ThinAirDesigns wrote:
@Andy Burns
No, they are claiming they can develop thrust by removing energy from
the wind by slowing it down as it passes through their propeller, the
reaction pushes the vehicle forwards, which spins the wheels, which
spins the propeller ... I think!

Hi Andy,

Actually, the propeller never spins the wheels (it can't -- it's a
propeller and thus doesn't produce an output torque).

Initially the wind merely starts blows the vehicle downwind. Once the
vehicle is moving the wheels provide the input torque to turn the
propeller. The propeller takes wind that was moving at say 10mph
across the ground and pushes back on it until it is only moving say
5mph across the ground. The energy removed from the wind when it is
slowed is the energy powering the vehicle.




Yes. The story is you can, using the prop and the wheels still obtain a
differential velocity to tap energy off, even when travelling at
windspeed. I still feel uneasy about it though.

@dennis@home
If you can do this then you should be able to go out on a
still day, push the cart to create an apparent wind and then
go from that.

You really should read the force/energy analysis -- there is a
paragraph near the end with the calculations showing why your
assertion is not true.

Can you show where those calculations are wrong?

@The Natural Philosopher

I still feel uneasy about it though.

As any good skeptic should. It's a bit of a mind bender that screws
with intuition (as any good brainteaser does).

Stick with it -- there's no magic and no laws are violated. It's a
simple but unusually looking application of long established
principles.

ThinAirDesigns wrote:
@dennis@home
If you can do this then you should be able to go out on a
still day, push the cart to create an apparent wind and then
go from that.

You really should read the force/energy analysis -- there is a
paragraph near the end with the calculations showing why your
assertion is not true.

Can you show where those calculations are wrong?

Dennis cant show any calculations are right or wrong. He is still trying
to use his microscope to count angels on the heads of pins.

On Sep 30, 4:27*am, "dennis@home" wrote:

Yes, but that is not enough, but you jumped on it without actually
understanding what I said or how it works.
Draw a vector diagram and you can work it out for yourself.

I understood exactly what you said. And thanks for the advice, but it
was the vector diagram I drew several years ago that led me to
conceive of the vehicle in question. I later learned that I wasn't
the first to have done so.


Well its been claimed you accelerate the wind in a negative direction using
energy from the vehicle

Never by us.

Let me know when you publish detailed plans and someone duplicates it.

I did so probably a year ago. You can find a set of 3 detailed build
videos on YouTube if you search for "spork33". Several people have
built them and duplicated our results. You can do the same.

On Sep 30, (Alan Braggins) wrote:

My apologies, I misinterpreted your "bull****" comment...

Care to expand on your comment?

JB said it just right - no apologies necessary (except perhaps from
me). I was just being a smart-ass - and giving him the response we
hear 99.927% of the time.

dennis@home wrote:

Have you seen the cr@p in this video?

I can do better than that - I spent several hours with JB making that
video. Welcome to my living room.

dennis@hom also wrote:

The statement that a cart on a treadmill in still air is the same as a
moving cart on road in the wind is just wrong.

Interesting theory. Newton, Galileo, and Einstein make the bold claim
that there is no such thing as a preferred inertial reference frame -
and that no instrument can be built or conceived of that can tell us
whether the air is moving over the surface or the surface is moving
under the air. In fact they tell us that it makes no sense to say
that one or the other is "actually" moving. So you'll have to take it
up with them.

dennis@home wrote:

Any fool can take energy from an electrically powered conveyor belt to move
the opposite way it just depends on friction. The energy comes from the
electric motor.

Really? Any fool? Are you up to that challenge? Let's see you do
that without reproducing something closely akin to our cart.

The claim is you can take energy from the apparent wind and accelerate the
cart into the apparent wind.

Wrong again. You really have to start quoting us rather than simply
telling us (incorrectly) what we claim.

If you can do this then you should be able to go out on a still day, push
the cart to create an apparent wind and then go from that.

Wrong again. It's really probably better if you ask questions rather
than tell us what our device can and can't do - and what you *think*
our claims are.

If you do that then that would be pretty difficult to deny. I won't hold my breath.

I definitely don't recommend holding your breath. I do recommend you
ask some questions and let us explain this. Others here seem to be
getting it pretty well.
:

On Sep 30, 5:53*am, ThinAirDesigns wrote:

Hi Andy,

Actually, the propeller never spins the wheels (it can't -- it's a
propeller and thus doesn't produce an output torque).

