Author Topic: Woodward's effect  (Read 285119 times)

Offline Povel

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Re: Woodward's effect
« Reply #1180 on: 12/02/2017 06:55 PM »
Quote
Povel,

You and Monomorphic are not using the word "Thrust" in the same sense. You are arguing the thrust is in the direction of movement. Monomorphic's diagram is indicating the thrust is out the back and its movement is in the opposite direction.

I see, thank you for clarification WarpTech.
It seems incorrect to me, like for example I've never seen a rocket diagram with the thrust vector pointed away from the engines to be honest (that would be the drag direction at best). I'm pretty sure Woodward claims the device moves in the direction of the brass mass, so its thrust is directed in the same way.

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Re: Woodward's effect
« Reply #1181 on: 12/02/2017 06:55 PM »
I'd argue it is actually opposite. Using the notation of the scheme device you posted, the displacement you highlighted is in the positive x verse, while the thrust expected is in the negative x verse.

Sorry, I think you are right and I have my labels for PZT and rubber backwards. This image is probably more accurate than the first.
« Last Edit: 12/02/2017 07:02 PM by Monomorphic »

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Re: Woodward's effect
« Reply #1182 on: 12/02/2017 06:58 PM »
You and Monomorphic are not using the word "Thrust" in the same sense. You are arguing the thrust is in the direction of movement. Monomorphic's diagram is indicating the thrust is out the back and its movement is in the opposite direction.

Thanks, I was noticing that too. If used per these images, the second corrected diagram is more pricise I think.
« Last Edit: 12/02/2017 06:59 PM by Monomorphic »

Offline Povel

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Re: Woodward's effect
« Reply #1183 on: 12/02/2017 07:36 PM »
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Sorry, I think you are right and I have my labels for PZT and rubber backwards. This image is probably more accurate than the first.

No problem.

So correct me if I'm wrong, but to mimic a (presumably on average zero) thrust signal this simulation shows that you basically need a quite thick rubber pad with very low damping.

It has been said in this thread that the purpose of these pads is to reduce the stress/act like dampers, so they would need to act in the exact opposite way for the sistem to act like in the simulation. It somehow sound strange to me.

It is well known though that rubber is a non-linear material, so its response might be not so easy to predict. It would be nice to have a more accurate simulation that includes this non-linear behaviour I think, as well as being able to show how friction/stiction can lead to false positives not averaging to zero.


Offline WarpTech

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Re: Woodward's effect
« Reply #1184 on: 12/02/2017 07:36 PM »
I'd argue it is actually opposite. Using the notation of the scheme device you posted, the displacement you highlighted is in the positive x verse, while the thrust expected is in the negative x verse.

Sorry, I think you are right and I have my labels for PZT and rubber backwards. This image is probably more accurate than the first.

Shawyer makes the same mistakes in his diagrams and I've seen it confuse a lot of people in the past few years. You need to be careful to use the term consistently with the Aerospace industry, not Shawyer.

I don't think you had rubber and PZT backwards. Your other diagram was correct. The rubber is a thin sheet, between the brass mass and the mounting bracket. The aluminum on the left is the mounting bracket, not the end cap. The aluminum on the right is the end cap, and the Thrust is toward that side.

Povel,

In the latest experiments and per Dr. Rodal's exact solution, the thrust is toward the aluminium end cap at the light-mass end of the stack.

Offline Povel

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Re: Woodward's effect
« Reply #1185 on: 12/02/2017 07:53 PM »
Quote
I don't think you had rubber and PZT backwards. Your other diagram was correct. The rubber is a thin sheet, between the brass mass and the mounting bracket. The aluminum on the left is the mounting bracket, not the end cap. The aluminum on the right is the end cap, and the Thrust is toward that side.

Since he's trying to model the device in the most "simple" regime tested by Woodward, the "thrust" direction in the first diagram is definitely wrong.


Quote
Povel,

In the latest experiments and per Dr. Rodal's exact solution, the thrust is toward the aluminium end cap at the light-mass end of the stack.


