Cycling against the wind

POHB said:

How come I can cycle into a 20-30 MPH headwind (with stronger gusts)
but I can't maintain that speed on the flat on a calm day?

I have no idea, but it was discussed and explained at length here:

http://groups.google.co.uk/group/uk.rec.cycling/browse_frm/thread/567c1ab40c8097e3
--
A

POHB said:

How come I can cycle into a 20-30 MPH headwind (with stronger gusts)
but I can't maintain that speed on the flat on a calm day?

Considerable power is needed to maintain 30 mph on the flat on a calm
day, certainly more than most mortals have at their command. However,
no power at all is required to maintain 0 mph in a 30 mph headwind.
Consquently only a small amount of power is required to reach a ground
speed of, say, 5 mph in a 30 mph headwind. It's not the same as doing
35 mph in still air.

I'm sure someone else will be along in a minute with "difficult sums".
:-)

--
Dave...

In article <[email hidden]>, POHB
[email hidden] says...

Quoted message said:

How come I can cycle into a 20-30 MPH headwind (with stronger gusts)
but I can't maintain that speed on the flat on a calm day?

I expect the wind speed is measured at some height and away from any
obstructions.

Quoting POHB <[email hidden]>:

Quoted message said:

How come I can cycle into a 20-30 MPH headwind (with stronger gusts)
but I can't maintain that speed on the flat on a calm day?

Power to overcome air resistance is proportional to airspeed times
airspeed times groundspeed.

On a calm day, trying to make 25mph, those three terms are the same.
However if you're trying to make, say, 5mph into a 20mph wind, that's 25 x
25 x 5; the power output is one-fifth that of the calm day even though the
net airspeed is the same. Neglecting rolling resistance (which isn't so
bad an assumption) you'd expect someone who can make 25mph on a calm day
to be able to make 13-14mph against a 25mph headwind.

The groundspeed term is there because it is the ground you are exerting
force against to move yourself.
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POHB wrote on 18/01/2007 16:33 +0100:

Quoted message said:

How come I can cycle into a 20-30 MPH headwind (with stronger gusts)
but I can't maintain that speed on the flat on a calm day?

Try it round here today with gusts nearby of 99mph!

--
Tony

"...has many omissions and contains much that is apocryphal, or at least
wildly inaccurate..."
Douglas Adams; The Hitchhiker's Guide to the Galaxy

Tony Raven said:

POHB wrote on 18/01/2007 16:33 +0100:

Quoted message said:

How come I can cycle into a 20-30 MPH headwind (with stronger gusts)
but I can't maintain that speed on the flat on a calm day?

Try it round here today with gusts nearby of 99mph!

Where on earth are you?!

cupra wrote on 18/01/2007 20:21 +0100:

Quoted message said:

Tony Raven said:

POHB wrote on 18/01/2007 16:33 +0100:

Quoted message said:

How come I can cycle into a 20-30 MPH headwind (with stronger gusts)
but I can't maintain that speed on the flat on a calm day?

Try it round here today with gusts nearby of 99mph!

Where on earth are you?!

Isle of Wight

--
Tony

"...has many omissions and contains much that is apocryphal, or at least
wildly inaccurate..."
Douglas Adams; The Hitchhiker's Guide to the Galaxy

Tony Raven said:

cupra wrote on 18/01/2007 20:21 +0100:

Quoted message said:

Tony Raven said:

POHB wrote on 18/01/2007 16:33 +0100:
> How come I can cycle into a 20-30 MPH headwind (with stronger
> gusts) but I can't maintain that speed on the flat on a calm day?
>
Try it round here today with gusts nearby of 99mph!

Where on earth are you?!

Isle of Wight

Ah, yes, I'd heard of the gusts up at the Needles - wouldn't want to have
been cycling in that!

Tony Raven said:

POHB wrote on 18/01/2007 16:33 +0100:

Quoted message said:

How come I can cycle into a 20-30 MPH headwind (with stronger gusts)
but I can't maintain that speed on the flat on a calm day?

Try it round here today with gusts nearby of 99mph!

Well, INTO the wind shouldn't be so bad, I reckon the drag force is
about 275 N, which for a bloke of my build is like going up a 1 in 3.6 hill.
Mind you, from the side, with your bigger area you're going to need to
lean at more than 20 degrees.
Not really an experiment that I'd like to try.

--
Roger Thorpe

My email address is spamtrapped. You can work it out!

Roger Thorpe wrote on 19/01/2007 10:18 +0100:

Quoted message said:

Tony Raven said:

POHB wrote on 18/01/2007 16:33 +0100:

Quoted message said:

How come I can cycle into a 20-30 MPH headwind (with stronger gusts)
but I can't maintain that speed on the flat on a calm day?

Try it round here today with gusts nearby of 99mph!

Well, INTO the wind shouldn't be so bad, I reckon the drag force is
about 275 N, which for a bloke of my build is like going up a 1 in 3.6
hill.
Mind you, from the side, with your bigger area you're going to need to
lean at more than 20 degrees.
Not really an experiment that I'd like to try.

I have a picture somewhere that I took from behind of a group of friends
cycling across the moor tops of Calderdale with all of them leaning over
between 10 and 20 degrees. Fortunately it was a steady gale not gusts
which would have made it a lot more difficult.

--
Tony

"...has many omissions and contains much that is apocryphal, or at least
wildly inaccurate..."
Douglas Adams; The Hitchhiker's Guide to the Galaxy

in message <[email hidden]>, Roger Thorpe

(') said:

Tony Raven said:

POHB wrote on 18/01/2007 16:33 +0100:

Quoted message said:

How come I can cycle into a 20-30 MPH headwind (with stronger gusts)
but I can't maintain that speed on the flat on a calm day?

Try it round here today with gusts nearby of 99mph!

Well, INTO the wind shouldn't be so bad, I reckon the drag force is
about 275 N, which for a bloke of my build is like going up a 1 in 3.6
hill. Mind you, from the side, with your bigger area you're going to need
to lean at more than 20 degrees.

It's also (trust me on this) quite interesting riding with bladed spokes on
your front wheel at right angles to a very strong wind...

Quoted message said:

Not really an experiment that I'd like to try.

BTDT, but the t-shirt blew away.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

'graveyards are full of indispensable people'

cupra said:

Ah, yes, I'd heard of the gusts up at the Needles - wouldn't want to have
been cycling in that!

Apart from anything else, you'd be in the sea.

--
Dave...

dkahn400 said:

cupra said:

Ah, yes, I'd heard of the gusts up at the Needles - wouldn't want to
have been cycling in that!

Apart from anything else, you'd be in the sea.

lol

dkahn400 wrote on 19/01/2007 13:13 +0100:

Quoted message said:

cupra said:

Ah, yes, I'd heard of the gusts up at the Needles - wouldn't want to have
been cycling in that!

Apart from anything else, you'd be in the sea.

No chance, the wind was onshore! You wouldn't have been able to leave
land however hard you tried ;-)

--
Tony

"...has many omissions and contains much that is apocryphal, or at least
wildly inaccurate..."
Douglas Adams; The Hitchhiker's Guide to the Galaxy

cupra said:

Tony Raven said:

cupra wrote on 18/01/2007 20:21 +0100:

Quoted message said:

Tony Raven wrote:
> POHB wrote on 18/01/2007 16:33 +0100:
>> How come I can cycle into a 20-30 MPH headwind (with stronger
>> gusts) but I can't maintain that speed on the flat on a calm day?
>>
> Try it round here today with gusts nearby of 99mph!

Where on earth are you?!

Isle of Wight

Ah, yes, I'd heard of the gusts up at the Needles - wouldn't want to have
been cycling in that!

I've sailed around the Needles on a 20 foot boat. The tide is very
interesting there too.

Tom Crispin wrote on 19/01/2007 17:06 +0100:

Quoted message said:

I've sailed around the Needles on a 20 foot boat. The tide is very
interesting there too.

That's if you survive the ferries.
http://news.bbc.co.uk/1/hi/england/hampshire/5366434.stm

--
Tony

"...has many omissions and contains much that is apocryphal, or at least
wildly inaccurate..."
Douglas Adams; The Hitchhiker's Guide to the Galaxy