Merged DDWFTTW in a “Real” Wind

[tobermoryphil]

Returning to Humber's vacuum balloons, as usual Humber has a few centuries to catch up. The idea was first proposed in 1670 by a Jesuit priest, Father Francesco de Lana, in his "Prodromo overo saggio". His drawing showed a craft supported by four evacuated spheres. However he was obviously of a similar mindset to Humber. His free floating balloon had a sail!

Humber's recent posting of the bike with the windmill like fans on either side also has an early antecedent. The King of France in 1328 was considering embarking on a crusade, and was presented with a military treatise by a doctor, Guido da Vigevano. His drawings showed a four-wheeled war chariot driven, via gearing, from side windmills looking exactly like those on the bike.

Keep going, Humber, you might make it to the the 21st century one day!

 

[humber]

So, Humber, so how do land yachts and ice yachts manage to have speeds of several times the wind speed?

OK, they are not proceeding directly down wind, but neither is a spot on the cart's prop blade.

If the first craft can do what they obviously do, why not the cart, with it's prop blade airfoil following an identical (if helical) path to the land yacht's airfoil sail?

Tacking. They all tack, and the prop does not.
The NALSA data quite clearly shows the BB is not a ddw craft by any stretch of the imagination. You have been had.
There is a definite correlation between changing wind and cart acceleration. It is worst ( not best, not better, no less good), when ddw. The illusion of to the contrary is a result of the prop regulating the cart's acceleration. It limits that, so it looks "better" when ddw.

 

[humber]

Returning to Humber's vacuum balloons, as usual Humber has a few centuries to catch up. The idea was first proposed in 1670 by a Jesuit priest, Father Francesco de Lana, in his "Prodromo overo saggio". His drawing showed a craft supported by four evacuated spheres. However he was obviously of a similar mindset to Humber. His free floating balloon had a sail!

Humber's recent posting of the bike with the windmill like fans on either side also has an early antecedent. The King of France in 1328 was considering embarking on a crusade, and was presented with a military treatise by a doctor, Guido da Vigevano. His drawings showed a four-wheeled war chariot driven, via gearing, from side windmills looking exactly like those on the bike.

Keep going, Humber, you might make it to the the 21st century one day!

And the common factor is that none worked.
So, thanks for pointing out even earlier antecedents of the cart's cranky and certain to fail claim.
There is a reason why I refer to Medieval villagers, so the history lesson was not actually necessary, thanks.

 

[Llyricist]

Tacking. They all tack, and the prop does not.
The NALSA data quite clearly shows the BB is not a ddw craft by any stretch of the imagination. You have been had.

No, it quite clearly shows that it performs best when closest to DDW.

 

[quarky]

I'm floundering a bit here.

I'm in need of someone telling me that ddwfttw is not do-able, even hypothetically, without this prop; these wheels; these gear ratios:

Please!

Jb; spork; humber; I ratant?

Am I this wrong?

 

[jadebox]

Do you mean that the very same rocket motor, running with the same fuel consumption will produce more thrust in the atmosphere than in vacuum?

A rocket motor is most effective when its exit pressure matches the ambient pressue. To match the ambient pressure of space, a rocket's exit pressure would have to be zero. Rockets are the least effective when the exit pressure is zero.

If the atmospheric pressure is higher than the exit pressure, performance will also suffer, of course. The extreme case being when the outside pressure is equal to or greater than the chamber pressure - in which case none of the gases from the rocket would escape.

But, generally, a rocket's efficiency is better in the atmosphere than in space because the nozzle can be designed to match the exit pressure to the atmospheric pressure.

Anyway, my main point has been lost ... I was responding mainly to the poster who suggested that the rocket was more effective in the atmosphere because it pushed against the atmosphere. That isn't true and I think that's what's most relevant to the topic of this thread.

Also, I meant "under-expanded" in reference to the water jet in my last message. "Under expansion" vs. "over expansion" look just the opposite of what you'd think they look like, so it's easy to get them backwards.

-- Roger

 

[tobermoryphil]

Tacking. They all tack, and the prop does not.
The NALSA data quite clearly shows the BB is not a ddw craft by any stretch of the imagination. You have been had.

The yachts do not HAVE to tack- they can keep going at the 30-40 degrees off the downwind direction for as long as they like, assuming that the surface they are running on is sufficiently large of course.

The prop blade does not tack either- the motion of a point on it's surface is also a continual angle off the downwind direction, albeit in a helical path.
You just do not grasp three dimensions, do you?

And the NALSA data shows the craft was within 4 degrees of DDW on average during the record run, and at about 8 seconds was EXACTLY ddw, however much you try to obfuscate and fiddle the graphs. It was also accelerating throughout the run.
Can any other craft can do anything remotely near this?

By the way, my genuine offer of £1000 if you can demonstrate your propless cart proceeding up a belt still stands. I wonder why you ducked out of that one? I assume it only works in the Humberverse.