Are you referring to this? (From Estes Park Proceedings)

Quote
As the first fundamental frequency due to piezoelectricity is approached from lower or higher frequencies that
are more than the (dimensionless) damping ratio (the ratio of the actual damping to the critical value of
damping) away from the resonant frequency peak,  the Mach effect force response is directed towards the
tail  (brass)  big  mass,  in  agreement  with  the  experiments  of  Woodward  and  Fearn
.   Inside  a  bandwidth
enveloped by the damping ratio, the Mach effect force response changes direction and is instead directed in
the opposite direction, towards the front (aluminum) small mass, reaching a peak value at the piezoelectric
natural frequency that is seven times greater than the peak value reached in the direction towards the tail
mass

I don't claim that the thrust cannot change sign in other regimes, just that in the one Woodward conducted much of his work (and the one Monomorphic is trying to imitate with his shakers/simulation) the thrust should be in the direction of the brass mass, like Rodal says here.
« Last Edit: 12/02/2017 08:00 PM by Povel »

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Re: Woodward's effect
« Reply #1186 on: 12/02/2017 08:08 PM »
So correct me if I'm wrong, but to mimic a (presumably on average zero) thrust signal this simulation shows that you basically need a quite thick rubber pad with very low damping.

The end-cap positions make no difference to the final simulation. I spaced them equally wide here so the brass mass can move a large distance and be easily seen for illustrative purposes.  I could more accurately model the relative spacing of components, but it would only make the effect smaller and harder to see. 

Perhaps a program like Autodesk Inventor would be a good candidate for simulating the various material properties.
« Last Edit: 12/02/2017 08:21 PM by Monomorphic »

Offline tdperk

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Re: Woodward's effect
« Reply #1187 on: 12/03/2017 12:27 PM »
In the latest experiments and per Dr. Rodal's exact solution, the thrust is toward the aluminium end cap at the light-mass end of the stack.

The thrust is dependent on the phase relationship of the mechanical vibrations and imposed voltages.  By moving them through 180 degrees, it can be nullified and reversed.  Of course none of it means anything until tested in a vacuum, and with the other tests in Woodward's protocol...

...Also many orders of magnitude more difficult to detect any signal produced by 250Hz, the effect is frequency dependent.

Offline PotomacNeuron

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Re: Woodward's effect
« Reply #1188 on: 12/04/2017 03:02 PM »
In the latest experiments and per Dr. Rodal's exact solution, the thrust is toward the aluminium end cap at the light-mass end of the stack.

The thrust is dependent on the phase relationship of the mechanical vibrations and imposed voltages.  By moving them through 180 degrees, it can be nullified and reversed.  Of course none of it means anything until tested in a vacuum, and with the other tests in Woodward's protocol...

...Also many orders of magnitude more difficult to detect any signal produced by 250Hz, the effect is frequency dependent.

So as I have said, the best way for a skeptic to test Woodward's experiments might be to grab their devices, seal them in a box, and hang the box on the torsion balance. Otherwise what ever the skeptic could have done, people would point out their differences from Woodward's experiments and do not take them seriously.
« Last Edit: 12/04/2017 03:05 PM by PotomacNeuron »
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Offline tdperk

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Re: Woodward's effect
« Reply #1189 on: 12/04/2017 05:58 PM »
In the latest experiments and per Dr. Rodal's exact solution, the thrust is toward the aluminium end cap at the light-mass end of the stack.

The thrust is dependent on the phase relationship of the mechanical vibrations and imposed voltages.  By moving them through 180 degrees, it can be nullified and reversed.  Of course none of it means anything until tested in a vacuum, and with the other tests in Woodward's protocol...

...Also many orders of magnitude more difficult to detect any signal produced by 250Hz, the effect is frequency dependent.

So as I have said, the best way for a skeptic to test Woodward's experiments might be to grab their devices, seal them in a box, and hang the box on the torsion balance. Otherwise what ever the skeptic could have done, people would point out their differences from Woodward's experiments and do not take them seriously.

You realize not operating the devices on something like a torsion balance while in a vacuum does fail to exclude confounding false positives or negatives from reaction with the air, right?

« Last Edit: 12/04/2017 06:00 PM by tdperk »

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Re: Woodward's effect
« Reply #1190 on: 12/04/2017 06:14 PM »
You realize not operating the devices on something like a torsion balance while in a vacuum does fail to exclude confounding false positives or negatives from reaction with the air, right?

If the magnitude of the vibrations is high enough (large stroke with large mass), then the contribution of the air is negligible. Certainly not enough to cast the amount of doubt you are claiming. The air is simply pushed out of the way.

