Does drafting help the guy in frount?

? the Platypus {aka David Formosa} said:

Ok first my understanding of the way drag (air resistence)
works. There is two main sources of drag, the first one is
from pushing the air away infrount of you, and the second
source of drag is from the air rushing in to fill the
partial vacume behind you.

It's more the turbulance you leave behind you that
slows you down.

Quoted message said:

This is why stuff designed for areodynamics normally has
the classic teardrop shape, with the tail out the end to
allow the air to rush back in smoothly.

The ideal shape isn't quite a teardrop. Aero modelling of
the ideal shape has been done before, and it tends to
appear a more bloated at the rear, rather than the sharp
classic teardrop shape you're talking about. But this is
besides the point anyway.

Quoted message said:

Wouldn't having a bike behind you transfur the second sort
of drag to him freeing you from this?

If you're talking about normal bodies on normal bicycles,
the aerodynamic shape of your typical human is complex,
and the turbulance you leave behind you is by far worse
than any effect the rider behind you is going to have. And
this turns out to be a moot point anyway, because the
frontal area exposed to the air has by far more of an
effect than the turbulance drag anyway. This is why
bicycles (most notably recuments) with even only small
front nosecoses, have such a marked effect on overall
average speed.

With normal bikes however, in theory, if you could get
close enough, it might have an effect, but due to the
physical construction of bikes in general, you can't get
close enough to make a difference.

Best you can hope for is the person in front helps you,
not you help them.

--
Linux Registered User # 302622 <counter.li.orgcounter.li.orgOpen ↗

On 12 Apr 2004 09:54:28 +1000, ? the Platypus {aka David Formosa}

may have said:

Wouldn't having a bike behind you transfur the second sort
of drag to him freeing you from this?

No. The speed at which this would be beneficial to the
drafted rider is not one that will be achieved on a human-
powered bike.

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? the Platypus {aka David Formosa} said:

Ok first my understanding of the way drag (air resistence)
works. There is two main sources of drag, the first one is
from pushing the air away infrount of you, and the second
source of drag is from the air rushing in to fill the
partial vacume behind you. This is why stuff designed for
areodynamics normally has the classic teardrop shape, with
the tail out the end to allow the air to rush back in
smoothly.

Wouldn't having a bike behind you transfur the second sort
of drag to him freeing you from this?

This can provide a significant advantage to first rider if
they are both in streamliners - quite important to the 30 or
40 people worldwide who race these.

A bigger advantage can be provided by having a closely
trailing large vehicle such a motor home (caravan), bus or
truck (lorry) that produces a significant bow wave.

--
Tom Sherman - Quad Cities (Illinois Side)

On Sun, 11 Apr 2004 20:09:49 -0500, Tom Sherman

may have said:

This can provide a significant advantage to first rider if
they are both in streamliners - quite important to the 30
or 40 people worldwide who race these.

A bigger advantage can be provided by having a closely
trailing large vehicle such a motor home (caravan), bus or
truck (lorry) that produces a significant bow wave.

However, the increase in power delivered to the pedals due
to the sheer terror induced by the close proximity of
several tons of screaming death metal probably will have a
greater effect on the rider's output than the bow wave will
have on his speed.

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Werehatrack said:

...

Quoted message said:

A bigger advantage can be provided by having a closely
trailing large vehicle such a motor home (caravan), bus or
truck (lorry) that produces a significant bow wave.

However, the increase in power delivered to the pedals due
to the sheer terror induced by the close proximity of
several tons of screaming death metal probably will have a
greater effect on the rider's output than the bow wave
will have on his speed.

IIRC, this has been an issue in some cycling competitions
where the bow wave effect has been used to gain an
advantage.

--
Tom Sherman - Quad Cities (Illinois Side

Werehatrack said:

On Sun, 11 Apr 2004 20:09:49 -0500, Tom Sherman

may have said:

A bigger advantage can be provided by having a closely
trailing large vehicle such a motor home (caravan), bus or
truck (lorry) that produces a significant bow wave.

However, the increase in power delivered to the pedals due
to the sheer terror induced by the close proximity of
several tons of screaming death metal probably will have a
greater effect on the rider's output than the bow wave
will have on his speed.

I found and subsequently confirmed that the best way to
heighten the adrenalin effect is to have one's front wheel
come into contact with the drafted vehicle under hard
braking resulting in significant rear wheel lift.

