-
#640 by TheTraveller on 27 Mar, 2016 13:59
-
Roger advised me the video was done at a SPR licensee and not at SPR. Was also told he could only show thrusters older than 5 years.
In the photo below Mr. Shawyer's rotating demo can be seen in the background. Why didn't he start it up and let BBC film that? It's over 5 years old. Also next time you talk to Mr. Shawyer can you ask him what the large bird cage apparatus is that hangs from the ceiling above him in this photo. It looks like it has fan blades on it. Why is it suspended from the roof beams?
It is my understanding that area was storage for old thrusters and other equipment. The EmDrive shown was 2008 tech. As for the Demonstrator, there is already a video that you can view on www.emdrive.com
Do believe a early cryo EmDrive was originally videoed on the air track. Was surprised to see the very old pre Flight Thruster on the air track. Do note the episode was scheduled for late Feb but was pulled and nothing was shown for the last week in Feb. Finally was shown late March. Wild guess was the cryo unit was replaced at the edit of USAF or UK MOD.
Would also add Roger said BBC did film both USAF & UK MOD but neither interview made the episode.
BTW who is "Coyote"? Seems the BBC left us a trail to follow.
Which is it? A licensee site or a storage area that SPR uses? Also what is the fan hanging from the roof beams used for? It looks like there are some spot lights around it. Is this another experiment that Mr. Shawyer is doing where the fan and spotlights are turned on? If so, what would be below the fan and illuminated by the spot lights?
The best way to demonstrate Shawyer's technology (and therefore to get funding to enable Shawyer's dreams for the EM Drive) was proposed by TheTraveller: to have the experiments demonstrated before an skeptical audience that could independently observe and assess the experiments. TheTraveller had earlier proposed to come to America with a rotating battery-powered unit that he would demonstrate before audiences. Such demonstrations could change skeptical minds and get needed funding.
Presently we see Mr. Shawyer all alone and SPR Ltd. is reported having negative net worth since 2008.
It would have been much more effective to demonstrate the Demonstrator EM Drive rotating around before the cameras of BBC Horizon. BBC could have had the aerospace engineer Dr Ron Evans (who appears repeatedly throughout the program except in the Shawer segment), Nasa aerospace engineer Marc Millis (who is skeptical of the EM Drive as per previous reports), Dr Martin Tajmar (who appears in his own segment) and Prof. John Ellis (who expressed skepticism) to be present for the Demonstrator being shown going around and around (instead of being shown in a video).
Also, is there a video of the Demonstrator shown rotating around that shows a large perspective, including whether anything that was in the ceiling? For example, concerning the fan hanging from the roof beams, if such a fan would have been operating on top of the Demonstrator rotating air bearing, such a powerful fan may have had an influence on its movement.
That's why TheTraveller's proposal to demonstrate these devices before skeptical audiences makes so much sense.
Despite what you and others may wish to try to convince others, SPR needs no funding. Why do I know that? Because I and others have offered the funding and it was rejected. Told not needed.
So the pathetic efforts here to paint SPR as cash strapped are really a waste of time & effort. Roger is really good at covering his tracks.
BTW good luck with your own efforts to replicate. May the best propellantless tech win the market. Be it SPR, a German heavy transport company, AirBus, Prof Woodward, EW or others. -
#641 by RotoSequence on 27 Mar, 2016 14:04
-
Roger is really good at covering his tracks.
But why is he covering his tracks? How long until we find out why? If he's already shared the tech with the biggest names in aerospace, who's left to hide it from? -
#642 by MaxIsp on 27 Mar, 2016 15:12
-
BTW who is "Coyote"? Seems the BBC left us a trail to follow.
Probably Col. M. V. "Coyote" Smith, USAF, at the School of Advanced Air and Space Studies, Maxwell AFB, Montgomery, Alabama.
