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#3540 by tchernik on 04 Jul, 2016 22:12
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OK, my bad. As I understand it: the "force" (being an anomalous or a mundane one) seems to be pushing the frustum in the direction going from the big to the small end. Exactly as Shawyer's.
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#3541 by zen-in on 04 Jul, 2016 22:48
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OK, my bad. As I understand it: the "force" (being an anomalous or a mundane one) seems to be pushing the frustum in the direction going from the big to the small end. Exactly as Shawyer's.
That's where everyone makes the mistake.Force and thrust are equal and opposite.I propose we use the term LITTLE-EMDIAN to describe Shawyer's and Dave's results. Of course it is doubtful we will hear from anyone with a BIG-EMDIAN emdrive. -
#3542 by Rodal on 04 Jul, 2016 22:56
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Since there is no satisfactory explanation for what is being proposed, I suggest to completely eliminate the concept of a force (which is an intuitive concept that ultimately is not measurable (*)) and use what is being measured: the displacement.
So describe in which direction it is moving as "moving in the direction from the big end towards the small end"
(*) for example rfmwguy is measuring a displacement, due to a rotational angle in his torsional pendulum
measurements of force often are really measurements of displacement or its derivatives:
Elastic force
F=kx measures displacement x (spring)
Viscous force
F=c dx/dt measures the velocity of a damping force (for Newtonian viscosity assumption in a viscous fluid)
Inertial force
F=ma measures the acceleration due to an inertial force (accelerometer)
piezoelectric force: (measure strain: displacement per unit length)
force = k*d33*(Voltage/Length)
= k*strain
electrostrictive force (measure strain)
force =k*q33*(Voltage/Length)^2
=k*strain
thermal force (measure strain)
force=k*deltaT*(coefficient of thermal expansion)
=k*strain
LORENTZ electromagnetic force: this one confuses a huge number of authors who often fail to include all terms !, and they get confused as to what they are measuring
and so and on.
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#3543 by meberbs on 04 Jul, 2016 22:57
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Hopefully this reduces confusion rather than increasing it:
As far as I am aware, EMdrive claims all are such that the EMdrive would move with the small end as the front. (What Zen-in calls little-emdian) For an object to accelerate, a force needs to be applied to it in the direction it accelerates. For vehicles such as airplanes or rockets the force applied to the vehicle in the forward direction is called thrust. Thrust is generally referred to as the force applied to the object in the direction you want it to accelerate. See this diagram: https://www.grc.nasa.gov/www/k-12/airplane/thrust1.html
As long as Newton's third law still works the vehicle applies an equal force on the environment in the opposite direction to the force that is applied to it, but we only care about the force the vehicle experiences. (expelled gases for a rocket become part of the environment)
[speculation]
I believe a lot of the confusion in this area can be traced back to Shawyer, as Shawyer's original theory, if correct, would have the EMdrive moving big end first (big-emdian), but depending which paper you read, he adds some form of confusion regarding reaction forces and ends up flipping everything inside out.
[/speculation]
Edit: what Rodal says above is probably the best for clarity. -
#3544 by TheTraveller on 04 Jul, 2016 23:27
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Dave just did a test to measure the beam return to centre time and oscillatory period as attached.
From the very sharp rate of change event it is clear when he hit the side of the beam with his pen, driving it down to hit the movement stop (flat period after pen impact) and then to plot out the oscillatory period and the time to damp the motion to background.
Also attached the raw output from his test software to compare against the plot from the collected data.
Time intervals in the plot of the Excel data are 0.8 sec.
Time to damp from the beam leaving the stop at ~180 to no motion at ~580 is 400 intervals * 0.8 sec = 320 secs or 5 minutes 20 seconds.
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#3545 by zen-in on 04 Jul, 2016 23:53
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Dave just did a test to measure the beam return to centre time and oscillatory period as attached.