You have to go back and read Andy's statement carefully. He got it
exactly right. We're too used to seeing people get it wrong.

ThinAirDesigns wrote:

@Andy Burns
No, they are claiming they can develop thrust by removing energy from
the wind by slowing it down as it passes through their propeller, the
reaction pushes the vehicle forwards, which spins the wheels, which
spins the propeller ... I think!

Actually, the propeller never spins the wheels (it can't -- it's a
propeller and thus doesn't produce an output torque).

I don't think I implied it did, certainly didn't intend to

Initially the wind merely starts blows the vehicle downwind. Once the
vehicle is moving the wheels provide the input torque to turn the
propeller. The propeller takes wind that was moving at say 10mph
across the ground and pushes back on it until it is only moving say
5mph across the ground.

That was was what I'd understood

The energy removed from the wind when it is
slowed is the energy powering the vehicle.

What is the transfer mechanism for that energy propelling (bad word
perhaps) the vehicle?

@Andy Burns

I don't think I implied it did, certainly didn't intend to

My apologies Andy -- Rick is correct in saying that I misread your
statement. Your statement was accurate.

I'll get to the your 'energy transfer' question in a bit when I have
time.

On 30 Sep, 12:24, Rick Cavallaro wrote:
On Sep 30, 3:31*am, "dennis@home" wrote:

This is in the same area as the numpties that think they can run a car on
water by splitting it into hydrogen and burning it by using the "spare"
power in the alternator. You can even see videos of them doing it (but none
without the batteries being connected).

You can see us doing this without batteries attached. *Moreover, we've
posted detailed build videos on YouTube so you can build your own
working model for about $40 and prove it to yourself. *Do the
perpetual motion nuts do that?

How do you think we managed to fool the aero departments at Stanford
and SJSU? *How did we manage to fool the official observers from the
North American Land Sailing Association?

Perhaps it's time you consider that you simply have to try harder to
understand what's being claimed and how it works. *There's no magic
(and no free energy) here.

Have you never heard of the law of conservation of energy?
You are a complete fool or liar.
http://en.wikipedia.org/wiki/Law_of_...tion_of_energy
It takes as much energy to split hydrogen ad oxygen as is released by
combining them. You don't get anything for nothing.

On 30 Sep, 13:30, "dennis@home" wrote:
"Rick Cavallaro" wrote in message

...





On Sep 30, 3:31 am, "dennis@home" wrote:

This is in the same area as the numpties that think they can run a car on
water by splitting it into hydrogen and burning it by using the "spare"
power in the alternator. You can even see videos of them doing it (but
none
without the batteries being connected).

You can see us doing this without batteries attached. *Moreover, we've
posted detailed build videos on YouTube so you can build your own
working model for about $40 and prove it to yourself. *Do the
perpetual motion nuts do that?

How do you think we managed to fool the aero departments at Stanford
and SJSU? *How did we manage to fool the official observers from the
North American Land Sailing Association?

Perhaps it's time you consider that you simply have to try harder to
understand what's being claimed and how it works. *There's no magic
(and no free energy) here.

Have you seen the cr@p in this video?http://www.youtube.com/watch?v=xHsXc...eature=related

The statement that a cart on a treadmill in still air is the same as a
moving cart on road in the wind is just wrong.
Any fool can take energy from an electrically powered conveyor belt to move
the opposite way it just depends on friction. The energy comes from the
electric motor.

The claim is you can take energy from the apparent wind and accelerate the
cart into the apparent wind.
If you can do this then you should be able to go out on a still day, push
the cart to create an apparent wind and then go from that. If you do that
then that would be pretty difficult to deny. I won't hold my breath.- Hide quoted text -

- Show quoted text -

Exactly so.

On Sep 30, 8:32*am, harry wrote:

Have you never heard of the law of conservation of energy?

Indeed I have. Thanks for asking. Does this somehow relate to our
current conversation?

You are a complete fool or liar.

Thanks for your completely unfounded and baseless opinion.

It takes as much energy to split hydrogen ad oxygen as is released by
combining them. *You don't get anything for nothing.

