Author Topic: EM Drive Developments - related to space flight applications - Thread 7  (Read 1696558 times)

Offline Rodal

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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


« Last Edit: 03/13/2016 11:47 pm by Rodal »

Offline rfmwguy

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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.

Offline Rodal

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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.

1) So , why are commercial waveguides with 0.28 m diameter made with thicker walls than 1mm? Or are you saying  that one might as well just use waveguides only 1 mm thick ?

2) There is a huge gap between rfmwguy defending the use of 1 mm thick walls for a fustrum and TheTraveller saying that Shawyer recommends 13 micrometer tolerance.

A whole lot of dissonance here.  It would be nice to be able to resolve this matter.

3) One should be able to defend the use of a given thickness without invoking uncertainty about the function of a magnetron: seems like that is a different thing...

4) The question here is what Q are you going to be able to achieve. The budget of DIY is not relevant to that question,  that is a different matter.  If a DIY's budget cannot get close to theoretical Q, that is a good thing to know.

It would be good if one could provide a calculation to defend the argument that 1 mm wall thickness is good enough to achieve high Q's close to theoretical
« Last Edit: 03/14/2016 01:08 am by Rodal »

Offline rq3

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Yes, 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

Perhaps 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:

Quote
Once 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"

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.

Offline Rodal

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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 tolerance

2) rfmwguyg polishing the copper to a mirror finish

the 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.
« Last Edit: 03/14/2016 12:25 am by Rodal »

Offline Monomorphic

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Build Update: MHT1003NR3 arrives on Tuesday. I spent part of the day reworking the frustum in an effort to reduce the number of custom metal cuts required. I also hope to purchase the remainder of the aluminum for the interferometer and air track structure this week.

 
« Last Edit: 03/14/2016 12:27 am by Monomorphic »

Offline rq3

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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.


Offline Rodal

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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.

Much more important and relevant to the EM Drive thread than many things we have discussed, most recently for example "spooky quantum entanglement"

Offline SeeShells

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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 tolerance

2) rfmwguyg polishing the copper to a mirror finish

the 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.

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.

Shell

Added: also there are outside circular copper strips on the sidewalls that could be used to increase the "stiffness dramatically. Builds have used this method.
« Last Edit: 03/14/2016 12:43 am by SeeShells »

Offline TheUberOverLord

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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




This brings up a good point.

Was/is there any particular reason for waveguide thickness being what it is at these microwave frequencies. Besides power levels alone?

As was albeit, in the old days. In the USAF we had some flexible microwave waveguide for combat communications gear, that was not at the same tolerances as fixed waveguide. Meaning, it was a thinner thickness for waveguide walls. Yet they were both using at or near the same microwave frequencies and only differences were power levels:

Fixed

http://airforce.togetherweserved.com/usaf/servlet/tws.webapp.WebApp?cmd=ShadowBoxPersonPhoto&maxphoto=32&order=Sequence_desc&show_grid_View=1&ID=149788&type=PersonExt&photoIndex=1&page=1

Flexible

http://airforce.togetherweserved.com/usaf/servlet/tws.webapp.WebApp?cmd=ShadowBoxPersonPhoto&maxphoto=32&order=Sequence_desc&page=1&show_grid_View=1&ID=149788&type=PersonExt&photoIndex=6

Don
« Last Edit: 03/14/2016 01:10 am by TheUberOverLord »
EM Drive builders can use these free Interfaces to show their tests live using any IP Cameras in websites Click for live demo examples

Offline Rodal

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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.

Shell

Added: 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
« Last Edit: 03/14/2016 01:12 am by Rodal »

Offline zellerium

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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



I 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?

Offline Rodal

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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



I 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?

It is a question of logical consistency:

1) Shawyer/TheTraveller regularly use open waveguide explanations to explain the EM Drive  (please refer to Shawyer's paper).  For example, the cutoff frequency concept only applies to open waveguides.

2) In the post above SeeShells argues that <<It's the endplates that set the resonance and Q. >>.  Rfmwguy is polishing the end plates to look like a  mirror. 



Both of these arguments run contrary to standing wave resonance inside a cavity at 2.45 GHz frequency (*):   for the eigenmodes and eigenfrequencies in a cavity, the roundness and concentricity of the walls is just as important as the end plates..   Both COMSOL and FEKO show this.  The exact solution also shows this.