From the very sharp rate of change event it is clear when he hit the side of the beam with his pen, driving it down to hit the movement stop (flat period after pen impact) and then to plot out the oscillatory period and the time to damp the motion to background.
Also attached the raw output from his test software to compare against the plot from the collected data.
Time intervals in the plot of the Excel data are 0.8 sec.
The plot is clearly a second order step response, as would be expected. Any emdrive thrust should have the same overshoot and decaying oscillation. A larger paddle in the oil bath would reduce the overshoot and settle time. What would be even more interesting is to see the response from a calibrated force. EagleWorks used charged capacitor plates to generate their calibration force. Just apply the force and hold it until everything settles down. The plot should look very similar. because both are step responses.
In the merged plot below I am assuming both X-axis units are seconds. I clipped 145 Sec from the long duration plot, starting from when RF power was applied and I expanded it so the width was the same as 145 Sec of the step response plot. Not enough information is available to compare the amplitudes of the two plots. It is apparent the two plots are very different. From the step response the time constant of the torque pendulum can be read as approximately 130 Sec. The forcing function there was the stored energy in the pendulum wire. In 2.5 Min. (the On time of the magnetron for the long duration test) there are 3 peaks in the step response waveform. This doesn't appear in the long duration waveform.
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#3546 by WarpTech on 04 Jul, 2016 23:59
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Dave just did a test to measure the beam return to centre time and oscillatory period as attached.
From the very sharp rate of change event it is clear when he hit the side of the beam with his pen, driving it down to hit the movement stop (flat period after pen impact) and then to plot out the oscillatory period and the time to damp the motion to background.
Also attached the raw output from his test software to compare against the plot from the collected data.
Time intervals in the plot of the Excel data are 0.8 sec.
Dave needs more resistance, thicker oil or more surface area on his dampers. It's no where near critically damped or over damped.
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#3547 by Rodal on 05 Jul, 2016 00:38
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Dave just did a test to measure the beam return to centre time and oscillatory period as attached.
From the very sharp rate of change event it is clear when he hit the side of the beam with his pen, driving it down to hit the movement stop (flat period after pen impact) and then to plot out the oscillatory period and the time to damp the motion to background.
Also attached the raw output from his test software to compare against the plot from the collected data.
Time intervals in the plot of the Excel data are 0.8 sec.
Dave needs more resistance, thicker oil or more surface area on his dampers. It's no where near critically damped or over damped.
OMG !
I'm so glad you are back
The great WarpTech is back
We hope you are here to stay !
PS: I agree with the fact that he needs thicker oil and more surface on the dampers. I advised that he should install another set symmetrically located on the other side from the center of rotation -
#3548 by masterharper1082 on 05 Jul, 2016 03:30
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Let's try again using the definitions created in the last couple of hours. I propose that pure thermally driven force due to natural convection from a heat source applied to the big end will be in the direction of the big end, thrust toward the small end. This is the opposite of what rfmwguy and other builders have seen with a working RF source. Thus, I am proposing that natural convection driven force/thrust is BIG-EMDIAN. The computer geek part of me sniggers while reading this. We've just started the next 30-year war. 😀
You understand my expectation properly. We'll see if real life matches my expectations...
This is exactly correct. There is a mechanism for a yaw moment to be produced. Heating of the end causes a natural convection air flow up due to buoyancy. Air velocity up can cause a pressure differential, and thus a force towards the hot end. This should cause a small displacement of the torsional pendulum in the direction of the hot end.
Use the heat lamp to get the end at a steady temperature similar to when the maggie is running. There may some small torque oscillations due to vortices being formed.
Sent from my SM-T710 using Tapatalk
In that case shouldn't the thermal thrust go towards the big end in Dave's setup?
AFAIK if his experiment the magnetron is place at the big end.
Sent from my SM-T710 using Tapatalk -
#3549 by WarpTech on 05 Jul, 2016 03:49
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Dave just did a test to measure the beam return to centre time and oscillatory period as attached.
