Quote from: frobnicat on 03/05/2015 05:54 pm...I don't think the tilt of the balance beam about the X axis would have to be very much for the resulting change in received light amplitude to register as a shift in position. The LDS has fractional micron resolution. Assuming the light pattern from the fiber optic cable has a circular gaussian distribution, for any given distance the maximum light level hitting the detector is when the plane of the mirror is perpendicular to the central axis of the light beam. Any small deviation ( arc-second) will reduce the light amplitude; which registers as a displacement. It is impossible to align the LDS perfectly so the angle between the mirror and the light beam is never exactly 90 degrees in X and Y. The expansion of the cavity due to heating has a very long time constant. The slow drift in the position between RF pulses looks like a thermal response.
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Prior to a test run data take, the LDS is positioned to a known displacement datum (usually 500 micrometers) via mechanical adjustments to its mounting platform. Gross adjustments are performed via set screws. Fine adjustments are performed using manually - operated calibrated screw mechanisms and a remotely controlled motorized mechanism that can be operated with the chamber door closed and the chamber at vacuum. The remote adjustment capability is necessary since the LDS datum will change whenever a change to the test facility environment affects the roll - out table or the chamber – e.g., whenever the chamber door is closed or latched and whenever the chamber is evacuated. Once the LDS displacement is adjusted in the final test environment, further adjustment between test run data takes is usually not required.
Quote from: DIYFAN on 03/06/2015 04:32 amQuote from: Notsosureofit on 03/03/2015 03:50 pmSame here. The EBay units I've got are #201065780928 and #131442703325 so far in case anyone want to try the same system.I've decided to try and live up to my screen name and throw my lot in with the replicators. I have a few questions before I kick off my effort:1) Why did you decide to go with #201065780928 rather than a frustrum of a cone? The #201065780928 part looks more like a rectangular slit shape rather than a cone shape. 2) How do you plan on hooking the MA86751B X band oscillator up to the waveguide assembly?3) It looks like the MA86751B X band oscillator is tunable from 9.9 GHz to 10.6 GHz with power output levels from 10 mW to 100 mW powered by 9-10 Volts DC. Did you pick this particular oscillator for a reason?4) Do you expect there to be a resonant frequency within the 9.9 GHz to 10.6 GHz frequency band?5) Do you plan on putting a dielectric toward one end of the waveguide assembly?6) With what material do you plan on capping each end of the waveguide assembly?Although I direct this friendly set of questions to Notsosureofit, Mulletron, and others who are attempting replications, I welcome any forum members to chime in with recommendations or insights. Can you imagine what would happen if the effect can be shown on such a small scale? It could cause some ripples and raise a quite a few eyebrows around the world.1. it matches the osc. waveguide and 1st cheap one on EBay.2. just bolt them together3. I had this one already4. probably, have to calculate when I get the waveguide5. that's an option6. TBD flat pate, detector fitting etc etcI'll just try a long ( 20 ft ?) pendulum First and see what happens. Vacuum later.
Quote from: Notsosureofit on 03/03/2015 03:50 pmSame here. The EBay units I've got are #201065780928 and #131442703325 so far in case anyone want to try the same system.I've decided to try and live up to my screen name and throw my lot in with the replicators. I have a few questions before I kick off my effort:1) Why did you decide to go with #201065780928 rather than a frustrum of a cone? The #201065780928 part looks more like a rectangular slit shape rather than a cone shape. 2) How do you plan on hooking the MA86751B X band oscillator up to the waveguide assembly?3) It looks like the MA86751B X band oscillator is tunable from 9.9 GHz to 10.6 GHz with power output levels from 10 mW to 100 mW powered by 9-10 Volts DC. Did you pick this particular oscillator for a reason?4) Do you expect there to be a resonant frequency within the 9.9 GHz to 10.6 GHz frequency band?5) Do you plan on putting a dielectric toward one end of the waveguide assembly?6) With what material do you plan on capping each end of the waveguide assembly?Although I direct this friendly set of questions to Notsosureofit, Mulletron, and others who are attempting replications, I welcome any forum members to chime in with recommendations or insights. Can you imagine what would happen if the effect can be shown on such a small scale? It could cause some ripples and raise a quite a few eyebrows around the world.