Awarded, with others, the NSS Space Pioneer award in 2008 for space power studies. -
#643 by rq3 on 27 Mar, 2016 15:15
-
Roger advised me the video was done at a SPR licensee and not at SPR. Was also told he could only show thrusters older than 5 years.
In the photo below Mr. Shawyer's rotating demo can be seen in the background. Why didn't he start it up and let BBC film that? It's over 5 years old. Also next time you talk to Mr. Shawyer can you ask him what the large bird cage apparatus is that hangs from the ceiling above him in this photo. It looks like it has fan blades on it. Why is it suspended from the roof beams?
It is my understanding that area was storage for old thrusters and other equipment. The EmDrive shown was 2008 tech. As for the Demonstrator, there is already a video that you can view on www.emdrive.com
Do believe a early cryo EmDrive was originally videoed on the air track. Was surprised to see the very old pre Flight Thruster on the air track. Do note the episode was scheduled for late Feb but was pulled and nothing was shown for the last week in Feb. Finally was shown late March. Wild guess was the cryo unit was replaced at the edit of USAF or UK MOD.
Would also add Roger said BBC did film both USAF & UK MOD but neither interview made the episode.
BTW who is "Coyote"? Seems the BBC left us a trail to follow.
Which is it? A licensee site or a storage area that SPR uses? Also what is the fan hanging from the roof beams used for? It looks like there are some spot lights around it. Is this another experiment that Mr. Shawyer is doing where the fan and spotlights are turned on? If so, what would be below the fan and illuminated by the spot lights?
The best way to demonstrate Shawyer's technology (and therefore to get funding to enable Shawyer's dreams for the EM Drive) was proposed by TheTraveller earlier in these EM Drive threads: to have the experiments demonstrated before an skeptical audience that could independently observe and assess the experiments. TheTraveller had earlier proposed to come to America with a rotating battery-powered unit that he would demonstrate before audiences. Such demonstrations could change skeptical minds and get needed funding.
Presently we see Mr. Shawyer all alone and SPR Ltd. is reported having negative net worth since 2008 (https://www.endole.co.uk/company/04097991/satellite-propulsion-research-limited).
It would have been much more effective to demonstrate the Demonstrator EM Drive rotating around before the cameras of BBC Horizon. For example, the BBC could have had the aerospace engineer Dr Ron Evans (who appears repeatedly throughout the program except in the Shawer segment), and/or Nasa aerospace engineer Marc Millis (who is skeptical of the EM Drive as per previous reports), and/or Dr Martin Tajmar (who appears in his own segment) and/or Prof. John Ellis (who expressed skepticism) to be present for the Demonstrator being shown going around and around (instead of being shown in a video).
Also, is there a video of the Demonstrator shown rotating around that shows a large perspective, including whether anything that was in the ceiling? For example, concerning the fan hanging from the roof beams, if such a fan would have been operating on top of the Demonstrator, such a powerful fan may have had an influence on the rotational movement of the EM Drive Demonstrator below the fan and illuminated by its spot lights.
That's why TheTraveller's proposal to demonstrate these devices before skeptical audiences makes so much sense to get funding and revert the present situation of Mr. Shawyer shown all alone pushing the EM Drive by hand and SPR having negative net worth.
A similar fan in a local aircraft hangar, roughly twice as far from the floor as the one illustrated, is fully capable of sucking a paper towel off of the floor and entraining it in the airflow vortex. I've personally witnessed this. Just saying. -
#644 by Rodal on 27 Mar, 2016 15:23
-
...Ask yourself why "Coyote" was included?
He probably was included simply because Colonel M.V. "Coyote" Smith, PhD, is a Professor of strategic space and cyber studies at the School of Advanced Air and Space Studies at Air University and prior to this, he served as the Director of the Center for Strategy and Technology, where he led project Blue Horizons for the Chief of Staff of the Air Force:
You are free to form your own opinions.
http://www.au.af.mil/au/awc/csat/blue_horizon/index.htm
http://nasawatch.com/archives/2012/02/colonel-futuris.html
<<What are the emerging technologies that will shape the US Air Force and the conflict arena in which it must operate in beyond 2025? What could air, space and cyberspace power look like beyond 2025? Who will have access to emerging technologies that can make a difference? How soon will these important technological achievements become fielded systems?>>
So ? why are you asking the question as to why Colonel M.V. "Coyote" Smith was included in the BBC Horizon program on Project Greenglow and the battle with gravity?
