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#1640 by rfmwguy on 12 Jan, 2016 01:29
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Interesting you say that...I happen to agree that it lacks anything new. Best I can tell is both projects produced paper/presentations only and no hardware...at least nothing I could find.Tangential - emdrive does not fit a current interstellar template for propulsion
The following paper describes a decades-old collaboration between scientists exploring interstellar missions (including propulsion methodologies). It began as Project Daedalus in the 70's and morphed into Project Icarus after 2000. Emdrive experimentation is not on their radar, but knowing there is a confederation of scientists aligned with a project like this is interesting IMO. Note some of the names...they have appeared in print somewhat recently.
The paper is here: http://arxiv.org/abs/1005.3833
Hmm. The paper is sort of underwhelming IMHO. There is really no significant breakthrough identified that would fundamentally change the Daedalus findings that I can see. And there are a lot of pages describing how CURRENT space systems work (to be used as backup systems???) and potential onboard computer architectures (is this really a key challenge??). I can't see what the purpose of this study would be other than "we haven't done it for a while". -
#1641 by Prunesquallor on 12 Jan, 2016 01:54
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Interesting you say that...I happen to agree that it lacks anything new. Best I can tell is both projects produced paper/presentations only and no hardware...at least nothing I could find.Tangential - emdrive does not fit a current interstellar template for propulsion
The following paper describes a decades-old collaboration between scientists exploring interstellar missions (including propulsion methodologies). It began as Project Daedalus in the 70's and morphed into Project Icarus after 2000. Emdrive experimentation is not on their radar, but knowing there is a confederation of scientists aligned with a project like this is interesting IMO. Note some of the names...they have appeared in print somewhat recently.
The paper is here: http://arxiv.org/abs/1005.3833
Hmm. The paper is sort of underwhelming IMHO. There is really no significant breakthrough identified that would fundamentally change the Daedalus findings that I can see. And there are a lot of pages describing how CURRENT space systems work (to be used as backup systems???) and potential onboard computer architectures (is this really a key challenge??). I can't see what the purpose of this study would be other than "we haven't done it for a while".
No,no. These are not hardware types. The interesting thing about the original Daedalus study was that it put together the then current and predicted characteristics of inertial fusion, pointed out its propulsion potential and wrapped a vehicle and mission concept around that. The whole thing was outside of engineering practicality, but the physics were probably OK.
The thing that would make a reevaluation interesting would be some significant change in fusion research that could move the concept closer to engineering practicality. The authors don't indicate anything like this has really happened. They even state there may be no significant changes in the results of the study.
So I don't get what the impetus of this relook really is. -
#1642 by rfmwguy on 12 Jan, 2016 02:14
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Yes, I understand. Too bad after nearly 40 years, there has been no significant leaps forward from the original daedalus project. If emdrive pans out...perhaps there will be. There are certainly competing visions out there. Vasimir and ion drives seem to be the only other alternative to daedalus' fusion engine right now...present thread topic not withstanding
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#1643 by TheTraveller on 12 Jan, 2016 04:12
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Hi All,
Have had my 1st flat end plate build design data confirmed. Thanks Roger. Most appreciated.
Estimated specific thrust of 389mN/kW. IF I get everything right and do a really high quality build. I'm happy with the data and the challenge to "Make It So".
Will go quiet now (on all forums) until I have something to report.
If you have a question or comment, please PM me.
Yes the 1st frustum build has started. Updates will be found on: https://groups.google.com/forum/#!forum/emdriveresearch
Phil
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#1644 by ThinkerX on 12 Jan, 2016 04:33
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Traveler - in light of your health issues and comments from other posters, do you plan to fabricate the frustum yourself or turn the task over to a machinist or musical instrument maker?
Also, rough timeline for your build/experiment?
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#1645 by RFPlumber on 12 Jan, 2016 04:51
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Traveler - in light of your health issues and comments from other posters, do you plan to fabricate the frustum yourself or turn the task over to a machinist or musical instrument maker?
Also, rough timeline for your build/experiment?
To continue the line... TT, based on my recollection of your (ambitious) project, it will likely take on the order of a few months to get it done... IMHO, it may be better to report progress at least once in a while...
