- #981
spork
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swerdna said:It’s so unbalanced I think any mechanical heterodyne vibrations should be well and truly nullified.
Cool - a mechanical superheterodyne!
swerdna said:It’s so unbalanced I think any mechanical heterodyne vibrations should be well and truly nullified.
swerdna said:Here’s a video of a crude, smaller, tiered TT to change the relative speeds. It was put together very quickly so “never mind the quality, feel the width”. It shows you don’t need to build a big TT to observe the effect. It’s so unbalanced I think any mechanical heterodyne vibrations should be well and truly nullified.
Subductionzon said:The Vice Grips is the source of the power
swerdna said:A smaller cart wheel (5.5cm dia). Sorry about the background glare and the now unbalanced TT (stupid tiered demo).
swerdna said:Here’s a video of a crude, smaller, tiered TT to change the relative speeds. It was put together very quickly so “never mind the quality, feel the width”. It shows you don’t need to build a big TT to observe the effect. It’s so unbalanced I think any mechanical heterodyne vibrations should be well and truly nullified.
ThinAirDesign said:~1.3x the wind - which of course again perfectly demonstrates schroder's theory. (Well, as long as you incorporate the square root of the average frequency played by the woodwind section during Beethoven's Fifth into the Fourier transform.)
JB
ThinAirDesign said:And this one 1.2x the wind speed -- also "exactly what schroder would expect".
swerdna said:Not sure if it was just more “run in” or because I re-washed the bearings but the cart is running more efficiently in this video -
In the first video it takes about one and a third revolutions of the cart before it “hovers” while in the second video it takes less than one revolution. You should find the TT speed is the same in both videos. The terminal speed in the second also seems much faster to me but I haven‘t measured it.
ThinAirDesign said:And this one ~1.6x the wind speed. And of course given the carefully controlled circumstances, this is precisely what schroder would have predicted from his mechanical heterodyne.
No this is common experience, as sailors have been doing it crudely starting ~2000 years ago with manipulations of the square sail, and doing it efficiently now for ~300 years. You agreed to this months ago BTW. To correct your counter factual: many kinds of wind powered craft, e.g. sailboats (water/ice), gliders, extract energy from the wind stream while moving against the wind.. As was pointed out months ago, ice sail boats commonly attain speeds of 4x the wind speed while moving up wind, and RF gliders have been clocked at hundreds of miles per hour in common ground winds.schroder said:.. Saying that you can extract energy from the headwind, in order to move against the headwind, is nonsense. ...
tsig said:Just take it outside in the wind see if it moves,
Why do you not want to test it in the wind?
schroder said:Because, spork, you have it all wrong! The way I see it, the original “inventor” of this cart did it as a joke, a spoof, and he himself admitted that it will not work. The original outdoor video is a hoax, as the propeller is turning as a wind turbine. The only chance to see the actual direction of the propeller turning comes right at the end of the video, when the cart slows down. It would be hard to doctor the video at that point, and have the propeller reverse direction, so they did the next best thing; have the cart go off camera until it is stopped, and then pan back on it showing the prop spinning as a prop! It is so obviously a hoax that it really is a joke! The reason why I am interested is because of what is happening on the turntable.
Apparent headwind. The wind speed versus ground speed is still being slowed by the prop wash, because the prop accelerates the apparent headwind to a faster still upwind speed, which opposes the true wind, slowing the true wind down, the same as any wind powered device.schroder said:Once the cart (if ever) exceeds the velocity of the wind, it is going against a headwind!
But that isn't what's happening. The energy for the cart is extracted from the true tailwind by slowing it down (true wind speed = (wind_speed - ground_speed). The headwind is an overhead, but not enough to prevent the prop from being able to generate thrust efficiently enough to slow down the wind while still moving DDWFTTW.Saying that you can extract energy from the headwind
The DDWFTTW carts function because they interact with air and ground that are moving at different speeds.extract energy from the force of the propeller, to drive the propeller
Correct. These carts extract energy from the tailwind by slowing it down. The headwind is an overhead, as explained in my previous post, but doesn't prevent DDWFTTW.schroder said:Saying that you can extract energy from the headwind, in order to move against the headwind, is nonsense.
extract energy from the headwind
No sailcraft extracts energy from an apparent headwind (except when it's using the wind to decelerate the sailcraft). A sailcraft extracts energy from an apparent tailwind or apparent crosswind. The highest speeds are achieved when a sailcraft extracts energy from an apparent crosswind. Note the apparent crosswind is independent of the sailcrafts speed (by definition, it's perpendicular to the path of the sailcraft), and is equal to the true wind (wind_speed - ground_speed) times sin(angle between wind and direction of sailcraft). The maximum speed of the sailcraft depends on how much apparent headwind and ground related drag the sailcraft can achieve for a given apparent crosswind.mheslep said:No this is common experience ... sailcraft ...