 

[quarky]

Returning to Humber's vacuum balloons, as usual Humber has a few centuries to catch up. The idea was first proposed in 1670 by a Jesuit priest, Father Francesco de Lana, in his "Prodromo overo saggio". His drawing showed a craft supported by four evacuated spheres. However he was obviously of a similar mindset to Humber. His free floating balloon had a sail!

Humber's recent posting of the bike with the windmill like fans on either side also has an early antecedent. The King of France in 1328 was considering embarking on a crusade, and was presented with a military treatise by a doctor, Guido da Vigevano. His drawings showed a four-wheeled war chariot driven, via gearing, from side windmills looking exactly like those on the bike.

Keep going, Humber, you might make it to the the 21st century one day!

To be fair to humber, it was I that brought up vacuum balloons.
Otherwise, welcome to the forum.

 

[Michael C]

I'm floundering a bit here.

I'm in need of someone telling me that ddwfttw is not do-able, even hypothetically, without this prop; these wheels; these gear ratios:

Please!

Jb; spork; humber; I ratant?

Am I this wrong?

I'm happy to try and help if you can fill me in a bit more on what your question is. Do you want to know if ddwfttw is possible with a different system that doesn't involve a prop geared to the wheels? Or do you want to know what are the conditions for the prop, the wheels and the gearing that makes ddwfttw possible?

 

[humber]

I'm floundering a bit here.

I'm in need of someone telling me that ddwfttw is not do-able, even hypothetically, without this prop; these wheels; these gear ratios:

Please!

Jb; spork; humber; I ratant?

Am I this wrong?

It is not possible, with or without a prop, quarky.
As I Ratant has already shown, the freewheeling cart beats the geared cart.
It may be possible to get that geared cart to run, but it will always be below WS, even if the free-wheeler does better or not, because that too will be restricted to a top speed of <WS.
The only peer-reviewed reference, by Blackford, says >WS is not possible either way.

A free-wheeling prop is complex because its behavior is dependent upon the relative velocity of wind and prop. The lift/drag ratio is not constant with airspeed, due to dynamic shift of what is generalized as the "attack angle".

That ratio governs the drag, and the amount of torque produced by the air flow through the rotor's disk area. It may take up a number of behaviors dependent upon the props physical design. Diameter, number of blades, profile, twist etc. The drag may simply overwhelm the torque ( lift component) and the rotor will stall at some speed and below WS, or take up very slow rotation when the airspeed is low.

An anemometer can never truly show WS. They work because the drag on the open face, is larger than the drag on the curved face. That shape simply prevents the air flow being the same at each point of any part of the cup's surfaces. It will stall when the balance on all cups is the same. With a 3 cup, that can't happen, ( unless the wind is not constant, in which case it may briefly stall ), but may with a two cup. Whatever the case, it would stall or all but do so, at some point below WS. A freewheeling prop will do the same.

Gearing the prop to the wheel, forces it to behave otherwise, and that can only serve to be a drag on the wheel. It will tend to regulate the sail force on both the prop and the body, as it works to comply with one demand against the other. That explains the cart's woeful starting ability, and low acceleration of 0.1ms-2. It looks like it works because of loose trial conditions, but it tacks and gains from the energy of changing winds, and that is how it works.
There is no energy available at WS, and forcing the prop against its intrinsic behavior, will not earn it any.

ETA: I should add that the prop of a plane has the same "problem", but there is an energy source (fuel) and an engine, that can force rotation on the prop, whereas the cart is driven by the air alone.

 

[jadebox]

Do any of you do any reading, or just go with whatever hunch passes by?

[... a lot of irrelevant stuff copied, without attribution, from Wikipedia ....]

You know, playing chess with someone who has no idea how the pieces are supposed to move is fun for a little while, but it's been going on too long.

-- Roger

 

[ynot]

The questions below ONLY relate to DIRECTLY DOWNWIND travel.

Let's see how many things there are that we can all currently agree on. If anyone disagrees with anything below please say what and why . . .

1. The cart is ONLY powered by the wind.
2. Wind can't DIRECTLY transfer power to anything that is moving faster than the wind.
3. When the cart is moving faster than the wind there MUST be some part of the cart or something that interacts with the cart that is moving slower than the wind so the wind can transfer power to it.

The explanations I have been giving have been in the form of anecdotes in an attempt to simplify. I agree that some of the things I have said have been totally wrong and I never intended to present myself as an faultless authority on the subject.

I’m disappointed that the two threads have been merged and I’m not sure if I want to continue in this repulsive atmosphere of argument and insult. Thanks to those that took part in the “Dummies“ thread with a positive and sociable attitude.

 

[humber]

[... a lot of irrelevant stuff copied, without attribution, from Wikipedia ....]You know, playing chess with someone who has no idea how the pieces are supposed to move is fun for a little while, but it's been going on too long.

-- Roger

Yeah, chess is not so much fun when losing.

