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Measurements & calculations

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Wed Apr 02, 2008 6:25 pm PostPost subject: Measurements & calculations
Wunderland
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Every theory is grey.
Therefore, I have performed some measurements on my OC MPMM replication.
I find these measurements interesting. They could show a new way to analyse the effects into this device.

The measurements are difficult to perform and a very exact work is necessary to prevent faulty results.
I opened a new topic because I do not want to mix all this together with the general considerations.
I hope, that I can setup a little corner, where engineers (and "engineers like") will talk about their measurements and some corresponding calculations.

Please forgive me my English and don't ever ask me about my school notes in English of the past!

The measurements:
I equipped one of my rotor magnets with a sensor coil and adapted the coil with a collector ring to the scope.

- rotor magnets: N48 / d=6mm l=13mm Type: S-06-13-N / www.supermagnete.de
- stator magnets: N42 diametric / d=12mm h=6mm Type: S-12-06-DN / www.supermagnete.de
- distance rotor magnet - stator magnet (centre to centre): 21.5mm
- sensor coil: n = 79 turns

I use a forked light barrier to synchronise the measurement witch the geometry of the device.
Imagine a line between the centre of the rotor an the centre of the stator magnet.
The first signal at the forked light barrier will be produced, if the rotor magnet enter this line.
The second signal will be produced, if the rotor magnet will leave this line again.

You can see a picture of the device at

http://i295.photobucket.com/albums/mm122/Imwunderland/WhipMag%20rotor%20001/pict0021.jpg


Fig. 1: The stator is rotating in GW mode.


- CH2 is measuring the signal of a forked light barrier.
- CH1 shows the voltage at the sensor coil
- M1 is the integral of CH1

With M1, we could calculate the changes of the magnetic flux inside the magnet.

U=n*A*dB/dt ==> B=1/(n*A)*intg(U)*dt

n*A = 2.23mm^2

M1 : 20ÁVs/Div / 0.00223m^2 = 8.95mT/Div

A Positive values of M1 means increasing magnetic intensity.
There is a symmetric change of the magnetic intensity surround the middle of the magnet (the centre between the two markers).
The maximum of the magnetic intensity is exactly between the two markers.
The magnetic field is strongest, if both magnets are close together (+0.7Div = 6.3mT increase).
There is no effect of hysteresis / magnetic viscosity or any other delay visible.
Notice the increase of M1 at the right side.
This is only an integrated offset of the scope and is no magnetic effect.

Fig. 2: The stator is rotating in AGW mode.


There are huge induction voltages but the magnetic intensity changes are smaller (10ÁVs/Div).
There are some asymmetries in this mode.

Fig. 3: The same as Fig. 2 in zoom Mode:



The markers and the corrected zero line of M1 are marked blue.
Red: degraded magnetic intensity
Green: encouraged magnetic intensity

I assume that:
- encouraged magnetic intensity cause attractive forces
- degraded magnetic intensity cause repulsive forces
This assumption should be discussed.


There are 5 phases:
1: weak repulsive forces while the magnets nears each other
2: very strong attractive forces while the magnets nears each other
3: very strong repulsive forces while the magnets are on the same high
There is a delay - the maximum force occurs, when the magnets are removing again from each other.
4: strong attractive forces while the magnets go away - not so strong as phase 2 but for a longer time.
5: very weak repulsive forces while the magnets go away (not so strong as phase 1)

At the first glance, phase 2 is stronger as phase 4 ==> there exist accelerating forces to the rotor - phase 3 helps anyway to this.

But we need to calculate the torque and integrate it over the time.
The torque is very weak at phase 3 because the forces are along the axis.

There is no difference in the scope-trace whether the rotor was rotating clockwise or anti clockwise (always AGW mode).
==> There is no mechanical asymmetry in my device.

As you can see, there is a lot to do for every one who want to help in this case:
- reproduce my measurements
- calculate the moments
- variate the distance between rotor and stator
- test different magnets (also N35 stator magnets)
- applicate a sensor coil to the stator magnet as well
- compare the measurements with some simulations
- why is there the delay in phase 3 - some kind of viscosity or a phase shift of the angle of the stator magnet?
What is the reason for this effect?
- install some resistance strain gauges on the stator to find out the absolute force
- ....

Everyone is invited to help here...
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Wed Apr 02, 2008 8:02 pm PostPost subject:
overconfident
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@Wunderland,

Nice to see someone do some serious tinkering and measurement.

At one point, I described a horizontal ladder sensor that might be used for sensing the dynamic magnetic field between the stator and rotor magnets. Do you think this might be worthwhile?

Code:

(+) _____________
        |||||||||
        ------------- (-)


Keep up the good work.
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Wed Apr 02, 2008 8:05 pm PostPost subject:
MADPROF
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@Wunderland

FIRST CLASS POST.. This has to be one of the best yet. I'am IN.

