-
Security incident: ISF was recently accessed by intruders. Please change your password, and change it anywhere else you used it. Read more
Merged DDWFTTW in a “Real” Wind
- Thread starter ynot
- Start date
- Status
Jack by the hedge
Safely Ignored
- Joined
- Oct 14, 2009
- Messages
- 27,886
But there is no energy gain; the energy comes from the wind moving over the ground and it is not a PM machine.
The evidence is a cart doing 2.8 x windspeed downwind. Don't like that evidence? Bring better-argued objections next time.
This kind of childish, mean-spirited bitterness just loses you any remaining sympathy. Seriously.
There is no energy gain asserted, claimed or otherwise implied with the cart. Except by you and Hyev.
And the cart will only run with a wind to provide energy. Not to mention a long enough, flat enough, surface that happens to be in line with the wind's direction to take advantage of it.
Plenty of things accelerate without being over unity, this is just a ridiculous statement on its face.
The only one claiming any "magic" is the straw man that you have created.
The BB is something that one may find in a parody, and mechanically, perhaps from The Three Stooges.
Woop...Woop...Woop....Boing!
But if you agree to the possibility, have given no reason why "this cart" won't work. I say it will. It's easy to throw in words like "extract" , "interface", "frame". Math separates the wheat from the chaff. So, that is how the matter is resolved, no who can "see" more.
The chain or rail which drives the geared wheel will be inefficient. As I said, you can see why if you work out the forces that make is turn CW or CCW. It could roll the other way. It's friction and the moment of the reel, which determines that. Force it, and there will be losses. Other than that, more force is needed and the work will be the same. There are no free lunches. Big ideas using sticks and stones have all been long exhausted, and that goes for gears.
The wine glass? No. That's a turkey. The hand which drives the finger, moves further than the glass. The finger rolls over the glass stem.
If the outer circumference is 2pi and the inner 1pi, then one turn sees the glass move 2pi. The finger moves 1pi wrt the glass, so the total motion for the hand is 3pi.
It's a joke. Don't you "get it". If "counter-intuitive" means that there is something that at first looks implausible but isn't, then what is something that at first looks plausible, but isn't?
A sophism
sophism
1.1 A specious but fallacious argument, either used deliberately in order to deceive or mislead, or employed as a means of displaying ingenuity in reasoning. .
And something that at first looks implausible, and is?
Guess what has generally been confused for the other?
Attachments
Last edited:
No. Upwind, The relative velocity of the wind wrt the rotor always increases.
The wind powers the motor and that drives the cart forwards. The cart does not produce the wind. No matter how fast it goes, there is always a real wind.
Your proposal is positive regenerative feedback. Possible and common, but if accompanied by a power gain, is over-unity.
Harold must really hate this one by now. On RatScep there were several DDWFTTW-skeptics. But as soon as they understood and accepted downwind VMG > windspeed, they immediately saw that a vehicle with moving parts can go DDWFTTW. They pointed out to Harold how inconsistent his position is, so he got angry and left.
Last edited:
Point out which statement is wrong.
Are you an aerodynamicicist, Captain? Say, involved in the design of F1 cars?
You want me to provide proof that the cart can work as a sailcart, but who are you to judge the answer? I'm not an aerodynamicist, and neither of us could prove the case without the necessary data, which Spork will not provide.
I think that evens the score on that point, so leaving the trial to demonstrate it one way or the other. I say the trial shows the cart is doing nothing that a sail boat can't do.
NALSA say that the average deviation is 10 degrees, I say it may be more, perhaps 30 or even 40. The raw data would allow that to be determined.
But, why do you object? If you say the cart works best ddw, why do you not say "well 20 degrees shows that it could do even better", rather than trying to wish it away? Meaning, you do see that the claim is dependent on it being ddw. If not, why is Spork so reluctant to show the data?
And steady state. Steve Smith has said he thinks that the cart could exploit the changing direction of the wind, rather than just the angle itself, or gradients. It's important to note changing. That is why simple static vectors will not give the correct answer. It is always changing, even if it remains within 10 degrees ( it doesn't but...)
If the claim had been "ddw changing wind, not steady-state" I would have said , why not? I proposed a cart that could do that. Goodman's is somewhat like that.
But, how honest is it to change the goal posts and claim victory?
What if I had a cart that could go >WS, but not when less that 9 degrees. I know that for a fact by testing it. I say to you that I have a ddw cart, and that is steady-state etc. You say "no way"
I arrange a trial, or agree to a trial, where the margin allowed is 10 degrees. I then claim ddw on that basis. That is underhanded to say the least. If I do that, make poor measurements, know the wind is gusty, filter the data, AND ensure the run is too short for steady state, then I am a whining pussy cheat.
Last edited:
Then don't make comparisons with vehicles which use combustion engines.
If an engine does not make a difference, then one is given pause to wonder why they are fitted.
See my reply to RossFW, but the chart says a lot.
As a simple peak speed under acceleration, the outcome is dependent on mass and pushing. Why not roll a dice?
But, the precise pattern of the wind over the short term can produce contradictory outcomes.
NASA claim that acceleration at the time of measurement when the cart is said to be close to ddw, "proves" is works best at ddw. Rubbish. Illogical.
According to the NALSA chart, the wind moves rapidly to the South, and is 25 degrees off at the end of the 10 second period, but the cart continues to accelerate. Surely it should slow quite rapidly. It always accelerates, and that is a general characteristic, so what is so special about is doing that when they want to measure the speed.
They don't even comment on the fact that it does just as well when the wind has changed. There is a strong relationship between a wind that changes direction, and acceleration. Steve Smith of NASA says he thinks that is a plausible mechanism, and the chart says that is what is happening.