Same here. The EBay units I've got are #201065780928 and #131442703325 so far in case anyone want to try the same system.
Quote from: frobnicat on 03/05/2015 05:54 pm...Frobnicat:Your analysis and comments made me go back and look at the current alignment of the Eagleworks torque pendulum and the attached picture indicates that my recollection of the leveling of the bottom beam of the TP being a quarter bubble high at the vacuum chamber door end was a bit exaggerated due to parallax error and a just plain bad memory. It looks now like less than tenth of bubble low at the door end of the vacuum chamber, but part of that apparent tilt may in reality be due to actual bending of the 1.50 inch square aluminum beam.Best, Paul M.
@ RODALStill struggling as to how to get the exact equation into the form;f^2 = k^2 + [asymmetric terms(x)] such that, (f(0)^2 - f(L)^2) = [asymmetric terms(0)] - [asymmetric terms(L)]That is, how to evaluate at constant k. Any ideas ?
Quote from: Notsosureofit on 03/06/2015 09:01 pm@ RODALStill struggling as to how to get the exact equation into the form;f^2 = k^2 + [asymmetric terms(x)] such that, (f(0)^2 - f(L)^2) = [asymmetric terms(0)] - [asymmetric terms(L)]That is, how to evaluate at constant k. Any ideas ?The force derivation for a truncated cone seems to have been of a physical, intuitive character (if not so, please correct me). From a physical standpoint, one can observe the following:1) My understanding of your prior derivation is that it modeled the truncated cone as being traveled by plane waves (*), just like a plane wave travels a cylindrical cavity from one end to the other. The difference is that in the truncated cone, the plane wave continuously, gradually experiences a lower natural frequency as it travels from the small diameter (cross-section with the highest natural frequency) end to the big diameter end (cross-section with the lowest natural frequency). It should also continuously, gradually experience attenuation (loss in intensity) as it travels from the small end to the big end.'___________(*) Note: truncated cones have spherical waves traveling inside them, rather than plane waves. So the model assumes a very large radius of curvature, such that the spherical wave is approximately flat.CONICAL PIPES (like the truncated cone: continuous gradual change in diameter)2) The behavior in a cylindrical pipe containing two dielectric mediums is fundamentally different: instead of the continuous, gradual change in natural frequency of the truncated cone, the cylindrical pipe containing two dielectric mediums experiences a discontinuous, step-change, a brutal change, going from medium 1 to dielectric medium 2. This would be more like a pipe experiencing a discontinuous step-change in diameter all of a sudden, causing a sudden change in natural frequency and a sudden change in attenuation.STEP-PIPE (the geometrical analog of the discontinuous step-change produced by a pipe having two dielectric mediums)
I know its a stretch thinking this fits in here but you guys have to see this: http://www.sciencedaily.com/releases/2015/03/150306091617.htmbecause QM and GRT reconciled? and gravitons. mustn't forget gravitons.
2) The behavior in a cylindrical pipe containing two dielectric mediums is fundamentally different: instead of the continuous, gradual change in natural frequency of the truncated cone, the cylindrical pipe containing two dielectric mediums experiences a discontinuous, step-change, a brutal change, going from medium 1 to dielectric medium 2. This would be more like a pipe experiencing a discontinuous step-change in diameter all of a sudden, causing a sudden change in natural frequency and a sudden change in attenuation.
