The foot of each table is on rollers so the table can be rotated and moved. I can easily add mass wherever desired. The aluminum structure that supports the torsional pendulum is what is supported by sorbothane pads and it does not touch the walls of the draft enclosure. The table and draft enclose also do not touch the walls.
Are these rollers stable enough, Jamie? Usually they are not.
Guys - the talk of complex damping mechanisms seems a little inopportune at this point.
You may already have a clear enough force signal to see through the noise. You can easily remove uncorrelated noise by averaging experimental results. You need to see the data to see if you have correlated noise.
(Basically, still on the edge of my seat...)
Indeed. I think the heat generation is a more serious problem. And maybe magnetic fields.
Are these rollers stable enough, Jamie? Usually they are not.
They are heavy duty rollers with three wheels each, for a total of 12 wheels. It is very stable. Night time and static non-powered runs have shown that vibrations from the environment are very minimal and not the major cause of noise.
...
This is what I'm doing for my isolation platform in the new lab from hardware I have sitting around so my costs are very low. You'll notice that I can vary the mass of the system thus isolating the resonate frequencies, by adding and removing water. This isn't as good as my system I did but it's much cheaper. http://tinyurl.com/jnu4omt
Shell
Mmmm, I don't know whether it is good to have your torsion balance on a platform which might be prone to a drifting horizontal (the inflatable tubes). This will mainly attenuate high frequency vibrations ('high' for the balance) while tilt is more a problem for a torsion balance.
If it is ground noise, then how do you explain this? Static test with no electrical components powered.
What I will do next is repeat this test with each of the main components powered individually. See which is interfering most, mitigate it and move to the next. Repeat until the trace is as flat as possible.
Forget the noise, it can be averaged out (well, to a certain extent, of course). But I see also drift: might be due to the wooden table (I had this always when using the balance on a wooden table, e.g., when setting it up at Starlab Brussels [https://en.wikipedia.org/wiki/Starlab]).
Are these rollers stable enough, Jamie? Usually they are not.
They are heavy duty rollers with three wheels each, for a total of 12 wheels. It is very stable. Night time and static non-powered runs have shown that vibrations from the environment are very minimal and not the major cause of noise.
I understand that there may be other bigger problems, like the wires you just found out, but it is not a good idea to have sensitive instruments sitting on rollers.
Rollers are subject to the laws of contact mechanics, for a stiff roller, Hertz law shows that the relationship between indentation and force is nonlinear:
and for Non-Hertzian contact (softer rollers and layer) the relationship is more nonlinear. Why? because the greater the force, the much greater the contact area, and the stress depends on the force/area.
This, plus the fact that rollers will give looser and asymmetric resistance to shear forces.
So, at some point in the future, when you have a chance, it would not hurt to substitute the rollers by Sorbothane pads that would provide isotropic, symmetric damping between the ground and the table.
2) since it is due to electronic components, which are under your control (unlike other sources of noise which are not under your control), you may be able to mitigate their level
I'm going to test the mini-PC by itself first. If it is causing most of the noise, then I would require either a wireless USB hub (preferred) or a liquid metal USB connection on the pendulum (less preferred).
This USB connection is also something I still have to solve. I guess very thin wires will be sufficient.
My experience with liquid metal (mercury) contacts for a torsion balance is not so positive (the huge surface tension causes stick-slip effects, buoyancy, ...).
Forgot to mention that I moved the wifi router down to the basement yesterday. I now have a full strength 5Ghz connection to the kangaroo mini-pc. Remote desktop to the torsional pendulum is working very well now. I'm testing the cavity with 2.45Ghz, while controlling the electronics using 5Ghz to minimize the potential for interference.
If it is ground noise, then how do you explain this? Static test with no electrical components powered.
What I will do next is repeat this test with each of the main components powered individually. See which is interfering most, mitigate it and move to the next. Repeat until the trace is as flat as possible.
