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#2900 by Monomorphic on 28 Feb, 2017 14:34
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Which way are you swiping the magnet on the beam? Vertically or horizontally?
Almost all swipes have been mostly horizontal, but it's more like an arcing motion actually. It may be necessary to build a small EM coil that I can energize in pulses. That way I can precisely control the intensity of the taps. -
#2901 by SeeShells on 28 Feb, 2017 14:49
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I played around with a mechanical momentary switch eliminating the bounce with a 9 volt battery, voice coil from a old speaker, RC filter ckt and a transistor that worked well, but decided it wasn't good enough as the pulse width would vary and have a 555 timer that I'm putting together as a single shot to get cleaner pulses.Which way are you swiping the magnet on the beam? Vertically or horizontally?
Almost all swipes have been mostly horizontal, but it's more like an arcing motion actually. It may be necessary to build a small EM coil that I can energize in pulses. That way I can precisely control the intensity of the taps.
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#2902 by Peter Lauwer on 28 Feb, 2017 19:43
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...
Clearly, to me, the way to proceed in these cases, is the way that Cavendish pendulums have been used in research institutions: using low damping (rather than using gear oil), and minimizing any sources of noise, rather than using a high-damping fluid with Non-Newtonian shear-rate dependence that makes the analysis of the experiment much more complicated under all the explanations that have been offered.
The torsion balances in research institutions (for measuring 'big G', 5-th forces, etc.) usually have to measure forces 2 or 3 orders of magnitude smaller (rough estimate). For the range of forces we hope to measure, less optimal devices might suffice. Isn't it? -
#2903 by Peter Lauwer on 28 Feb, 2017 19:45
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Which way are you swiping the magnet on the beam? Vertically or horizontally?
Almost all swipes have been mostly horizontal, but it's more like an arcing motion actually. It may be necessary to build a small EM coil that I can energize in pulses. That way I can precisely control the intensity of the taps.
Indeed, a coil is much better. Will only take 10 minutes if you have the right copper wire. -
#2904 by Monomorphic on 28 Feb, 2017 22:00
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Indeed, a coil is much better. Will only take 10 minutes if you have the right copper wire.
I had to make a trip to radio shack to pick up the momentary switch, but I had some enameled magnet wire already.
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#2905 by oyzw on 28 Feb, 2017 22:48
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Hello, are you going to make YBCO superconducting cavity? I recommend the use of antenna coupling, the use of low-power solid-state amplifier. I can send you the simulation drawings for reference. Coaxial cables and connectors and antennas are also easy to be cooled by liquid nitrogen.
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#2906 by Monomorphic on 01 Mar, 2017 00:08
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First tap test using the new electromagnet set-up. This is a 10 second duration test. ~9.35uN
How does the damping look?
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#2907 by Rodal on 01 Mar, 2017 00:11
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First tap test using the new electromagnet set-up. This is a 10 second duration test. ~9.35uN
Fantastic. That is a very well-formed damped oscillation, this time one can see many periods
How does the damping look?
Estimating the damping using the logarithmic decrement of two successive peaks:
https://en.wikipedia.org/wiki/Logarithmic_decrement
I calculate the logarithmic decrement and the damping ratio ζ as follows:
Mean of noise floor:~ 12.675
And using the peak maxima from the Excel file:
x0 = 12.7417 - 12.675 = 0.06670
x1 = 12.6904 - 12.675 = 0.01543
Logarithmic decrement
δ=ln (xo/x1) = ln (0.06670/0.01543) = 1.46389
which is practically identical with the one estimated the last time ! 1.468815
Damping ratio
ζ = 0.227 practically identical with the one estimated the last time also ζ = 0.227
And reasonably close to the one before that: ζ = 0.22
The water-anti-freeze suggested by Shell is fantastic !!!, you get the identical damping ratio ζ = 0.23 experiment after experiment !!!
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The second resonant peak after the tap first occurs at 12:37:13 PM, therefore the damped period, is (subtracting the time at which the peak of the tap occurs)
T = 12:37:13 PM - 12:36:32 PM = 41 seconds
the period is now shorter (the last time was estimated as 48 seconds)
It looks like you reduced the Moment of Inertia of the beam (like you reduced the mass)
And using the relationship ω=ωo √(1- ζ2) where ωo is the undamped natural frequency, therefore the undamped period should be:
To = T √(1- ζ2) = 41 √(1- 0.2272) = 39.93 seconds ~ 40 seconds
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#2908 by SeeShells on 01 Mar, 2017 01:25
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First tap test using the new electromagnet set-up. This is a 10 second duration test. ~9.35uN
Looks GREAT! The decay is clean of any artifacts and a clean symmetrical decay.
How does the damping look?
Good Job!
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#2909 by masterharper1082 on 01 Mar, 2017 03:20
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First tap test using the new electromagnet set-up. This is a 10 second duration test. ~9.35uN
Excellent work! That result, together with your newly reduced noise floor, vastly improves my hopes for a successful result, whether positive for anomalous thrust or not.
How does the damping look?
mh -
#2910 by WarpTech on 01 Mar, 2017 05:34
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First tap test using the new electromagnet set-up. This is a 10 second duration test. ~9.35uN
How does the damping look?
I like how it returns to where it started.
It will be interesting to see if it does the same with the frustum powered. Good job!
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#2911 by Nerm999 on 01 Mar, 2017 06:55
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First tap test using the new electromagnet set-up. This is a 10 second duration test. ~9.35uN
How does the damping look?
