Merged DDWFTTW in a “Real” Wind

[69dodge]

By the time it reaches wind speed, the only opposing force to the torque from the wheels is pure drag on the propeller blades, which is considerable, but has nothing to do with the prop wanting to turbine.

I guess the reason for the opposing torque isn't as important as its magnitude. Do you have any typical values for the thrust produced by a propeller spinning in stationary air, compared to the torque driving the propeller?

 

[Llyricist]

I guess the reason for the opposing torque isn't as important as its magnitude. Do you have any typical values for the thrust produced by a propeller spinning in stationary air, compared to the torque driving the propeller?

In the past, other people have plugged in the numbers to java prop and other propeller programs to get static thrust figures, I think spork might have that data for the prop in question from the dynamo tests, but I have never seen it.

I've only run the numbers for beyond wind speed, since that's the only regime the formulas I know can develop useful numbers for thrust vs power. They don't work for speeds of 0 or less through the air.

 

[spork]

In the past, other people have plugged in the numbers to java prop and other propeller programs to get static thrust figures, I think spork might have that data for the prop in question from the dynamo tests, but I have never seen it.

I've only run the numbers for beyond wind speed, since that's the only regime the formulas I know can develop useful numbers for thrust vs power. They don't work for speeds of 0 or less through the air.

I do have the theoretical prop performance results somewhere. I can dig them up if someone really wants to see them. And yes, they only cover the case 0 relative wind speed and greater. There are a number of ways to try to compute the values for a prop in reversed flow, but they vary from poor approximation to relatively poor approximation and difficult.

 

[humber]

To educate himself. I know that the concept is foreign to you, but it is what many of us do when we realize our understanding may in fact be limited by lack of knowledge.

And what do you use as a surrogate for that certainly limited understanding?

Many people are uncomfortable when they realize that due to spouting opinions from a position of ignorance they have become a laughingstock.

Such as yourself?

The Huff really put that cart under scrutiny. After taking the trouble to plan the flight, he did nothing to prepare for any tests that would satisfy his curiosity or vindicate or deny his skepticism.
There is definite unease in his voice when he says "significant headwind". The remainder of his bar-stool diatribe concerned the usual Sporkian stuff about being right and eating hats.

 

[humber]

I assumed NALSA would post it either upon receipt or upon analysis. Is there some reason they wouldn't?

I am keeping it from you, and to prevent you associating yourself with NALSA by proxy, so taring them with the same brush. It is clear that Bob Dill is largely unaware of the forum activity.

 

[A.T.]

This might be a good time for someone to post a link to Platt's ridiculous cart.

Here it is:
http://www.make-digital.com/make/vol11/?pg=60&pm=2&u1=friend#pg60

The prop is funny enough. But when you read his article, you realize that he was completelly clueless how it was supposed to work. He was poking in the dark just like I Ratant. His gearing was wrong so with positive advance ratio the cart went UPwind (ratio > 1).

Recently MAKE corrected his errors:
http://www.make-digital.com/make/vol26?pg=59#pg59

 

[69dodge]

I do have the theoretical prop performance results somewhere. I can dig them up if someone really wants to see them. And yes, they only cover the case 0 relative wind speed and greater. There are a number of ways to try to compute the values for a prop in reversed flow, but they vary from poor approximation to relatively poor approximation and difficult.

I'd be interested to see them, if it's not too much trouble.

What do you mean by 'theoretical'?

 

[humber]

I guess the reason for the opposing torque isn't as important as its magnitude. Do you have any typical values for the thrust produced by a propeller spinning in stationary air, compared to the torque driving the propeller?

Yes. You can see it in two of the videos. One being "First Spin Up", the other is "High Speed Momentum Test" or name to that effect.

In the former, the BB's prop is rotated by hand, and from the change in angular velocity between input from the hand turning it, it is readily calculated that the prop is producing no more than 3W at 15rpm.

 

[ThinAirDesigns]

All from TAD, Joby and Volvo racing and other sundry zealots.

Humber's definition of "independent" -- someone who still claims DDWFTTW is impossible. Once you become convinced that it's doable, or perhaps even try it yourself and succeed, you are no longer independent.

Jenkins' response is odd.

Only to you.