--
R.

<> Richard Brockie "Categorical statements <> The tall
blond one. always cause trouble." <>
[email hidden]

In "]news:[email hidden],
? the Platypus {aka David Formosa} <[email hidden]> typed:

Quoted message said:

Ok first my understanding of the way drag (air resistence)
works. There is two main sources of drag, the first one is
from pushing the air away infrount of you, and the second
source of drag is from the air rushing in to fill the
partial vacume behind you. This is why stuff designed for
areodynamics normally has the classic teardrop shape, with
the tail out the end to allow the air to rush back in
smoothly.

Wouldn't having a bike behind you transfur the second sort
of drag to him freeing you from this?

According to this yes.

exploratorium.comaerodynamics2.htmlOpen ↗

Mike

"? the Platypus {aka David Formosa}" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Ok first my understanding of the way drag (air resistence)
works. There is two main sources of drag, the first one is
from pushing the air away infrount of you, and the second
source of drag is from the air rushing in to fill the
partial vacume behind you. This is why stuff designed for
areodynamics normally has the classic teardrop shape, with
the tail out the end to allow the air to rush back in
smoothly.

<SNIP>

As a follow up question, has any reputable research been
done to analyze the effects of having a rider in your draft
at different speeds. I always find it interesting to listen
to announcers of road bike races say things like:

When a rider breaks from the pack on a major climb and
someone jumps on his wheel: "That will slow him down, having
a rider in your draft on a climb has the effect of you
towing him uphill. It is much harder for the lead rider than
going alone."

When the whole peleton is together and flying on the
flats: "The effects of riding in a group can save as much
as 50% effort."

I know that bicycle racing has a long history of traditions
without any supporting facts, but I don't a lot concerning
the truth in this area.

Bob.

Quoted message said:

As a follow up question, has any reputable research been
done to analyze the effects of having a rider in your draft
at different speeds.

There's been tons done on race cars. Of course, the speeds
are a bit different. <G>

FWIW, The common thinking in auto racing is that in a two
car draft, both cars are helped in a straight line.
Cornering, there may or may not be an advantage, due to
changes in down force induced by the draft. Usually, the
more cars that join a single file draft, the faster the
pack goes.

Barry

There are different types of drag. The main one affecting
cyclists is form drag, produced by the flow of air around
you. You push at the air in front, increasing pressure, and
its flow is turbulent because of your shape. This causes a
decrease of pressure behind you which tends to suck you
backwards (triathletes will know about this). Swimming has
changed heaps over the years as this has become better
understood - a longer, streamlined shape causes less
turbulence in the flow so there is not such a low pressure
area behind. The second cyclist takes it easy because the
low pressure behind the cyclist in front sucks him/her
forward - and the pressure behind the 2nd cyclist will be
higher than it was behind the first cyclist (because of less
turbulence from a longer, more streamlined body). Most
people understand this bit.

The way that the rear cyclist would help the front cyclist
most is if they increased the pressure in between them.
Given that there is reduced turbulent flow behind the first
cyclist, the pressure might not drop so low. However a lot
of this cyclist's energy is going to the second cyclist - as
they are pushing the air out of the way for both.

Or, to think of it in laymans terms, if there was 2 litres
of air in front that one cyclist had to displace (push out
of the way) leaving a 2 litre hole behind him, and lots of
energy is wasted in creating this hole and the air flows
turbulently back in behind him/her. But when there's 2
cyclists there's less turbulence (seen) which effectively
means there's a smaller hole behind them - maybe only 1
litre - but the first cyclist still displaced 2 litres,
which means there had to be a smaller hole behind him too,
thanks to the other cyclist.

I think a fish-shaped pack would work better, widening
quickly from the first cyclist and then tapering slowly.

T

Quoted post said:

Originally posted by Anonymous
As a follow up question, has any reputable research been
done to analyze the effects of having a rider in your draft
at different speeds. I always find it interesting to listen
to announcers of road bike races say things like:

When a rider breaks from the pack on a major climb and
someone jumps on his wheel: "That will slow him down, having
a rider in your draft on a climb has the effect of you
towing him uphill. It is much harder for the lead rider than
going alone."

When the whole peleton is together and flying on the
flats: "The effects of riding in a group can save as much
as 50% effort."

I know that bicycle racing has a long history of traditions
without any supporting facts, but I don't a lot concerning
the truth in this area.