Fantastic
Now, forgive me if I'm being dumb here... but the force from the magnet is constant (ignoring distance), is it not, whereas the displacement is clearly (and reasonably linearly) increasing with time? So shouldn't the force measurement be displacement/time, eg the slope/derivative of the graph, rather than just the maximum displacement? Although I guess the damping and resistance of the wire are also working against the initial force -
#2912 by Flyby on 01 Mar, 2017 07:50
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Monomorphic,
That was a magnetic tap test with all devices turned off or on? (looks like everything was off?) -
#2913 by RERT on 01 Mar, 2017 10:25
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Sorry, I don't think that is what is going on...
That's OK, we'll just have to differ - I think the simple model fits the data well, but it doesn't matter much in the static case - see the image below. I would still urge future DIY builders to use two dampers to avoid an undamped axis.QuoteMonomorphic's pendulum behavior is much better using the (low damping) Newtonian fluid water+antifreeze suggested by Shell.
Agreed... and by the way, have got to say the last 'tap' test looks great!Quote..a multi-degree of freedom system of coupled differential equations with different damping coefficients...
Sadly, we don't get a choice about that, that's the what the physics of this is.Quote... Your "cure": to use different paddle damping for different degrees of freedom further complicates the analysis of the experiment: as it would take significant analysis and interpretation to select the amount of damping for different degrees of freedom (and then the coupled differential equations may result in very complicated motions depending on slightly initial conditions).
Yes, setting the damping could be fiddly. But note the purpose of the balance is really to measure a constant deflection with a constant applied force. In that case there is no movement and damping is irrelevant to the measurement. We try to get the damping correct so that that state is obtained quickly.QuoteClearly, to me, the way to proceed in these cases, is the way that Cavendish pendulums have been used in research institutions: using low damping (rather than using gear oil), and minimizing any sources of noise, rather than using a high-damping fluid with Non-Newtonian shear-rate dependence that makes the analysis of the experiment much more complicated under all the explanations that have been offered.
I completely agree 100% with you on this, which probably makes a good place to stop before everybody else loses the will to live!
(modified dynamics->measurement, correctly->correct penultimate para)
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#2914 by RERT on 01 Mar, 2017 10:35
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First tap test using the new electromagnet set-up. This is a 10 second duration test. ~9.35uN
How does the damping look?
Fantastic
Now, forgive me if I'm being dumb here... but the force from the magnet is constant (ignoring distance), is it not, whereas the displacement is clearly (and reasonably linearly) increasing with time? So shouldn't the force measurement be displacement/time, eg the slope/derivative of the graph, rather than just the maximum displacement? Although I guess the damping and resistance of the wire are also working against the initial force
I think that's right. The total displacement is only proportional to the applied force once the beam has stabilised at a different position. Monomorphic would have to leave the 'tap' force on for a while (?a minute or so?) to see that. That said, the purpose of this test was so that we could analyse the 'd' word for the rig, for which it was very successful.
Hopefully when the Frustrum is under power we can wait for the whole thing to settle to get a clear static displacement/force. -
#2915 by Monomorphic on 01 Mar, 2017 11:40
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Monomorphic,
That was a magnetic tap test with all devices turned off or on? (looks like everything was off?)
Correct, the most recent electromagnetic tap test was with all devices turned off. I was charging the nickel-metal hydride batteries at the time. I hope to perform some tests today with all components powered.
I purchased a 10 AA battery holder and 10 more 1.2V 2700mAh AA nickel-metal hydride batteries to replace the main 12V 4000mAh lipo battery for these lower powered (~2W) tests. The nickel-metal hydride batteries are less noisy than the lipo. The high discharge lipo will come in handy when I eventually need to power the 20W spectran board. -
#2916 by Flyby on 01 Mar, 2017 12:45
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I must say i was highly surprised by your results that a battery discharge causes horizontal movement/momentum.
It is all fine to understand the abstract theory behind it, it remains astonishing to see it happen in such an obvious way...
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#2917 by PotomacNeuron on 01 Mar, 2017 13:39
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I must say i was highly surprised by your results that a battery discharge causes horizontal movement/momentum.
It is all fine to understand the abstract theory behind it, it remains astonishing to see it happen in such an obvious way...
The culprit may be the electronic circuits built in the battery other than the battery itself. Monomorphic implicated that in his post. -
#2918 by Monomorphic on 01 Mar, 2017 14:01
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Two more electromagnetic tap tests. This time with all electronic components powered and ready to start injecting RF with the click of a mouse. There is a slight drift on the long test but the signal is still very clear, even down to 6uN.
The 10 second duration was probably a second or so more than 10. It's hard to click a button while holding another one down! I need to run a wire from the electromagnet to the 4th channel in the ADC for it to be exact.
I don't think I can get the noise much better than this, so we are getting very close to running more powered tests.
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#2919 by Rodal on 01 Mar, 2017 14:18
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Two more electromagnetic tap tests. This time with all electronic components powered and ready to start injecting RF with the click of a mouse. There is a slight drift on the long test but the signal is still very clear, even down to 6uN.
The 10 second duration was probably a second or so more than 10. It's hard to click a button while holding another one down! I need to run a wire from the electromagnet to the 4th channel in the ADC for it to be exact.
I don't think I can get the noise much better than this, so we are getting very close to running more powered tests.
The noise has been well-taken care of.
Now, if you ever want to further perfect this, what remains is a little drift (this time, from the left lower end towards the right upper end.
I agree, the balance is very good for testing the EM Drive ! (noise and drift are minimal)
All aboard !
It will be interesting to see if it does the same with the frustum powered. Good job!