From the very sharp rate of change event it is clear when he hit the side of the beam with his pen, driving it down to hit the movement stop (flat period after pen impact) and then to plot out the oscillatory period and the time to damp the motion to background.
Also attached the raw output from his test software to compare against the plot from the collected data.
Time intervals in the plot of the Excel data are 0.8 sec.
Dave needs more resistance, thicker oil or more surface area on his dampers. It's no where near critically damped or over damped.
OMG !
I'm so glad you are back
The great WarpTech is back
We hope you are here to stay !
PS: I agree with the fact that he needs thicker oil and more surface on the dampers. I advised that he should install another set symmetrically located on the other side from the center of rotation
Just on a little vacation from work. Thought I'd drop in and see if anyone launched one off the ground yet.
Happy 4th!
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#3550 by masterharper1082 on 05 Jul, 2016 03:50
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LITTLE-EMDIAN and BIG-EMDIAN is a SUPERB science pun.OK, my bad. As I understand it: the "force" (being an anomalous or a mundane one) seems to be pushing the frustum in the direction going from the big to the small end. Exactly as Shawyer's.
That's where everyone makes the mistake.Force and thrust are equal and opposite.I propose we use the term LITTLE-EMDIAN to describe Shawyer's and Dave's results. Of course it is doubtful we will hear from anyone with a BIG-EMDIAN emdrive.
Reminds me of another from Jerome Bixby in his sci-fi short story, "The Holes Around Mars" (which fits extremely well given that a successful EM-Drive is likely first targeted for Mars).
That night in the ship, while we all sat around, still shaking our heads every once in a while, Allenby talked with Earth. He sat there, wearing the headphones, trying to make himself understood above the god-awful static.
". . . an exceedingly small body," he repeated wearily to his unbelieving audience, "about four inches in diameter. It travels at a mean distance of four feet above the surface of the planet, at a velocity yet to be calculated. Its unique nature results in many hitherto unobserved—I might even say unimagined—phenomena." He stared blankly in front of him for a moment, then delivered the understatement of his life. "The discovery may necessitate a reexamination of many of our basic postulates in the physical sciences."
[. . .]
"Inasmuch as Mars's outermost moon is called Deimos, and the next Phobos," he said, "I think I shall name the third moon of Mars—Bottomos."
Zen-in, simply glorious.
We should insist that all peer-reviewed papers use this terminology going forward.
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#3551 by SeeShells on 05 Jul, 2016 04:47
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Dave just did a test to measure the beam return to centre time and oscillatory period as attached.
From the very sharp rate of change event it is clear when he hit the side of the beam with his pen, driving it down to hit the movement stop (flat period after pen impact) and then to plot out the oscillatory period and the time to damp the motion to background.
Also attached the raw output from his test software to compare against the plot from the collected data.
Time intervals in the plot of the Excel data are 0.8 sec.
Dave needs more resistance, thicker oil or more surface area on his dampers. It's no where near critically damped or over damped.
OMG !
I'm so glad you are back
The great WarpTech is back
We hope you are here to stay !
PS: I agree with the fact that he needs thicker oil and more surface on the dampers. I advised that he should install another set symmetrically located on the other side from the center of rotation
Just on a little vacation from work. Thought I'd drop in and see if anyone launched one off the ground yet.
Happy 4th!
Good to see your post and taking a break. You are missed.
I tried to launch but couldn't find all the pieces after.
Happy 4th.
Shell -
#3552 by TheTraveller on 05 Jul, 2016 13:39
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Here is Dave's latest data, with my mm scaled plot with rate of change as mm/100. Note the image of his improved oil damper.
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#3553 by Rodal on 05 Jul, 2016 15:30
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Here is Dave's latest data, with my mm scaled plot with rate of change as mm/100. Note the image of his improved oil damper.
Excellent test.
What is the meaning of the first downward and then up spike trace? Is that a transient that was tested on purpose? Do you know how it was produced? Known force or known initial velocity?