Interesting hypothesis. You say that in this case the LDS readings would be more sensitive to a change in angle of the reflective mirror than a change in distance. The LDS is a small distance below the X axis, so a small angular deviation around X would amount to tiny displacement (d' - d) but the small angular deviation would itself tilt the mirror and that could change the LDS readings that is roughly proportional to the reflected light.But then this coupling between angular effect and displacement would also be present for the main movements around Z. LDS is at 35cm from Z axis, I would say it is one order of magnitude more than the distance of mirror below X axis, the lever effect of displacement/angle ratio would be lower (less angle for same displacement) but still if angle deviation is to have a significant effect in case around X it should also have a significant effect around Z.I read "most materials : including smooth but scattering surfaces", not only mirrors. Actually, mirrors may be a very special case. My question is now if the gain control of the system is consistent with the use of a mirror reflecting target. As seen qualitatively from attached figure : a perfect mirror would bounce back in the signal detector a lot more photons than a matte white. If the gain is calibrated against matte material (say, as hypothesis, default factory settings) the baseline distance from the mirror to have a tension that shows as 500µm would be much greater than 500µm. Edit : BTW, how comes that at some very near distance there start to be less photons bouncing back in the signal detector ? Thank zen-in for bringing up interesting questions about LDS...
Quote from: Rodal on 03/06/2015 10:00 pm2) The behavior in a cylindrical pipe containing two dielectric mediums is fundamentally different: instead of the continuous, gradual change in natural frequency of the truncated cone, the cylindrical pipe containing two dielectric mediums experiences a discontinuous, step-change, a brutal change, going from medium 1 to dielectric medium 2. This would be more like a pipe experiencing a discontinuous step-change in diameter all of a sudden, causing a sudden change in natural frequency and a sudden change in attenuation. Yes, the case of a gradually changing dielectric constant is very similar to that of the tapered cavity.The step-change involves a much more complicated situation w/ the necessity of including the reflected waves from the discontinuity. But, it may well offer enhanced performance. (?) ....
Quote from: ThinkerX on 03/05/2015 01:07 am...maybe he envisions this device as some sort of 'turbo-charger?' That is something that adds to an already existing velocity, but won't function well, if at all when 'at rest.' ...A turbocharger, is a device that increases an engine's efficiency and power by forcing extra air into the combustion chamber. What is the "engine" that the EM Drive is turbocharging?The bizarre nature of something needing to be free to accelerate for it to produce a force doesn't apply to the turbocharger or to the engine: the engine that is being turbocharged does not need to be accelerating or even be in rigid body motion. Its center of mass can be completely stationary, and the turbocharged engine can then be used for electric power generation, for example, instead of for transporting people as in an automobile.
...maybe he envisions this device as some sort of 'turbo-charger?' That is something that adds to an already existing velocity, but won't function well, if at all when 'at rest.' ...
Quote from: zen-in on 03/06/2015 04:22 amQuote from: frobnicat on 03/05/2015 05:54 pm...I don't think the tilt of the balance beam about the X axis would have to be very much for the resulting change in received light amplitude to register as a shift in position. The LDS has fractional micron resolution. Assuming the light pattern from the fiber optic cable has a circular gaussian distribution, for any given distance the maximum light level hitting the detector is when the plane of the mirror is perpendicular to the central axis of the light beam. Any small deviation ( arc-second) will reduce the light amplitude; which registers as a displacement. It is impossible to align the LDS perfectly so the angle between the mirror and the light beam is never exactly 90 degrees in X and Y. The expansion of the cavity due to heating has a very long time constant. The slow drift in the position between RF pulses looks like a thermal response.Interesting hypothesis. You say that in this case the LDS readings would be more sensitive to a change in angle of the reflective mirror than a change in distance. The LDS is a small distance below the X axis, so a small angular deviation around X would amount to tiny displacement (d' - d) but the small angular deviation would itself tilt the mirror and that could change the LDS readings that is roughly proportional to the reflected light.But then this coupling between angular effect and displacement would also be present for the main movements around Z. LDS is at 35cm from Z axis, I would say it is one order of magnitude more than the distance of mirror below X axis, the lever effect of displacement/angle ratio would be lower (less angle for same displacement) but still if angle deviation is to have a significant effect in case around X it should also have a significant effect around Z.Unfortunately the documentation for the Philtec D63 displacement sensor seems to give no information on reflective surface angular deviation impact on measurements. It