And the simulations I am running are performed in a "simulated" vacuum. Air is not a contributing factor there.
« Last Edit: 12/04/2017 06:23 PM by Monomorphic »

Offline PotomacNeuron

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Re: Woodward's effect
« Reply #1191 on: 12/04/2017 06:52 PM »
In the latest experiments and per Dr. Rodal's exact solution, the thrust is toward the aluminium end cap at the light-mass end of the stack.

The thrust is dependent on the phase relationship of the mechanical vibrations and imposed voltages.  By moving them through 180 degrees, it can be nullified and reversed.  Of course none of it means anything until tested in a vacuum, and with the other tests in Woodward's protocol...

...Also many orders of magnitude more difficult to detect any signal produced by 250Hz, the effect is frequency dependent.

So as I have said, the best way for a skeptic to test Woodward's experiments might be to grab their devices, seal them in a box, and hang the box on the torsion balance. Otherwise what ever the skeptic could have done, people would point out their differences from Woodward's experiments and do not take them seriously.

You realize not operating the devices on something like a torsion balance while in a vacuum does fail to exclude confounding false positives or negatives from reaction with the air, right?

Air might be a confounding factor if there is movement/"thrust". However, it is not a confounding factor if there is no movement. So no, for my proposed experiment, it is not. That is the beauty of the experiment. Now the question is whether "they" are willing to lend their devices out.
« Last Edit: 12/04/2017 06:53 PM by PotomacNeuron »
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Offline tdperk

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Re: Woodward's effect
« Reply #1192 on: 12/05/2017 12:18 AM »
In the latest experiments and per Dr. Rodal's exact solution, the thrust is toward the aluminium end cap at the light-mass end of the stack.

The thrust is dependent on the phase relationship of the mechanical vibrations and imposed voltages.  By moving them through 180 degrees, it can be nullified and reversed.  Of course none of it means anything until tested in a vacuum, and with the other tests in Woodward's protocol...

...Also many orders of magnitude more difficult to detect any signal produced by 250Hz, the effect is frequency dependent.

So as I have said, the best way for a skeptic to test Woodward's experiments might be to grab their devices, seal them in a box, and hang the box on the torsion balance. Otherwise what ever the skeptic could have done, people would point out their differences from Woodward's experiments and do not take them seriously.

You realize not operating the devices on something like a torsion balance while in a vacuum does fail to exclude confounding false positives or negatives from reaction with the air, right?

Air might be a confounding factor if there is movement/"thrust". However, it is not a confounding factor if there is no movement. So no, for my proposed experiment, it is not. That is the beauty of the experiment. Now the question is whether "they" are willing to lend their devices out.

Uhuh.  Why can't you build you own per their specs?  Like the other people replicating their work did?  For that matter, what is the difference between operating the device in an evacuated box on a torsion balance, and putting the whole thing in the vacuum?

Offline PotomacNeuron

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Re: Woodward's effect
« Reply #1193 on: 12/05/2017 02:15 AM »

Uhuh.  Why can't you build you own per their specs?  Like the other people replicating their work did?  For that matter, what is the difference between operating the device in an evacuated box on a torsion balance, and putting the whole thing in the vacuum?

Because I expect to see no thrust if I correctly control for the Bull's effect. Then you will say that's because my build is different and it can not be used to invalidate Woodward's experiment. That's why.
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Offline birchoff

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Re: Woodward's effect
« Reply #1194 on: 12/05/2017 03:02 AM »

Uhuh.  Why can't you build you own per their specs?  Like the other people replicating their work did?  For that matter, what is the difference between operating the device in an evacuated box on a torsion balance, and putting the whole thing in the vacuum?

Because I expect to see no thrust if I correctly control for the Bull's effect. Then you will say that's because my build is different and it can not be used to invalidate Woodward's experiment. That's why.

That critique is only valid if your build deviate from the specs. If it doesnt then the critique is invalid. As a supporter of the work without the resources to do such a test myself I would love to see someone else do the test if they have the ability and resources. As long as they are going to be open about their build and willing to answer questions. I think if you did do a perfect build and got negative results I would want to know if the PZT stack is good.

Offline PotomacNeuron

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Re: Woodward's effect
« Reply #1195 on: 12/05/2017 03:26 AM »

Uhuh.  Why can't you build you own per their specs?  Like the other people replicating their work did?  For that matter, what is the difference between operating the device in an evacuated box on a torsion balance, and putting the whole thing in the vacuum?

Because I expect to see no thrust if I correctly control for the Bull's effect. Then you will say that's because my build is different and it can not be used to invalidate Woodward's experiment. That's why.