Forget the noise, it can be averaged out (well, to a certain extend, of course). But I see also drift: might be due to the wooden table (I had this always when using the balance on a wooden table, e.g., when setting it up at Starlab Brussels [https://en.wikipedia.org/wiki/Starlab]).
Interesting point about the drift, which at this point in time it appears to not be well understood.
Thanks
...
Suppose Monomorphic switches to two dampers, half the size of the current one, each the same distance as the present one on opposite sides of the beam. Damping about the vertical suspension axis would be the same. Damping about the Horizontal axis through the pivot along the beam would be the same.
The second pot would provide high damping about the axis through the first (&vv), because the paddle must move much farther through the pot for a given angular displacement in that mode of vibration. Damping in any pot of twisting about an axis through the pot is always much lower, because of the reverse: the travel of the paddle through the damping fluid drops to zero at the axis of rotation.
Changing the shape of the paddle might help, but adding a second damper is simpler and will obviously be effective.
I can see the need for this when Monomorphic had a damping ratio =13.35 (according to your calculations), and a strange initial undamped motion:
(RERT snips image)
But now with damping ratio = 0.23 this may not be as important as taking care of the noise source. Do you agree?
(RERT snips image)
The damping is however something important to take into account if Monomorphic later decides to test also with a higher damping ratio near, equal to or exceeding critical damping.
I think it would be great to find and eliminate the noise source. Whatever it is, it is exciting and oscillation with a period of around 40 seconds, which is probably a natural mode of the rig - the noise itself seems very unlikely to have that characteristic period. The noise would probably be greatly reduced if that mode was properly damped.
I think moving to multiple dampers would probably also eliminate the noise, and should be tried if the source can't be found or can't be eliminated. In general, if designing such a setup from scratch (with 20/20 hindsight) one would not have a system where the level of damping was highly mode-dependent, and would probably go for 3 non-co-linear dampers.
Actually I suspect multiple dampers would make it possible to lower the overall damping to produce a more responsive system, and/or one with less noise. So I don't think it is more applicable in a more highly damped case.
Yes, this could very well be the case. Using an asymmetric damper (only on one side), will cause additional movements. There are already movements around several axes and the interference between them might be chaotic.
...
Not really: I wasn't discussing this phenomenon. .....I postulated that the rig rotated about a horizontal axis parallel to the beam and through the pivot. If you work through the geometry, you will see that the motion about that axis produces horizontal and vertical displacements:
Well, they say that a picture is worth a thousand words, and after so many words and no drawings describing what you mean by << the rig rotated about a horizontal axis parallel to the beam
and through the pivot.>> I drew a picture to let you see what I understood you mean. In the interest of brevity and clarity it would be most helpful if you would show us a drawing of what you mean by << the rig rotated about a horizontal axis parallel to the beam
and through the pivot.>> and your variables. Perhaps you could sketch a drawing by hand and scan it and post it ?
...
yes, another horizontal sensor at the pivot point would show if other rotations were happening. The angular displacement of the beam would then be a function of the difference between the two horizontal displacements.
Then, it is important to find out whether the optical measurement is measuring only what we want.
Whether the measurement involves displacements produced by other rotations, besides what we are intending to measure: the displacement produced just by the rotation of the torsional pendulum around its vertical axis.
Monomorphic clarified the measurement sensors:
I am using two laser displacement sensors. One to monitor horizontal and one to monitor vertical. If they are not perfectly aligned with the pendulum beam, then there will be subtle effects on the data. Check pages 8 and 9 of the manual for the LDS to see what I'm talking about: http://www.omronkft.hu/pdf_en/z4m.pdf
If it is ground noise, then how do you explain this? Static test with no electrical components powered.
What I will do next is repeat this test with each of the main components powered individually. See which is interfering most, mitigate it and move to the next. Repeat until the trace is as flat as possible.