When you write...Do believe a early cryo EmDrive was originally videoed on the air track. Was surprised to see the very old pre Flight Thruster on the air track. Do note the episode was scheduled for late Feb but was pulled and nothing was shown for the last week in Feb. Finally was shown late March. Wild guess was the cryo unit was replaced at the edit of USAF or UK MOD.
I emphasize that you recognize that what you write is your <<Wild guess>>
Would also add Roger said BBC did film both USAF & UK MOD but neither interview made the episode.
BTW who is "Coyote"? Seems the BBC left us a trail to follow.
You have shown no supporting evidence anywhere that the BBC Horizon program <<the cryo unit was replaced at the edit of USAF>> or that the US Air Force has any such involvement with Shawyer's EM Drive.
Actually, there is evidence to the contrary, in the following Forbes article (http://www.forbes.com/sites/billtucker/2015/12/06/the-power-of-the-force-the-curious-case-of-the-emdrive/2/#2fbca7612919):Quote from: Bill Tucker, ForbesI reached out to the US Air Force as Shawyer claims a legal relationship with that branch of our military services. According to Ed Gulick in the Public Affairs Office,
“The Air Force is aware of EmDrive and the ongoing research but is simply watching to see if and when the technology becomes viable. We could not find any evidence that the AF has an investment in or a licensing agreement for the technology.” -
#645 by CW on 27 Mar, 2016 15:45
-
Roger advised me the video was done at a SPR licensee and not at SPR. Was also told he could only show thrusters older than 5 years.
In the photo below Mr. Shawyer's rotating demo can be seen in the background. Why didn't he start it up and let BBC film that? It's over 5 years old. Also next time you talk to Mr. Shawyer can you ask him what the large bird cage apparatus is that hangs from the ceiling above him in this photo. It looks like it has fan blades on it. Why is it suspended from the roof beams?
It is my understanding that area was storage for old thrusters and other equipment. The EmDrive shown was 2008 tech. As for the Demonstrator, there is already a video that you can view on www.emdrive.com
Do believe a early cryo EmDrive was originally videoed on the air track. Was surprised to see the very old pre Flight Thruster on the air track. Do note the episode was scheduled for late Feb but was pulled and nothing was shown for the last week in Feb. Finally was shown late March. Wild guess was the cryo unit was replaced at the edit of USAF or UK MOD.
Would also add Roger said BBC did film both USAF & UK MOD but neither interview made the episode.
BTW who is "Coyote"? Seems the BBC left us a trail to follow.
Which is it? A licensee site or a storage area that SPR uses? Also what is the fan hanging from the roof beams used for? It looks like there are some spot lights around it. Is this another experiment that Mr. Shawyer is doing where the fan and spotlights are turned on? If so, what would be below the fan and illuminated by the spot lights?
I think I can see, where this whole thing is moving. Mr. Shawyer will get older and older, and suddenly he will be gone. Meanwhile, decades will have passed and no credible demonstrations been made. Just another story of someone who could have changed the world for the better, but didn't, because.. reasons .
I take it you have read and accepted nothing of what Roger shared with me and I passed on?
If any replicator reads ALL of what Roger, Prof Yang & myself has shared they will suceed. If they modify the recipe, well they are skiing "Off Piste" & good luck.