That critique is only valid if your build deviate from the specs. If it doesnt then the critique is invalid. As a supporter of the work without the resources to do such a test myself I would love to see someone else do the test if they have the ability and resources. As long as they are going to be open about their build and willing to answer questions. I think if you did do a perfect build and got negative results I would want to know if the PZT stack is good.

Agree. I was talking about if it were me how I would do it. I will not do the experiment for reasons presented on page 55. I'd like to see somebody to do the experiment. Monomorphic's experiment, however, as expected, drew critiques of being different.
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Re: Woodward's effect
« Reply #1196 on: 12/05/2017 01:12 PM »
Agree. I was talking about if it were me how I would do it. I will not do the experiment for reasons presented on page 55. I'd like to see somebody to do the experiment. Monomorphic's experiment, however, as expected, drew critiques of being different.

My prediction is Woodward's MET wouldn't work as well on my torsional pendulum due to the mechanical differences between the two systems. Mine is much longer to accommodate a laser displacement sensor (LDS) with 3um resolution vs Woodward's 0.25um. A shorter stroke, as what is produced by the PZT, would be harder for me to detect. It may even fall below the resolution of my laser displacement sensors.   :-\

The most economical way for me to proceed is to complete this last series of physical tests with the asymmetric shaker, but then concentrate on producing a more accurate physics-based simulation. If the same effect can be produced with simple known physics via simulation, then there shouldn't be the need for anything else.

« Last Edit: 12/05/2017 01:28 PM by Monomorphic »

Offline birchoff

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Re: Woodward's effect
« Reply #1197 on: 12/05/2017 02:29 PM »
Agree. I was talking about if it were me how I would do it. I will not do the experiment for reasons presented on page 55. I'd like to see somebody to do the experiment. Monomorphic's experiment, however, as expected, drew critiques of being different.

My prediction is Woodward's MET wouldn't work as well on my torsional pendulum due to the mechanical differences between the two systems. Mine is much longer to accommodate a laser displacement sensor (LDS) with 3um resolution vs Woodward's 0.25um. A shorter stroke, as what is produced by the PZT, would be harder for me to detect. It may even fall below the resolution of my laser displacement sensors.   :-\

The most economical way for me to proceed is to complete this last series of physical tests with the asymmetric shaker, but then concentrate on producing a more accurate physics-based simulation. If the same effect can be produced with simple known physics via simulation, then there shouldn't be the need for anything else.

Was this done in a vaccum chamber?

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Re: Woodward's effect
« Reply #1198 on: 12/05/2017 03:16 PM »
Was this done in a vaccum chamber?

No, as it was not necessary. The mass of air displaced during tests is very small <0.1g (1.225 x10−3 g/cm3). The amount of stainless steel is 40g (7.8 g/cm3). The first two shakers did not produce vibrations of sufficient magnitude, but version 3 and especially version 4 did. I would be willing to wager that Woodward's device "works" in air due to the large mass of the brass end-cap, but a vacuum is used so that the experiment is taken to be more rigorous. At any rate, it is better to create a more accurate simulation so I am not out the expense of more equipment. If the effect can be produced with simple rigid and soft body physics via simulation, then that is enough for me.
« Last Edit: 12/05/2017 09:51 PM by Monomorphic »

Offline Povel

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Re: Woodward's effect
« Reply #1199 on: 12/07/2017 06:29 PM »
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I would be willing to wager that Woodward's device "works" in air due to the large mass of the brass end-cap, but a vacuum is used so that the experiment is taken to be more rigorous.

What do you mean by this? In his book there's a section dedicated to assessing the effect of air by testing the device at different atmospheric pressure. The result is that the presence of air doesn't seem to change that much the signals magnitude and shape.

Beside all the differences due to the different set up, I noticed that the "thrusts" signals you obtained (reply #1142, third figure) are all different both in magnitude and shape. I don't see the same level on consistency between the input and the output compared to those obtained by Woodward, Tajmar and Buldrini.

As for the simulations, it seems to me that the asymmetric shaker mounted on an ideal thrust/torsion balance can only produce constant oscillations at the same frequency of the shaker.
Without invoking some non-ideality causing Dean drive effects there's no way to get a steady deflection, since at the end of each cycle it would go to zero.




By the way, have there been any new developments? 
NIAC Phase I 9 months research-grant ends in January from what I know. Is there any possibility for Fearn&co to apply for Phase II?