IMHO Jamie you're not seeing very much seismic activity. When I lived in California my partner and I belonged to the seismic net and had string pendulums of different lengths hung from the ceiling. With these simple weights, on a string, we could deduce what direction we were seeing a propagating P or S wave, how strong and which direction a tremor or quake was was. We even wrote a program in Basic running on our XT-PC to semi-automate the process.
With your power off your beam oscillations disappear.
I think your seeing a Lorentz motor action from some "harmonic beat" magnetic fields created in your hardware that's causing your beam to fluctuate, doesn't matter that your unit is made from Aluminum, it still will respond to Time-varying magnetic fields.
If this is the case where it's your hardware shielding with mu-metal could help to minimize it. http://www.ebay.com/itm/Mumetal-Nikel-Permalloy-Magnetic-shielding-foil-Sheet-Mu-metal-0-1T-30-45cm-/171173026902?hash=item27dab51c56:g:T24AAOxyyjpRxam8
My Best,
Shell
Relative magnetic permerabilty of aluminum = 1.000022 (barely distinguishable from free space)
of air = 1.00000037
of Mu-metal = 20,000
of electrical steel = 4,000
Since the noise displays random behavior, I would suspect instead of the aluminum being influenced by magnetic fields, that the noise is due to thermal excitations from the electronic equipment (damping heat).
We will see
Actually his lectures related to this run 11-17
Lentz Laws and how to induce counter Eddy currents from a field passing through metals.
https://en.wikipedia.org/wiki/Lenz's_lawMonomorphic has magnetic fields that change with time generated by his electronics sitting on a free swinging torsion wire pendulum, surrounded by a fixed aluminum frame.
These changing magnetic fields on the pendulum bar from his electronics will induce counter Eddy currents into the frame of his test fixture.
My Very Best,
Shell
If it is ground noise, then how do you explain this? Static test with no electrical components powered.
What I will do next is repeat this test with each of the main components powered individually. See which is interfering most, mitigate it and move to the next. Repeat until the trace is as flat as possible.
IMHO Jamie you're not seeing very much seismic activity. When I lived in California my partner and I belonged to the seismic net and had string pendulums of different lengths hung from the ceiling. With these simple weights, on a string, we could deduce what direction we were seeing a propagating P or S wave, how strong and which direction a tremor or quake was was. We even wrote a program in Basic running on our XT-PC to semi-automate the process.
With your power off your beam oscillations disappear.
I think your seeing a Lorentz motor action from some "harmonic beat" magnetic fields created in your hardware that's causing your beam to fluctuate, doesn't matter that your unit is made from Aluminum, it still will respond to Time-varying magnetic fields.
If this is the case where it's your hardware shielding with mu-metal could help to minimize it. http://www.ebay.com/itm/Mumetal-Nikel-Permalloy-Magnetic-shielding-foil-Sheet-Mu-metal-0-1T-30-45cm-/171173026902?hash=item27dab51c56:g:T24AAOxyyjpRxam8
My Best,
Shell
Relative magnetic permerabilty of aluminum = 1.000022 (barely distinguishable from free space)
of air = 1.00000037
of Mu-metal = 20,000
of electrical steel = 4,000
Since the noise displays random behavior, I would suspect instead of the aluminum being influenced by magnetic fields, that the noise is due to thermal excitations from the electronic equipment (damping heat).
We will see
Actually his lectures related to this run 11-17
Lentz Laws and how to induce counter Eddy currents from a field passing through metals.
https://en.wikipedia.org/wiki/Lenz's_law
Monomorphic has magnetic fields that change with time generated by his electronics sitting on a free swinging torsion wire pendulum, surrounded by a fixed aluminum frame.
These changing magnetic fields on the pendulum bar from his electronics will induce counter Eddy currents into the frame of his test fixture.
My Very Best,
Shell
OK Shell, now I understand what you meant
Thank you for taking the time to answer.