Wishing you the best of luck with it! -
#1646 by JokerAndThief on 12 Jan, 2016 06:49
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Hello.
I am a new guy who has followed this topic for the last 3 Threads sporadicaly (Managed to read maybe 50-70% of the pages written....you guys DO have some amazing output^^ ).
While i can't say that i can grasp all the formulars you are writing about i defenitly had some good time reading it and i hope i got at least the general idea about what is discussed here.
So i just have a quick question and (hopefully) a tipp that seems to have not been disscused before (again IF i got the idea behind all this right).
Question:
One of the main factors defining the ammount of thrust this drive produces (if it realy does) is the Q loading of the frustrum, right?
If the answer is true than: One of the main factors defining the max Q is the electric resistance of the material the frustrum is build whit, right?
If that is true, than has anyone thought about building the frustrum of a material that is not/only little affected by heat expansion (like the endplates from SheSheels frustrum) and covering the inside whit Graphene powder?
Graphene seems to have a electric resistance a lot lower than copper (like, 1/100 of copper, if i read the numbers in the papers correctly). It is comercialy awayable to buy in different shapes (like as powder, as liquid (like a paint?)).
Prices i found where somewhere in the order of 400 $ per 500 mg ... someone whit a lot more knowlege than me is needed to deside how much you would need to cover the frustrum and if that would be finacialy doable.
I just post a link to one of the firms producing that stuff here, but i do not garantee that this is best money/value... someone whit good google-fu might find a better producer.
http://www.acsmaterial.com/product.asp?cid=25&id=20
anyway, my apologies for my bad english and for distrupting the discussion,
i am back to silent reading^^
good luck whit the data @ every builder :-)
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#1647 by Rodal on 12 Jan, 2016 12:52
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Hello.
I am a new guy who has followed this topic for the last 3 Threads sporadicaly (Managed to read maybe 50-70% of the pages written....you guys DO have some amazing output^^ ).
While i can't say that i can grasp all the formulars you are writing about i defenitly had some good time reading it and i hope i got at least the general idea about what is discussed here.
So i just have a quick question and (hopefully) a tipp that seems to have not been disscused before (again IF i got the idea behind all this right).
Question:
One of the main factors defining the ammount of thrust this drive produces (if it realy does) is the Q loading of the frustrum, right?
If the answer is true than: One of the main factors defining the max Q is the electric resistance of the material the frustrum is build whit, right?
If that is true, than has anyone thought about building the frustrum of a material that is not/only little affected by heat expansion (like the endplates from SheSheels frustrum) and covering the inside whit Graphene powder?
Graphene seems to have a electric resistance a lot lower than copper (like, 1/100 of copper, if i read the numbers in the papers correctly). It is comercialy awayable to buy in different shapes (like as powder, as liquid (like a paint?)).
Prices i found where somewhere in the order of 400 $ per 500 mg ... someone whit a lot more knowlege than me is needed to deside how much you would need to cover the frustrum and if that would be finacialy doable.
I just post a link to one of the firms producing that stuff here, but i do not garantee that this is best money/value... someone whit good google-fu might find a better producer.
http://www.acsmaterial.com/product.asp?cid=25&id=20
anyway, my apologies for my bad english and for distrupting the discussion,
i am back to silent reading^^
good luck whit the data @ every builder :-)
Hello and welcome to the forum !
1) Graphene's conductivity, for a perfect, defect-free, 3 angstrom thick layer, works out to a conductivity of 1.00×10^8 S/m, this is only 68% better than copper (5.96×10^7 S/m): 1.68 times better than copper, instead of being 100.00 times better than copper.
2) The practical problem with using graphene is that a lot of its amazing properties only work when you have continuous perfect sheets of it, and making graphene like this is currently beyond practical, particularly for DoItYourself people working in their garage. When people quote Graphene's conductivity being so much better than copper, they assume (but many times do not state that) that one can make a perfectly continuous Graphene surface structure, with no imperfections. While graphene is incredibly strong on a relative basis, graphene sheets are extremely thin and fragile in their native state. Strength is not the same property as fracture toughness. Graphene is very brittle, not tough, and the extreme thinness of 3 angstrom thick Graphene makes it extremely fragile.