Jeff Reid said:No sailcraft extracts energy from an apparent headwind (except when it's using the wind to decelerate the sailcraft). A sailcraft extracts energy from an apparent tailwind or apparent crosswind.
Jeff Reid said:No sailcraft extracts energy from an apparent headwind (except when it's using the wind to decelerate the sailcraft). A sailcraft extracts energy from an apparent tailwind or apparent crosswind.
Which is exactly what I meant. I separate the apparent wind into components in the direction of and perpendicular to the direction of the sailcraft (wrt to the ground). The component in the direction of sailcraft is an apparent headwind or apparent tailwind (or zero). The component perpendicular to the sailcraft is an apparent crosswind (or zero).ThinAirDesign said:Unless you define "apparent headwind" as only coming from directly ahead ... Also, if you were to use that definition you would also have to use the term "apparent crosswind" only when the wind is coming from 90d cross.
DDWFTTW carts extract energy from the apparent ground speed (times thrust, to drive the prop), not the apparent headwind. The apparent headwind is an overhead. The force from the ground that drives the prop is also opposing the carts forward motion, so it's a power input and at the same time an overhead in the system that must be overcome by higher thrust (at slower air speed) at the prop.extracted energy from this apparent headwind. The DDWFTTW cart does it as well.
Perhaps a clarification of terms? All we're really talking about here is the work done by an airfoil, in this case a sail based airfoil. The sail will generate lift above any angle that does not 'back' the sail, typically from 20 degrees off the wind all the way up to the stall angle. The sail airfoil will generate lift from a vessel dead stop from a wind stream at any angle above the backing angle, do work and accelerate the craft over the surface. As the craft accelerates the apparent wind speed does indeed increase and the apparent wind direction moves toward the bow.Jeff Reid said:...No sailcraft extracts energy from an apparent headwind (except when it's using the wind to decelerate the sailcraft). A sailcraft extracts energy from an apparent tailwind or apparent crosswind. The highest speeds are achieved when a sailcraft extracts energy from an apparent crosswind. Note the apparent crosswind is independent of the sailcrafts speed (by definition, it's perpendicular to the path of the sailcraft), and is equal to the true wind (wind_speed - ground_speed) times sin(angle between wind and direction of sailcraft). The maximum speed of the sailcraft depends on how much apparent headwind and ground related drag the sailcraft can achieve for a given apparent crosswind.
No sailcraft extracts energy from an apparent headwind
I did that in post #999 (congrats on having the 1000th post). I separate the apparent wind into components in the direction of and perpendicular to the direction of the sailcraft (wrt to the ground). The component in the direction of sailcraft is an apparent headwind or apparent tailwind (or zero). The component perpendicular to the sailcraft is an apparent crosswind (or zero).mheslep said:Perhaps a clarification of terms?
I prefer to separate the components with respect to the direction of the sailcraft. In this case, the purpose of a sail is to generate thrust (wrt to sailcraft). The "lift" component (wrt to sailcraft) only results in an equal and opposing force from the ground. It doesn't directly contribute to the forward speed of the sailcraft. If a sailcraft experiences an apparent headwind, then the thrust from the sail is related to the apparent crosswind, not the apparent headwind. The sail also needs to divert (accelerate) the apparent wind (both headwind and crosswind components) to true upwind sufficiently so that the true wind (wrt to ground) is decelerated.work done by an airfoil, in this case a sail based airfoil. The sail will generate lift.
This is a case of my terminology, not the physics of the airfoil. I should have made myself more clear. I tried to cover this in post #999.Perhaps you meant that the craft would fail to do work ... lift vector is perpendicular to the vessel.
Jeff Reid said:I prefer to separate the components with respect to the direction of the sailcraft...
No sailcraft extracts energy from an apparent headwind
swerdna said:Good to see you’re still “with us”. Don’t see how two videos where everything is the same except the efficiency of the cart can give the same mathematical results when the observed results are so different.
Wheel running Radius of TT = 60cm. Wheel diameter = 8cm.
swerdna said:A smaller cart wheel (5.5cm dia). Sorry about the background glare and the now unbalanced TT (stupid tiered demo).
Jeff Reid said:No sailcraft extracts energy from an apparent headwind.