The point is not, what you or others passed on. This effort is certainly not about spreading annecdotal history, is it? The point is, Mr. Shawyer has been promoting this apparatus for many years now. You write "(..) If any replicator reads ALL of what Roger, Prof Yang & myself has shared they will suceed. (..)". Succeed in what exactly? Succeed in not demonstrating advanced versions of his apparatus, although claiming he has them? Also, having studied the largest parts of what is available, I am positive that Mr. Shawyer's theory of operation is not correct. Falling in love with one's theory doesn't make it correct.
Also, the only relevant testing to be done of an allegedly advanced technology like this, has to be done in the vacuum of space, in orbit around the Earth. If it works as predicted in vacuum, separated from any other masses, it will 100% work on Earth. If it is guaranteed, that there really is no coupling mass for impulse exchange in the surroundings like Earth's mass, and the device is shielded from any fields it may interact with in contrived ways, that no human may ever find, then it can be proven whether the device shows an unknown physical property. This alone would be revolutionary.
I think that the Aachen guys from hackaday.io might have a shot on showing us, if there is something real going on. The goal is putting a mini version into a cubesat and do some real vacuum of space, no-coupling-masses-present testing. -
#646 by Flyby on 27 Mar, 2016 16:03
-
OOOOOOOOOOOOOOOHHHHHHHHH, NOOOOOOOOOOO!!!!!!
Could you please explain to why you take the 24cm the way you did (in green)?
No it's not Mister Bill, but something much worse: IT"S THE RETURN OF THE DREADED------>
CHINESE FRUSTUM
It's 5:14 AM and as you can see I did this all by hand.
***Important to note: the frustum is "upside down"per the way it copied off the site.
***Also note: the top plate is raised all the way to the top of the frustum, and the bottom plate is raised
to it's highest position. Of course both plates could be adjusted in combination.
It appears as though Yang could adjust up to a little over 2 and 1/4 wavelengths. , Fatty Lumpkin
I would rather expect you take either the blue line or red line as the reference distance of 24cm...
you interpretation strikes me as ..odd?
In the past , i made a few comparative setups , based upon all the different drawing we have of Yang's setup. The red version was the calculated one, the purple version is what I got out of the drawings. In my interpretation the 24cm goes from plate to plate, regardless the top/bottom straight wall part.
It is however impossible to verify how accurate the drawings are, iow, it is impossible the assert if these were mere illustrative drawings or real engineering drawings. They do give the impression to be engineering drawings, but that could be deceptive (on purpose or not).
with that uncertainty in mind I drew up the cavity once more, but this time in percentage, with the length being 100%...the dimensions become then parametric, in relation to the chosen length.
-
#647 by Monomorphic on 27 Mar, 2016 16:09
-
Oxidation.
I've noticed significant oxidation on the copper since it has been exposed for several days. Those polishing their frustums early will need to use a chemical cleaner like acetone to remove the oxidation before testing.
-
#648 by CW on 27 Mar, 2016 16:22
-
Oxidation.
I've noticed significant oxidation on the copper since it has been exposed for several days. Those polishing their frustums early will need to use a chemical cleaner like acetone to remove the oxidation before testing.
Are you sure this is not dark matter residue?
-
#649 by Rodal on 27 Mar, 2016 16:25
-
Oxidation.
For consideration of anybody interested in experience with processing oxidation free surfaces (otherwise please skip this
I've noticed significant oxidation on the copper since it has been exposed for several days. Those polishing their frustums early will need to use a chemical cleaner like acetone to remove the oxidation before testing.
):
What matters are the internal surfaces. SeeShells advice to use a material with higher conductivity like Silver makes more sense IMHO. But anyway, the advice concerning removing the oxidation before testing implies that the EM Drive would need to be dis-assembled prior to testing to remove the oxidation.
For individuals soldering the EM Drive prior to testing, or other permanent means to assemble it, it means that they would need to solder or permanently attach it after removing the internal oxidation.
For those of us that have been involved in industrial processes where a surface free of oxidation is important (for example adhesion to metal surfaces), it is important to understand that time is of the essence, as the surface oxidates in a matter of minutes. (To a first approximation, oxidation is an Arhenius process: exponentially dependent on temperature and moisture content).