The fantastic properties of graphene are usually taken from single atomic layer graphene that is literally thinner than one nanometer (3-4 angstroms to be precise). If one tries to make a bigger 'pipe' for carrying current by stacking or growing multiple layers of graphene, the amazing properties of the material degrade quickly with each additional added layer. In fact, at around 10+ layers graphene begins to perform much like its allotropic parent, graphite, that is composed of many layers of graphene. If you were to use Graphene as powder or a paint, you would lose the conductivity advantage: it would be worse than copper's conductivity, because of discontinuity, and you would have to rely on a percolation effect for electrical conductivity
CONDUCTIVITY (S/m at 20 deg C) https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity
PERFECT Graphene (3-4 angstroms) 1.00×10^8
Silver 6.30×10^7
Copper 5.96×10^7
Graphite 2.00×10^5 to 3.00×10^5 //basal plane
3.30×10^2 ⊥basal plane
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PS: Your English is great, so no need to apologize. Wish I could write in German as well as you write in English
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#1648 by Mulletron on 12 Jan, 2016 13:51
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Actual graphene sheets on the market:
https://graphene-supermarket.com/Conductive-Graphene-Sheets.html
The electrical performance isn't good. -
#1649 by JokerAndThief on 12 Jan, 2016 14:11
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I stand corected :-) Reading all those mixed unit numbers and interpreting them doesn't seem to be my strong side ^^
Well move on, nothing to see here, pls don't get distracted by this layman interruption :-) -
#1650 by Rodal on 12 Jan, 2016 14:37
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Hi All,
Have had my 1st flat end plate build design data confirmed. Thanks Roger. Most appreciated.
Estimated specific thrust of 389mN/kW. IF I get everything right and do a really high quality build. I'm happy with the data and the challenge to "Make It So".
Will go quiet now (on all forums) until I have something to report.
If you have a question or comment, please PM me.
Yes the 1st frustum build has started. ...
Phil
Concerning Feynman's above quotation on the importance of experimental data to justify any claims, please let us know whether you can find published experimental data from Roger Shawyer supporting his strange claim that the cut-off condition (we learnt at school and we know from other's resonance experiments applies only) for open waveguides, somehow applies also to the completely closed EM Drive according to Shawyer.
I have not seen any experimental data reported by Shawyer justifying that unusual claim. What would be appreciated (in the spirit of Feynman's quote) is to show experimental data for the "anomalous force" for a frustum having a small diameter slightly above cut-off and compared to the "anomalous force" measured for a frustum having a small diameter slightly below cut-off for a completely closed resonant truncated cone cavity. (*)
_______
(*) we already know that the cut-off condition does not apply to closed cavities like the EM Drive regarding resonance (https://forum.nasaspaceflight.com/index.php?topic=39214.msg1469685#msg1469685 ). All that remains is to have experimental evidence concerning the "anomalous force". -
#1651 by SteveD on 12 Jan, 2016 17:38
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So, even if for a given box 100W electric did thrust 30µN, 1000W electric did thrust only 40µN, 10000W electric did thrust only 50µN etc... that would be a very bad scaling for a single device, but the over-unity argument would still hold at any operating point for which φ>3.33µN/kW.
We tell you, this thing needs either an "aethereal" auxiliary source of power, or to not operate beyond a range of velocity spanning less than 1/φ (and the question of "relative to what ?" remains)
Side note :
I'm not saying any of the experiments so far have ever approached the conditions that the thrust would actually generate such amount of output power in a measurable manner. But an actually working EMdrive with φ>5000µN/kW (0.005N/kW) operated such as thrusting always (or only when) roughly in the forward orbit direction of the solar system around the Galaxy is already in a situation that increases the rotational energy content of the Galaxy more than its cost in fed electric energy... (contrary to relative translational kinetic energy, rotational energy does have a natural intrinsic absolute value). Even while sitting on the bench and pushing a little spring by a few µm, which indeed shows locally in the lab as a minuscule return power under 1µW (or 0 when static equilibrium reached) relative to a few 10W of fed electric power.
This post got me thinking. First propellantless thrust at greater efficiency than a photon rocket has been experimentally proven to exist. It's called a photonic laser thruster. https://en.wikipedia.org/wiki/Photonic_laser_thruster.
