OT: Can a wind powered land craft go faster than a tail wind speed?...

[Rick C]

I say yes. I haven\'t watched the video, but looking at the contraption and seeing how it would work says to me that it can indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a solar wind powered craft. They talked about the high speeds they could achieve as if they were tacking or something, but unless they had invented an æther rudder, they were smoking wacky weed.

--

Rick C.

- Get 1,000 miles of free Supercharging
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[server]

Rick C <gnuarm.deletethisbit@gmail.com> wrote in news:27601b00-e707-
476b-a61a-1e1550b9f012n@googlegroups.com:

> I say yes.

Only if the operator holds his tongue a certain way.

Or do the test down at \"The Racetrack\" in Death Valley National Park.

The surface winds push 700 Lb stones around like heavy ice skaters.

Slip Slidin\' Away...

It\'s just a tack to the left...

And then a tack to the riiiight!

With your hands on your hips...
You bring your knees in tight...

Let\'s do the tail wind again!

(that didn\'t sound right)

 

[bitrex]

On 12/20/2021 8:44 PM, Rick C wrote:

I say yes. I haven\'t watched the video, but looking at the contraption and seeing how it would work says to me that it can indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a solar wind powered craft. They talked about the high speeds they could achieve as if they were tacking or something, but unless they had invented an æther rudder, they were smoking wacky weed.

Does conservation of energy hold OK in the proposed contraption? I don\'t
think the energy available in a tailwind somehow becomes zero when your
speed >= tailwind speed it sounds like an extraction problem, not an
availability problem.

 

[legg]

On Mon, 20 Dec 2021 19:14:55 -0800 (PST), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>long thread about it here, https://www.eevblog.com/forum/chat/mess-with-your-minds-a-wind-powered-craft-going-faster-than-a-tail-wind-speed/

The sailing analogy is more than apt, considering that
by tacking, a sailboat moves into the wind\'s direction.

The sail would still work, if rotating on it\'s average
plane. Converting this rotation through a gearbox
is going to add complexity to a relatively handsome
physical exchange, simply to avoid the \'tack\'.

RL

 

[whit3rd]

On Monday, December 20, 2021 at 5:44:48 PM UTC-8, gnuarm.del...@gmail.com wrote:
> I say yes. I haven\'t watched the video, but ...

Oh, I can imagine doing it; just hold a balsa toy plane backward in the wind to wind its propellor
up and twist that rubber band tight... then aim it downwind and let it fly.

Wind powered? check. Airspeed pius windspeed greater than windspeed? check.

 

[Rick C]

On Tuesday, December 21, 2021 at 1:04:11 AM UTC-4, whit3rd wrote:

On Monday, December 20, 2021 at 5:44:48 PM UTC-8, gnuarm.del...@gmail.com wrote:
I say yes. I haven\'t watched the video, but ...

Oh, I can imagine doing it; just hold a balsa toy plane backward in the wind to wind its propellor
up and twist that rubber band tight... then aim it downwind and let it fly.

Wind powered? check. Airspeed pius windspeed greater than windspeed? check.

That is very disingenuous. The time while you are holding the plane is simply storing energy. That energy runs out and the plane no longer flies faster than the wind.

The guy said something near the end that makes it work for me. When the car is moving at the wind speed the prop is pushing the car still but the wheels are resisting. The reason why the prop can overcome the wheels is because the ground speed is more than the air speed. So a smaller force on the wheels can create a larger force through the prop from essentially the gearing and prop pitch. The power is constant through the gearing, so the prop can create more force at a slower speed.

We all remember that acceleration is determined by the force, not the power, right?

Interesting that this can be done with boats on the water where the keel provides resistance to allow the boat to travel at an angle to the wind and so faster. This can be done in a car where the wheels contact with the ground can provide the force to make it run faster than the wind. But you can\'t do this in the air at all. That would be a neat trick to figure out how to do it in the air alone!

--

Rick C.

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[John Robertson]

On 2021/12/20 5:44 p.m., Rick C wrote:

I say yes. I haven\'t watched the video, but looking at the contraption and seeing how it would work says to me that it can indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a solar wind powered craft. They talked about the high speeds they could achieve as if they were tacking or something, but unless they had invented an æther rudder, they were smoking wacky weed.

I would trust this more if the panels on the vehicle were clear. Isn\'t
it possible to hide batteries and electric motors?