He was in the past, totally dismissive, yet, he bothers to fly out ( at his own expense, I am told) to attend the trial. Why would one do that?

Because he believe is was impossible and yet was being told by people he trusted that it not only was possible, but had already been done.

What he sees, is an affront to his current understanding of wind vehicles, ...

Not true --, in fact it meshed perfectly with his understanding once he got passed the counterintuitive nature of the device.

... but is apparently not at all curious to find out what may be at work, so that he may learn from the experience he paid for.

Again not true. He was so curious that he paid his own way to the test in SoCal. It's hard to get more curious than that.

He conducts not specific tests to isolate what may be the root mechanism.

Again not true -- he tested the root mechanism on the Greenbird. He's spent years testing the root mechanism.

humber fail.

JB

 

[humber]

I'd be interested to see them, if it's not too much trouble.

What do you mean by 'theoretical'?

There you go Spork, direct interest form me too. So, "dig that up"

 

[ThinAirDesigns]

I assumed NALSA would post it either upon receipt or upon analysis.

NALSA will be perfectly open. They have responded positively to any and all requests for information/data regarding the record. This would be no different.

JB

 

[humber]

All from TAD, Joby and Volvo racing and other sundry zealots.

Humber's definition of "independent" -- someone who still claims DDWFTTW is impossible. Once you become convinced that it's doable, or perhaps even try it yourself and succeed, you are no longer independent.

All were quite convinced prior to the trial, including JoeBen Bevirt himself.
All of the FTW/TAD team, and Volvo have direct interest on the boat "PlayStation" and with Sportsvison.

Jenkins' response is odd.

Only to you.

A distinct lack of curiosity, and a road to Damascus conversion in one day.
I would expect that any engineer would be fired for that.

He was in the past, totally dismissive, yet, he bothers to fly out ( at his own expense, I am told) to attend the trial. Why would one do that?
Because he believe is was impossible and yet was being told by people he trusted that it not only was possible, but had already been done.
What he sees, is an affront to his current understanding of wind vehicles, ...

Not true --, in fact it meshed perfectly with his understanding once he got passed the counterintuitive nature of the device.

I see, you are saying the his former stance was due to ignorance, but his change of mind won't be? Is it simply a case of last in, last correct?
And you can keep that "counter-intuitive" line for the tourists.

... but is apparently not at all curious to find out what may be at work, so that he may learn from the experience he paid for.

Again not true. He was so curious that he paid his own way to the test in SoCal. It's hard to get more curious than that.

I would have prepared some specific tests. I can think of a several that could be done with a fishing scale and a length of rope, and others with an accelerometer attached to the cart with Gaffer tape.

He conducts not specific tests to isolate what may be the root mechanism.
Again not true -- he tested the root mechanism on the Greenbird. He's spent years testing the root mechanism.

Name one.
And another contradiction from TAD. According to you, he "spent years testing the root mechanism" but concluded that it would not work, but you some how managed to instantly contradict all the supposed effort, which would rather undermine his value as an expert.

 

[Dr. Keith]

NALSA will be perfectly open. They have responded positively to any and all requests for information/data regarding the record. This would be no different.

JB

That's what I assumed, but it seemed like humber was expecting them to keep it under wraps and others were agreeing that we would never see it.

Maybe if humber keeps posting here we may never see anything. That's stuff's not going to write itself!

 

[humber]

Here it is:
http://www.make-digital.com/make/vol11/?pg=60&pm=2&u1=friend#pg60

The prop is funny enough. But when you read his article, you realize that he was completelly clueless how it was supposed to work. He was poking in the dark just like I Ratant. His gearing was wrong so with positive advance ratio the cart went UPwind (ratio > 1).

Recently MAKE corrected his errors:
http://www.make-digital.com/make/vol26?pg=59#pg59

There you go, direct insults without the credentials to come even close to backing then up.
And yes, the gearing is chosen to show that it is an upwind cart, blown downwind.

 

[humber]

That's what I assumed, but it seemed like humber was expecting them to keep it under wraps and others were agreeing that we would never see it.

Maybe if humber keeps posting here we may never see anything. That's stuff's not going to write itself!

Bob Dill has been very open and co-operative, and that is why he gets to see the report before you do, because of those characteristics. You will not find one post where I accused him of dishonesty or collusion, but saying that he was deceived, and all but press-ganged into agreement by sheer weight of numbers. He was the only NALSA representative.

