-
#1160
by
Rodal
on 26 Aug, 2015 14:58
-
Just a newbie but been following these threads closely - my thought on the movement 'up' towards the large end which wasnt expected - potentially still thermal effects? The magnetron heats the air in the frustum, it vents through the mesh and is trapped like a hot air balloon under the solid top plate and flange.
No idea if that volume of air could create that much force, but as long as there is area outside (or even inside?) the frustum on the top plate, it could be solved with a few holes to vent?
Have put magnetron on top side and will look for similar effects in Flight Test #2 soon.
Found it interesting that if it were thermal, it didn't start sooner...only the last 1/3 or so of test. Mag should have been up to temperature within the first min or so of tests.
It my guess for its thermal, but more data is coming...
Is there any way for you to guesstimate whether your cavity was resonating during the experiment with the magnetron on ?
Whether the Q was ~ 0 , ~1,000 or ~10,000 ?
-
#1161
by
rfmwguy
on 26 Aug, 2015 15:08
-
Just a newbie but been following these threads closely - my thought on the movement 'up' towards the large end which wasnt expected - potentially still thermal effects? The magnetron heats the air in the frustum, it vents through the mesh and is trapped like a hot air balloon under the solid top plate and flange.
No idea if that volume of air could create that much force, but as long as there is area outside (or even inside?) the frustum on the top plate, it could be solved with a few holes to vent?
Have put magnetron on top side and will look for similar effects in Flight Test #2 soon.
Found it interesting that if it were thermal, it didn't start sooner...only the last 1/3 or so of test. Mag should have been up to temperature within the first min or so of tests.
It my guess for its thermal, but more data is coming...
Is there any way for you to guesstimate whether your cavity was resonating during the experiment with the magnetron on ?
Whether the Q was ~ 0 , ~1,000 or ~10,000 ?
Wish I could. Without connectors, can't take it to my VNA pals just yet. If positive results from test #2, might slap an N connector with monopole on it. While its only going to give me return loss peaks, guess we could do the -3dB BW points like others have done (shudder).
-
#1162
by
Rodal
on 26 Aug, 2015 15:11
-
Just a newbie but been following these threads closely - my thought on the movement 'up' towards the large end which wasnt expected - potentially still thermal effects? The magnetron heats the air in the frustum, it vents through the mesh and is trapped like a hot air balloon under the solid top plate and flange.
No idea if that volume of air could create that much force, but as long as there is area outside (or even inside?) the frustum on the top plate, it could be solved with a few holes to vent?
Have put magnetron on top side and will look for similar effects in Flight Test #2 soon.
Found it interesting that if it were thermal, it didn't start sooner...only the last 1/3 or so of test. Mag should have been up to temperature within the first min or so of tests.
It my guess for its thermal, but more data is coming...
Is there any way for you to guesstimate whether your cavity was resonating during the experiment with the magnetron on ?
Whether the Q was ~ 0 , ~1,000 or ~10,000 ?
Wish I could. Without connectors, can't take it to my VNA pals just yet. If positive results from test #2, might slap an N connector with monopole on it. While its only going to give me return loss peaks, guess we could do the -3dB BW points like others have done (shudder).
It is fascinating how all the stars have aligned perfectly for your next radio show, as hopefully you will have the two tests accomplished by the time of your next show
-
#1163
by
rfmwguy
on 26 Aug, 2015 15:14
-
One thing I noticed during testing is the transformer certainly kicks in with a loud hum, reminding me of a stuck electric motor. I read somewhere that this can induce a torsional movement, or at least vibration.
Think other builders need to be wary of this, especially if no liquid metal (isolation) is being used. The forces we are trying to measure are so small, air currents can disrupt tests, not to mention vibrations or movement transmitted along hard-wired setups.
-
#1164
by
SteveD
on 26 Aug, 2015 15:19
-
When I designed NSF-1701, I built it to be reconfigurable.
So I did just that...Doc, here's the new setup with the magnetron centered on the big base as you recommended. Its all ready for a second flight test!
But, its been a big day and I need a break form the shop. I'll test it again in a couple of days.
A heartfelt thanks for all the support!
I simple optical trick that may improve the sharpness of the laser dot in the movie is to move the camera back as far as possible and then to use the zoom (I hope your camera has one). This will make the paper with the laser dot sharper when you focus on the rig.