3) I am not discussing anything to do with heat dissipation or thermal effects.  I am just arguing dimensional tolerance.

4) You write <<Commercial waveguides are designed to transmit power, not resonate>>.  That is not strictlly correct.  Commercial waveguides "resonate" only in the cross-dimensional direction: that is what TE01 for example means.  The mode shapes for waveguides are the result of solving the eigenvalue problem.

Here are the first "resonant" eigenmodes "mode shapes" for a waveguide with circular cross-section:




  It is important for a waveguide to have certain tolerances in their cross-section, in order to maintain a given mode shape.

5) The question here is to justify the 1 mm thickness being used by DIY while they simultaneously polish the endplates like a mirror.  Where did that come from?  How is that justified?

6) It is not logical to say that only longitudinal resonance matters: that only the "p" matters in TEmnp for example.

7) How can people say that tight tolerances are needed in the longitudinal direction for "p" but not in the cross-section for "mn". ???

8) How could one say that the endplates need to look like a mirror (for 2.45 GHz frequency with wavelength of several cm) and that it is OK for example for the cross section  to look like an out-of-center star instead of  centered and circular ???

9) It seems to me that a logical proposition would be that if the walls can be 1 mm thick, then the endplates do not need to be polished like a mirror ... Alternatively, if the endplates need to look like a mirror, then dimensional tolerance in roundness and concentricity is just as crucial

___________

(*) optical resonance inside an optical "cavity" used in lasers is a completely different matter.  In that case one might as well have NO walls, as lasers (unlike masers) have open cavities.  However masers have closed cavities, and the roundness is just as important as the ends...
« Last Edit: 03/14/2016 01:55 am by Rodal »

Offline SeeShells

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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.

Shell

Added: 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 hope I can clarify what I'm talking about here as it is important.

Where I stand is that the endplates need to be of a good quality finish without any visible scratches. But do I think that a 13um or better finish is needed for what we're doing? No.

There is a large difference between 13um which is only 0.013mm in any deformations in the sidewalls.

Note: Although I have sidestepped that finishing issue by using a 99% pure silver electroplate process that fills in the slight scratches and buffs out to a mirror finish, also provides a real world increase in Q.

In every calculation you want to use the endplate spacing is shown to be the most critical. The sidewalls not so much and we cannot compare apples and oranges with the same analogies of the sidewall quality and slight deformation versus the endplates.

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. Maybe he has it still. Maybe he could using his spreadsheet vary one of his circular sections by 1mm and see what happens?

Do I think a 13um finish is really needed for what we're doing? No. Do I think that it needs to be carried out to the sidewalls? No.

Shell

Offline rfmwguy

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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.

Offline Rodal

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...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. ...

Of relevance here is the roundness , instead of "side wall angles".

What would be required (I hope that monomorphic can run this) is to compare the following:

1) Random out-of-roundness  with perfect flat plates
(by this I mean an irregular random shape for the cross-section, using the random function in FEKO to model the cross-sectional shape)

vs

2) Random surface end plates with perfectly round conical walls

« Last Edit: 03/14/2016 02:07 am by Rodal »

Offline rfmwguy

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Initial test of alphalabs trifield meter:

Offline RotoSequence

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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.

It's not a question of methodology as it is of logical consistency. Unless the side walls do not contribute meaningfully to the behavior of the EM drive system, the care and attention going into the end plates seems strange when the walls themselves have rough surfacing and some dimensional inconsistency.

Offline Rodal

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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.

Rather than discourage my comments on DIY construction and challenging me to do my own DIY, when questioning the 1 mm wall thickness you are using while simultaneously polishing the ends like a mirror, I would expect that you would encourage such comments, since they are more relevant to the subject matter of this thread, than, for example, your recent posts about spooky quantum entanglement.


The NSF threads are here for the user community to discuss subjects like these between the different members, they are not supposed to be just for people to post "look at what I'm doing, but don't comment on what I'm doing, if you don't like what I'm doing, go and conduct your own DIY or go and write your own DIY guide."
« Last Edit: 03/14/2016 02:54 am by Rodal »

Offline A_M_Swallow

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I suspect that the mathematical models can be modified to to show what happens when the side walls are deformed by 1 mm. A long dent may be easier to program.

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