Here is a schematic of a photonic laser thrust so that we all know what we're talking about:
Equations for a photon rocket that reusues its photons:
And Bae's equations for a photonic laser rocket, which are actually the same as a recycling photon rocket but have been obfuscated so that you have to look at them for a bit to realize this is the case:
I did some numbers to see what you are talking about on the over unity issue. The equation for the kinetic energy of a rocket is KE=1/2*m*v^2., where m is mass and v is velocity.
So a 1kg object moving at 100,000 m/s would have a KE of 5,000,000,000 joules. That's a considerable amount of energy.
Now let's say that a mass invariant drive, either an EMDrive or a photonic laser thrust producing 0.1N/kilowatt acts on it. Adding 2 m/s (20 kilowatts of input power). We now have 5,000,200,002 joules of kinetic energy, an overage of 180,002 joules.
Ok, fair enough. This seems like an over unity. Unfortunately it brings up three conundrum.
Conundrum 1: A solar system has been ejected from its host galaxy at 100,000 m/s. The inhabitants of one of it's planets put a photonic laser thrust setup into orbit. One end is point towards the direction the system is moving, the other is pointed opposite it. If I understand relativity right (could be wrong) the acceleration of all objects in the system causes neither blueshift nor redshift with reference to light within that system (in other words somebody on a planet moving at 100,000 m/s that shines a flashlight on another object on that planet would observe light in the same wavelengths and manner as if went outside tonight and shined a flashlight on a similar object).
The photonic laser thrust accelerates both ends of the setup by 2m/s. This means that the end moving against the systems direction of movement has lost an extra 180,002 joules of energy and that moving in the direction of acceleration has gained an extra 180,002 joules of energy. How? The only connection between the two points in space is 20 kilowatts of photons. How are 20 kw of photons moving 180,002 watts worth of additional KE from one object to another?
Conundrum 2: Both ends of a photonic laser thruster system, each weighing 1kg are moving away from each other at 2 m/s. The system is capable of producing 0.1N/kw of thrust. Application of 20 kilowatts brings each ends of the system to 4 m/s. Each end now has a kinetic energy of 8 joules. What happened to all the other energy I put into this system? Remember this is creating thrust through absorption and emission of photons. Unless a photon can emit a photon the missing energy cannot go to heat. So what happened to my missing 9994
watts of energy?
Conundrum 3: The same photonic laser system as the above two examples is at rest in space. Both ends accelerate to 5000 m/s. Each end now has a kinetic energy of 12,500,000 joules. Now each end continues to accelerate to 5002 m/s so each end now has a KE of 12,510,002 after application of 20kw of power. That leaves an over unity of 4 joules between the two ends. Where did the energy come from.
These conundrums seem to point toward some form of relativistic explanation not considered in the classic equations.
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#1652 by gargoyle99 on 12 Jan, 2016 20:14
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This post got me thinking. First propellantless thrust at greater efficiency than a photon rocket has been experimentally proven to exist. It's called a photonic laser thruster. https://en.wikipedia.org/wiki/Photonic_laser_thruster.
...
Ok, fair enough. This seems like an over unity. Unfortunately it brings up three conundrum.
...
These conundrums seem to point toward some form of relativistic explanation not considered in the classic equations.
Bae's photonic laser thruster is never over-unity and does not violate any relativistic equations for conservation of energy or conservation of momentum. However, it is VERY COOL and looks promising to me. It doesn't have "efficiency" any greater than a photon rocket, since it really is just a photon rocket; just one where the photons are reused. (In general, a photon rocket has the highest possible efficiency of using momentum, although generally a very poor efficiency for using energy.)
If you read Bae's papers you will see he addresses the problems of conservation of energy and efficiency and works out the relevant relativistic equations. In summary, the thrust changes based on the relative velocity so there isn't constant thrust for constant laser power. (The math is fairly accessible and the paper is understandable to a non-physicist.) Here is the first link google provides:
http://ykbcorp.com/downloads/Bae_photon_propulsion_STAIF2_Paper_Circulation.pdfQuoteOne of important factors in the rocketry is how efficient the energy transfer from the propellant energy to the spacecraft kinetic energy. This factor, as it was shown in the previous section, is governed by the fundamental law of physics: the energy is proportional to v2 while the momentum and thrust to v, where v is the propellant velocity. Thus, regardless of propellants, the energy transfer efficiency, specific thrust, is always proportional to 1/v. In order to provide relativistic velocities, a propulsion system should have a relativistic v, and at such high v~c, the propellant based on particles, such as protons or electrons, and photons have similar specific thrust.