When you use a zoom lens things not on the plane of focus become blurrier. A shallow depth of the field looks like, say, a picture in sport illustrated where the guy is in focus and the background is a bunch of circles and blobs. I'd think the best way to improve sharpness on the laser would be multiple cameras, with one solely on the target and some way to create a visible mark (for example if both cameras showed the laser, you could pass your hand in front of the beam to mark the time).
-
#1165
by
TheTraveller
on 26 Aug, 2015 15:32
-
Wish I could. Without connectors, can't take it to my VNA pals just yet. If positive results from test #2, might slap an N connector with monopole on it. While its only going to give me return loss peaks, guess we could do the -3dB BW points like others have done (shudder).
Well that will at least give you a picture of the return loss resonant dip frequencies and the approx bandwidth / Q. At least then you are not flying blind and pumping Rf energy into a frustum you have no hard S11 data on.
Go on, be devil. Do it. Please record the S11 data scans and share. I suspect you may get a surprise.
For an antenna use a 1/4 wave stub and a loop like the one EW uses. As you sides are mesh can insulate the bottom of the antenna and stick it through the mesh at various places (simple to do with the 1/4 wave stub, bit more difficult with the EW loop but still doable) to test out how side wall insertion location and orientation change the max rtn loss dBs and resonant frequency. Doing this could really feed the MEEP team a lot of real world data.
If you built another antenna, like that on your magnetron, you could get a good idea of what sort of load your magnetron is working into.
-
#1166
by
rfmwguy
on 26 Aug, 2015 15:50
-
Wish I could. Without connectors, can't take it to my VNA pals just yet. If positive results from test #2, might slap an N connector with monopole on it. While its only going to give me return loss peaks, guess we could do the -3dB BW points like others have done (shudder).
Well that will at least give you a picture of the return loss resonant dip frequencies and the approx bandwidth / Q. At least then you are not flying blind and pumping Rf energy into a frustum you have no hard S11 data on.
Go on, be devil. Do it. Please record the S11 data scans and share. I suspect you may get a surprise.
No theory supports any particular resonance on return loss for a broad spectral signal source. The shape was based on your spreadsheet and nasa data, so I hardly say its flying blind.
I am just not convinced Q is part of the equation for force generation; at least I've not seen that. It is an arbitrary measure of frequency and amplitude performance. Useful only in my mind for source matching.
Let me know if you discover a force formula listing Q.
-
#1167
by
TheTraveller
on 26 Aug, 2015 15:53
-
Wish I could. Without connectors, can't take it to my VNA pals just yet. If positive results from test #2, might slap an N connector with monopole on it. While its only going to give me return loss peaks, guess we could do the -3dB BW points like others have done (shudder).
Well that will at least give you a picture of the return loss resonant dip frequencies and the approx bandwidth / Q. At least then you are not flying blind and pumping Rf energy into a frustum you have no hard S11 data on.
Go on, be devil. Do it. Please record the S11 data scans and share. I suspect you may get a surprise.
No theory supports any particular resonance on return loss for a broad spectral signal source. The shape was based on your spreadsheet and nasa data, so I hardly say its flying blind.
I am just not convinced Q is part of the equation for force generation; at least I've not seen that. It is an arbitrary measure of frequency and amplitude performance. Useful only in my mind for source matching.
Let me know if you discover a force formula listing Q.
I updated my post. Please review.
Both Shawyer and Prof Yangs Force equations involve Q.
-
#1168
by
WarpTech
on 26 Aug, 2015 16:15
-
...
EDIT: Good Lord, when I wrote "toroidal" I really wanted to write poloidal field lines (around a torus shape) and not toroidal field lines (in the azimuthal direction, there is no magnetic field in that direction of course) 
I edited the drawing in my prior post.
I knew what you meant. What @Rodal calls azimuthal, I refer to as "circular", when the flux lines are circling the minor diameter, I call it "toroidal" like you did. The word "poloidal" was not in my vocabulary. 
Thanks!
Todd
Sorry to get wonky, but let's discuss this further to agree on a common language to describe the complicated field distributons inside the truncated cone's EM Drive.
OK, to clarify this, I do agree that FluxCapacitor was correct that the word toroidal is a good description of the magnetic field as a solid, but with the magnetic field vectors oriented in the theta polar θ angle direction. The problem is that the word "torus" does not uniquely describe the direction of the magnetic vector field: the magnetic vector field is not in the azimuthal φ direction of the surface of the torus, but instead it is directed in the polar θ direction, of the cross section of the torus, in the plane {θ,r}, with normal φ
There are no magnetic field vectors on the surface of the torus. The magnetic field vectors are in cross-sectional cuts of the torus.