Also remember that the skin depth at these frequencies is only 1 micrometer. If oxidation is an issue, the oxidation only needs to be within a micrometer of depth to have an effect. Thus, conductivity in an oxidated surface may be more important in lowering Q than the surface finish. A surface can oxidate to a very small thickness in a small amount of time when exposed to humid air.
I have done many such experiments. It is well-reported in the literature that it would be ineffective to remove the oxidation hours before any operation that requires a surface free of oxidation. Companies that are involved in processing surfaces free of oxidation (either mechanically and/or chemically) know that this must be done minutes before prior to the process requiring an oxidation free-surface.
Either that, or you would need to coat the oxidation-prone surface, within minutes of removing any oxidation, with a coating that is impermeable to water. (remember here that many polymers, like polyurethane are very, very permeable to water).
(Or you would need to have the internal surfaces in an environment completely free of any moisture, and not exposed to humid air).
Furthermore, another thing to consider is that it is well known that permeability to water of any permeable coating is greatly enhanced if there is a thermal gradient such that the metal is colder than the polymer surface. (Thermal gradient driven permeation).
-
#650 by Rodal on 27 Mar, 2016 17:01
-
The (to me at first sight, unusual) requirement to polish the surfaces to a surface roughness of much less than a micrometer, for operation at microwave wavelengths of several cm (2.45 GHz), may actually be due to the oxidation problem. (Strictly due to the fact that an oxidated or corroded surface has less conductivity).
http://www.mdpi.com/2075-4701/2/4/450/pdf
The relationship between surface roughness and wettability was defined already in 1936 by Wenzel (https://en.wikipedia.org/wiki/Wetting#Wenzel.27s_model) who stated that adding surface roughness will enhance the wettability of a surface. Simply stated, a rough surface has much more contact area with the humid air.
In essence it is the surface free-energy that is important (it can be readily be measured by measuring the contact angle with water).
Perhaps the big problem here with Q is oxidation and what we have is that some people have empirically found that a polished surface experiences less oxidation in a given amount of time (all other things being equal: humidity in air, temperature, etc.) than a rough surface, which would make sense.
But if this is the case, perhaps more effort (or at least, as much effort) should go into preventing oxidation of the surface than in over-polishing the surface. -
#651 by SeeShells on 27 Mar, 2016 17:18
-
Oxidation.
For consideration of anybody interested in experience with processing oxidation free surfaces (otherwise please skip this
I've noticed significant oxidation on the copper since it has been exposed for several days. Those polishing their frustums early will need to use a chemical cleaner like acetone to remove the oxidation before testing. ):
What matters are the internal surfaces. SeeShells advice to use a material with higher conductivity like Silver makes more sense IMHO. But anyway, the advice concerning removing the oxidation before testing implies that the EM Drive would need to be dis-assembled prior to testing to remove the oxidation.
For individuals soldering the EM Drive prior to testing, or other permanent means to assemble it, it means that they would need to solder or permanently attach it after removing the internal oxidation.
For those of us that have been involved in industrial processes where a surface free of oxidation is important (for example adhesion to metal surfaces), it is important to understand that time is of the essence, as the surface oxidates in a matter of minutes. (To a first approximation, oxidation is an Arhenius process: exponentially dependent on temperature and moisture content).
Also remember that the skin depth at these frequencies is only 1 micrometer. If oxidation is an issue, the oxidation only needs to be within a micrometer of depth to have an effect. Thus, conductivity in an oxidated surface may be more important in lowering Q than the surface finish. A surface can oxidate to a very small thickness in a small amount of time when exposed to humid air.
I have done many such experiments. It is well-reported in the literature that it would be ineffective to remove the oxidation hours before any operation that requires a surface free of oxidation. Companies that are involved in processing surfaces free of oxidation (either mechanically and/or chemically) know that this must be done minutes before prior to the process requiring an oxidation free-surface.
