I think if we look at monomorphics distortion models, the effects of sidewall deformation will have far less impact on resonance than magnetron frequency drift. Thin sidewalls are a not going to make or break an experiment imho. If we see unsustainable emdrive force, my bet would be on mag freq, not sidewall deformation due to heat. I measured very little heat rise on the sidewall mesh. We need to focus on reasonable materials for diy projects...thick sidewalls are not part of this. Perhaps institutional players can do this.
Quote from: SeeShells on 03/13/2016 06:36 pmQuote from: Rodal on 03/13/2016 06:10 pmQuote from: rfmwguy on 03/13/2016 04:24 pmQuote from: Monomorphic on 03/13/2016 03:23 pmQuote from: rfmwguy on 03/13/2016 02:05 pmYes, the cone is not cut yet. What thickness copper side walls? The 1/8 or sticking with 1mm?1mm sidewalls. Was going to to spin thicker copper but no spinners responded with decent prices. A fully funded institutional project could spin then polish. A user here also suggested a lost wax pocess.It is not going to be possible to have a high Q (quality of resonance) close to theoretical with 1 mm walls: very compliant (the opposite of stiff). For a length of 0.26 meters and diameter of 0.28 meters, a 1 mm wall thickness is easy to deform out of shape just by applying hand pressure, and hence difficult to maintain geometrical tolerance.I hope you don't mind me adding my .02 cents on a 1mm or .039" copper wall. Once the endplates are secured by soldering you could literally stand on the frustum, I did. That's not the biggest issue we face in deforming, it's the thermal aspect of deformation that is the Q killer. ShellPerhaps what I wrote was not readily understandable, so I will try to explain it further. The issue I was concerned with is the issue of tolerance that DIY people should use. TheTraveller quoted Shawyer as invoking a tolerance of 13 micrometers (which to me is way too stringent for 2.45 GHz microwaves with a free-space wavelength of 0.122 m). On the other hand, it appears that rfmwguy and SeeShells have a much, much loser tolerance.With a shell structure that is 1 mm thick but 0.28 m diameter and 0.26 m long the issue is deformation, not strength.Stiffness is not the same thing as strength.Strength is the highest stress that a structure can carry before it fails (it can be defined as permanent deformation (*) for a tough material or fracture for a brittle material).On the other hand, stiffness is the ratio of strain (change in length per unit original length) to stress, or the ratio of deformation by force.A structure can be strong but not stiff enough for a given application.The issue with the quality of resonance is not at all anything to do with strength.When you say:QuoteOnce the endplates are secured by soldering you could literally stand on the frustum, I did.you may be able to determine just by standing on it is whether you exceeded the strength of the structure, certainly if it fractures, or perhaps if it permanently deforms and the permanent deformation is large enough to be perceived.To check the stiffness, you would need to be able to apply a load (stand on it) and simultaneously measure the deformation while the load is being applied. This is usually done with universal testers (either mechanical, screw-driven, or servo-hydraulic testers). For elastic deformation, the structure will return to its original shape once you unload from it.The concern is that the Q quality of deformation will be affected by deformations of the order of a mm. There is a huge dissonance between TheTraveller writing that Shawyer is asking for a tolerance of 13 micrometers in order to achieve a Q close to theoretical and on the other hand, saying that all the tolerance needed is whether one can observe deformation of truncated cone just by standing on it. I don't think that you would be able to determine an elastic deformation of a mm just by standing on it (you would need to have mirrors and an incredible vision to be able to tell a mm deformation !!! ). (*)So what is needed here is to quantify stiffness: to quantify deformation of the structure. Even when looking for permanent deformation, since the expected permanent deformation is of the order of a mm (the wall thickness) (**) standing on the truncated cone may not be an accurate way to determine it..And what is needed is for DIY experimenters to agree on a tolerance: there is a huge gap between the 13 micrometer tolerance invoked by TheTraveller/Shawyer and on the other hand invoking that if one can stand on the truncated cone, that is good enough._____(*) Actually, one does not need to really stand on the structure to be able to figure out the deformation of a cylinder that is 0.26 m long by 0.28 m diameter with a wall thickness of only 1 mm . One can readily use the theory of elasticity for thin shells to figure the deformation of cylindrical shell under load . The problem, though, is what is the boundary condition fixing the end plates to the cylindrical section: is it simply supported (appropriate for thin end plates) or is it cantilevered ends (which would be appropriate for very thick end plates). (**) The "standing on the cone" structure did serve as a test that you did not reach snap-through permanent buckling, but permanent deformation of the order of thickness (mm) was still certainly possible.The Q of the truncated cone will be affected by deformations much smaller than something like the snap-through buckling permanent deformation shown in this picture :It would be good for DIY to agree on a tolerance that may not be as extreme as the 13 micrometers invoked by TheTraveller/Shawyer, but yet is not as loose as "standing on it"