The problem with using @WarpTech's proposed word "circular" is that in spherical polar coordinates (which are the intrinsic coordinates to describe the spherical waves inside the truncated cone) there are two circular directions in spherical coordinates, hence "circular" does not uniquely describe what circular direction one is talking about:
the azimuthal angle φ (phi)
the spherical polar angle, or "zenith angle" θ (theta)
https://en.wikipedia.org/wiki/Spherical_coordinate_system
"Circular" uniquely describes a direction for a cylinder, but not for a spherical cone, because "circular" does not uniquely identify what circular direction one is describing, since both φ and θ describe circles in different directions. Hence the word "circular" can lead to confusion as to what one is talking about.
CONCLUSION: It appears that the only unique way to describe these vector components is to identify the vector component directions: whether they are in:
the azimuthal angle φ (phi) direction
the spherical polar angle, or "zenith angle" θ (theta) direction
the spherical radial "r" direction
The problem is not one of definition, it is vocabulary. It is obvious to me what you are saying, but in my vocabulary, the phi direction is around the major diameter and the theta direction is around the minor diameter. I have always referred to the theta direction as "toroidal". The phi direction is cylindrical or circular. It's just how I learned it.
Todd
-
#1169
by
SteveD
on 26 Aug, 2015 16:52
-
Just some random thought after a nights reflection:
Because of the ease or configuration and seemingly positive test result, I think rmfguy's mesh setup just became one of the preferred research setups for future test.
I think the idea that nothing will happen with the feed near the small base is not looking good. Fortunately rmfguy's setup seems perfect for a series of tests comparing feeds at the small and large base as well as mesh and solid endplates.
I'm seeing multiple indications that force builds up relatively slowly over time. I'm afraid to say it, but I think we might need some meep runs showing what is going at least until projected force stops increasing with time (which might be several minutes in realtime). Can we get an estimate about how much computing power we're talking about here? Is this supercomputer range stuff? I've got a Linux box with ok specs (but in need of a bigger hard drive) that I could donate to the cause for a month. I suspect the computing requirements are somewhere far north of a desktop system.
If it weren't for inertia on the beam, I'd say these results indicate that the point of maximum efficiency differs from the point of maximum power.
I wonder if one of the laser rangerfinders used in golf (about $20) or hunting (about $150) would provide a better beam than the current laser pointer.
Speaking of mirrors, somebody mentions cannibalizing an old film SLR for a better mirror. I should add that a larger mirror might be available from one of the Pentax medium format SLRs.
-
#1170
by
rfmwguy
on 26 Aug, 2015 17:38
-
Wish I could. Without connectors, can't take it to my VNA pals just yet. If positive results from test #2, might slap an N connector with monopole on it. While its only going to give me return loss peaks, guess we could do the -3dB BW points like others have done (shudder).
Well that will at least give you a picture of the return loss resonant dip frequencies and the approx bandwidth / Q. At least then you are not flying blind and pumping Rf energy into a frustum you have no hard S11 data on.
Go on, be devil. Do it. Please record the S11 data scans and share. I suspect you may get a surprise.
No theory supports any particular resonance on return loss for a broad spectral signal source. The shape was based on your spreadsheet and nasa data, so I hardly say its flying blind.
I am just not convinced Q is part of the equation for force generation; at least I've not seen that. It is an arbitrary measure of frequency and amplitude performance. Useful only in my mind for source matching.
Let me know if you discover a force formula listing Q.
I updated my post. Please review.
Both Shawyer and Prof Yangs Force equations involve Q.
Yet, each measure Q differently...see my point?
-
#1171
by
wallofwolfstreet
on 26 Aug, 2015 17:58
-
@rfmwguy, it seems like many people are saying that the movement of the laser dot should be interpreted as a thrust signal and therefore the test should in fact be considered positive as opposed to null [1].
In your opinion, is the test result null or positive (or indeterminate)? Are you standing by your previous statement that the test result was null?
[1] - Ignoring the fact that the laser moves in the wrong direction and the beam displays an unusual dynamic, where deflection seems to grow at a constant rate over the course of power on.
-
#1172
by
VAXHeadroom
on 26 Aug, 2015 18:34
-
RFMWGUY - great work, even better reporting
Two simple suggestions on the laser pointer that hopefully won't break the bank:
1) use a first-surface mirror, not one that's silvered on the back of the glass. Check with a local glass/mirror supply house, jewelry shops use them in displays sometimes so a small piece like you need may be cheap.