Either that, or you would need to coat the oxidation-prone surface, within minutes of removing any oxidation, with a coating that is impermeable to water. (remember here that many polymers, like polyurethane are very, very permeable to water).
(Or you would need to have the internal surfaces in an environment completely free of any moisture, and not exposed to humid air).
Furthermore, another thing to consider is that it is well known that permeability to water of any permeable coating is greatly enhanced if there is a thermal gradient such that the metal is colder than the polymer surface. (Thermal gradient driven permeation).
I'd recommend using a Clear silicon coating after polishing.
http://www.amazon.com/MG-Chemicals-Silicone-Conformal-Coating/dp/B008O9YGQI
Also I've used for cleaning and it works well, rinse after use.
http://www.amazon.com/Tarn-X-TX-6-Tarnish-Remover-12-Ounce/dp/B000VPEA4Q/ref=sr_1_3?s=industrial&ie=UTF8&qid=1459099222&sr=1-3&keywords=copper+cleaner -
#652 by zen-in on 27 Mar, 2016 17:45
-
Oxidation.
I've noticed significant oxidation on the copper since it has been exposed for several days. Those polishing their frustums early will need to use a chemical cleaner like acetone to remove the oxidation before testing.
Acetone will not make the Copper bright again. Acetone is good for removing oils, etc from handling. You could wash it with an acid, like hot vinegar or very dilute H2 SO4. But that leaves a residue of Copper on the surface of the metal. I think the effect of Copper oxidation is over rated. That oxidation layer is extremely thin - on the order of a single molecule. The skin depth does not include the oxidation layer even iff it were much thicker because it is an insulator. If the Copper was covered in green verdigris that would be a different matter. The big issue with corrosion is when it acts like a diode junction, causing the RF to produce mixing products. I challenges someone to measure the difference in Q between cavity with a bright mirror surface inside and one that is brown Copper. -
#653 by Rodal on 27 Mar, 2016 17:53
-
Oxidation.
I've noticed significant oxidation on the copper since it has been exposed for several days. Those polishing their frustums early will need to use a chemical cleaner like acetone to remove the oxidation before testing.
Acetone will not make the Copper bright again. Acetone is good for removing oils, etc from handling. You could wash it with an acid, like hot vinegar or very dilute H2 SO4. But that leaves a residue of Copper on the surface of the metal. I think the effect of Copper oxidation is over rated. That oxidation layer is extremely thin - on the order of a single molecule. The skin depth does not include the oxidation layer even iff it were much thicker because it is an insulator. If the Copper was covered in green verdigris that would be a different matter. The big issue with corrosion is when it acts like a diode junction, causing the RF to produce mixing products. I challenges someone to measure the difference in Q between cavity with a bright mirror surface inside and one that is brown Copper.
Can you think of a reason why polishing to within fractions of a micrometer <<with a bright mirror surface>> would be required when operating at a frequency of 2.45GHz, with wavelengths orders of magnitude longer than the surface roughness? -
#654 by Rodal on 27 Mar, 2016 18:34
-
...
Silicone rubber is permeable to water and to gases. Due to their long intramolecular bond lengths, flexible backbones and weak intermolecular forces, silicones have a much larger free volume compared to carbon based polymer systems. Also, the bonds between alternating silicon and oxygen atoms make the silicone network more polar than carbon based polymeric systems.
I'd recommend using a Clear silicon coating after polishing.
http://www.amazon.com/MG-Chemicals-Silicone-Conformal-Coating/dp/B008O9YGQI
Also I've used for cleaning and it works well, rinse after use.
http://www.amazon.com/Tarn-X-TX-6-Tarnish-Remover-12-Ounce/dp/B000VPEA4Q/ref=sr_1_3?s=industrial&ie=UTF8&qid=1459099222&sr=1-3&keywords=copper+cleaner
If you like to use silicone polymer, it would be good to have a silicone polymer filled with fillers that decrease its water permeability:
https://www.silicone-polymers.co.uk/pdf2011/Moisture%20Permeability%20of%20Silicone%20Systems%20-%20Case%20Study%202.pdf
I do agree that to retard oxidation, using a silicone polymer coating is much better than using no coating whatsoever.