You are correct that you cannot analyze a photonic thruster without using (special) relativity, because energy transfer using photon doppler shifts is a relativistic effect.
The most interesting conclusion to me is how a photon rocket or a photonic thruster increase in energy efficiency as they approach the speed of light. I suggest you read the paper and see if it addresses your questions. Unfortunately, it does not provide much insight to the theory of the EmDrive. -
#1653 by graybeardsyseng on 12 Jan, 2016 22:20
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Thanks Zen...do you have a gut feel as to what the mil thickness should be?
A friend with a lathe spun some 10 GHz and 24 GHz feedhorns designed by Paul Wade, W1GHZ. He had no problem with the .020" Copper disks I gave him for the 10 GHz feedhorns but the .010" material just crumpled. For something as large as a fustrum my guess would be .030" - .040". I have raised metal with hammers (smithing) but have not done any metal spinning. I have heard from a good source it can be dangerous. The only downside of moving metal with hammers is your neighbors get very annoyed.
http://www.onlinemetals.com/merchant.cfm?id=966&step=2&top_cat=87&showunits=mm
Thanks - Dave
Concur on safety. We did a lot of metal spinning on some feedhorn construction a decade or so ago. It works very well but - like any lathe operation - it can be dangerous; there are lots of ways to detach body parts from portions of fingers up to major limbs and the blood is hard to clean off the lathe and the unit under construction LOL . It is also a heck of a lot of fun; I had an excellent instructor (an old machinist who had done metal spinning for a LOT of years) and once you learned how and how to do it safely it was a real hoot.
Smithing (hammers) is also a lot of fun but as you point out your neighbors may express a different opinion.
Herman -W5HLP -
#1654 by SeeShells on 12 Jan, 2016 22:29
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http://s1039.photobucket.com/user/shells2bells2002/library/CE%20Electromagnetic%20Reaction%20Thruster?sort=3&page=2Thanks Zen...do you have a gut feel as to what the mil thickness should be?
A friend with a lathe spun some 10 GHz and 24 GHz feedhorns designed by Paul Wade, W1GHZ. He had no problem with the .020" Copper disks I gave him for the 10 GHz feedhorns but the .010" material just crumpled. For something as large as a fustrum my guess would be .030" - .040". I have raised metal with hammers (smithing) but have not done any metal spinning. I have heard from a good source it can be dangerous. The only downside of moving metal with hammers is your neighbors get very annoyed.
http://www.onlinemetals.com/merchant.cfm?id=966&step=2&top_cat=87&showunits=mm
Thanks - Dave
Concur on safety. We did a lot of metal spinning on some feedhorn construction a decade or so ago. It works very well but - like any lathe operation - it can be dangerous; there are lots of ways to detach body parts from portions of fingers up to major limbs and the blood is hard to clean off the lathe and the unit under construction LOL . It is also a heck of a lot of fun; I had an excellent instructor (an old machinist who had done metal spinning for a LOT of years) and once you learned how and how to do it safely it was a real hoot.
Smithing (hammers) is also a lot of fun but as you point out your neighbors may express a different opinion.
Herman -W5HLP
Sorry been a little under the weather for a few days. Just getting back on my feet.
I considered a fabricator to spin the copper but I needed to have the endplates bonded to ceramic plates and the small top plate movable for tuning. This process I detailed out seemed to work well for me.
http://s1039.photobucket.com/user/shells2bells2002/media/CE%20Electromagnetic%20Reaction%20Thruster/EM%20thruster%20025_zpsyrpkmdmv.jpg.html?sort=3&o=29
added..
Another tip, use a torch to heat, but heat from under the copper and let the silver solder flow through the seam. You'll get a much better and stronger and air tight seam.
Shell -
#1655 by frobnicat on 12 Jan, 2016 22:39
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.../...
This is more than I can take. Sorry.
Care to comment about https://forum.nasaspaceflight.com/index.php?topic=39004.msg1461319#msg1461319 where relative velocities are clearly stated and where there is no acceleration involved (i.e. no need to getting lost with KE deltas) ?