indicates Ø 1.6 mm Target Spot Size. This is 3 times more than nominal operating distance of 500µm (0.5mm) so your drawing is a bit misleading with proportions. In reality the reflected dot is big relative to distance from reflector, would an angular deviation still impact the amount of light swallowed back ? Is it you drawing or you found it elsewhere ? I ask the question because you mention the reflecting surface as being mirror. It does appear as a mirror in the pictures of pendulum at Eagleworks and this is stated explicitly in Brady's report page 3 (together with that LDS is photon time of flight, which is not, but let's proceed). But I don't find in the D63 documentation that a mirror should or could be used. It does say that These specifications represent best case performance where: the target is flat, smooth and highly reflectiveThis implies that the target may not be highly reflective (at the cost of decreased performance) but does highly reflective imply that a mirror is the best case ? My reading (but I'm not native English reader) is that reflective can mean a matte white material, that is a surface that does bounce near 100% of incoming photons, but in a more or less scattering manner, not necessarily as per perfect reflection. See attached picture : top the situation at hand at Eagleworks, bottom the default situation for which the LDS might be initially calibrated.This could explain a lot about the disparity between vertical readings in the charts and stiffness parameters : when charts indicate ~1µm LDS deviation for 29.1µnN calibration pulses for instance, all could be much better explained and consistent if it meant 10µm instead.To me there is no doubt that the LDS is operating in the far range : the cal. pulses are attractive by nature, and correspond to a displacement to the right (Y+) and that lowers the measured distance, as in the charts. Also operating in the near range would not only reverse this consistent orientation but would also increase the sensitivity : that would go against what is to be explained (apparent higher µm/µN stiffness than compatible with other known parameters, for 2 separate predictions from the dynamic periods of oscillations and the known stiffness of flexure bearings)So, what anyone wanting to understand clearly the charts need is a way to explain a reduced sensitivity of the LDS, that would show 1µm displacement when in fact it is 10µm. Following on the D63 doc, there is a calibration procedure :The effect of changing target reflectance is to shift the voltage output higher or lower. Factory calibrations havethe Peak Voltage set to 5.000 volts. A gain control is provided for calibration of the sensor output to various target surfaces. In-situ calibration is performed simply, by adjusting the sensors tip-to-target gap until the peak output voltage is attained, and then by using the gain control to set the peak voltage to full scale (5.000 volts). After setting the peak to 5 volts, the factory gap calibration chart applies for the target being measured. This procedure allows the sensor to be used to perform precision linear motion measurements on most materials.I read "most materials : including smooth but scattering surfaces", not only mirrors. Actually, mirrors may be a very special case. My question is now if the gain control of the system is consistent with the use of a mirror reflecting target. As seen qualitatively from attached figure : a perfect mirror would bounce back in the signal detector a lot more photons than a matte white. If the gain is calibrated against matte material (say, as hypothesis, default factory settings) the baseline distance from the mirror to have a tension that shows as 500µm would be much greater than 500µm. The protocol of tuning for nominal 500µm distance between optical fibre head and mirror is on page 3 of Brady et al report (anomalous...) :Quote from: Brady et al. Anomalous thrust... Prior to a test run data take, the LDS is positioned to a known displacement datum (usually 500 micrometers) via mechanical adjustments to its mounting platform. Gross adjustments are performed via set screws. Fine adjustments are performed using manually - operated calibrated screw mechanisms and a remotely controlled motorized mechanism that can be operated with the chamber door closed and the chamber at vacuum. The remote adjustment capability is necessary since the LDS datum will change whenever a change to the test facility environment affects the roll - out table or the chamber e.g., whenever the chamber door is closed or latched and whenever the chamber is evacuated. Once the LDS displacement is adjusted in the final test environment, further adjustment between test run data takes is usually not required.How this displacement of 500µm is known ? Has the procedure followed the step (as per D63 documentation) of homing to the distance corresponding to peak signal (whatever it's absolute level), calibrating the gain so that at this peak the signal is now 5V, and then stepping back until meeting ~4.3 V corresponding to 500µm nominal distance ? If this was not followed, or if the D63 is not mean to be operated with perfect mirror target (doubtful it wouldn't be mentioned in documentation, but who knows ?), it is possible the LDS is operating in a far range that has a much lower sensitivity (and linearity) than the nominal -2.7 mv/µm.Edit : BTW, how comes that at some very near distance there start to be less photons bouncing back in the signal detector ? Thank zen-in for bringing up interesting questions about LDS...