Attachments
Last edited:
Jack by the hedge
Safely Ignored
- Joined
- Oct 14, 2009
- Messages
- 27,886
My bits in red.
The cart performs best at 0 degrees off the wind, dead dw but no one has said it will not perform at all 4 degrees off the wind. Humber says it should slow "quite rapidly" as the cart gets further away from ddw. It does.
Humber either lies about the charts or is unable to understand the data. It does not matter how many times his errors are pointed out to him. I would encourage anyone who wishes to obtain the NALSA data and look at it for themselves.
You miss the beauty of humber... never talk about a statement when you can claim an entire concept, nay, an entire branch of 'simple' physics has been misunderstood...
Dave
I notice as I was replying he edited his post to include one of his most hilarious arguments ever. I hope everyone will get as many laughs out of it as I have.
Notice his charts with the white A B and C lines. He thinks it matters how the cart got up to wind speed. No one has ever been able to get him to say when the clock starts ticking on his average speed targets. No one knows if lunch breaks and flat tire changes should be included as well as pushing time.
I notice he also slipped in some more wrongness in the form of his misunderstanding of the meaning of steady state.
Notice his charts with the white A B and C lines. He thinks it matters how the cart got up to wind speed. No one has ever been able to get him to say when the clock starts ticking on his average speed targets. No one knows if lunch breaks and flat tire changes should be included as well as pushing time.
I notice he also slipped in some more wrongness in the form of his misunderstanding of the meaning of steady state.
Last edited:
Have done. Posted 3 times. I will fish it out.
Math says not.
Nope. I have a video for that. I was going to post it today, but feedback from this forum says I should extend it a bit.
That is a deliberate trick, or poor experimental control. video shows why.
Is it technical ignorance?
NALSA submission report. The Chief Expounds
Proof that the vehicle performs best Dead Downwind
As can readily be seen from the above analysis, the vehicle performance is
driven significantly by the prop efficiency. This of course is primarily a function of the Lift/Drag ratio of the propeller airfoil at its operating angle of attack. The propeller on the Blackbird is based on the NACA 6412 airfoil which has it’s maximum L/D at 4.0 degrees, and has a twist such that the airfoil at each spanwise station is presented at that angle of attack (AOA). When the relative flow is aligned with the propeller axis, that AOA can be maintained at all spanwise stations throughout the complete rotation. As the prop rotates counter-
clockwise when viewed from in front of the vehicle, any cross-wind component from the right will cause the AOA for the top blade to increase while the angle of attack of the bottom blade is decreased. A cross wind component from the left will have the same effect in the opposite direction. In both cases the AOA will depart from its optimum value to varying degrees over the full rotation of the prop in this case – reducing the propeller performance – and thus the overall performance of the cart. The cart employs no other aerodynamic surfaces that can take advantage of a cross-wind component.
Assume I am lying,. Show me where.
Attachments
Last edited:
So we will see it "by Monday" then?
Worried? Do you think I dance to the beat of your drum, especially when you are being hammered?
ETA:
I am not all that interested in the wheel thing. Do you remember Mark CC's "A real Bozo Atones?"
He was right the first time, but capitulated in a grovelling way. That is to play into the hands of those who see science as the cult of personality. His retraction was wrong. There are comments on that. He then faced the problem of changing again. His promised follow-up never came, all because of "face".
The video will appear, but in the meantime, you can discuss the topic of the cart in the wind, and how the trial data supports that.
Last edited:
Jack by the hedge
Safely Ignored
- Joined
- Oct 14, 2009
- Messages
- 27,886
Really?
If the point of contact with the chain is A and the point of contact with the track is B, then when the chain is pulled to the right there is a torque applied to the gearwheel between points A and B trying to turn the wheel clockwise. (Why would it go anticlockwise?)
As the chain moves to the right, the cogwheel has to move right with it (inertia might tend it to rotate anticlockwise in place, but it can't rotate in place because it cannot slip against the rail. The lever AB compels it to turn clockwise).
Since the wheel must move to the right, it must also roll along the rail.
If the small gear has diameter X and the large wheel has diameter Y, then for each revolution of the wheel, the point of contact B moves Y Pi along the rail, and the point of contact A moves X Pi along the chain.
Since the points of contact remain perpendicular to each other at all times we can see that the displacement of B relative to the rail equals the displacement of A relative to the rail.
The displacement of A along the chain is X Pi and along the rail is Y Pi.
The difference between Y Pi and X Pi is the displacement of the chain.
For each rotation of the wheel, the chain moves (Y-X)Pi relative to the rail.
As far as everyone else is concerned thanks Humber, you have again done what you so often do. Introduced incontrovertible proof of your own wrongness as evidence in your defense.
I do not know if you are capable of being shown where you are lying/wrong but I do know for certain that you cannot accept being shown. I know this because you have been shown all your errors and misunderstandings regarding the chart more than a hundred times.
I also know that you will not, or are not capable of understanding, even the most basic concepts required; such as the difference between instantaneous and averaged data points.
When a wheel rolls, there is an opposing force of rolling resistance.
A tyre rolled down a ramp on to a level surface will eventually stop because of that (and drag with the air). That "roll down test" is used to test both car and bike tyres. Friction opposes the wheel, so is a force decelerating it - applied to turn the wheel the other way. Without it, the wheel will not roll, but slide. Friction may be a loss, but no wheel can roll without it.
Which way it turns depends of the direction of that frictional force.
I will find the calculation for that, when I find the post again. Nobody responded when I posted it - 3 times. Will you do that, this time?
That will cost energy.
Tried it have you? There's more to it than that. It is best via video.
So you say. The driving thing is a rack, so its a rack and pinion. Instead of "imagining" that, make the rack a fixed length and push on the end. See how far that end moves.
- Status