Bob.

Bob, I've been following the sport for years and I've never ever ever heard a TV commentator saying that a rider drafting the rider in front will slow down the front rider. Yes, in the Tour Phil Liggett often says that so and so is basically being towed up the climb by the lead rider. And it's true. The rider sitting on the lead rider's wheel saves a lot of energy. He doesn't have to do any work up fron to break the wind. That doesn't mean it is making it harder on the front rider. Although, as the rider sits behind and literally does no work by taking in pulls at the front, it going to be harder for the lead rider (who is doing all the work at the front) to respond once the fresher "towed" rider puts in an attack.

have said:

As a follow up question, has any reputable research been
done to analyze the effects of having a rider in your draft
at different speeds.

I haven't heard of any that involved actual measurements,
and I don't know how you would measure this outside a wind
tunnel, which isn't a real-world setting.

However, by way of a reality check from auto racing:

In my direct experience, having another car drafting me at
50 mph at a distance of less than two feet when going down a
straight makes zero difference in *my* speed. On a curve at
drafting speeds, it's very hard to say whether it helps,
hurts, or has no effect. At 120 to 130mph on a straight, it
does make a noticeable difference; I can see a speed gain of
two or three mph (rarely more) as the other driver smooths
the airflow off my rear...but this comes with a potentially
disastrous penalty if something goes wrong. I haven't been
involved in racing at higher speeds in which drafting was a
factor. (For that matter, it's been 20 years since I was
last on the track, but the air's behavior hasn't changed.)

Long-haul truck drivers, whose vehicles have a much
greater frontal area, report that a closely tailgating big
rig may boost the speed for the leader by a mile an hour
at highway speeds (70mph), but the risk involved is
considered too great by most. At a more reasonable but
still not really safe following distance, only the
drafting truck gets any benefit.

Extrapolating that back to bikes, I cannot see where a
smaller body at a lower speed has any chance whatsoever of
producing the "boost for the leader" effect. It's just not
going to happen.

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Werehatrack said:

In my direct experience, having another car drafting me at
50 mph at a distance of less than two feet when going down
a straight makes zero difference in *my* speed. On a curve
at drafting speeds, it's very hard to say whether it helps,
hurts, or has no effect. At 120 to 130mph on a straight, it
does make a noticeable difference; I can see a speed gain
of two or three mph (rarely more) as the other driver
smooths the airflow off my rear...but this comes with a
potentially disastrous penalty if something goes wrong. I
haven't been involved in racing at higher speeds in which
drafting was a factor. (For that matter, it's been 20 years
since I was last on the track, but the air's behavior
hasn't changed.)

Have you ever been "bump drafted"? <G>

Barry

On Thu, 15 Apr 2004 01:02:05 GMT, B a r r y

may have said:

Werehatrack said:

At 120 to 130mph on a straight, it does make a noticeable
difference; I can see a speed gain of two or three mph
(rarely more) as the other driver smooths the airflow off
my rear...but this comes with a potentially disastrous
penalty if something goes wrong.

Have you ever been "bump drafted"? <G>

Not twice by the same driver.

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On Sat, 17 Apr 2004 11:13:36 -0400, [email hidden] (Chris

Zacho 'The Wheelman') may have said:

From: [email hidden] (Werehatrack)

Quoted message said:

In my direct experience, having another car drafting me at
50 mph at a distance of less than two feet when going down
a straight makes zero difference in *my* speed.

Just curious, Do you indulge in auto racing?

As was stated in the post quoted, yes, I did, in the past.
My reaction times are no longer fast enough for me to be
comfortable in anything beyond autocross now.

Quoted message said:

If not, you have some real nasty tailgaters where you live!

It's much worse in Nashville.

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"B a r r y" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Quoted message said:

As a follow up question, has any reputable research been
done to analyze

the

Quoted message said:

Quoted message said:

effects of having a rider in your draft at different
speeds.

There's been tons done on race cars. Of course, the speeds
are a bit different. <G>

FWIW, The common thinking in auto racing is that in a two
car draft, both cars are helped in a straight line.
Cornering, there may or may not be an advantage, due to
changes in down force induced by the draft. Usually, the
more cars that join a single file draft, the faster the
pack goes.

Barry

I understand the effect in auto racing, but in addition to
the speed the front of the trailing car is much different
than a bike.

Can anyone point me to research from bike racing?