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#1200 by Star One on 31 Dec, 2016 10:26
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I believe this has been waited for by some on here.
Excellent article !!! simply the best I've seen so far on the EMdrive....
......
http://www.centauri-dreams.org/?p=36830
I really liked this quote because it totally embodies my current sentiment on the EMdrive :QuoteI realize the urge within human behavior for fast, definitive answers that we can act on. This lingering uncertainty is aggravating, even more so when peppered with distracting hype or dismissive disdain. To get to the underlying reality, we must continue with a focus on the fidelity of the methods to produce reliable results, rather than jumping to conclusions on the implications.
Unfortunately the comments underneath seem to be the usual fractious mix.
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#1201 by mboeller on 31 Dec, 2016 10:47
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He's made it clear the laptop doesn't have a fan. The only way it could blow air in any direction is by heating it.
what about the HDD? The force from the EM-drive is very small. Therefore even something like a rotating hard drive could mess up the experiment.
edit: it seems the laptop has an SSD -
#1202 by Peter Lauwer on 31 Dec, 2016 10:47
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The 1st test thruster dimensions, so far, are:
BD: 0.2800m,
SD: 0.1487m
LN: 0.3244m
Df: 0.837
Mode: TE013
Freq: 2.45GHz
Qu: 60k
End plates are flat and made from single sided FR4 PCB blank. Use of the single sided pcb was done as those end plates should be very flat as opposed to what a DIYer may buy from their copper plate supplier. Plus they reduce the thruster weight. The end plates will be hand cut, drilled and very highly polished from the PCB stock
Side wall is rolled 0.5mm 101 copper with a soldered butt side wall joint. 10mm wide 1mm copper flanges will be soldered to the small and big ends of the side wall section so the end plates can be bolted to the side wall section. Hoop rings will be used to ensure a circular form and to assist side wall construction. Side wall 0.5mm copper will be laser/water cut to ensure high accuracy to the SD and that the end plates should be highly parallel to each other and orthogonal to the thruster Z axis. Will later build a few thrusters that have the 0.5mm side wall copper hand cut to compare the Qu. Hopefully the KISS esign will be able to be hand cut and hand rolled.
This design is based around the Df that Roger achieved with the Demonstrator. I took his BD of 280mm, Df 0.844 and freq 2.45 and using his Df equation obtained the SD of 0.1487. Was actually 0.14862, which I rounded up to the next 0.1mm so to allow some manufacturing tolerance.
The length (which doesn't factor into the Df equation) was then calculated to achieve TE013 resonance at 2.45GHz.
Antenna will be a 1/4 wave stub, sticking out from the side wall and into the max E field of the central TE013 lobe. Insertion depth and angle / orientation to the side wall are adjustable so to get the lowest VSWR. As the input power and E field intensity are low, due to the 8W, don't expect the end of the stub to turn into a match stick. This should be a much easier antenna to make and align than a 1/2 side wall loop.
Would appreciate those of you with other modeling tools to have a look at this design. It is NOT the EW thruster, which I will do next. Please check the freq and the Qu so I can get this design bolted down and started to be made real.
As always comments and advise are sought as I feel we all want to see this thruster doing several revs on the test bed.
Thanks,
Phil
Phil's TE013 EmDrive based on Shawyer's Demonstrator Thruster is a slender one!
Longer than the Eagleworks frustum, but with a slightly lower cone half-angle of 11.39° (14.72° for Eagleworks). Also the difference between the two plate surface areas (small end is 71.8% smaller than big end) is greater than the difference in the Eagleworks frustum (where small end is 67.7 % smaller than big end).
I rendered it in plain copper so we can better visualize its shape.
EDIT: I keep thinking the EmDrive needs to be encapsulated within a box, and ideally within a transparent acrylic sphere, because if the platform rotates some people will argue it is because air is convecting around the frustum. Phil's demonstrator would fit inside a 18" diameter ball at least.
I like these dimensions. It is about what I planned to use (a little shorter maybe, with bigger cone angle). What will be the TE012 frequency? -
#1203 by mclumber1 on 31 Dec, 2016 12:50
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The laptop has no fan. no moving parts except kb. SSD drive. Sofrware that sets freq and does sweep to test modes, antenna & lowest reflected power runs on the laptop which will be closed and in sleep mode when rotary test runs are done. 4 runs will be done with thruster orientations that should not cause movement, so to verify there are no rotational thrust sources.