Agreed. Perhaps you aren't aware that we're not splitting hydrogen
and oxygen. This cart is wind powered (dumbass).

@harry

Have you never heard of the law of conservation of energy?

I have.

Can you explain how using the energy harvested from slowing down the
wind violates said law?

JB

So, what we have currently in this exchange:

A: I have asserted that usable energy can be obtained from slowing
down the wind relative to the ground (this isn't exactly a ground
breaking assertion).

So far, no one has even attempted to present any argument against
"A" (other than perhaps something to the effect of 'Oh, no you can't')

B: I have illustrated that regardless of it's speed relative to the
wind, given an input torque a propeller can be used to slow down the
wind relative to the ground (this isn't exactly a ground breaking
assertion).

So far, no one has even attempted to present any argument against
"B" (other than perhaps something to the effect of 'Oh, no you can't')

C: I have provide the simple force and energy calculations to show
that the power available from slowing the wind relative to the ground
is more than enough to power the mechanism (prop) which is slowing the
wind down. (this isn't exactly a ground breaking assertion).

So far, no one has even attempted to present any argument against
"C" (other than perhaps something to the effect of 'Oh, no you can't')

So if:

"A" is true (there is usable power in slowing the wind)
and
"B" is true (a prop can be used to slow the wind)
and
"C" is true (slowing the wind provides enough energy to turn the prop)

where is the violation of natural law?

Rather than some version of "Oh, no you can't", would one of the
critics actually step up and document an actual flaw in "A", "B" or
"C"

"Rick Cavallaro" wrote in message
...
On Sep 30, (Alan Braggins) wrote:

My apologies, I misinterpreted your "bull****" comment...

Care to expand on your comment?

JB said it just right - no apologies necessary (except perhaps from
me). I was just being a smart-ass - and giving him the response we
hear 99.927% of the time.

dennis@home wrote:

Have you seen the cr@p in this video?

I can do better than that - I spent several hours with JB making that
video. Welcome to my living room.

dennis@hom also wrote:

The statement that a cart on a treadmill in still air is the same as a
moving cart on road in the wind is just wrong.

Interesting theory. Newton, Galileo, and Einstein make the bold claim
that there is no such thing as a preferred inertial reference frame -
and that no instrument can be built or conceived of that can tell us
whether the air is moving over the surface or the surface is moving
under the air. In fact they tell us that it makes no sense to say
that one or the other is "actually" moving. So you'll have to take it
up with them.

Well you can hire a wind tunnel with a rolling road built in so that you
could actually simulate what is really happening, I guess nobody told them
that they didn't need to go to that expense and could have just used a
rolling road to do the job.


dennis@home wrote:

Any fool can take energy from an electrically powered conveyor belt to
move
the opposite way it just depends on friction. The energy comes from the
electric motor.

Really? Any fool? Are you up to that challenge? Let's see you do
that without reproducing something closely akin to our cart.

Why would I need to build something different, that is what the cart does, I
don't need to build something else that does.


The claim is you can take energy from the apparent wind and accelerate the
cart into the apparent wind.

Wrong again. You really have to start quoting us rather than simply
telling us (incorrectly) what we claim.

If you can do this then you should be able to go out on a still day, push
the cart to create an apparent wind and then go from that.

Wrong again. It's really probably better if you ask questions rather
than tell us what our device can and can't do - and what you *think*
our claims are.

Your claims are that you can travel down wind at a speed faster than the
wind and extract energy from the vehicle to power a prop while at the same
time taking energy from the wind you are going faster than.
You then quote some total garbage like in that video to justify what you
claim.
I guess we will just have to disagree until you have a proper convincing
explanation.


If you do that then that would be pretty difficult to deny. I won't hold
my breath.

I definitely don't recommend holding your breath. I do recommend you
ask some questions and let us explain this. Others here seem to be
getting it pretty well.

You can fool some of the people all the time, maybe even yourself.
You have convinced yourself that a treadmill duplicates an airflow so
anything is possible.

Anyway you remind me of Bart Kahn and he was a fraud I met in the early
80's, he had a number of companies convinced enough to invest cash when I
had to evaluate his claim. needless to say he didn't get any cash from us.
He also used the same argument that you do "you aren't clever enough to work
out why it works". Its more like you haven't put a convincing case even if
you can convince a small number of others.