Prior to a test run data take, the LDS is positioned to a known displacement datum (usually 500 micrometers) via mechanical adjustments to its mounting platform. Gross adjustments are performed via set screws. Fine adjustments are performed using manually - operated calibrated screw mechanisms and a remotely controlled motorized mechanism that can be operated with the chamber door closed and the chamber at vacuum. The remote adjustment capability is necessary since the LDS datum will change whenever a change to the test facility environment affects the roll - out table or the chamber e.g., whenever the chamber door is closed or latched and whenever the chamber is evacuated. Once the LDS displacement is adjusted in the final test environment, further adjustment between test run data takes is usually not required.
Folks:The Philtec fiber-optic cable used in their D63 reflective displacement sensor uses TWO (2) fiber optic bundles in the armored cable with one bundle being used as the transmit and the other bundle the receiver. A description of how Philtec uses these two fiber-optic bundles to measure a distance with sub-micron resolutions is provided at their website: http://www.philtec.com/downloadssupport/documentlibrary/documents/applicationnotes/AboutTheSensors.pdf Hope that helpsBest, Paul M.
Quote from: Rodal on 03/06/2015 10:00 pm2) The behavior in a cylindrical pipe containing two dielectric mediums is fundamentally different: instead of the continuous, gradual change in natural frequency of the truncated cone, the cylindrical pipe containing two dielectric mediums experiences a discontinuous, step-change, a brutal change, going from medium 1 to dielectric medium 2. This would be more like a pipe experiencing a discontinuous step-change in diameter all of a sudden, causing a sudden change in natural frequency and a sudden change in attenuation. Yes, the case of a gradually changing dielectric constant is very similar to that of the tapered cavity.The step-change involves a much more complicated situation w/ the necessity of including the reflected waves from the discontinuity. But, it may well offer enhanced performance. (?) These types of calculations have been done w/ iterative matrix math. I'm going to try some ideas w/ programs I have to see if I can get a better feel for this case. (1D calculations at least)Added: 1D modes suggest that we only have to consider terms which contain b (ie. X or X') The others are plain waves and cancel.
Quote from: Star-Drive on 03/07/2015 01:41 pmFolks:The Philtec fiber-optic cable used in their D63 reflective displacement sensor uses TWO (2) fiber optic bundles in the armored cable with one bundle being used as the transmit and the other bundle the receiver. A description of how Philtec uses these two fiber-optic bundles to measure a distance with sub-micron resolutions is provided at their website: http://www.philtec.com/downloadssupport/documentlibrary/documents/applicationnotes/AboutTheSensors.pdf Hope that helpsBest, Paul M.That would explain the near side of the response curve better than my theory. The response to small angular shifts of the mirror would be similar. If the change in CM from heating caused the angle of the mirror to shift closer to a perpendicular wrt to the LDS, it would register as a decreasing displacement. This is an attempt to explain the small negative deviations in position as shown in the curve below.
If the change in CM from heating caused the angle of the mirror to shift closer to a perpendicular wrt to the LDS, it would register as a decreasing displacement.