What model of laptop will you use? I think to just alleviate all doubt (assuming the setup rotates) I would remove the computer completely from the beam. Use IR or some other form of communication from the laptop (not on the test rig) to the test rig. If the setup rotates, people will claim it's due to the computer, which I have no doubt will be incredibly frustrating to you. -
#1204 by Monomorphic on 31 Dec, 2016 12:53
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Big apology. The spreadsheet was not set up correctly, which produced that silly length.
These are the latest data:
Big Diam: 280mm
Small Diam: 149.16mm (derived from the Df equation based on Big diam, mode and freq to obtain Df 0.844)
Length: 276mm
Df: 0.844 as was the Demonstrator
Mode: TE013
Freq: 2.45GHz
Qu: 57,800
Force with 8W forward and Qu at 75%: 1.95mN
Have advised Roger of this project and asked him to do a double check of the above.
What Qu values have you guys calculated?
With these dims I get TE013 at ~2.4735Ghz. There are still cutoff issues with the small end.
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#1205 by TheTraveller on 31 Dec, 2016 13:59
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Sorry, I may have missed your message, in December 25th there is no conference in Beijing, there is no information about the test on orbit announced, many rumors have been confirmed rumors.Sorry - are you saying it was a rumour that the EMdrive was to be discussed at a conference? Or that it was a rumour that there was a conference? Or that it was a rumour that the conference finished on the 25th?
OYZW may not notice that this was (probably?) addressed to him?
Unless I'm hallucinating, this news/?rumour? generated much interest. Not rounding things out with some report on what happened seems wrong. Even if the report is 'It was a mistake, the EMdrive was not discussed', it would be better than nothing.
The 24-25 Dec 2016 Chinese Electric Propulsion conference was held in Harbin and not Beijing as attached.
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#1206 by SeeShells on 31 Dec, 2016 14:02
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He is skeptical, as all researchers should be. I expect healthy skepticism and that's just fine. It shows me the path that must be taken for good science.I believe this has been waited for by some on here.
QuoteNow that the EmDrive has made its way into the peer-reviewed literature, it falls in range of Tau Zero’s network of scientist reviewers. Marc Millis, former head of NASA’s Breakthrough Propulsion Physics project and founding architect of the Tau Zero Foundation, has spent the last two months reviewing the relevant papers. Although he is the primary author of what follows, he has enlisted the help of scientists with expertise in experimental issues, all of whom also contributed to BPP, and all of whom remain active in experimental work. The revisions and insertions of George Hathaway (Hathaway Consulting), Martin Tajmar (Dresden University), Eric Davis (EarthTech) and Jordan Maclay (Quantum Fields, LLC) have been discussed through frequent email exchanges as the final text began to emerge. Next week I’ll also be presenting a supplemental report from George Hathaway. So is EmDrive new physics or the result of experimental error? The answer turns out to be surprisingly complex.
http://www.centauri-dreams.org/?p=36830
Good. About time. I believe Marc Millis was always rather skeptical about the EMDrive.
This new year has be rebuilding my lab and test bed and simply put I wouldn't be doing it if I could get this anomaly tamed and identified.
On that note I wish all here to have a great and Happy New Year. It looks to be VERY interesting indeed.
My Very Best,
Shell
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#1207 by TheTraveller on 31 Dec, 2016 14:09
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Big apology. The spreadsheet was not set up correctly, which produced that silly length.
These are the latest data:
Big Diam: 280mm
Small Diam: 149.16mm (derived from the Df equation based on Big diam, mode and freq to obtain Df 0.844)
Length: 276mm
Df: 0.844 as was the Demonstrator
Mode: TE013
Freq: 2.45GHz
Qu: 57,800
Force with 8W forward and Qu at 75%: 1.95mN
Have advised Roger of this project and asked him to do a double check of the above.
What Qu values have you guys calculated?
With these dims I get TE013 at ~2.4735Ghz. There are still cutoff issues with the small end.