On Sep 30, 10:16*am, ThinAirDesigns wrote:

So, what we have currently in this exchange...

You forgot maybe the most important element - the proof by absolute
assertion that we're fools and liars.

dennis@home

Your claims are that you can travel down wind at a speed faster than the
wind and extract energy from the vehicle to power a prop ....

We claim no such thing.

There is no energy extracted from the vehicle during acceleration nor
during steady state operation.

You might want to get our claims straight before attempting to render
judgement.

On Sep 30, 11:05*am, "dennis@home" wrote:

Well you can hire a wind tunnel with a rolling road built in so that you
could actually simulate what is really happening.

Why do you think I need a wind tunnel. We can move the air or the
road. In our treadmill tests we move the road.

Why would I need to build something different, that is what the cart does, I
don't need to build something else that does.

You claim our cart is not able to go downwind faster than the wind
steady-state. So you clearly don't understand what our cart does.

Your claims are that you can travel down wind at a speed faster than the
wind and extract energy from the vehicle...

You're wrong - plain and simple. Don't put words in my mouth. If you
want to say what I claim then QUOTE ME.

I guess we will just have to disagree until you have a proper convincing explanation.

Translation: we'll just have to agree to disagree until I come up with
a way to convince someone that doesn't know the first thing about
physics, and is intent on not learning. Fine - we can agree to
disagree.


You can fool some of the people all the time, maybe even yourself.
You have convinced yourself that a treadmill duplicates an airflow so
anything is possible.

You're an idiot. Sorry - it had to be said.

"you aren't clever enough to work
out why it works". Its more like you haven't put a convincing case even if
you can convince a small number of others.

I'm sorry that you can't or won't follow even the most basic
analysis. Not my problem.

@Dennis@home:

Repeating a suggestion from my previous post:

"Rather than some version of "Oh, no you can't", would one of the
critics actually step up and document an actual flaw in "A", "B" or
"C" "

You know dennis - you look a bit silly simply ranting that we're
liars, fools, and hoaxters without even attempting to tell us
specifically how you believe we violate any law of physics. If there
is a problem with the analysis JB posted point it out. It's about the
simplest derivation you could hope for.

"ThinAirDesigns" wrote in message
...
So, what we have currently in this exchange:

A: I have asserted that usable energy can be obtained from slowing
down the wind relative to the ground (this isn't exactly a ground
breaking assertion).

So far, no one has even attempted to present any argument against
"A" (other than perhaps something to the effect of 'Oh, no you can't')

Perhaps that's because we think its true.
Do you feel we need to argue against the truth?


B: I have illustrated that regardless of it's speed relative to the
wind, given an input torque a propeller can be used to slow down the
wind relative to the ground (this isn't exactly a ground breaking
assertion).

This is also true.


So far, no one has even attempted to present any argument against
"B" (other than perhaps something to the effect of 'Oh, no you can't')

C: I have provide the simple force and energy calculations to show
that the power available from slowing the wind relative to the ground
is more than enough to power the mechanism (prop) which is slowing the
wind down. (this isn't exactly a ground breaking assertion).

So far, no one has even attempted to present any argument against
"C" (other than perhaps something to the effect of 'Oh, no you can't')



So if:

"A" is true (there is usable power in slowing the wind)
and
"B" is true (a prop can be used to slow the wind)
and
"C" is true (slowing the wind provides enough energy to turn the prop)

where is the violation of natural law?

Because you don't do all three.
You are travelling at 2.9 times the speed of the wind.
You claim to slow down the wind.
The only way to slow down the real wind would be for you to push wind back
at 2.9 times the speed you are travelling at.
So you are now going to tell me that the energy needed to get that pushing
back wind up to 2.9 times the real wind is less than the energy you get by
slowing the real wind down.
You do not make any sense with your argument.



Rather than some version of "Oh, no you can't", would one of the
critics actually step up and document an actual flaw in "A", "B" or
"C"

Citing three effects isn't the same as actually using them.

"Rick Cavallaro" wrote in message
...
On Sep 30, 11:05 am, "dennis@home" wrote:

Well you can hire a wind tunnel with a rolling road built in so that you
could actually simulate what is really happening.

Why do you think I need a wind tunnel. We can move the air or the
road. In our treadmill tests we move the road.

Why would I need to build something different, that is what the cart
does, I
don't need to build something else that does.

You claim our cart is not able to go downwind faster than the wind
steady-state. So you clearly don't understand what our cart does.

I understand that it can extract energy from the drive belt to power the
prop so it moves in the opposite direction to the belt.
maybe its you that doesn't understand your cart?


Your claims are that you can travel down wind at a speed faster than the
wind and extract energy from the vehicle...

You're wrong - plain and simple. Don't put words in my mouth. If you
want to say what I claim then QUOTE ME.

You are making claims that aren't true and expecting people to agree.


I guess we will just have to disagree until you have a proper convincing
explanation.

Translation: we'll just have to agree to disagree until I come up with
a way to convince someone that doesn't know the first thing about
physics, and is intent on not learning. Fine - we can agree to
disagree.

You are the one that doesn't know what you are talking about.
the very fact that you think a rolling road is the same as moving air shows
that you don't have a clue.



You can fool some of the people all the time, maybe even yourself.
You have convinced yourself that a treadmill duplicates an airflow so
anything is possible.

You're an idiot. Sorry - it had to be said.

Well I think you are either an idiot or think everyone else is.


"you aren't clever enough to work
out why it works". Its more like you haven't put a convincing case even
if
you can convince a small number of others.

I'm sorry that you can't or won't follow even the most basic
analysis. Not my problem.

The fact that you are wrong is not my problem either.

On 30/09/2010 19:23, Rick Cavallaro wrote:
You know dennis - you look a bit silly simply ranting that we're
liars, fools, and hoaxters without even attempting to tell us
specifically how you believe we violate any law of physics. If there
is a problem with the analysis JB posted point it out. It's about the
simplest derivation you could hope for.

Ignoring Dennis, who delights in proving how wrong he can be on a
regular basis, I have to say I found the explanation of how it works a
bit opaque. I'm pretty sure I've got it, but the text and diagrams
didn't really help that.

And metric just makes things easier :-)

On 30/09/2010 20:58, Clive George wrote:
On 30/09/2010 19:23, Rick Cavallaro wrote:
You know dennis - you look a bit silly simply ranting that we're
liars, fools, and hoaxters without even attempting to tell us
specifically how you believe we violate any law of physics. If there
is a problem with the analysis JB posted point it out. It's about the
simplest derivation you could hope for.

Ignoring Dennis, who delights in proving how wrong he can be on a
regular basis, I have to say I found the explanation of how it works a
bit opaque. I'm pretty sure I've got it, but the text and diagrams
didn't really help that.

It does require a bit of a twist in the way of thinking about it - that
the wheels drive the windmill, not the other way around as you'd expect!


And metric just makes things easier :-)

Hey, they're Americans. They like to make things hard for themselves by
mixing units. Just ask NASA...

Rick, JB, if you want another challenge... there's a bunch of guys over
on uk.rec.sailing who don't believe you either. Which bearing in mind
that most of them have seen fast boats tacking downwind at more than
windspeed is impressive. It's come up before, but never with first hand
experience - and that's why I didn't need persuading. The streamers on
the video I saw persuaded me it was no fake - the effects were too good
for Hollywood!

Andy

"Clive George" wrote in message
o.uk...
On 30/09/2010 19:23, Rick Cavallaro wrote:
You know dennis - you look a bit silly simply ranting that we're
liars, fools, and hoaxters without even attempting to tell us
specifically how you believe we violate any law of physics. If there
is a problem with the analysis JB posted point it out. It's about the
simplest derivation you could hope for.

Ignoring Dennis, who delights in proving how wrong he can be on a regular
basis, I have to say I found the explanation of how it works a bit opaque.
I'm pretty sure I've got it,

You think you got it? and you think I am wrong?
Why don't you explain it then?

On 30/09/2010 21:11, Andy Champ wrote:
On 30/09/2010 20:58, Clive George wrote:
On 30/09/2010 19:23, Rick Cavallaro wrote:
You know dennis - you look a bit silly simply ranting that we're
liars, fools, and hoaxters without even attempting to tell us
specifically how you believe we violate any law of physics. If there
is a problem with the analysis JB posted point it out. It's about the
simplest derivation you could hope for.

Ignoring Dennis, who delights in proving how wrong he can be on a
regular basis, I have to say I found the explanation of how it works a
bit opaque. I'm pretty sure I've got it, but the text and diagrams
didn't really help that.

It does require a bit of a twist in the way of thinking about it - that
the wheels drive the windmill, not the other way around as you'd expect!


And metric just makes things easier :-)

Hey, they're Americans. They like to make things hard for themselves by
mixing units. Just ask NASA...

Rick, JB, if you want another challenge... there's a bunch of guys over
on uk.rec.sailing who don't believe you either. Which bearing in mind
that most of them have seen fast boats tacking downwind at more than
windspeed is impressive. It's come up before, but never with first hand
experience - and that's why I didn't need persuading. The streamers on
the video I saw persuaded me it was no fake - the effects were too good
for Hollywood!

Trouble is it needs the connection to the ground that a boat doesn't
have, so having a sailing background will naturally confuse things.

ThinAirDesigns wrote:

My apologies Andy -- Rick is correct in saying that I misread your
statement. Your statement was accurate.

I'll get to the your 'energy transfer' question in a bit when I have
time.

Just wondering how a multi-blade prop would change the balance of power
required to drive it vs thrust that the slowed air imparts to the craft?

On 30/09/2010 21:15, dennis@home wrote:


"Clive George" wrote in message
o.uk...
On 30/09/2010 19:23, Rick Cavallaro wrote:
You know dennis - you look a bit silly simply ranting that we're
liars, fools, and hoaxters without even attempting to tell us
specifically how you believe we violate any law of physics. If there
is a problem with the analysis JB posted point it out. It's about the
simplest derivation you could hope for.

Ignoring Dennis, who delights in proving how wrong he can be on a
regular basis, I have to say I found the explanation of how it works a
bit opaque. I'm pretty sure I've got it,

You think you got it? and you think I am wrong?
Why don't you explain it then?

The best explanation for me is that there's three things involved, and
hence two relative velocities, which allows us to extract energy.

Let's try a different drive method - not a prop. Instead, we'll have the
road and a very long conveyor belt.

I've got a little car, with 6 wheels - 4 straddling the belt, 2 on the belt.

Can I arrange a drive mechanism such that my little car can go faster
than the conveyor belt? (no engines, stored energy, etc, just simple
mechanical connections)

(actually, this is all quite like the various cotton reel problems
covered in 1st year physics)

Clive George wrote:

Let's try a different drive method - not a prop. Instead, we'll have the
road and a very long conveyor belt.

I've got a little car, with 6 wheels - 4 straddling the belt, 2 on the
belt.

Can I arrange a drive mechanism such that my little car can go faster
than the conveyor belt? (no engines, stored energy, etc, just simple
mechanical connections)

I'm imagining something involving planetary gears, we're getting
dangerously close to Pious territory now ...

On Sep 30, 12:58*pm, Clive George wrote:
Ignoring Dennis, who delights in proving how wrong he can be on a
regular basis, I have to say I found the explanation of how it works a
bit opaque. I'm pretty sure I've got it, but the text and diagrams
didn't really help that.

Clive, there a a BUNCH of ways to describe what's happening here.
We've found that some people respond to one description and think all
others are nonsense, and others find one of the others useful. We'll
be happy to answer your questions and tailor the discussion to help
bring it across. Just let us know what's making sense and what's not
making sense to you. The energy analysis is very compelling to me at
one level, but it's also useful for me to think of each blade of the
propeller as being on a continuous broad reach - spiraling downwind
faster than the wind.

On Sep 30, 1:24*pm, Clive George wrote:

Trouble is it needs the connection to the ground that a boat doesn't
have, so having a sailing background will naturally confuse things.

I disagree. Whether the vehicle is a boat or land vehicle it exploits
the energy available at the wind/surface interface. In the case of a
boat the keel just acts as a wing underwater while the sail acts as a
wing sticking up in the air. We know there are sailboats that can
tack their way downwind much faster than the wind, so all we need to
do is connect two such boats side-by-side with a long telescoping
pole. Now they can go downwind staying on alternate tacks and the
whole contraption constitutes a "boat" that goes directly downwind
faster than the wind.

On Sep 30, 1:31*pm, Clive George wrote:

I've got a little car, with 6 wheels - 4 straddling the belt, 2 on the belt.

Can I arrange a drive mechanism such that my little car can go faster
than the conveyor belt? (no engines, stored energy, etc, just simple
mechanical connections)

(actually, this is all quite like the various cotton reel problems
covered in 1st year physics)

Spool video:
http://www.youtube.com/watch?v=E7vcQcIaWSQ

Under the ruler faster than the ruler:
http://www.youtube.com/watch?v=k-trDF8Yldc

Equivalence of reference frames:
http://www.youtube.com/watch?v=9Yt4zxYuPzI

On 30/09/2010 21:37, Rick Cavallaro wrote:
On Sep 30, 12:58 pm, Clive George wrote:
Ignoring Dennis, who delights in proving how wrong he can be on a
regular basis, I have to say I found the explanation of how it works a
bit opaque. I'm pretty sure I've got it, but the text and diagrams
didn't really help that.

Clive, there a a BUNCH of ways to describe what's happening here.
We've found that some people respond to one description and think all
others are nonsense, and others find one of the others useful. We'll
be happy to answer your questions and tailor the discussion to help
bring it across. Just let us know what's making sense and what's not
making sense to you. The energy analysis is very compelling to me at
one level, but it's also useful for me to think of each blade of the
propeller as being on a continuous broad reach - spiraling downwind
faster than the wind.

I prefer working with the forces rather energy - I think introducing
time into it unnecessarily complicates things.

Playing with the dynamics of the propellor also doesn't help me - see
how I've started my own explanation. The propellor comes later.

On Sep 30, 1:28*pm, Andy Burns wrote:

Just wondering how a multi-blade prop would change the balance of power
required to drive it vs thrust that the slowed air imparts to the craft?

Another counterintuitive aspect to this thing is that the propeller
acts just like any other propeller. It's tempting to think of the
wind pushing on a cushion of air being produced by the prop, but this
isn't the case. The propeller simply pulls its way through a (moving)
mass of air in exactly the same way an aircraft prop does. There are
trade-offs with number of blades, pitch, diameter, etc. Each affects
prop efficiency and practical engineering aspects (like having a thick
enough camber to contain the spar).

On Sep 30, 1:46*pm, Clive George wrote:
On 30/09/2010 21:37, Rick Cavallaro wrote:

On Sep 30, 12:58 pm, Clive George wrote:
Ignoring Dennis, who delights in proving how wrong he can be on a
regular basis, I have to say I found the explanation of how it works a
bit opaque. I'm pretty sure I've got it, but the text and diagrams
didn't really help that.

Clive, there a a BUNCH of ways to describe what's happening here.
We've found that some people respond to one description and think all
others are nonsense, and others find one of the others useful. *We'll
be happy to answer your questions and tailor the discussion to help
bring it across. *Just let us know what's making sense and what's not
making sense to you. *The energy analysis is very compelling to me at
one level, but it's also useful for me to think of each blade of the
propeller as being on a continuous broad reach - spiraling downwind
faster than the wind.

I prefer working with the forces rather energy - I think introducing
time into it unnecessarily complicates things.

Playing with the dynamics of the propellor also doesn't help me - see
how I've started my own explanation. The propellor comes later.

If you prefer the forces approach I can post a vector diagram that
shows how an ice boat can achieve a downwind VMG (velocity made good)
faster than wind speed on a broad reach. This works strictly on lift
and drag of the sail and keel/blades. From there you can imagine the
two ice-boats side-by-side connected by a telescoping pole, or you can
picture two ice boats circling their way down a cylindrical earth on a
continuous broad reach. In this case their sails are doing exactly
the same job as our prop - and in the same manner.

On 30/09/2010 21:43, Rick Cavallaro wrote:
On Sep 30, 1:31 pm, Clive George wrote:

I've got a little car, with 6 wheels - 4 straddling the belt, 2 on the belt.