Looking at how the propeller is turning it isn\'t turning as if it is
being pushed by the wind from the rear - it would turn in reverse then.
Based on what I see, the prop is turning the wrong way for the apparent
visible blade pitch and a rear source of energy (wind).

Looks like a trick to me. Was this filmed on April 1?

John

 

[John Robertson]

On 2021/12/20 10:32 p.m., John Robertson wrote:

On 2021/12/20 5:44 p.m., Rick C wrote:
I say yes.  I haven\'t watched the video, but looking at the
contraption and seeing how it would work says to me that it can indeed
go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a
solar wind powered craft.  They talked about the high speeds they
could achieve as if they were tacking or something, but unless they
had invented an æther rudder, they were smoking wacky weed.


I would trust this more if the panels on the vehicle were clear. Isn\'t
it possible to hide batteries and electric motors?

Looking at how the propeller is turning it isn\'t turning as if it is
being pushed by the wind from the rear - it would turn in reverse then.
Based on what I see, the prop is turning the wrong way for the apparent
visible blade pitch and a rear source of energy (wind).

Looks like a trick to me. Was this filmed on April 1?

John

James Randi (the magician) used to say that scientists (and possibly
engineers) were easy to fool because they assumed the equipment wasn\'t
cheating...

https://www.youtube.com/watch?v=SbwWL5ezA4g

John :-#)#

 

[Rick C]

On Tuesday, December 21, 2021 at 2:32:17 AM UTC-4, John Robertson wrote:

On 2021/12/20 5:44 p.m., Rick C wrote:
I say yes. I haven\'t watched the video, but looking at the contraption and seeing how it would work says to me that it can indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a solar wind powered craft. They talked about the high speeds they could achieve as if they were tacking or something, but unless they had invented an æther rudder, they were smoking wacky weed.

I would trust this more if the panels on the vehicle were clear. Isn\'t
it possible to hide batteries and electric motors?

Looking at how the propeller is turning it isn\'t turning as if it is
being pushed by the wind from the rear - it would turn in reverse then.
Based on what I see, the prop is turning the wrong way for the apparent
visible blade pitch and a rear source of energy (wind).

Looks like a trick to me. Was this filmed on April 1?

The propeller doesn\'t look like the wind is turning it because the wind isn\'t turning it. The wheels turn the prop! That\'s the whole point. As the wind starts pushing, the prop is more of a kite than a prop. As the car moves, the wheels turn the prop faster so it is pulling the car in the direction it is already moving. As the car speeds up the propeller spins faster and pushes the car harder. By the time the car is matching the wind speed, the prop is pushing fairly hard and the car will continue to speed up.

I think it is funny that you suspect batteries in the body.

I\'m really impressed anyone would actually build this.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

 

[Rick C]

On Tuesday, December 21, 2021 at 2:35:29 AM UTC-4, John Robertson wrote:

On 2021/12/20 10:32 p.m., John Robertson wrote:

On 2021/12/20 5:44 p.m., Rick C wrote:
I say yes. I haven\'t watched the video, but looking at the
contraption and seeing how it would work says to me that it can indeed
go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a
solar wind powered craft. They talked about the high speeds they
could achieve as if they were tacking or something, but unless they
had invented an æther rudder, they were smoking wacky weed.


I would trust this more if the panels on the vehicle were clear. Isn\'t
it possible to hide batteries and electric motors?

Looking at how the propeller is turning it isn\'t turning as if it is
being pushed by the wind from the rear - it would turn in reverse then.
Based on what I see, the prop is turning the wrong way for the apparent
visible blade pitch and a rear source of energy (wind).

Looks like a trick to me. Was this filmed on April 1?

John
James Randi (the magician) used to say that scientists (and possibly
engineers) were easy to fool because they assumed the equipment wasn\'t
cheating...

https://www.youtube.com/watch?v=SbwWL5ezA4g

In this case there is also the fact that the idea actually makes sense. Some people can\'t see it, but it\'s as real as LENR! No, wait...

Ecat SKLep https://e-catworld.com/

Wow! That guy is still raking it in with his frauds.

--

Rick C.