For highest Df and highest thrust, the small end should operate just above cutoff, which happens if the Df is as close to 1 as possible. The low small end eddy currents are indicative of very low radiation pressure on the small end plate, which is the design goal.
The 0.82 rule is an easy calc to get a starting small end diameter. Then a spreadsheet with the Df calc allows the small end diameter to be finely calculated and yes it will probably be a slightly smaller diameter than the 0.82 rule. The Df calc is the final determination. -
#1208 by Star-Drive on 31 Dec, 2016 14:16
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Big apology. The spreadsheet was not set up correctly, which produced that silly length.
These are the latest data:
Big Diam: 280mm
Small Diam: 149.16mm (derived from the Df equation based on Big diam, mode and freq to obtain Df 0.844)
Length: 276mm
Df: 0.844 as was the Demonstrator
Mode: TE013
Freq: 2.45GHz
Qu: 57,800
Force with 8W forward and Qu at 75%: 1.95mN
Have advised Roger of this project and asked him to do a double check of the above.
What Qu values have you guys calculated?
With these dims I get TE013 at ~2.4735Ghz. There are still cutoff issues with the small end.
For highest Df and highest thrust, the small end should operate just above cutoff, which happens if the Df is as close to 1 as possible. The low small end eddy currents are indicative of very low radiation pressure on the small end plate, which is the design goal.
The 0.82 rule is an easy calc to get a starting small end diameter. Then a spreadsheet with the Df calc allows the small end diameter to be finely calculated and yes it will probably be a slightly smaller diameter than the 0.82 rule. The Df calc is the final determination.
Phil:
What TE01X Bessel function value are you using in your Shawyer spreadsheet to calculate these latest frustum dimensions?
Best, Paul M. -
#1209 by flux_capacitor on 31 Dec, 2016 14:24
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Big apology. The spreadsheet was not set up correctly, which produced that silly length.
These are the latest data:
Big Diam: 280mm
Small Diam: 149.16mm (derived from the Df equation based on Big diam, mode and freq to obtain Df 0.844)
Length: 276mm
Df: 0.844 as was the Demonstrator
Mode: TE013
Freq: 2.45GHz
Qu: 57,800
Force with 8W forward and Qu at 75%: 1.95mN
Have advised Roger of this project and asked him to do a double check of the above.
What Qu values have you guys calculated?
With these dims I get TE013 at ~2.4735Ghz. There are still cutoff issues with the small end.
For highest Df and highest thrust, the small end should operate just above cutoff, which happens if the Df is as close to 1 as possible. The low small end eddy currents are indicative of very low radiation pressure on the small end plate, which is the design goal.
The 0.82 rule is an easy calc to get a starting small end diameter. Then a spreadsheet with the Df calc allows the small end diameter to be finely calculated and yes it will probably be a slightly smaller diameter than the 0.82 rule. The Df calc is the final determination.
Read my previous post about the cutoff issue. Using the resonant frequency computed by Monomorphic (2.4735 GHz) your cutoff diameter for TE01 modes is now compatible with your small end plate as it becomes:*
Ds = (X'01 *c)/(Pi*frequency)
= (3.83170597020751*299792458)/(Pi*2.4735*10^9)
= 0.14783 m
* Table of Bessel zeros and Bessel Derivative zeros: http://wwwal.kuicr.kyoto-u.ac.jp/www/accelerator/a4/besselroot.htmlx -
#1210 by TheTraveller on 31 Dec, 2016 14:34
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The laptop has no fan. no moving parts except kb. SSD drive. Sofrware that sets freq and does sweep to test modes, antenna & lowest reflected power runs on the laptop which will be closed and in sleep mode when rotary test runs are done. 4 runs will be done with thruster orientations that should not cause movement, so to verify there are no rotational thrust sources.
What model of laptop will you use? I think to just alleviate all doubt (assuming the setup rotates) I would remove the computer completely from the beam. Use IR or some other form of communication from the laptop (not on the test rig) to the test rig. If the setup rotates, people will claim it's due to the computer, which I have no doubt will be incredibly frustrating to you.
Before each test run, the 1.2kg laptop will be closed flat, powering it down and putting it into sleep mode.