Something similar to Lorentz force eddy current testing (
http://www.ndt.net/article/wcndt2016/papers/fr1f3.pdf ), where one uses a moving
permanent magnet to test aluminum for flaws,
except that in this case
instead of a moving permanent magnet you have here a fluctuating magnetic field producing the eddy currents on the aluminum.But this effect could also produce a force on the EM Drive itself and not just the aluminum beam, since such an alternating magnetic field will also produce eddy currents on the copper and hence produce Lorentz forces on the EM Drive. Thus this exposes a possible experimental artifact force on the EM Drive ! My very best,
JR
If it is ground noise, then how do you explain this? Static test with no electrical components powered.
What I will do next is repeat this test with each of the main components powered individually. See which is interfering most, mitigate it and move to the next. Repeat until the trace is as flat as possible.
IMHO Jamie you're not seeing very much seismic activity. When I lived in California my partner and I belonged to the seismic net and had string pendulums of different lengths hung from the ceiling. With these simple weights, on a string, we could deduce what direction we were seeing a propagating P or S wave, how strong and which direction a tremor or quake was was. We even wrote a program in Basic running on our XT-PC to semi-automate the process.
With your power off your beam oscillations disappear.
I think your seeing a Lorentz motor action from some "harmonic beat" magnetic fields created in your hardware that's causing your beam to fluctuate, doesn't matter that your unit is made from Aluminum, it still will respond to Time-varying magnetic fields.
If this is the case where it's your hardware shielding with mu-metal could help to minimize it. http://www.ebay.com/itm/Mumetal-Nikel-Permalloy-Magnetic-shielding-foil-Sheet-Mu-metal-0-1T-30-45cm-/171173026902?hash=item27dab51c56:g:T24AAOxyyjpRxam8
My Best,
Shell
Relative magnetic permerabilty of aluminum = 1.000022 (barely distinguishable from free space)
of air = 1.00000037
of Mu-metal = 20,000
of electrical steel = 4,000
Since the noise displays random behavior, I would suspect instead of the aluminum being influenced by magnetic fields, that the noise is due to thermal excitations from the electronic equipment (damping heat).
We will see
Actually his lectures related to this run 11-17
Lentz Laws and how to induce counter Eddy currents from a field passing through metals.
https://en.wikipedia.org/wiki/Lenz's_law
Monomorphic has magnetic fields that change with time generated by his electronics sitting on a free swinging torsion wire pendulum, surrounded by a fixed aluminum frame.
These changing magnetic fields on the pendulum bar from his electronics will induce counter Eddy currents into the frame of his test fixture.
My Very Best,
Shell
OK, now I understand what you meant
Something similar to Lorentz force eddy current testing ( http://www.ndt.net/article/wcndt2016/papers/fr1f3.pdf ), where one uses a moving permanent magnet to test aluminum for flaws, except that instead of a moving permanent magnet you have here a fluctuating magnetic field producing the eddy currents on the aluminum.
But this effect could also produce a force on the EM Drive itself and not just the aluminum beam, since such an alternating magnetic field will also produce eddy currents on the copper. This is a possible experimental artifact !
Yes.
This is one of the other reasons I'm doing my new test-bed and new lab.
Added:
Not as sure on the copper frustum as the frustum sits on the same beam as the electronics and the frustums fields would need to act on a solid object outside its area, remember the frustum fields are very very small.
The same for a field acting on the frustum, it would need to be off the pendulum arm and fixed.
My Best,
Shell
Recent corro from Roger contained this breadcrumb:
Remember there are two forces at work simultaneously, one that I call thrust (small end to big end) and the opposite which I refer to as the reaction force. When the cavity is free to move, acceleration occurs in the direction of the reaction force. When the cavity stops, both forces cancel out. This is the only way Newtons laws are satisfied, and has been verified many times.
As an EmDrive thruster must be free to move / accelerate or the Reaction force generation stops, would not that occur when the torsion wire has absorbed all the torque a EmDrive thruster could generate and then the stored torque in the torsion wire drives the now stopped EmDrive in reverse, even though there is still power applied?