2) try the pin-hole card trick (I don't think you did this already?) which should clean up the spot itself.
Seems like what you really want for the liquid current transfer mechanism is mercury...
Edit: O $hit. I just remembered I have a 5mw HeNe laser - WAY better spot definition than what you have. But it would need 120v power... I will gladly loan this to the cause if there's any way it would be helpful.
-
#1173
by
rfmwguy
on 26 Aug, 2015 18:48
-
@rfmwguy, it seems like many people are saying that the movement of the laser dot should be interpreted as a thrust signal and therefore the test should in fact be considered positive as opposed to null [1].
In your opinion, is the test result null or positive (or indeterminate)? Are you standing by your previous statement that the test result was null?
[1] - Ignoring the fact that the laser moves in the wrong direction and the beam displays an unusual dynamic, where deflection seems to grow at a constant rate over the course of power on.
Wolfy, one thing I learned is not to judge too quickly on results for such a small measurement. I had not gone to the great effort of clipping the laser out and putting it into a time line.
That being said, I personally think thermal is a likely cause, what confuses me a bit about this hypothesis is thermal effects should have shown up alot sooner than the last 1/3 of the video as the mag comes up to temp rather quickly. There are no other variable that make sense to me other than an Electromagnetic Engine effect that somehow grows over a 5 minute timeline.
If that is the case, we'll have to look at this as more than an instantaneous burst of motion.
As a side note, when I came back near the experiment at the end of the test run, I felt no warmer air than when I started, but did notice an unusual "ambience'" to the air. Best way I can describe it as metallic, ionized air. This is not scientific obviously, just a minor observation I did not notice during static testing.
-
#1174
by
rfmwguy
on 26 Aug, 2015 18:54
-
RFMWGUY - great work, even better reporting
Two simple suggestions on the laser pointer that hopefully won't break the bank:
1) use a first-surface mirror, not one that's silvered on the back of the glass. Check with a local glass/mirror supply house, jewelry shops use them in displays sometimes so a small piece like you need may be cheap.
2) try the pin-hole card trick (I don't think you did this already?) which should clean up the spot itself.
Seems like what you really want for the liquid current transfer mechanism is mercury...
Edit: O $hit. I just remembered I have a 5mw HeNe laser - WAY better spot definition than what you have. But it would need 120v power... I will gladly loan this to the cause if there's any way it would be helpful.
Appreciate it, guess I could use the static laser firing on a moving mirror. Let me get back with you on that...after flight test #2. Did the pinhole trick, simply attenuated the output. Its a cheapo laser pointer with no focusing capability, but its super lightweight. Thanks for the mirror heads-up. I'd love to get one locally.
-
#1175
by
SeeShells
on 26 Aug, 2015 19:20
-
RFMWGUY - great work, even better reporting
Two simple suggestions on the laser pointer that hopefully won't break the bank:
1) use a first-surface mirror, not one that's silvered on the back of the glass. Check with a local glass/mirror supply house, jewelry shops use them in displays sometimes so a small piece like you need may be cheap.
2) try the pin-hole card trick (I don't think you did this already?) which should clean up the spot itself.
Seems like what you really want for the liquid current transfer mechanism is mercury...
Edit: O $hit. I just remembered I have a 5mw HeNe laser - WAY better spot definition than what you have. But it would need 120v power... I will gladly loan this to the cause if there's any way it would be helpful.
Appreciate it, guess I could use the static laser firing on a moving mirror. Let me get back with you on that...after flight test #2. Did the pinhole trick, simply attenuated the output. Its a cheapo laser pointer with no focusing capability, but its super lightweight. Thanks for the mirror heads-up. I'd love to get one locally.
I just ordered 2 under 8 bucks with shipping.
American Science & Surplus
MIRROR, FIRST SURFACE/39MM X 97MM X 3MM THK
Item Number: 31016P1
Quantity: 2
Back to the shop...
-
#1176
by
VAXHeadroom
on 26 Aug, 2015 19:25
-
RFMWGUY - great work, even better reporting
Two simple suggestions on the laser pointer that hopefully won't break the bank:
1) use a first-surface mirror, not one that's silvered on the back of the glass. Check with a local glass/mirror supply house, jewelry shops use them in displays sometimes so a small piece like you need may be cheap.
2) try the pin-hole card trick (I don't think you did this already?) which should clean up the spot itself.
Seems like what you really want for the liquid current transfer mechanism is mercury...