There will be 12 test sequences, 4 with null thrust settings. If there are 4 CW rotations, 4 CCW rotations and 4 NULL rotations, all with the same no fan, closed lid and in sleep mode laptop how can the laptop be causing CW rotational acceleration for 4 runs, then CCW rotational acceleration for 4 runs and finally no rotational acceleration for the 4 x NULL runs? -
#1211 by TheTraveller on 31 Dec, 2016 14:46
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Big apology. The spreadsheet was not set up correctly, which produced that silly length.
These are the latest data:
Big Diam: 280mm
Small Diam: 149.16mm (derived from the Df equation based on Big diam, mode and freq to obtain Df 0.844)
Length: 276mm
Df: 0.844 as was the Demonstrator
Mode: TE013
Freq: 2.45GHz
Qu: 57,800
Force with 8W forward and Qu at 75%: 1.95mN
Have advised Roger of this project and asked him to do a double check of the above.
What Qu values have you guys calculated?
With these dims I get TE013 at ~2.4735Ghz. There are still cutoff issues with the small end.
For highest Df and highest thrust, the small end should operate just above cutoff, which happens if the Df is as close to 1 as possible. The low small end eddy currents are indicative of very low radiation pressure on the small end plate, which is the design goal.
The 0.82 rule is an easy calc to get a starting small end diameter. Then a spreadsheet with the Df calc allows the small end diameter to be finely calculated and yes it will probably be a slightly smaller diameter than the 0.82 rule. The Df calc is the final determination.
Phil:
What TE01X Bessel function value are you using in your Shawyer spreadsheet to calculate these latest frustum dimensions?
Best, Paul M.
Paul,
Bessel table attached.
Also attached is the thruster's axial plot of guide wavelength vs radiation pressure based on approx 65k end to end stacked varying diameter cylinders.
The sharp drop in radiation pressure can be indirectly seen in the reduced small end plate eddy currents in Jamie's FEKO plot.
As you can see the small end plate action occurs very quickly and rapidly. I believe getting this right is very important to achieving good thrust generation as the goal is to operate the small end just above cutoff so there are still some eddy currents in the small end plate to cause the dual travelling waves to be reflected but with the guide wavelength becoming very long and dropping the radiation pressure on the small end plate to a very low value.
Based on Cullen's equations, the end plate radiation pressure forces are calculated at:
Big end plate: 1.95905mN
Small end plate: 0.01862mN
Will shortly see if the thruster does generate ~2mN for 8W Rf, TE013, with a Qu of 75% of the theoretical value of 57.8K.
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#1212 by X_RaY on 31 Dec, 2016 15:03
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If you dont like to have radiation pressure at the small plate, put it far below cut off diameter (for cylindrical WG).Big apology. The spreadsheet was not set up correctly, which produced that silly length.
These are the latest data:
Big Diam: 280mm
Small Diam: 149.16mm (derived from the Df equation based on Big diam, mode and freq to obtain Df 0.844)
Length: 276mm
Df: 0.844 as was the Demonstrator
Mode: TE013
Freq: 2.45GHz
Qu: 57,800
Force with 8W forward and Qu at 75%: 1.95mN
Have advised Roger of this project and asked him to do a double check of the above.
What Qu values have you guys calculated?
With these dims I get TE013 at ~2.4735Ghz. There are still cutoff issues with the small end.
For highest Df and highest thrust, the small end should operate just above cutoff, which happens if the Df is as close to 1 as possible. The low small end eddy currents are indicative of very low radiation pressure on the small end plate, which is the design goal.
The 0.82 rule is an easy calc to get a starting small end diameter. Then a spreadsheet with the Df calc allows the small end diameter to be finely calculated and yes it will probably be a slightly smaller diameter than the 0.82 rule. The Df calc is the final determination.
Phil:
What TE01X Bessel function value are you using in your Shawyer spreadsheet to calculate these latest frustum dimensions?
Best, Paul M.
Paul,
Bessel table attached.
Also attached is the thruster's axial plot of guide wavelength vs radiation pressure based on approx 65k end to end stacked cylinders.
The sharp drop in radiation pressure can be indirectly seen in the reduced small end plate eddy currents in Jamie's FEKO plot.