+- Get 1,000 miles of free Supercharging
+- Tesla referral code - https://ts.la/richard11209

 

[David Brown]

On 21/12/2021 02:44, Rick C wrote:

I say yes. I haven\'t watched the video, but looking at the
contraption and seeing how it would work says to me that it can
indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a
solar wind powered craft. They talked about the high speeds they
could achieve as if they were tacking or something, but unless they
had invented an æther rudder, they were smoking wacky weed.

I believe the force of the wind on a propeller works in much the same
way as on the sail of a boat that is tacking. If that is correct, a
propeller based car can go faster than the wind, precisely because it
/is/ tacking - even when the car is going in a straight line.

It is also possible for a propeller powered car to run directly into the
wind.

 

[Rick C]

On Tuesday, December 21, 2021 at 5:57:31 AM UTC-4, David Brown wrote:

On 21/12/2021 02:44, Rick C wrote:
I say yes. I haven\'t watched the video, but looking at the
contraption and seeing how it would work says to me that it can
indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a
solar wind powered craft. They talked about the high speeds they
could achieve as if they were tacking or something, but unless they
had invented an æther rudder, they were smoking wacky weed.

I believe the force of the wind on a propeller works in much the same
way as on the sail of a boat that is tacking. If that is correct, a
propeller based car can go faster than the wind, precisely because it
/is/ tacking - even when the car is going in a straight line.

It is also possible for a propeller powered car to run directly into the
wind.

You might actually give that one a bit of thought. Look at the two cars and consider the detailed forces and how they are generated. I think you will find it\'s the same car and always goes downwind, just with more or less efficiency, i.e. forwards or backwards.

--

Rick C.

++ Get 1,000 miles of free Supercharging
++ Tesla referral code - https://ts.la/richard11209

 

[John Larkin]

On Mon, 20 Dec 2021 22:32:07 -0800, John Robertson <spam@flippers.com>
wrote:

On 2021/12/20 5:44 p.m., Rick C wrote:
I say yes. I haven\'t watched the video, but looking at the contraption and seeing how it would work says to me that it can indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a solar wind powered craft. They talked about the high speeds they could achieve as if they were tacking or something, but unless they had invented an æther rudder, they were smoking wacky weed.


I would trust this more if the panels on the vehicle were clear. Isn\'t
it possible to hide batteries and electric motors?

Looking at how the propeller is turning it isn\'t turning as if it is
being pushed by the wind from the rear - it would turn in reverse then.
Based on what I see, the prop is turning the wrong way for the apparent
visible blade pitch and a rear source of energy (wind).

Looks like a trick to me. Was this filmed on April 1?

John

Some guys who built one posted here for a while. The concept
apparently started as a college thesus. I recall that the wheels drive
the prop, and the prop spins in the direction to push the cart faster
than the tailwind. Something like that.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[Phil Hobbs]

Lasse Langwadt Christensen wrote:

long thread about it here,
https://www.eevblog.com/forum/chat/mess-with-your-minds-a-wind-powered-craft-going-faster-than-a-tail-wind-speed/

We went over this in great detail some years ago in sci.electronics.basics:

<https://groups.google.com/g/sci.electronics.basics/c/4cMIVQZEXlw>

You really can do it.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Robertson]

On 2021/12/21 7:38 p.m., Phil Hobbs wrote:

Lasse Langwadt Christensen wrote:
long thread about it here,
https://www.eevblog.com/forum/chat/mess-with-your-minds-a-wind-powered-craft-going-faster-than-a-tail-wind-speed/




We went over this in great detail some years ago in sci.electronics.basics:

https://groups.google.com/g/sci.electronics.basics/c/4cMIVQZEXlw

You really can do it.

Cheers

Phil Hobbs

I thought I posted a link to ice boats - they can go multiples of wind
speed when tacking...and water yachts can also go faster than the wind -
when they are tacking...

https://www.straightdope.com/21344013/how-can-racing-yachts-sail-faster-than-the-wind

John

 

[Phil Hobbs]

Sylvia Else wrote:

On 21-Dec-21 12:44 pm, Rick C wrote:
I say yes.  I haven\'t watched the video, but looking at the
contraption and seeing how it would work says to me that it can
indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a
solar wind powered craft.  They talked about the high speeds they
could achieve as if they were tacking or something, but unless they
had invented an æther rudder, they were smoking wacky weed.


Yes.

What\'s more, there\'s no theoretical upper limit to its speed (if we
ignore relativistic effects).

The trick is to have the part of the craft that\'s catching the wind (the
wind catcher) moving relative to the rest of the craft, and cause that
part to be connected to the wheels. The craft\'s overall equilibrium
speed is then when the wind catcher is not moving relative to the wind.

The rest is just engineering to minimise friction in the linkage between
the wheels and the wind catcher, the frontal area of the body of the
craft, and so on.

Sylvia.

Solar sails are a different issue. Most of the momentum comes from
solar wind particles, which AIUI mostly stick to the sail, so you only
get \'downwind\' force regardless of sail orientation.

Radiation bounces off a silvered sail, so you potentially get twice the
momentum transfer, and you can tack.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Rick C]

On Tuesday, December 21, 2021 at 3:56:15 PM UTC-4, John Robertson wrote:

On 2021/12/20 11:17 p.m., Rick C wrote:
On Tuesday, December 21, 2021 at 2:32:17 AM UTC-4, John Robertson wrote:
On 2021/12/20 5:44 p.m., Rick C wrote:
I say yes. I haven\'t watched the video, but looking at the contraption and seeing how it would work says to me that it can indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a solar wind powered craft. They talked about the high speeds they could achieve as if they were tacking or something, but unless they had invented an æther rudder, they were smoking wacky weed.

I would trust this more if the panels on the vehicle were clear. Isn\'t
it possible to hide batteries and electric motors?

Looking at how the propeller is turning it isn\'t turning as if it is
being pushed by the wind from the rear - it would turn in reverse then..
Based on what I see, the prop is turning the wrong way for the apparent
visible blade pitch and a rear source of energy (wind).

Looks like a trick to me. Was this filmed on April 1?

The propeller doesn\'t look like the wind is turning it because the wind isn\'t turning it. The wheels turn the prop! That\'s the whole point. As the wind starts pushing, the prop is more of a kite than a prop. As the car moves, the wheels turn the prop faster so it is pulling the car in the direction it is already moving. As the car speeds up the propeller spins faster and pushes the car harder. By the time the car is matching the wind speed, the prop is pushing fairly hard and the car will continue to speed up.

I think it is funny that you suspect batteries in the body.

I\'m really impressed anyone would actually build this.

In the OP\'s video the vehicle was not tacking so I\'d still need to see a
better explanation - math would help - but for now call me unconvinced,
but curious.

What does tacking have to do with it??? You would tack if you were using a sail. I\'ve tried to explain to you the propeller is turning the OTHER way, pushing back against the wind, not being turned by the wind, turned by the gearing from the wheels. It is only at the very beginning that the prop acts as a sail, catching enough wind to set the car in motion. After that the rotation is like on an airplane, pushing air backwards as the car moves forward.

I may yet have to reconsider my position...ice boats can go several
multiples of wind speed when tacking.

https://sites.google.com/site/yoavraz2/sailingboatspeedvs.windspeed

One last time, tacking has nothing to do with it unless you wish to consider the blades of the propeller being angled against the wind to be tacking and dragging the car along. The video shows this with two boats tacking on a cylindrical earth essentially forming an earth sized propeller.

Always happy to be proven wrong (or right!) - that is the only way
knowledge grows!

I\'m not convinced any of the math is right. They have a formula for the effectiveness of the prop (using a word for this I\'d never heard of before) that has a term (w-v) in the denominator which makes the equation blow up as the car reaches the wind speed. I\'m not sure why w-v is in there to begin with. When w-v is zero, it\'s just the force generated by a stationary propeller. Yeah, they generate plenty of force. In the second video the author shows an alternate equation which does not put a naked (w-v) in the denominator. The point is the math is all off the cuff. But you can\'t argue with the video that shows it working unless you want to say they are cheating.

A physics professor lost $10,000 on the bet. Do you really think he would let cheating slide?

Then there are the small models that work on a treadmill. They pretty clearly have no batteries or motor.

These things should be reversible. If you turn it around, the wheels will turn the other way and the prop turns the other way making it work down wind still. Seems the models would be more stable with the prop in front.

When do you think they will market these for use on the highways? Kinda like balloon or glider flights. One way with a carriage back.

--

Rick C.

--- Get 1,000 miles of free Supercharging
--- Tesla referral code - https://ts.la/richard11209

 

[Rick C]

On Wednesday, December 22, 2021 at 8:01:02 AM UTC-4, Jasen Betts wrote:

On 2021-12-21, Rick C <gnuarm.del...@gmail.com> wrote:
On Tuesday, December 21, 2021 at 5:57:31 AM UTC-4, David Brown wrote:
On 21/12/2021 02:44, Rick C wrote:
I say yes. I haven\'t watched the video, but looking at the
contraption and seeing how it would work says to me that it can
indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a
solar wind powered craft. They talked about the high speeds they
could achieve as if they were tacking or something, but unless they
had invented an æther rudder, they were smoking wacky weed.

I believe the force of the wind on a propeller works in much the same
way as on the sail of a boat that is tacking. If that is correct, a
propeller based car can go faster than the wind, precisely because it
/is/ tacking - even when the car is going in a straight line.

It is also possible for a propeller powered car to run directly into the
wind.

You might actually give that one a bit of thought. Look at the two cars and consider the detailed forces and how they are generated. I think you will find it\'s the same car and always goes downwind, just with more or less efficiency, i.e. forwards or backwards.
If you change the gearing so the propeller/impeller screws into the wind faster than
the wheels work against the ground it will go upwind. If you set it lower
than the wheels, downwind.

Has anyone tested an upwind version? If the wind is pushing it downwind the wheels will turn the prop in the opposite direction to go downwind. If the car is pushed upwind everything turns the right way, but how does it get started? Even then, I\'m not convinced the details work. The only way I could make the idea work in my head for the downwind car is to consider the gearing to turn the prop slower producing more force than the force on the wheels to start the whole thing. If you reverse that gear ratio I don\'t see how the thing can work. The prop would exert less force because of the constant power through the gear train.

--

Rick C.

--+ Get 1,000 miles of free Supercharging
--+ Tesla referral code - https://ts.la/richard11209

 

[Jasen Betts]

On 2021-12-23, Rick C <gnuarm.deletethisbit@gmail.com> wrote:

On Wednesday, December 22, 2021 at 8:01:02 AM UTC-4, Jasen Betts wrote:
On 2021-12-21, Rick C <gnuarm.del...@gmail.com> wrote:
On Tuesday, December 21, 2021 at 5:57:31 AM UTC-4, David Brown wrote:
On 21/12/2021 02:44, Rick C wrote:
I say yes. I haven\'t watched the video, but looking at the
contraption and seeing how it would work says to me that it can
indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a
solar wind powered craft. They talked about the high speeds they
could achieve as if they were tacking or something, but unless they
had invented an æther rudder, they were smoking wacky weed.

I believe the force of the wind on a propeller works in much the same
way as on the sail of a boat that is tacking. If that is correct, a
propeller based car can go faster than the wind, precisely because it
/is/ tacking - even when the car is going in a straight line.

It is also possible for a propeller powered car to run directly into the
wind.

You might actually give that one a bit of thought. Look at the two cars and consider the detailed forces and how they are generated. I think you will find it\'s the same car and always goes downwind, just with more or less efficiency, i.e. forwards or backwards.
If you change the gearing so the propeller/impeller screws into the wind faster than
the wheels work against the ground it will go upwind. If you set it lower
than the wheels, downwind.

Has anyone tested an upwind version?

I\'m faily sure it\'s been done.

I searched \"propeller car upwind\"; this was on the first page:

https://www.youtube.com/watch?v=F7PNSyAfCjk



> If the wind is pushing it downwind the wheels will turn the prop in the opposite direction to go downwind.

Yeah but the gearing between the \"fan\" and the wheels is such that the
fan has machnical advantage over the wheels (for downwind the wheels
have the mechanical advantage). thus the \"propeller\" (actually impeller or turbine in this case)
turns the wheels driving the vehicle into the wind, and at the same
time increasing the amount of wind encountered.

If the car is pushed upwind everything turns the right way, but how
does it get started?

The wind turns the propeller

Even then, I\'m not convinced the details work.
The only way I could make the idea work in my head for the downwind
car is to consider the gearing to turn the prop slower producing more
force than the force on the wheels to start the whole thing.
If you reverse that gear ratio I don\'t see how the thing can work.
The prop would exert less force because of the constant power through
the gear train.

Consider the case where 1000 turs of the propeller cause 1 rotation of
the axle, clearly it\'s at-least possible to travel upwind at some (low) speed


Now think aboput it this way, there is some gear ratio where the converted
propeller torque exactly matches the axle torque, with this gear ratio the
vehicle is immune to the wind and doesn\'t need a parking brake. you can
push or pull on the front of the car and only feel the friction (and
innertia), not the wind.

If the ratio is increased the axle torque produced by the propeller is
insuficient to hold the car stationary and it travels down wind with a
mechanical assist from the wheels driving the propeller

If the ratio is reduced instead, the propeller now drives the wheels
and the car travels upwind, with a wind enhancement due to its
direction of travel.


Ideal shapes for impellers and propellers are similar but probably not
the same, but there is presumably some compromise shape that can travel
in both directions given suitable gear ratios (or perhaps adjusatable
blade pitch).

--
Jasen.

 

[Jasen Betts]

On 2021-12-23, Rick C <gnuarm.deletethisbit@gmail.com> wrote:

On Wednesday, December 22, 2021 at 8:01:02 AM UTC-4, Jasen Betts wrote:
On 2021-12-21, Rick C <gnuarm.del...@gmail.com> wrote:
On Tuesday, December 21, 2021 at 5:57:31 AM UTC-4, David Brown wrote:
On 21/12/2021 02:44, Rick C wrote:
I say yes. I haven\'t watched the video, but looking at the
contraption and seeing how it would work says to me that it can
indeed go faster than the wind without tacking.

https://www.youtube.com/watch?v=jyQwgBAaBag

I didn\'t shorten the URL to avoid the wrath of sed.

I recall watching a scene in a sci-fi show where they were flying a
solar wind powered craft. They talked about the high speeds they
could achieve as if they were tacking or something, but unless they
had invented an æther rudder, they were smoking wacky weed.

I believe the force of the wind on a propeller works in much the same
way as on the sail of a boat that is tacking. If that is correct, a
propeller based car can go faster than the wind, precisely because it
/is/ tacking - even when the car is going in a straight line.

It is also possible for a propeller powered car to run directly into the
wind.

You might actually give that one a bit of thought. Look at the two cars and consider the detailed forces and how they are generated. I think you will find it\'s the same car and always goes downwind, just with more or less efficiency, i.e. forwards or backwards.
If you change the gearing so the propeller/impeller screws into the wind faster than
the wheels work against the ground it will go upwind. If you set it lower
than the wheels, downwind.

Has anyone tested an upwind version?

I\'m faily sure it\'s been done.

I searched \"propeller car upwind\"; this was on the first page:

https://www.youtube.com/watch?v=F7PNSyAfCjk



> If the wind is pushing it downwind the wheels will turn the prop in the opposite direction to go downwind.

Yeah but the gearing between the \"fan\" and the wheels is such that the
fan has machnical advantage over the wheels (for downwind the wheels
have the mechanical advantage). thus the \"propeller\" (actually impeller or turbine in this case)
turns the wheels driving the vehicle into the wind, and at the same
time increasing the amount of wind encountered.

If the car is pushed upwind everything turns the right way, but how
does it get started?

The wind turns the propeller

Even then, I\'m not convinced the details work.
The only way I could make the idea work in my head for the downwind
car is to consider the gearing to turn the prop slower producing more
force than the force on the wheels to start the whole thing.
If you reverse that gear ratio I don\'t see how the thing can work.
The prop would exert less force because of the constant power through
the gear train.

Consider the case where 1000 turs of the propeller cause 1 rotation of
the axle, clearly it\'s at-least possible to travel upwind at some (low) speed


Now think about it this way, the wind blows on the propeller and
creates a torque in the propeller shaft and also a force on the
vehicle, the force on the vehicle creates a torque in the wheel axles.
There is some gear ratio where the converted propeller torque exactly
matches the axle torque, with this gear ratio the vehicle is immune to
the wind and doesn\'t need a parking brake. you can push or pull on the
front of the car and only feel the friction (and innertia), not the wind.

If the ratio is increased the axle torque produced by the propeller is
insuficient to hold the car stationary and it travels down wind with a
mechanical assist from the wheels driving the propeller

If the ratio is reduced instead, the propeller now drives the wheels
and the car travels upwind, with a wind enhancement due to its
direction of travel.


Ideal shapes for impellers and propellers are similar but probably not
the same, but there is presumably some compromise shape that can travel
in both directions given suitable gear ratios (or perhaps adjusatable
blade pitch).

--
Jasen.