Edit: O $hit. I just remembered I have a 5mw HeNe laser - WAY better spot definition than what you have. But it would need 120v power... I will gladly loan this to the cause if there's any way it would be helpful.
Appreciate it, guess I could use the static laser firing on a moving mirror. Let me get back with you on that...after flight test #2. Did the pinhole trick, simply attenuated the output. Its a cheapo laser pointer with no focusing capability, but its super lightweight. Thanks for the mirror heads-up. I'd love to get one locally.
I just ordered 2 under 8 bucks with shipping.
American Science & Surplus
MIRROR, FIRST SURFACE/39MM X 97MM X 3MM THK
Item Number: 31016P1
Quantity: 2
Back to the shop...
Love that store. They always had the FUNNEST catalogs with the craziest stuff!
-
#1177
by
aero
on 26 Aug, 2015 19:26
-
from wikipedia -
Stiction is the static friction that needs to be overcome to enable relative motion of stationary objects in contact.[1] The term is a portmanteau of the term "static friction",[2] perhaps also influenced by the verb "stick".
Any solid objects pressing against each other (but not sliding) will require some threshold of force parallel to the surface of contact in order to overcome static cohesion. Stiction is a threshold, not a continuous force.
In situations where two surfaces with areas below the micrometer range come into close proximity (as in an accelerometer), they may adhere together. At this scale, electrostatic and/or Van der Waals and hydrogen bonding forces become significant. The phenomenon of two such surfaces being adhered together in this manner is also called stiction. Stiction may be related to hydrogen bonding or residual contamination.
@rfmwguy - You mentioned transformer vibration. I wonder if a vibrator attached near the knife edges would help reduce stiction without causing worse problems elsewhere? Or would it cause the weight to cut into the edges. And is there any indication of knife edge wear at the point of contact?
-
#1178
by
SeeShells
on 26 Aug, 2015 19:42
-
from wikipedia -
Stiction is the static friction that needs to be overcome to enable relative motion of stationary objects in contact.[1] The term is a portmanteau of the term "static friction",[2] perhaps also influenced by the verb "stick".
Any solid objects pressing against each other (but not sliding) will require some threshold of force parallel to the surface of contact in order to overcome static cohesion. Stiction is a threshold, not a continuous force.
In situations where two surfaces with areas below the micrometer range come into close proximity (as in an accelerometer), they may adhere together. At this scale, electrostatic and/or Van der Waals and hydrogen bonding forces become significant. The phenomenon of two such surfaces being adhered together in this manner is also called stiction. Stiction may be related to hydrogen bonding or residual contamination.
@rfmwguy - You mentioned transformer vibration. I wonder if a vibrator attached near the knife edges would help reduce stiction without causing worse problems elsewhere? Or would it cause the weight to cut into the edges. And is there any indication of knife edge wear at the point of contact?
You would be better off if you used the backside of a old stainless steel butter knife with a rounded edge for the bottom. Rolling on a curved surface is better than the knife edges. My first tests with weights I chipped the edges of the blades when they were together like yours.
sorry back to the shop... again.
Shell
-
#1179
by
rfmwguy
on 26 Aug, 2015 19:42
-
from wikipedia -
Stiction is the static friction that needs to be overcome to enable relative motion of stationary objects in contact.[1] The term is a portmanteau of the term "static friction",[2] perhaps also influenced by the verb "stick".
Any solid objects pressing against each other (but not sliding) will require some threshold of force parallel to the surface of contact in order to overcome static cohesion. Stiction is a threshold, not a continuous force.
In situations where two surfaces with areas below the micrometer range come into close proximity (as in an accelerometer), they may adhere together. At this scale, electrostatic and/or Van der Waals and hydrogen bonding forces become significant. The phenomenon of two such surfaces being adhered together in this manner is also called stiction. Stiction may be related to hydrogen bonding or residual contamination.
@rfmwguy - You mentioned transformer vibration. I wonder if a vibrator attached near the knife edges would help reduce stiction without causing worse problems elsewhere? Or would it cause the weight to cut into the edges. And is there any indication of knife edge wear at the point of contact?
Good news is before the test, I lifted and slightly moved the fulcrum to an unused part of the blades. Realize I can only do this so often, but really haven't seen any gouging. I did get the more expensive blades. Have 2 more unused!
I have doubts about static/stiction since the contact surface is so small and the wood beam itself is not likely to store or transfer a static charge as a plastic or composite might. With more surface area in contact, a ball-bearing assembly might be more prone to this than a knife-edge, not sure.