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#1213 by TheTraveller on 31 Dec, 2016 15:11
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If you dont like to have radiation pressure at the small plate, put it far below cut off diameter (for cylindrical WG).
And the Qu and 5x TC cavity fill / decay time are?
As I see it, no significant standing waves at the small end = no significant travelling waves at the small end = no significant reflection of the travelling waves at the small end back to the big end= very low Qu = very low force generation.
However it is good to see a plot showing cutoff does indeed occur in a tapered waveguide cavity. Your image is a keeper. -
#1214 by X_RaY on 31 Dec, 2016 15:28
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If this is of interest I could model it in EMPro after holidays to get Qu? Related values like your TC can solved based on this.If you dont like to have radiation pressure at the small plate, put it far below cut off diameter (for cylindrical WG).
And the Qu and 5x TC cavity fill / decay time are?
As I see it, no significant standing waves at the small end = no significant travelling waves at the small end = no significant reflection of the travelling waves at the small end back to the big end= very low Qu = very low force generation.
However it is good to see a plot showing cutoff does indeed occur in a tapered waveguide cavity. Your image is a keeper.
Fact is that this kind of cavity can store energy as well as one with SD above cutoff.
The cutoff design rule is not compatible with your goal:
¯\_(ツ)_/¯Quote from: TheTraveller... very low radiation pressure on the small end plate, which is the design goal ...
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#1215 by TheTraveller on 31 Dec, 2016 15:52
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Don't know yet. ¯\_(ツ)_/¯ If this is of interest I could model it in EMPro after holidays to get Qu? Related values like your TC can solved based on this.If you dont like to have radiation pressure at the small plate, put it far below cut off diameter (for cylindrical WG).
And the Qu and 5x TC cavity fill / decay time are?
As I see it, no significant standing waves at the small end = no significant travelling waves at the small end = no significant reflection of the travelling waves at the small end back to the big end= very low Qu = very low force generation.
However it is good to see a plot showing cutoff does indeed occur in a tapered waveguide cavity. Your image is a keeper.
Fact is that this kind of cavity can store energy as well as one with SD above cutoff.
The cutoff design rule is not compatible with your goal:Quote from: TheTraveller... very low radiation pressure on the small end plate, which is the design goal ...
Dr Rodal's paper never discussed the effect on Qu of these beyond cutoff cavities. Focusing on just how far cutoff diam could be reduced and not factoring in the effect on Qu makes the work of little interest. Would like to see the Qu calcs for these cavities.
As I see it Roger walks a thin between achieving the smallest diam small end delivering the longest guide wavelength, lowest radiation pressure AND the highest Qu.
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#1216 by TheTraveller on 31 Dec, 2016 16:03
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Fact is that this kind of cavity can store energy as well as one with SD above cutoff.
Until the Qu of these very pointy cavities are calculated, how can you be so sure? I would be delighted for this geometry to work better than the existing geometry. But until I see a Qu or S pram Ql showing higher Q, I'll stick with the Df equation and the 0.82 rule of thumb as I suspect that value comes from building and testing many SPR thrusters and is an engineering compromise between reducing small end radiation pressure as much as possible vs optimal Qu from having the max number of non thermalised photons that are there to make the journey small end plate to big end plate. We want the largest number of photons possible to form the travelling waves that efficiently reflect back & forth the largest number of times.
As I see it max numbers of photons x max number of return journeys = max Qu.
Have you figured out how to get FEKO to calc Q? SuperFish can do it but using it effectively is another learning curve. -
#1217 by Donosauro on 31 Dec, 2016 16:08
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The laptop has no fan. no moving parts except kb. SSD drive. Sofrware that sets freq and does sweep to test modes, antenna & lowest reflected power runs on the laptop which will be closed and in sleep mode when rotary test runs are done. 4 runs will be done with thruster orientations that should not cause movement, so to verify there are no rotational thrust sources.
What model of laptop will you use? I think to just alleviate all doubt (assuming the setup rotates) I would remove the computer completely from the beam. Use IR or some other form of communication from the laptop (not on the test rig) to the test rig. If the setup rotates, people will claim it's due to the computer, which I have no doubt will be incredibly frustrating to you.