Quote from: Rodal on 03/13/2016 06:10 pmQuote from: rfmwguy on 03/13/2016 04:24 pmQuote from: Monomorphic on 03/13/2016 03:23 pmQuote from: rfmwguy on 03/13/2016 02:05 pmYes, the cone is not cut yet. What thickness copper side walls? The 1/8 or sticking with 1mm?1mm sidewalls. Was going to to spin thicker copper but no spinners responded with decent prices. A fully funded institutional project could spin then polish. A user here also suggested a lost wax pocess.It is not going to be possible to have a high Q (quality of resonance) close to theoretical with 1 mm walls: very compliant (the opposite of stiff). For a length of 0.26 meters and diameter of 0.28 meters, a 1 mm wall thickness is easy to deform out of shape just by applying hand pressure, and hence difficult to maintain geometrical tolerance.I hope you don't mind me adding my .02 cents on a 1mm or .039" copper wall. Once the endplates are secured by soldering you could literally stand on the frustum, I did. That's not the biggest issue we face in deforming, it's the thermal aspect of deformation that is the Q killer. Shell
Quote from: rfmwguy on 03/13/2016 04:24 pmQuote from: Monomorphic on 03/13/2016 03:23 pmQuote from: rfmwguy on 03/13/2016 02:05 pmYes, the cone is not cut yet. What thickness copper side walls? The 1/8 or sticking with 1mm?1mm sidewalls. Was going to to spin thicker copper but no spinners responded with decent prices. A fully funded institutional project could spin then polish. A user here also suggested a lost wax pocess.It is not going to be possible to have a high Q (quality of resonance) close to theoretical with 1 mm walls: very compliant (the opposite of stiff). For a length of 0.26 meters and diameter of 0.28 meters, a 1 mm wall thickness is easy to deform out of shape just by applying hand pressure, and hence difficult to maintain geometrical tolerance.
Quote from: Monomorphic on 03/13/2016 03:23 pmQuote from: rfmwguy on 03/13/2016 02:05 pmYes, the cone is not cut yet. What thickness copper side walls? The 1/8 or sticking with 1mm?1mm sidewalls. Was going to to spin thicker copper but no spinners responded with decent prices. A fully funded institutional project could spin then polish. A user here also suggested a lost wax pocess.
Quote from: rfmwguy on 03/13/2016 02:05 pmYes, the cone is not cut yet. What thickness copper side walls? The 1/8 or sticking with 1mm?
Yes, the cone is not cut yet.
Once the endplates are secured by soldering you could literally stand on the frustum, I did.
...Well, Mr. Euler can be demonstrated with an empty beer can. Stand on it, carefully, and it will support your weight. Have a friend flick the can with a finger, and it will collapse. Just sayin'. The reality of mathematics when it's reduced to real world phenomenon is often non-intuitive.
Quote from: rq3 on 03/14/2016 12:06 am...Well, Mr. Euler can be demonstrated with an empty beer can. Stand on it, carefully, and it will support your weight. Have a friend flick the can with a finger, and it will collapse. Just sayin'. The reality of mathematics when it's reduced to real world phenomenon is often non-intuitive.That buckling load limits are very sensitive to initial imperfections is well known and accounted for by Aerospace Engineers in their daily engineering life. The sensitivity to initial imperfections can be taken into account.Anyway, the issue at hand is that there is a huge gap between TheTraveller/Shawyer recommending 13 micrometers tolerance and rfmwguy polishing the plates to look like a mirror, while simultaneously using 1 mm wall thickness.
Quote from: Rodal on 03/14/2016 12:10 amQuote from: rq3 on 03/14/2016 12:06 am...Well, Mr. Euler can be demonstrated with an empty beer can. Stand on it, carefully, and it will support your weight. Have a friend flick the can with a finger, and it will collapse. Just sayin'. The reality of mathematics when it's reduced to real world phenomenon is often non-intuitive.That buckling load limits are very sensitive to initial imperfections is well known and accounted for by Aerospace Engineers in their daily engineering life. The sensitivity to initial imperfections can be taken into account.Anyway, the issue at hand is that there is a huge gap between TheTraveller/Shawyer recommending 13 micrometers tolerance and rfmwguy polishing the plates to look like a mirror, while simultaneously using 1 mm wall thickness.We are in complete agreement. This forum has wandered between materials, fabrication techniques, wave models, magnetron tuning, thermal effects, vacuum issues, power supplies, antenna placement, and what have you. Not one experimenter has said:1)What Shawyer claims (inject microwaves from a standard oven magnetron into a sealed frustrum and produce thrust) is testable, and I intend to prove it. If I don't, I'll know why.2) If I do 1 above I will prove or disprove Shawyer's claim.