[... a lot of irrelevant stuff copied, without attribution, from Wikipedia ....]

Which you managed to find, but had not previously read. Anything more complex would be difficult for you, so you may expect that source to be the lowest common denominator of wiki. You guessed well.
On the other hand, you accept what TAD tells you without a blink.

ETA: Basic Newton tells of the condition where maximum efficiency will occur. On the other hand, you don't want that to happen, just at the point where the rocket runs out of fuel.

 

[quarky]

I'm happy to try and help if you can fill me in a bit more on what your question is. Do you want to know if ddwfttw is possible with a different system that doesn't involve a prop geared to the wheels? Or do you want to know what are the conditions for the prop, the wheels and the gearing that makes ddwfttw possible?

No, I get the prop and wheels and gears thingy...
I'm merely seeing alternative ways of achieving this, much easier on the mind.

 

[humber]

The yachts do not HAVE to tack- they can keep going at the 30-40 degrees off the downwind direction for as long as they like, assuming that the surface they are running on is sufficiently large of course.

The prop blade does not tack either- the motion of a point on it's surface is also a continual angle off the downwind direction, albeit in a helical path.
You just do not grasp three dimensions, do you?

And the NALSA data shows the craft was within 4 degrees of DDW on average during the record run, and at about 8 seconds was EXACTLY ddw, however much you try to obfuscate and fiddle the graphs. It was also accelerating throughout the run.
Can any other craft can do anything remotely near this?

By the way, my genuine offer of £1000 if you can demonstrate your propless cart proceeding up a belt still stands. I wonder why you ducked out of that one? I assume it only works in the Humberverse.

Again, anyone who wants to act as my proxy, PM me. You get to keep the 1000 pounds for the effort.
It is not a good idea Tobermoryphil, to risk your pension on Spork's ideas, and his delight at
Ynot's misfortune. Think about that before pressing ahead
As for the need for a proxy, I am not going to risk said Spork finding my name, address and bank account details.

 

[windgrins]

Michael C is the man!

No, I get the prop and wheels and gears thingy...
I'm merely seeing alternative ways of achieving this, much easier on the mind.

Quarky,

Michael C has good info. The most easy to understand vehicle that achieves this and sort of fills all the letter of the law is two iceboats tacking downwind with a VMG > Windspeed with a string or pole between them. If they perform one tack towards the center at the halfway point, the composite vehicle they comprise will have gone DDWFTTW and the vehicle will be in the same configuration as it started. This is probably the best real world example.

I hope this helps.

WindGrins

 

[tobermoryphil]

Again, anyone who wants to act as my proxy, PM me. You get to keep the 1000 pounds for the effort.
It is not a good idea Tobermoryphil, to risk your pension on Spork's ideas, and his delight at
Ynot's misfortune. Think about that before pressing ahead
As for the need for a proxy, I am not going to risk said Spork finding my name, address and bank account details.

Thanks for the advice, Humber, but I am quite happy to put my money where my mouth is when I know I am right.
In spite of you having a probable world record for trolling posts, you are obviously not.

But carry on with the comedy!

 

[Michael C]

No, I get the prop and wheels and gears thingy...
I'm merely seeing alternative ways of achieving this, much easier on the mind.

There are alternative ways. In the old thread there are some suggestions for possible non-prop ddwfttw vehicles, for instance:

http://www.internationalskeptics.com/forums/showpost.php?p=4191830&postcount=41
http://www.internationalskeptics.com/forums/showpost.php?p=4195040&postcount=136
http://www.internationalskeptics.com/forums/showpost.php?p=4216082&postcount=833
http://www.internationalskeptics.com/forums/showpost.php?p=4217307&postcount=892
http://www.internationalskeptics.com/forums/showpost.php?p=4221704&postcount=987

All these ideas have something in common:

- First construct a vehicle where a part of the vehicle is always moving forward slower than the vehicle as a whole. This isn't hard: if you consider just a simple wheel rolling along the ground, there are points on the wheel moving forward faster than the centre of the wheel (any point above the centre) and points moving slower (any point below the centre).
- Then make sure that the wind is always blowing on a part that moves slower than the vehicle as a whole. This is where you need to be more ingenious.

To my knowledge nobody has yet constructed a non-propeller ddwfttw vehicle that actually goes faster than the wind, but there's nothing that says it's theoretically impossible.

 

[humber]

Thanks for the advice, Humber, but I am quite happy to put my money where my mouth is when I know I am right.
In spite of you having a probable world record for trolling posts, you are obviously not.

But carry on with the comedy!

OK. Your offer stands. You will pay me or someone of my choice, the 1000 pounds when the video is shown. Agree?

 

[humber]

To my knowledge nobody has yet constructed a non-propeller ddwfttw vehicle that actually goes faster than the wind, but there's nothing that says it's theoretically impossible.

But it is not possible, and that is why none of those Heath Robinson/Rube Goldberg machines have been shown to work.