It's just my opinion, but I believe TT has done enough to remove concerns that the laptop will be the source of rotational artifacts. As the saying goes, let's not make the perfect the enemy of the good. Let the testing proceed. (So saying, I agree with the idea that, at some point, the frustrum should be put into a sphere to reduce possible convective asymmetries as a source of rotational artifacts. But that can wait until testing shows significant rotation, if it does.)
Edited: covective -> convective; assymetries -> asymmetries. -
#1218 by X_RaY on 31 Dec, 2016 16:23
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Fact is that this kind of cavity can store energy as well as one with SD above cutoff.
1. Until the Qu of these very pointy cavities are calculated, how can you be so sure?
2. Have you figured out how to get FEKO to calc Q? SuperFish can do it but using it effectively is another learning curve.
1. Based on experimental work in the K-Band with cavities with one end below standard cutoff (TE01). In this case measurements with a VNA show that mode is still present even without an endplate at all. Q depends on how far below cutoff due to radiation losses. Reflections on sidewalls...
2. Using FEKO it is a long process to get impedance match, when this is reached one can simple measure the loaded QL (f/df @ -3dB) --> 2*QL=QU (factor of 2 is true for impedance match only)
Other suggestions to get QU out of FEKO are very welcome!
EMPro generated QU directly from the dimensions of the cavity when using the Eigen-frequency solver -
#1219 by Rodal on 31 Dec, 2016 16:28
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That's an interesting viewpoint: that Shawyer's "cut-off" for a truncated conical closed cavity is not an actual cut-off as it occurs in open constant cross-section waveguides but instead has to do with a gradual decrease of quality factor of resonance Q for truncated cone closed cavities.
Don't know yet. ¯\_(ツ)_/¯ If this is of interest I could model it in EMPro after holidays to get Qu? Related values like your TC can solved based on this.If you dont like to have radiation pressure at the small plate, put it far below cut off diameter (for cylindrical WG).
And the Qu and 5x TC cavity fill / decay time are?
As I see it, no significant standing waves at the small end = no significant travelling waves at the small end = no significant reflection of the travelling waves at the small end back to the big end= very low Qu = very low force generation.
However it is good to see a plot showing cutoff does indeed occur in a tapered waveguide cavity. Your image is a keeper.
Fact is that this kind of cavity can store energy as well as one with SD above cutoff.
The cutoff design rule is not compatible with your goal:Quote from: TheTraveller... very low radiation pressure on the small end plate, which is the design goal ...
Dr Rodal's paper never discussed the effect on Qu of these beyond cutoff cavities. Focusing on just how far cutoff diam could be reduced and not factoring in the effect on Qu makes the work of little interest. Would like to see the Qu calcs for these cavities.
As I see it Roger walks a thin between achieving the smallest diam small end delivering the longest guide wavelength, lowest radiation pressure AND the highest Qu.
You are correct that in my report (from June 2015, that is a year and a half ago) I only focused on proving that it is NOT an actual cut-off, and that electromagnetic resonance is still present. Your point that the electromagnetic resonance may be present at a sub-optimal Q quality factor of resonance is a good one, your point should be researched. (*)
When you state that my report is of no interest because I did not calculate the quality factor for the cases beyond "Shawyer's cut-off" rule, if you were objective, you should say the same about Shawyer's reports: because Shawyer never wrote (to my recollection) a report comparing calculations of the quality factor of resonance for geometries that do not have his cut-off rule and for geometries that are more pointy than allowed by his cut-off rule.
I would be surprised if you recognize this objective fact, as I always see you portraying Shaywer's reports in the most positive glowing fashion and never pointing out what he could have done better.
I am very busy with other work and the holiday season, but if others have not done these quality factor of resonance calculations for these geometries beyond Shawyer's cut-off by the end of January, I may be interested in carrying them out and posting some results.
Happy New Year to all
---------------
(*) As my picture shows, the situation (well beyond) Shawyer's cut-off rule is one where the pointy end becomes a "dead zone" for resonance, and hence wasted in that sense, I expect that indeed the quality factor of resonance for the whole cavity will be lower, and hence your interpretation of Shawyer's cut-off rule puts this in a new light. A very good observation that, better explains Shawyer's cut-off rule.
