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 <http://counter.li.org>

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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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.

http://www.exploratorium.com/cycling/aerodynamics2.html

Mike

? 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]

"? 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.

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

On Mon, 12 Apr 2004 17:58:46 -0700, "RWM" <[email hidden]> may

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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"B a r r y" wrote

Quoted message said:

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. 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.)

Sure as hell works for the NASCAR guys.

Theo

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

Quoted message said:

On Mon, 12 Apr 2004 17:58:46 -0700, "RWM" <[email hidden]>

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?

Quoted message said: