Henri Wilson wrote:
On Wed, 12 Jan 2005 10:13:28 +0100, "Paul B. Andersen"
wrote:


Henri Wilson wrote:

I was once laughed at for proposing a vehicle that used a windmill to drive its
wheels.

Something like this?
http://www.dcss.org/bauer_cart.jpg


Yes.
Gord! He stole my idea!

This picture was taken sometimes in the 1950s.
But I cheated.
This cart isn't going upwind.
It is going downwind faster than the wind. :-)
See below.

My windmill was mounted on a crown wheel and pinion so it could rotate.


I claimed it could run directly into the wind. Everyobody else said it
couldn't.

Everybody else? So who did you ask?
You must have pretty dumb friends. :-)


Actually they were fellow scientists, but the type who would accept einsteinian
relativity, I'm afraid.

I have a hard time believing that a physicist
would claim it can't be done.
What sociologists might think is of little interest. :-)

Guess what? It did. What is more, as it built up speed, so did the
windmill accelerate.

What's more? :-)
Pretty obvious, isn't it?


What is the theoretical limit speed of this device. Is it infinity?

It's c.
As long as the wind speed is 0, that is.


Mine went c


Incidentally, I also made a model catamaran using the same principle. A
windmill type arrangement on top drove the propeller through a gear
arrangement.

Like this?
http://home.planet.nl/~albert.goudriaan/


Yes. The crew has to keep its head down.

I also read about some other fellow who used the principle on a rather large
yacht. He claimed only about four knots in a moderate breeze though, which is
not very good.

But it is about as well as a normal yacht will do, tacking at 6 knots.
Which sounds reasonable.
It's hard to make a windmill - screw more efficient than a sail - keel.
(A tacking boat uses exactly the same principle, only the sail
and keel are going back and forth in stead of in circles.)

I made the first one well before that. I always suspected that some of my
colleagues were spies.



Do you think it sailed straight into the wind, Ghost?

No reason why it shouldn't.

But did you have a point?
You don't actually think that this idea
is new in any way, do you?
http://liesl.sharecom.ca/bewick/vignettes/9042117.html


Yes. The inventor was probably a distant ancestor of mine.

Actually, there is no indication in the painting that the windmill drove a
propellor. It may have just worked on the autogyro principle.

If you look carefully, you will see that it has paddle wheels.


A challenge:
Can you make a vehicle going downwind faster than the wind?


That is indeed a problem.

My windmill was designed so it could be turned into an ordinary sail for going
downwind. The blades could be pulled together.

The fact that such a boat can sail faster into the wind than with it seems to
violate all principles.

Actually that's wasn't my first reaction.
That may be because I have been sailing boats
in a headwind all my life. :-)

I find the idea of going downwind faster than
the wind much more counter intuitive.
But it IS possible to make such a vehicle.
Let's stay on land and make a cart.
A weel on the ground is driving the propeller,
which drives the cart downwind faster than the wind.
Your first reaction is probably that this is
a perpetum mobile. (Mine was!)
And it would be - if there were no wind.
But if there is a wind, it is perfectly possible.

Let's analyze what's happenning in the ground frame.
The propeller is blowing the air in the opposite direction
of the the wind. So even if the cart is going faster than
the wind, it will slow the wind air flow. That means that kinetic
energy is taken out of the wind, and is transferred to the cart.
No perpetum mobile.
And there is in principle no limit to how fast it can go.
(But the energy lost to drag will of course give a practical
limit.)

And as I said above, Bauer made this vehicle in the 1950s.
http://www.dcss.org/bauer_cart.jpg

I am not sure if the components (air propeller - water impeller)
can be made efficient enough and the drag low enough to work in a boat.


I have noticed here that, strangely, migrating birds appear to prefer a
headwind to a tail wind.
I cannot see any connection, though, unless they can make better use of
turbulence that way..

The principle we have discussed only works for vehicles
at the interface between two relatively moving media.
They must "have a grip on" both media.

Paul

robert j. kolker wrote:


Paul B. Andersen wrote:

A challenge:
Can you make a vehicle going downwind faster than the wind?


Yes. Turn around and tack. Ice boats routinely go 60 mph close hauled to
a 40 mph wind.

Bob Kolker

Right.
But I was actually thinking of a vehicle going
directly downwind faster than the wind,
An ice boat will indeed be able to go with
a downwind velocity component faster than the wind,
which proves that the principle is possible.

See my response to Henri.

Paul

On Thu, 13 Jan 2005 15:43:33 +0100, "Paul B. Andersen"
wrote:

Henri Wilson wrote:
On Wed, 12 Jan 2005 10:13:28 +0100, "Paul B. Andersen"
wrote:


Henri Wilson wrote:

I was once laughed at for proposing a vehicle that used a windmill to drive its
wheels.

Something like this?
http://www.dcss.org/bauer_cart.jpg


Yes.
Gord! He stole my idea!

This picture was taken sometimes in the 1950s.
But I cheated.
This cart isn't going upwind.
It is going downwind faster than the wind. :-)
See below.

Hmm!


My windmill was mounted on a crown wheel and pinion so it could rotate.


I claimed it could run directly into the wind. Everyobody else said it
couldn't.

Everybody else? So who did you ask?
You must have pretty dumb friends. :-)


Actually they were fellow scientists, but the type who would accept einsteinian
relativity, I'm afraid.

I have a hard time believing that a physicist
would claim it can't be done.
What sociologists might think is of little interest. :-)

They were all physicists. They didn't exactly say it wouldn't work. They didn't
know.


Like this?
http://home.planet.nl/~albert.goudriaan/


Yes. The crew has to keep its head down.

I also read about some other fellow who used the principle on a rather large
yacht. He claimed only about four knots in a moderate breeze though, which is
not very good.

But it is about as well as a normal yacht will do, tacking at 6 knots.
Which sounds reasonable.

Fair.
The normal yacht will probably go faster cross wind though.

It's hard to make a windmill - screw more efficient than a sail - keel.
(A tacking boat uses exactly the same principle, only the sail
and keel are going back and forth in stead of in circles.)

I have a better idea for the windmill than present conventional ones. I will
make it one day. It would also work on wind power devices. No more bird kill
either.


I made the first one well before that. I always suspected that some of my
colleagues were spies.



Do you think it sailed straight into the wind, Ghost?

No reason why it shouldn't.

But did you have a point?
You don't actually think that this idea
is new in any way, do you?
http://liesl.sharecom.ca/bewick/vignettes/9042117.html


Yes. The inventor was probably a distant ancestor of mine.

Actually, there is no indication in the painting that the windmill drove a
propellor. It may have just worked on the autogyro principle.

If you look carefully, you will see that it has paddle wheels.

Oh right.

I thought is had an outboard motor on the back



A challenge:
Can you make a vehicle going downwind faster than the wind?


That is indeed a problem.

My windmill was designed so it could be turned into an ordinary sail for going
downwind. The blades could be pulled together.

The fact that such a boat can sail faster into the wind than with it seems to
violate all principles.

Actually that's wasn't my first reaction.
That may be because I have been sailing boats
in a headwind all my life. :-)

I find the idea of going downwind faster than
the wind much more counter intuitive.
But it IS possible to make such a vehicle.

No it isn't.
When the vehicle reaches exactly wind speed, no further energy can be
transferred to it. The windmill will be still. So it can never pass through
that barrier.


Let's stay on land and make a cart.
A weel on the ground is driving the propeller,
which drives the cart downwind faster than the wind.
Your first reaction is probably that this is
a perpetum mobile. (Mine was!)
And it would be - if there were no wind.
But if there is a wind, it is perfectly possible.

Let's analyze what's happenning in the ground frame.
The propeller is blowing the air in the opposite direction
of the the wind. So even if the cart is going faster than
the wind, it will slow the wind air flow. That means that kinetic
energy is taken out of the wind, and is transferred to the cart.
No perpetum mobile.
And there is in principle no limit to how fast it can go.
(But the energy lost to drag will of course give a practical
limit.)

I know what you are saying.

It is wrong.

If the vehicle is moving faster than the wind and the gearing is not reversed
then the windmill pumps the wind FORWARD (not backward into the wind) faster
than it is already moving. The windmill accelerates the wind and the vehicle
decelerates back to windspeed.

If the gearing IS reversed so the vehicle's movement blows air backwards, then
you might achieve something.


And as I said above, Bauer made this vehicle in the 1950s.
http://www.dcss.org/bauer_cart.jpg

I am not sure if the components (air propeller - water impeller)
can be made efficient enough and the drag low enough to work in a boat.

You still have to get through the zero energy barrier.



I have noticed here that, strangely, migrating birds appear to prefer a
headwind to a tail wind.
I cannot see any connection, though, unless they can make better use of
turbulence that way..

The principle we have discussed only works for vehicles
at the interface between two relatively moving media.
They must "have a grip on" both media.

Yes. .but gliders seem to work well in any direction as long as updrafts are
present.
Maybe the migrating birds have to depart on certain days...the moon maybe.


Paul


HW.
www.users.bigpond.com/hewn/index.htm

"If it's repeated often enough they'll eventually believe it" __Albert Bush

Henri Wilson wrote:
On Thu, 13 Jan 2005 15:43:33 +0100, "Paul B. Andersen"
wrote:


Henri Wilson wrote:

On Wed, 12 Jan 2005 10:13:28 +0100, "Paul B. Andersen"
wrote:

I find the idea of going downwind faster than
the wind much more counter intuitive.
But it IS possible to make such a vehicle.


No it isn't.
When the vehicle reaches exactly wind speed, no further energy can be
transferred to it. The windmill will be still. So it can never pass through
that barrier.

No. You are wrong. Think again.

Let's stay on land and make a cart.
A weel on the ground is driving the propeller,
which drives the cart downwind faster than the wind.
Your first reaction is probably that this is
a perpetum mobile. (Mine was!)
And it would be - if there were no wind.
But if there is a wind, it is perfectly possible.

Let's analyze what's happenning in the ground frame.
The propeller is blowing the air in the opposite direction
of the the wind. So even if the cart is going faster than
the wind, it will slow the wind air flow. That means that kinetic
energy is taken out of the wind, and is transferred to the cart.
No perpetum mobile.
And there is in principle no limit to how fast it can go.
(But the energy lost to drag will of course give a practical
limit.)


I know what you are saying.

It is wrong.

If the vehicle is moving faster than the wind and the gearing is not reversed
then the windmill pumps the wind FORWARD (not backward into the wind) faster
than it is already moving. The windmill accelerates the wind and the vehicle
decelerates back to windspeed.

If the gearing IS reversed so the vehicle's movement blows air backwards, then
you might achieve something.

I think you should think again, because you are wrong.

It is interesting to note that a "downwind vehicle"
and an "upwind vehicle" are of exactly the same basic
design. And they are in principle symmetrical.
That is, your upwind vehicle will go upwind even if you
turn it with its backside to the wind. (If we assume
that the propeller has a symmetric profile and works
equally well in both directions.)
I think the difference between the "upwind vehicle"
and "downwind vehicle" is only the pitch of the propeller
(and maybe the gearing ratio, which is related).

I will try to elaborate on this.

Let's start with a propeller with an infinite pitch,
that is, the propeller blades are fore and aft.
When the vehicle is stationary, nothing happens.
There is no lift and no drag (ideally) on the propeller
blades.
Now we give the blades a small angle from fore-and aft.
(That is, the pitch is very high, but not infinite).
Now there will be a torque on the propeller from the wind.
The propeller will have a high torque, and low drag.
The force on the wheel will be higher than the drag,
and the vehicle will move upwind.

Now let the pitch be zero, that is, the propeller blades
are transverse.
When the vehicle is stationary, there will be a high
drag on the propeller, and no torque.
The vehicle will move downwind, and the propeller
will turn. But it will never go faster than the wind.
Now we let the propeller have a small pitch.
When the vehicle is stationary, the propeller blades will
be stalled, the drag is high and the torque trying to move
the vehicle upwind will be too small to overcome the drag.
The vehicle will move downwind. Now the propeller will turn,
and drive the air backwards, that is in the opposite direction
of the wind. The vehicle will move faster downwind.
There will of course be a torque on the propeller which
will make an upwind torque (braking torque) on the wheel,
but due to the small pitch this will not be big enough
to overcome the downwind pull from the propeller.
The vehicle may now move downwind faster than wind.

There will obviously be a pitch between these extremes
which will make the vehicle not move at all.

I think it would be desirable to be able to adjust
the pitch to the speed and the strength of the wind.
I am pretty sure this can be done on Bauer's cart,
notice the small wheels in front of the propeller:
http://www.dcss.org/bauer_cart.jpg

Paul

On Sun, 16 Jan 2005 21:49:26 +0100, "Paul B. Andersen"
wrote:

Henri Wilson wrote:
On Thu, 13 Jan 2005 15:43:33 +0100, "Paul B. Andersen"
wrote:


Henri Wilson wrote:

On Wed, 12 Jan 2005 10:13:28 +0100, "Paul B. Andersen"
wrote:

I find the idea of going downwind faster than
the wind much more counter intuitive.
But it IS possible to make such a vehicle.


No it isn't.
When the vehicle reaches exactly wind speed, no further energy can be
transferred to it. The windmill will be still. So it can never pass through
that barrier.

No. You are wrong. Think again.

Yes. OK It will never reach wind speed because in that condition, the windmill
would NOT be rotating but the propeller WOULD BE.

The propeller can never drive the windmill because the gearing direction is
dependent on the density and viscosity.


Let's stay on land and make a cart.
A weel on the ground is driving the propeller,
which drives the cart downwind faster than the wind.
Your first reaction is probably that this is
a perpetum mobile. (Mine was!)
And it would be - if there were no wind.
But if there is a wind, it is perfectly possible.

Let's analyze what's happenning in the ground frame.
The propeller is blowing the air in the opposite direction
of the the wind. So even if the cart is going faster than
the wind, it will slow the wind air flow. That means that kinetic
energy is taken out of the wind, and is transferred to the cart.
No perpetum mobile.
And there is in principle no limit to how fast it can go.
(But the energy lost to drag will of course give a practical
limit.)


I know what you are saying.

It is wrong.

If the vehicle is moving faster than the wind and the gearing is not reversed
then the windmill pumps the wind FORWARD (not backward into the wind) faster
than it is already moving. The windmill accelerates the wind and the vehicle
decelerates back to windspeed.

If the gearing IS reversed so the vehicle's movement blows air backwards, then
you might achieve something.

I think you should think again, because you are wrong.

It is interesting to note that a "downwind vehicle"
and an "upwind vehicle" are of exactly the same basic
design. And they are in principle symmetrical.
That is, your upwind vehicle will go upwind even if you
turn it with its backside to the wind. (If we assume
that the propeller has a symmetric profile and works
equally well in both directions.)
I think the difference between the "upwind vehicle"
and "downwind vehicle" is only the pitch of the propeller
(and maybe the gearing ratio, which is related).

I will try to elaborate on this.

Let's start with a propeller with an infinite pitch,
that is, the propeller blades are fore and aft.
When the vehicle is stationary, nothing happens.
There is no lift and no drag (ideally) on the propeller
blades.
Now we give the blades a small angle from fore-and aft.
(That is, the pitch is very high, but not infinite).
Now there will be a torque on the propeller from the wind.
The propeller will have a high torque, and low drag.
The force on the wheel will be higher than the drag,
and the vehicle will move upwind.

Now let the pitch be zero, that is, the propeller blades
are transverse.
When the vehicle is stationary, there will be a high
drag on the propeller, and no torque.
The vehicle will move downwind, and the propeller
will turn. But it will never go faster than the wind.
Now we let the propeller have a small pitch.
When the vehicle is stationary, the propeller blades will
be stalled, the drag is high and the torque trying to move
the vehicle upwind will be too small to overcome the drag.
The vehicle will move downwind. Now the propeller will turn,
and drive the air backwards, that is in the opposite direction
of the wind. The vehicle will move faster downwind.
There will of course be a torque on the propeller which
will make an upwind torque (braking torque) on the wheel,
but due to the small pitch this will not be big enough
to overcome the downwind pull from the propeller.
The vehicle may now move downwind faster than wind.

There will obviously be a pitch between these extremes
which will make the vehicle not move at all.

Ah yes, by adjusting the pitch this can probably be achieved... on land anyway.

Not sure about water though. I don't think it would work unless the propeller
area relative to that of the windmill could be adjusted. Even then, the gain
would not be great because the windmill would be too small to have much effect.


I think it would be desirable to be able to adjust
the pitch to the speed and the strength of the wind.
I am pretty sure this can be done on Bauer's cart,
notice the small wheels in front of the propeller:
http://www.dcss.org/bauer_cart.jpg

You could be right there.


Paul


HW.
www.users.bigpond.com/hewn/index.htm

"If it's repeated often enough they'll eventually believe it" __Albert Bush