Quote from: rq3 on 03/14/2016 12:06 am...Well, Mr. Euler can be demonstrated with an empty beer can. Stand on it, carefully, and it will support your weight. Have a friend flick the can with a finger, and it will collapse. Just sayin'. The reality of mathematics when it's reduced to real world phenomenon is often non-intuitive.(*) The issue at hand is that there is a huge gap between TheTraveller/Shawyer recommending 13 micrometers tolerance and rfmwguy polishing the plates to look like a mirror, while simultaneously using 1 mm wall thickness.It seems to me more important to get to the bottom of this gap:1) Shawyer recommending 13 micrometer tolerance2) rfmwguyg polishing the copper to a mirror finishthe above appears incompatible with:1 mm wall thickness.Why do the endplates need to be polished like a mirror while the sidewalls can be 1 mm thick and hence susceptible to deformations (lack of straightness) of the order of 1 mm ?Did any computer run by Monomorphic indicate that the endplates had to be polished like a mirror?________(*) That buckling load limits are very sensitive to initial imperfections is accounted for by Aerospace Engineers in their daily engineering life. The sensitivity to initial imperfections can, and has been taken into account with mathematical formulations. It can also be numerically analyzed (but it involves nonlinear formulations).But I am not talking about buckling loads here, I'm just concerned with the stiffness of a shell that is 1 mm thick and 0.28 m in diameter.
I propose that a common-sense tolerance for EM Drive thickness that DIY testing people should use for their frustums is the thickness of a commercial waveguide with similar diameter.In this case, a common sense tolerance is that DIY people should use a thickness of waveguides with a diameter of 0.28 m to be used at ~2 GHz
...For me to see how a deformation in the sidewall of the cavity would seriously effect the resonate and tuning versus the distance required for resonance in the endplates I'd need to see some numbers. It's my contention that a deformation in the sidewalls of 1mm would not be seen or effect the Q of this system to anyserious degree. It's the endplates that set the resonance and Q. I think on my next run I'll take a ball peen hammer and ding the sidewall to see if what I'm thinking here is true. Otherwise maybe someone could "ding" a depression in a FEKo sim to see what effects a sidewall deformation has in the Q and resonance.ShellAdded: also there are outside circular copper strips on the sidewalls that could be used to increase the "stiffness dramatically. Builds have used this method.
Quote from: Rodal on 03/13/2016 11:41 pmI propose that a common-sense tolerance for EM Drive thickness that DIY testing people should use for their frustums is the thickness of a commercial waveguide with similar diameter.In this case, a common sense tolerance is that DIY people should use a thickness of waveguides with a diameter of 0.28 m to be used at ~2 GHzI don't understand your reasoning Dr. Rodal, commercial waveguides are designed to transmit power, not resonate, as I'm sure you're well aware of. I would expect the amount of conductive heat dissipation required by a transmission line (with a typical .5 dB loss per meter) is significantly less than a resonator with no output. Why not create the thickest frustum possible within price constraints so that the steady state temperature is lower?
Quote from: SeeShells on 03/14/2016 12:40 am...For me to see how a deformation in the sidewall of the cavity would seriously effect the resonate and tuning versus the distance required for resonance in the endplates I'd need to see some numbers. It's my contention that a deformation in the sidewalls of 1mm would not be seen or effect the Q of this system to anyserious degree. It's the endplates that set the resonance and Q. I think on my next run I'll take a ball peen hammer and ding the sidewall to see if what I'm thinking here is true. Otherwise maybe someone could "ding" a depression in a FEKo sim to see what effects a sidewall deformation has in the Q and resonance.ShellAdded: also there are outside circular copper strips on the sidewalls that could be used to increase the "stiffness dramatically. Builds have used this method.But where do you stand on the following, which is the source of this huge contradictions in the last few pages of this thread:1) Do you agree with TheTraveller/Shawyer that a tolerance of 13 micrometers is needed for the EM Drive?2) Do you agree with rfmwguy that one needs to polish the end plates to look like a mirror?It appears contradictory to argue for 13 micrometer tolerance and polishing the end plates to look like a mirror for the Q, and simultaneously to say that a deformation of 1 mm of the side walls doesn't matter for the Q
...I've tried to do a search for when X_Ray did some calculations of the differences in Q and mode generation by varying the sidewall angles and couldn't find what I was looking for. I do remember is wasn't a large effect. ...
Dr rodal, you seem to be bothered by diy methodology. I suggest no diyer has a correct methodology and neither do you. This topic has advanced well beyond being a roger shawyer comment thread to diy and theory beyond one person. My advice is to build one yourself and show others where errors are being made. Either that or publish a diy guide you would recommend to new diyers.