 

[ThinAirDesigns]

All were quite convinced prior to the trial, including JoeBen Bevirt himself.

No, Richard was *not* convinced before the trial. Certainly *most* were convinced before the trial because

A: most could do a high entry level Galilean transform
B: it had already been done in natural wind in Ivanpah.

All of the FTW/TAD team, and Volvo have direct interest on the boat "PlayStation" and with Sportsvison.

A: No.

B: It's very weird that you take guys who work for the conceptual design studios for Volvo cars and somehow think they are related to the Volvo sailboat racing series. I have a friend that works for a company that makes components for Volvo cars -- I suppose that means he's no longer independent as well.

A distinct lack of curiosity, and a road to Damascus conversion in one day. I would expect that any engineer would be fired for that.

No, a quality engineer would be fired for having the mechanism explained to him, understanding it and then watching it happen and upon return claim that it didn't happen.

JB

 

[humber]

In the past, other people have plugged in the numbers to java prop and other propeller programs to get static thrust figures, I think spork might have that data for the prop in question from the dynamo tests, but I have never seen it.

I've only run the numbers for beyond wind speed, since that's the only regime the formulas I know can develop useful numbers for thrust vs power. They don't work for speeds of 0 or less through the air.

And how much thrust is generated at 0.1rpm, as the cart begins to move?
The programme does not even produce a result for that AV. All of the math behind that programme is available in the given references, and that will would tell you why.

A Cessna's engine is not geared to the wheels, such that the forward velocity is directly related to the engine's RPM. There are no planes anywhere, specialist or not, that employ the technique, including aircraft carriers where a short runway is the only option.

The gearing forces the engine to accelerate the prop, and the entire plane at the same time, and laughably in the case of the BB, to drive it the other way.

Gearing to the wheels is not an enhancement, but a naive error, based upon barefoot physics of literally "screwing props".

The trial conditions, and test procedure are rigged to see that error is not exposed. Replace Jenkins with me, and I would take on 100 zealots, and leave them with a lot to explain. You can be assured of that.

Llyricist is busy trying to deny the established RMS technique, upon the absurd basis that is gives "the bigger number", but does not seem to consider that the simple average may have been inculcated, because it produces the lowest number.

 

[Jack by the hedge]

Don't you mean advancing?

I hesitate to mention frames of reference, but from the air's point of view it's retreating.

Imagine a streamline of wind, moving forward at windspeed. As the leading edge of the propeller blade cuts the streamline, that edge is advancing faster than the air but turning fast too, which means that the part of the blade cutting the streamline is a point which moves across the face of the blade. The pitch of the propeller means that as the point moves across the blade, it also moves backward on the blade. In fact it retreats fast enough that it moves backwards relative to the air (though still forwards relative to the ground).

So from the air's point of view, it encounters an "object" (in reality a travelling point on a real object) which is moving backwards.

From the ground's point of view (just to please the stubbornly earthbound) the streamline encounters an "object" which is travelling forwards at less than windspeed.

 

[ThinAirDesigns]

For those wondering about the whole silly "Volvo" thing that humber is rambling about.

Stan Honey is a friend of ours (and former boss) but completely unrelated to our project. Stan Honey was the winning navigator on a recent Volvo (sponsored) around the world sailing race. From reading about the scheduled tests on our blog, several guys from the Volvo (car) design studios in LA showed up unannounced (we had never heard of or from them) at the El Mirage record runs.

The tests were a sham because of this.

Humberspiracies abound.

JB

 

[humber]

For those wondering about the whole silly "Volvo" thing that humber is rambling about.

Stan Honey is a friend of ours (and former boss) but completely unrelated to our project. Stan Honey was the winning navigator on a recent Volvo (sponsored) around the world sailing race. From reading about the scheduled tests on our blog, several guys from the Volvo (car) design studios in LA showed up unannounced (we had never heard of or from them) at the El Mirage record runs.

The tests were a sham because of this.

Humberspiracies abound.

JB

That bluff acceptance of contradictions, explains the trail and error TM, and so the cart. No hoaxer would be that obvious, and post it, so the conclusion is that self-deception is the driving force.