Ie initially in "Motor mode", then when stopped in "Idle mode" and then as it moves backward in "Generator mode" opposing the torsion wire torque driving it backward.
Spooky action on the torsion pendulum or just how a part of the operational characterists of an EmDrive thruster works?
As attached.
Phil, however unlikely I regard this to be true, I will still try to test this. As a first step: my optical sensors have a linear range of 1-1.5 mm, when I place them more inward (towards the centre of the balance), the frustum can move ~5 mm. I can compare this with the normal measurement mode (displacement of the order of 1 µm/µN).
...
Added:
Not as sure on the copper frustum as the frustum sits on the same beam as the electronics and the frustums fields would need to act on a solid object outside its area, remember the frustum fields are very very small.
..
This effect: time varying magnetic fields (from sources outside the frustum) will certainly induce eddy currents on the external surface of the copper EM Drive (penetrating to the skin depth, on the external surface) and produce a force on the EM drive just as much as it would produce a force on the Aluminum beam, if the external time-varying magnetic field is close enough to the EM Drive copper to produce such a force.
------------------------
Note on fields from inside the EM Drive: no microwave (2 GHz) frequency magnetic field from inside the EM Drive itself can escape the EM drive itself because the copper thickness is much greater than the skin depth (~1.3 micrometers) at this frequency. Hence magnetic fields at microwave frequencies from the EM drive are not an issue (except for strange experiments as the one from rfmwguy where he had the Magnetron protruding outside the EM Drive going into a hole through the end plate), except any leakage that may occur from improperly sealed connections in the EM Drive copper construction, and any low-frequency (or DC) fields produced by a magnetron (low frequency enough such that the skin depth at that frequency is greater than the copper thickness).
...
Added:
Not as sure on the copper frustum as the frustum sits on the same beam as the electronics and the frustums fields would need to act on a solid object outside its area, remember the frustum fields are very very small.
..
No microwave (2 GHz) magnetic field from inside the EM Drive itself can escape the EM drive itself because the copper thickness is much greater than the skin depth (~1.3 micrometers) at this frequency. Hence magnetic fields at microwave frequencies from the EM drive are not an issue (except for strange experiments as the one from rfmwguy where he had the Magnetron outside the EM Drive going into a hole through the end plate), except any leakage that may occur from improperly sealed connections in the EM Drive copper construction.
This effect: time varying magnetic fields (from sources outside the frustum) will certainly induce eddy currents on the external surface of the copper EM Drive (penetrating to the skin depth, on the external surface) and produce a force on the EM drive just as much as it would produce a force on the Aluminum beam, if the external time-varying magnetic field is close enough to the EM Drive copper to produce such a force.
produce a force on the EM drive just as much as it would produce a force on the Aluminum beam, if the external time-varying magnetic field is close enough to the EM Drive copper to produce such a force.
Only if the EM-Field generation was off the torsion pendulum beam. It can't "push on itself" to generate thrust.
My Best,
Shell
...
Only if the EM-Field generation was off the torsion pendulum beam. It can't "push on itself" to generate thrust.
My Best,
Shell
Yes, agreed of course, but this is true for this effect acting on the aluminum beam as well.
No electronic equipment attached to the aluminum beam can cause the aluminum beam to self-accelerate either
Whatever is producing the alternating magnetic field has to be external to what is acting on (the aluminum beam or the copper EM Drive) to get it to accelerate.
...
Only if the EM-Field generation was off the torsion pendulum beam. It can't "push on itself" to generate thrust.
My Best,
Shell
Yes, agreed of course, but this is true for this effect acting on the aluminum beam as well.
No electronic equipment attached to the aluminum beam can cause the aluminum beam to self-accelerate either
But can make it rotate up to 180 degrees when interacting with static external magnetic field.
Whatever is producing the alternating magnetic field has to be external to what is acting on (the aluminum beam or the copper EM Drive) to get it to accelerate.