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#1656 by graybeardsyseng on 12 Jan, 2016 22:57
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This is very interesting, so the mold is wax (the interior of the frustum) and the external surface is electroplated to 20-30 mils copper? Am I getting the visual right?After much research, I've determined that this is the best way to construct a frustum...seamless at the small diameter:
...
This horizontal lathe was modified to include a spinning "form", or shape, that the copper sheet "folds" over. The left side of the lathe uses a compression disc that snugs the copper sheet onto the top of the form, which could be any shape. A frustum would be one of the more simpler forms to have constructed.
The brass-smith said he could make a bell/frustum but it would have a brazed seam that would have to be ground/polished away. More labor costs.
The cost is similar for both ways to do it. Looks like the spinning copper method is superior. Interior polishing would be needed.
I agree, metal-spinning would be best method as long 101 alloy (99.9% pure Cu) is used. A machinest may prefer using another alloy for safety or other reasons. Metal spinning is another way of moving metal. Part of the process involves keeping the periphery of the disk from getting too thick and cracking. The inside surface would be reasonably smooth and so would have very good surface conductivity. The outside would show the characteristic rings the turning tool leaves. Polishing the inside wouldn't be too difficult. Just clamp the fustrum to a workbench and have at it with a 6" Dia buffer wheel and some pumice compound for starters. The form is turned from laminated hardwood.
The problem with spinning copper and its alloys is that they work harden quite rapidly. You may have to anneal the copper several times during the process. I know. I've done it. Anyone with a decent wood lathe can spin sheet metal at home fairly easily (just watch your fingers and wrists!!!).
Many threads ago I suggested a machined wax substrate, electroformed with copper to whatever desired thickness. The wax provides the final surface finish, and can be microns RMS. Many, if not most, custom wavequides are made this way. Often the interior surface is silver plated for conductivity reasons after fabrication. Back when cameras actually used film that required developing, the spent developer made an excellent electroless immersion silver plating solution.
The beauty of the machinable wax is that you can "weld" strange wax structures like ports, studs, and rectangular wavequides onto the frustum substrate before electroforming, and end up with one contiguous structure. No joints, seams, soldering. Done that too, although something the size of the frustum at 2.4 GHz would be problematic in a home shop environment.
Exactly. And there is no practical limit as to the thickness of the plating. I have seen as much as an inch. The thickness can also be selectively varied during the plating process by masking different areas at different times during the plating process.
Vacuum or pressure tolerant frustum, anyone? This stuff is a pretty common industrial process. In fact, the master "press" discs for old LP vinyl records were made this way, so you can imagine the fidelity of the plating that followed the acoustic grooves cut into the wax master at the recording studio.
EDIT: spelling and additional technical bloviating (I don't trust spear chuckers, um, spiel chesters, um...SPELL CHECKERS).
This is a fascinating idea - sorry I missed it earlier. Reminds me of the "Lost Wax" processes for clay/ceramic manufacture. I had no idea the process worked well enough (had enough fidelity) for generating master discs for vinyl LPs. That level of accuracy - with the flexibility you mention for adding non-symmetric or unique shapes (feeds etc) - has real potential. Spinning's other big problem - besides the work hardening you mention - is that of course it is limited to shapes symmetric about the rotation axis.
A good example of this is the aircraft propeller spinners mentioned in another post. Full spinners, those which attached to a plate behind the prop, had to have openings added by hand for the prop blades to pass through. If not done correctly this allowed for stresses to be set into the metal and increased the odds of a fracture at the wrong time.
Herm -
#1657 by Stormbringer on 12 Jan, 2016 23:16
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That Orange County Chopper guy (Jesse James) had a shop with antique metal hammers as well as rollers and benders. He said that such machines (manual metal hammer rigs) are now quite rare and the people who know how to use them are getting rare too. But custom bike shops might be a place to look for metal shapers.Thanks Zen...do you have a gut feel as to what the mil thickness should be?
