short introduction.

Yeah, if there's one comprehensive handbook on aerodynamics it's without a
doubt Bicycle Science.

Carry on, Bill. You're fun to watch!

You've proven once again that you'll resort to mindless rhetoric,
which seems to be all you are capable of. Where you perchance fool
enough to vote for Bush?

Your real name backwards: yoB samaM