.
Saran (tradename for polyvinylidene chloride or PVDC) has very low permeability to water, however coating PVDC is a very complex process (by comparison) which requires expertise. It has good thermal stability, but above 125 °C decomposes to produce HCl.
The advantage of Silicone polymers is that they have good resistance to extreme temperatures, being able to operate normally to 300 °C . -
#655 by SeeShells on 27 Mar, 2016 18:55
-
...
Silicone rubber is permeable to water and to gases. Due to their long intramolecular bond lengths, flexible backbones and weak intermolecular forces, silicones have a much larger free volume compared to carbon based polymer systems. Also, the bonds between alternating silicon and oxygen atoms make the silicone network more polar than carbon based polymeric systems.
I'd recommend using a Clear silicon coating after polishing.
http://www.amazon.com/MG-Chemicals-Silicone-Conformal-Coating/dp/B008O9YGQI
Also I've used for cleaning and it works well, rinse after use.
http://www.amazon.com/Tarn-X-TX-6-Tarnish-Remover-12-Ounce/dp/B000VPEA4Q/ref=sr_1_3?s=industrial&ie=UTF8&qid=1459099222&sr=1-3&keywords=copper+cleaner
If you like to use silicone polymer, it would be good to have a silicone polymer filled with fillers that decrease its water permeability:
https://www.silicone-polymers.co.uk/pdf2011/Moisture%20Permeability%20of%20Silicone%20Systems%20-%20Case%20Study%202.pdf
I do agree that to retard oxidation, using a silicone polymer coating is much better than using no coating whatsoever.
http://www.mgchemicals.com/downloads/tds/tds-422b-a.pdf
Thought it was a inexpensive solution and that it's permeability water and hygroscopic characteristics were so low that it wasn't going to be a issue to worry about. I know they use this in microwave waveguides to good effect but I guess it's like polishing to a mirror finish if you can make it just a little bit better then do it.
This next step for the DYIers has been to take it to the level that approaches and in some cases exceeds care I've seen in a lab setting so it can't hurt.
Shell -
#656 by Rodal on 27 Mar, 2016 19:35
-
Saran's coefficient of water permeability is dozens of thousands of times (many orders of magnitude) less permeable to water than silicone polymers and many other polymers (http://www.faybutler.com/pdf_files/HowHoseMaterialsAffectGas3.pdf ). Although Saran coating is a very complex process, due to the fact that so many people are buying "Saran wrap" for their kitchen uses, it is quite affordable to buy Saran wrap from a supermarket. Also a film of any material is much less permeable to water than an air-sprayed polymer (because of the huge amount of free volume in an air-sprayed polymer)....
Silicone rubber is permeable to water and to gases. Due to their long intramolecular bond lengths, flexible backbones and weak intermolecular forces, silicones have a much larger free volume compared to carbon based polymer systems. Also, the bonds between alternating silicon and oxygen atoms make the silicone network more polar than carbon based polymeric systems.
I'd recommend using a Clear silicon coating after polishing.
http://www.amazon.com/MG-Chemicals-Silicone-Conformal-Coating/dp/B008O9YGQI
Also I've used for cleaning and it works well, rinse after use.
http://www.amazon.com/Tarn-X-TX-6-Tarnish-Remover-12-Ounce/dp/B000VPEA4Q/ref=sr_1_3?s=industrial&ie=UTF8&qid=1459099222&sr=1-3&keywords=copper+cleaner
If you like to use silicone polymer, it would be good to have a silicone polymer filled with fillers that decrease its water permeability:
https://www.silicone-polymers.co.uk/pdf2011/Moisture%20Permeability%20of%20Silicone%20Systems%20-%20Case%20Study%202.pdf
I do agree that to retard oxidation, using a silicone polymer coating is much better than using no coating whatsoever.