I already did.spork said:Let's consider a direct-upwind prop-cart.
I wasn't considering an upwind cart as a sailcraft. If an upwind cart is to be considered as sailcraft, then upwind sailcraft are the exception to the rule.Jeff Reid said:Upwind carts extract energy from an apparent headwind, but not downwind carts.
Sails on a front to back track on the cart could be used instead, with no crosswind component required, just movement of the sails relative to the cart. Slower backwards relative to cart speed for a downwind cart, faster backwards for an upwind cart. (The sails would retract and redeploy at the ends of the track, sort of a linear like paddle wheel).Of course the blades of the prop are not going directly upwind
The pull will get stronger, but only in the direction perpendicular to travel. The thrust will diminish as speed increases.I still struggle with this statement (sailcraft don't extract energy from a headwind) because we definitely feel a very significant effect of apparent wind while kiteboarding. When going 90 degrees to the true wind the pull of the kite and performance overall definitely improves as our speed increases. Clearly the only thing changing in such a situation is that the apparent headwind is increasing (working from your definition), yet we definitely seem to extract energy from it.
uart said:Ok this really takes the cake. Are you just straight out lying or do you really expect us to believe that you don't understand the "strobe" effect of low frame rate movies (as per the old wagon wheels appear to turn backwards on movie films etc).
Here's the original outdooor test that Schroder is referring to.
Note that the device will be acting as a propeller if it turns counter-clockwise looking from behind and that it will be acting as a wind turbine if it turns clockwise when looking from behind. You can very clearly see that it turns counter-clockwise (from behind) when it is running very slowly, both at the start and at the end of the video. Now Schroder is telling us that this prop is actually rotating clockwise (from behind) because it appears to turn this way due to strobe effect at about 2.55 in the video. If you watch the whole video you can clearly see that it appears to change rotation direction many times throughout the clip, obviously due to strobe effect at different speeds.
Is there anyone else here that's seriously in doubt about the direction of rotation here (counter-CW from behind), or is this just another instance of Schroder being unbelievably silly?
Jeff Reid said:The fastest cart so far is only going 1.6 times wind speed, say 16 mph in a 10 mph wind. From the cart's frame of reference, apparent headwind = 6 mph, apparent ground speed = 16 mph, an overall efficiency factor of a paltry 37.5%.
Jeff Reid said:Correct. These carts extract energy from the tailwind by slowing it down. The headwind is an overhead, as explained in my previous post, but doesn't prevent DDWFTTW.
No sailcraft extracts energy from an apparent headwind (except when it's using the wind to decelerate the sailcraft). A sailcraft extracts energy from an apparent tailwind or apparent crosswind. The highest speeds are achieved when a sailcraft extracts energy from an apparent crosswind. Note the apparent crosswind is independent of the sailcrafts speed (by definition, it's perpendicular to the path of the sailcraft), and is equal to the true wind (wind_speed - ground_speed) times sin(angle between wind and direction of sailcraft). The maximum speed of the sailcraft depends on how much apparent headwind and ground related drag the sailcraft can achieve for a given apparent crosswind.
vanesch said:Yes!
1002 reached ! Brilliant. You guys have been great. With a special thanks to Schroder
The DDWFTTW carts don't need a crosswind component.schroder said:no crosswind component.
For DDWFTTW carts, the only thing that has to move slower than wind speed is the air from the prop wash. The craft will experience an apparent headwind, but the prop will be accelering the apparent headwind faster still, so that the prop wash still opposes the true wind, slowing the true wind down as required for any wind powered device.If the craft exceeds wind velocity, it will be going directly upwind!
schroder said:OH crap! What happened there? The cart goes off camera! How strange is that anyway? Right at the very point where we can see the direction of rotation! Accident or hoax? You be the judge.
And if you believe this video, I have a bridge for sale in Brooklyn, very good price special for you!
schroder said:Do you have any evidence for this? The best I have seen is Swerdna’s turntable during the heterodyne run with a ratio of 2.4 : 1
I have seen exactly Zero evidence of anything greater than wind velocity.
schroder said:Let us please leave sailboats and iceboats that are tacking at an angle, out of this discussion.
schroder said:this thread can stop as soon as you admit to the following:
1) There is NO evidence at all that any cart has ever or will ever go directly down wind faster than the wind.
2) That what is happeneing on the turntable, while interesting, has NO relationship to what happens in the wind.
schroder said:1) There is NO evidence at all that any cart has ever or will ever go directly down wind faster than the wind.
2) That what is happeneing on the turntable, while interesting, has NO relationship to what happens in the wind.