A friend with a lathe spun some 10 GHz and 24 GHz feedhorns designed by Paul Wade, W1GHZ. He had no problem with the .020" Copper disks I gave him for the 10 GHz feedhorns but the .010" material just crumpled. For something as large as a fustrum my guess would be .030" - .040". I have raised metal with hammers (smithing) but have not done any metal spinning. I have heard from a good source it can be dangerous. The only downside of moving metal with hammers is your neighbors get very annoyed.
http://www.onlinemetals.com/merchant.cfm?id=966&step=2&top_cat=87&showunits=mm
Thanks - Dave
Concur on safety. We did a lot of metal spinning on some feedhorn construction a decade or so ago. It works very well but - like any lathe operation - it can be dangerous; there are lots of ways to detach body parts from portions of fingers up to major limbs and the blood is hard to clean off the lathe and the unit under construction LOL . It is also a heck of a lot of fun; I had an excellent instructor (an old machinist who had done metal spinning for a LOT of years) and once you learned how and how to do it safely it was a real hoot.
Smithing (hammers) is also a lot of fun but as you point out your neighbors may express a different opinion.
Herman -W5HLP -
#1658 by VAXHeadroom on 13 Jan, 2016 00:05
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These guys:
That Orange County Chopper guy (Jesse James) had a shop with antique metal hammers as well as rollers and benders. He said that such machines (manual metal hammer rigs) are now quite rare and the people who know how to use them are getting rare too. But custom bike shops might be a place to look for metal shapers.Thanks Zen...do you have a gut feel as to what the mil thickness should be?
A friend with a lathe spun some 10 GHz and 24 GHz feedhorns designed by Paul Wade, W1GHZ. He had no problem with the .020" Copper disks I gave him for the 10 GHz feedhorns but the .010" material just crumpled. For something as large as a fustrum my guess would be .030" - .040". I have raised metal with hammers (smithing) but have not done any metal spinning. I have heard from a good source it can be dangerous. The only downside of moving metal with hammers is your neighbors get very annoyed.
http://www.onlinemetals.com/merchant.cfm?id=966&step=2&top_cat=87&showunits=mm
Thanks - Dave
Concur on safety. We did a lot of metal spinning on some feedhorn construction a decade or so ago. It works very well but - like any lathe operation - it can be dangerous; there are lots of ways to detach body parts from portions of fingers up to major limbs and the blood is hard to clean off the lathe and the unit under construction LOL . It is also a heck of a lot of fun; I had an excellent instructor (an old machinist who had done metal spinning for a LOT of years) and once you learned how and how to do it safely it was a real hoot.
Smithing (hammers) is also a lot of fun but as you point out your neighbors may express a different opinion.
Herman -W5HLP
http://www.BaltimoreKnife.com and
https://www.youtube.com/aweme (the Man at Arms:Reforged series)
are my brothers I have plenty of connections in and through them to get pretty much anything fabricated They have 4 power hammers and an english wheel among LOTS of other stuff.
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#1659 by meberbs on 13 Jan, 2016 01:24
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...
These conundrums seem to point toward some form of relativistic explanation not considered in the classic equations.
First, you are dealing with photons, they are by definition relativistic, so you need to include relativity if you want things to add up.
Second, I do not recommend you try to think about relativity until you understand basic physics first. You keep using Watts (Power which is energy per time) and Joules (energy) interchangeably. The difference between them is the difference between a constantly running faucet and a bucket of water sitting on a table. I do not believe this is the right place for me to teach these concepts, and I recommend taking an actual class in physics to learn them.
Brief answers to the points you brought up:
1. You subtracted watts from joules, which is nonsensical. Also, special relativity velocity transforms should be used, and conservation laws must be applied within a consistent reference frame.
2. Assuming you meant 20 kW applied for 1 second, or equivalently 2 W applied for 10000 seconds, the answer is that it turned into heat.
3. Again you confused J and W. Your calculation is simply wrong and I believe your claim of constant force per power would be false due to the redshift of the reflections when the mirrors are traveling at higher relative velocities.
I could take your examples 1 and 3, redefine them correctly and work through them, but I don't think that would be beneficial at this point. First you should get a better understanding of physics 101.
As Elon Musk said:QuoteI think most people can learn a lot more than they think they can. They sell themselves short without trying.
One bit of advice: it is important to view knowledge as sort of a semantic tree — make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to.
You are trying, which puts you ahead of many people, but you need to work on the trunk for this area first.