.
Saran (tradename for polyvinylidene chloride or PVDC) has very low permeability to water, however coating PVDC is a very complex process (by comparison) which requires expertise. It has good thermal stability, but above 125 °C decomposes to produce HCl.
The advantage of Silicone polymers is that they have good resistance to extreme temperatures, being able to operate normally to 300 °C .
http://www.amazon.com/saran-premium-plastic-wrap-100/dp/b00jpkw1rq/ref=sr_1_2_a_it?ie=utf8&qid=1459109116&sr=8-2&keywords=saran+wrap&tag=mit-tb-20
The problem is how to apply Saran wrap to an internal surface of a truncated cone.
Perhaps DIY could think about cutting narrow strips of Saran wrap [make sure that your plastic wrap is actually Saran polymer and not made from an inferior polymer] and placing the strips along the longitudinal direction (stretching it so that it is not wrinkled). And overlap it over the edges. Saran wrap "sticks" to itself for internal overlap between the narrow strips.
Since Saran wrap is inexpensive, all that it is involved is the time to do this. If you find out that is impractical, it is trivial to remove, no harm done.
Again, Saran has good thermal stability, but above 125 °C decomposes to produce HCl, while silicone polymer is good up to 300 °C
At optical frequencies, Saran wrap can also be used as a pellicle mirror (it practically eliminates beam or image doubling due to a non-coincident weak second reflection)
http://petapixel.com/2011/12/27/plastic-wrap-can-be-used-as-a-pellicle-mirror-substitute/
-
#657 by FattyLumpkin on 27 Mar, 2016 19:36
-
Flyby, does the 100 = the reported 24 cm height of the frustum? And to complicate things further, I just received this:
-
#658 by Rodal on 27 Mar, 2016 19:47
-
If slight surface oxidation was a problem, wouldn't that prevent aluminium frustums from working, as this material spontaneously develops rather quickly an oxide layer when exposed to the atmosphere? Have there been reports of successful experiments with aluminium frustrums?
If you are referring to NASA Eagleworks tests, NASA Eagleworks has pointed out that they quickly coat all the internal surfaces of their frustums (including the aluminum frustums) to prevent corrosion. -
#659 by X_RaY on 27 Mar, 2016 20:53
-
You are right with the corrosion conditions of aluminum, however due to the fact that aluminium have a much lower conductivity and using it instead of copper it would leads to a greater impact on the Q than a thin layer of copper oxide.If slight surface oxidation was a problem, wouldn't that prevent aluminium frustums from working, as this material spontaneously develops rather quickly an oxide layer when exposed to the atmosphere? Have there been reports of successful experiments with aluminium frustrums?
If you are referring to NASA Eagleworks tests, NASA Eagleworks has pointed out that they coat all the internal surfaces of their frustums (including the aluminum frustums) to prevent corrosion.
Actually I was thinking of the frustums used by the Hackaday team, which as far as I am aware of are 3D printed from a solid aluminium block. It's perhaps not the best example as their results to date have been ambiguous and thus I was wondering if other teams reported less ambiguous ones with this material.
When exposed to air, aluminium very quickly develops a homogeneous aluminum oxide layer of thickness in the order of a few nanometers which prevents further oxidation (and corrosion).
This is no bogus, in the past I tested both, cylindrical and conical K-Band cavity resonators using very different metals with different conductivities (Aluminium, steel, nickel alloys, brass and copper)
BTW, copper has a terrible thermal expansion coefficient
Therefore I like the idea of copper, silver or gold plating on thermal less active alloys like this:
https://en.wikipedia.org/wiki/Kovar
The first problem is it is quite expensive and hard to work with, the second is the low conductivity, it must be plated to achieve high Q.
):