===>if that initial spike was done on purpose by rfmwguy, it is a good way to quantify the dynamic response of the torsional pendulum
===> could you please show a plot with your rate of change that includes that initial first transient as well for comparison ? -
#3554 by TheTraveller on 05 Jul, 2016 15:34
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===> could you please show a plot with your rate of change that includes that initial first transient as well for comparison ?
Dave said it was a horizontal tap test to ensure the data collection system was working.
Like saying into a mike "Testing 1 2 3". -
#3555 by TheTraveller on 05 Jul, 2016 16:08
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Here are the Force calculations from each of the 3 test runs in Dave's latest data.
Very consistent 15mN, which suggest Dave could leave the maggie power on for a longer time and achieve a higher force result?
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#3556 by Rodal on 05 Jul, 2016 17:10
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Here are the Force calculations from each of the 3 test runs in Dave's latest data.
Very consistent 15mN, which suggest Dave could leave the maggie power on for a longer time and achieve a higher force result?
Isn't that another argument (besides the fact that there is an exponential fast rise and a slow exponential decay) that this force is thermal in nature?
That the longer he heats the more displacement he gets?
Wasn't the EM Drive supposed to give a constant force for a constant power input?
Isn't his power input a constant during the test ? 900 watts? -
#3557 by zen-in on 05 Jul, 2016 17:28
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Here are the Force calculations from each of the 3 test runs in Dave's latest data.
Very consistent 15mN, which suggest Dave could leave the maggie power on for a longer time and achieve a higher force result?
Isn't that another argument (besides the fact that there is an exponential fast rise and a slow exponential decay) that this force is thermal in nature?
That the longer he heats the more displacement he gets?
Wasn't the EM Drive supposed to give a constant force for a constant power input?
Isn't his power input a constant during the test ? 900 watts?
I agree. The torque pendulum acts like a spring. A constant force acting against it will cause an angular displacement. If the force acts for a longe time the angular displacement will not increase. Heating, on the other hand does integrate and will eventually reach an asymptotic level as the heat produced by the magnetron equals the heat that is continually dissipated by convection. Run the magnetrons longer and see if the displacement stays the same (a real em-drive force) or if it continues to rise then rolls off (thermal). -
#3558 by TheTraveller on 05 Jul, 2016 17:44
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Here are the Force calculations from each of the 3 test runs in Dave's latest data.
Very consistent 15mN, which suggest Dave could leave the maggie power on for a longer time and achieve a higher force result?
Isn't that another argument (besides the fact that there is an exponential fast rise and a slow exponential decay) that this force is thermal in nature?
That the longer he heats the more displacement he gets?
Wasn't the EM Drive supposed to give a constant force for a constant power input?
Isn't his power input a constant during the test ? 900 watts?
I agree. The torque pendulum acts like a spring. A constant force acting against it will cause an angular displacement. If the force acts for a longe time the angular displacement will not increase. Heating, on the other hand does integrate and will eventually reach an asymptotic level as the heat produced by the magnetron equals the heat that is continually dissipated by convection. Run the magnetrons longer and see if the displacement stays the same (a real em-drive force) or if it continues to rise then rolls off (thermal).
We have a non constant excitation freq and non constant power (is altered by the amount of maggie freq pulling), which varies as the maggie temperature varies. Were this being excited by a single freq generator then to a Rf amp, with real time lowest VSWR tracking, the Force should remain constant.
My asking for a longer power run was based on maybe there was more force delivered than had been balanced by resistant torque as the maggie was maybe powered down too quickly. -
#3559 by dustinthewind on 05 Jul, 2016 18:04
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So locking the frustum in its own little Styrofoam box for a short time should eliminate all thermal convection thrust? Assuming you can safely keep it in there long enough to tell. Maybe some way for it to heat a small dish of water that is inside as a heat sink.
Maybe a box with holes where the air can exit and enter would give vertical thermal thrust, allowing air cooling, and eliminating horizontal air flow.
Happy 4th.