Can I arrange a drive mechanism such that my little car can go faster
than the conveyor belt? (no engines, stored energy, etc, just simple
mechanical connections)

(actually, this is all quite like the various cotton reel problems
covered in 1st year physics)

Spool video:
http://www.youtube.com/watch?v=E7vcQcIaWSQ

Under the ruler faster than the ruler:
http://www.youtube.com/watch?v=k-trDF8Yldc

Equivalence of reference frames:
http://www.youtube.com/watch?v=9Yt4zxYuPzI

Glad to see I'm having the same thoughts :-)

On 30/09/2010 21:50, Rick Cavallaro wrote:
On Sep 30, 1:46 pm, Clive wrote:
On 30/09/2010 21:37, Rick Cavallaro wrote:

On Sep 30, 12:58 pm, Clive George wrote:
Ignoring Dennis, who delights in proving how wrong he can be on a
regular basis, I have to say I found the explanation of how it works a
bit opaque. I'm pretty sure I've got it, but the text and diagrams
didn't really help that.

Clive, there a a BUNCH of ways to describe what's happening here.
We've found that some people respond to one description and think all
others are nonsense, and others find one of the others useful. We'll
be happy to answer your questions and tailor the discussion to help
bring it across. Just let us know what's making sense and what's not
making sense to you. The energy analysis is very compelling to me at
one level, but it's also useful for me to think of each blade of the
propeller as being on a continuous broad reach - spiraling downwind
faster than the wind.

I prefer working with the forces rather energy - I think introducing
time into it unnecessarily complicates things.

Playing with the dynamics of the propellor also doesn't help me - see
how I've started my own explanation. The propellor comes later.

If you prefer the forces approach I can post a vector diagram that
shows how an ice boat can achieve a downwind VMG (velocity made good)
faster than wind speed on a broad reach. This works strictly on lift
and drag of the sail and keel/blades. From there you can imagine the
two ice-boats side-by-side connected by a telescoping pole, or you can
picture two ice boats circling their way down a cylindrical earth on a
continuous broad reach. In this case their sails are doing exactly
the same job as our prop - and in the same manner.

Go for it.

On Sep 30, 1:55*pm, Clive George wrote:

Go for it.

Here's a simple vector analysis:

https://rcpt.yousendit.com/958723733...d7d26acf72285e

And here's the explanation that goes with it:

Here is the vector diagram for an ice-boat that’s maintaining a course
such that its downwind velocity component is faster than the wind.
I've assumed a boat going 45 degrees downwind at a speed of twice the
wind speed. The ticket is to then compute the necessary L/D of the
sail and keel to make this possible (this would have the boat making a
downwind velocity component of 1.414 times the wind-speed).

Given the wind velocity and the boat velocity, we can easily compute
the apparent wind over the sail. From this we see the direction of
lift and drag on the sail. What we need to do to make sure this
sailing configuration is possible is to insure that "alpha" is small
enough so that the resultant force has a forward pointing component
(relative to the boat). In this case alpha would have to be 45 - 16.3
degrees or 28.7 degrees (or less). That relates to a sail whose L/D is
1.83. Obviously this is easily achievable. However, I've assumed a
keel with infinite L/D in this case. The drawing gets a little more
cluttered if we include the keel's L/D. So I'll try to describe it in
words. I'm going to assume an L/D of 10:1 for the keel (easily done
with an ice-boat). This will trim 5.7 degrees off of my 28.7 degree
budget. That leaves me with an allowable 23 degrees(L/D = 2.35:1) to
achieve this configuration. So with a keel that has a 10:1 L/D and a
sail/boat that has an overall 2.35:1 or better L/D this configuration
can be achieved (we can achieve a downwind component about 40 percent
faster than the wind speed).

"Rick Cavallaro" wrote in message
...
On Sep 30, 1:31 pm, Clive George wrote:

I've got a little car, with 6 wheels - 4 straddling the belt, 2 on the
belt.

Can I arrange a drive mechanism such that my little car can go faster
than the conveyor belt? (no engines, stored energy, etc, just simple
mechanical connections)

(actually, this is all quite like the various cotton reel problems
covered in 1st year physics)

Spool video:
http://www.youtube.com/watch?v=E7vcQcIaWSQ

Under the ruler faster than the ruler:
http://www.youtube.com/watch?v=k-trDF8Yldc

Equivalence of reference frames:
http://www.youtube.com/watch?v=9Yt4zxYuPzI



What is that supposed to demonstrate?
that if you pull the centre along it goes faster because of the gearing
between the centre and the edge?
that's all it does show.

On Sep 30, 2:43*pm, "dennis@home" wrote:

What is that supposed to demonstrate?

I'll let one of the locals explain it to you.