OC will love this, I think you might have found THE SPIN ZONE Laughing where the outside energy enters the system.

You say

There are huge induction voltages Laughing but the magnetic intensity changes are smaller (10ÁVs/Div).
There are some asymmetries in this mode.

Q. What would happen if we dumped a MASSIVE ELECTRIC CHARGE into this zone???

Prof
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Wed Apr 02, 2008 10:15 pm PostPost subject:
Mr.Entropy
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Your scope integrates? I am jealous.
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Thu Apr 03, 2008 7:15 pm PostPost subject:
Wunderland
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Thank you for your comments!

@OC:
I could not find your post with the "ladder" on Fizzx.com.
Can you describe this some more?
To sense the field at only one point at a fix pace will make no sense (IMHO):
You will just see a strong alternating field as a result of rotor & stator movement.
But we can do a scan:
- hold the device at constant speed with a DC motor.
- trigger the scope with the forked light barrier.
- move the sensor coil surround the stator (some cm) and save the trace to a reference each cm.
My scope has 4 references. Therefore, I could display 5 quasi time correlated traces on the scope.
I will try this at weekend.

The problem:
holding the coil by hand is very inaccurate and I expect a higher error than our effect might be.

@Prof:
It would be fantastic to watch at the scope at the moment as you shot with 30KV on the magnets.


BUT:
---
Digital scopes an high voltage are an absolute "exclusive or" - sorry.
Maybe I will set the device under high voltage one day.
But far away from the scope and not posted in "Measurements & calculations"


@Entrophy:
Nice, isn't it?
I have a TDS460A (4 Ch. / 400MHz) with the XL option.
The "XL" option is very important:
- 120K memory
- Math (eg. integrate)
- ....

My electronic lab is really OK.
However it is not so easy for me to construct something like an "OC MPMM".

If your scope cannot integrate, you could integrate with the PC as well.
If your scope is analog, you could integrate with an OpAmp (OPV).
Or you could look at some pages like this:

http://cgi.ebay.com/Tektronix-TDS460A-XL-400Mhz-BW-OPT-13-1F-1M-05_W0QQitemZ120165756218QQihZ002QQcategoryZ1504QQrdZ1QQssPageNameZWD1VQQ_trksidZp1638.m118.l1247QQcmdZViewItem
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Thu Apr 03, 2008 7:58 pm PostPost subject:
overconfident
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@Wunderland,

I really don't know what I'm talking about. I was just trying to think of a sensor that would slip in between the rotor and stator. Most coils are too thick. A single wire would probably do the same thing. I just figured the ladder (multiple short wire segments soldered between two wires) would give a higher, more readable output than 1 wire would and could be easily moved to different positions, to show the magnetic dynamics as the rotor magnet approaches, passes in close proximity, and as it retreats.

Just kibitzing. I am thoroughly untrained in the art of using an oscilloscope to provide useful measurements.

I am very happy to see someone gathering some interesting data. Don't let me get in the way.

OC
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Thu Apr 03, 2008 9:32 pm PostPost subject:
MADPROF
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@Wunderland

If you need any components making to take your research to the next level please ask, I am more than willing to help.

Prof
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Fri Apr 04, 2008 10:51 am PostPost subject:
Harvey
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Good work so far Wunderland.

It appears your stator magnet is not a ring magnet but that could just be lighting.

I don't have the deep understanding of Calculus that my two younger boys do. One is in Japan and the other in California with little time for extra stuff from dear old dad but I may be able to squeeze some calcs out of them as needed.

I do wonder what function you are using for the integral in M1.

Looking at your sensors in the photo I trust you have painstakenly aligned the trip wire on CH2 to coincide with the CH1 sensor / stator timing as stated. This is evident from the slopes in Fig 1. Its noteworthy that what you are measuring is the flux transitions of the stator as it passes through the coil wrapped around the rotor magnet. The interactions of the rotor B field also becomes part of the reading.

In Fig 1. the fields are meshing in fluidity as the rotor pulls the stator in along in GW mode.

But in Fig 2. & 3. The fields are in both attraction and repulsion simultaneously during AGW mode. Only at the transition between poles (equitorial pass) do all forces become zero. This very brief transition is dead center between negative torque and postive torque maximums. Normally we would expect phase 3 to be centered directly over this region but when comparing CH1 with CH2 timing we find the stator lagging the rotor. This is because the rotor is driving the stator in your tests. If you powered the stator instead of the rotor I think you would see phase 3 shift to the other side.

What CH1 is showing us is the induced voltage from the stator. Since the stator switches poles at the equitorial pass you will see both positive and negative voltage in your sensor. When the magnets are separated they are in full attraction. As they approach, the stator equator transits 90 degrees from parallel to perpendicular to the rotor path. At about 45 degrees the stator is in both attraction and repulsion and at 89 degrees it is in full repulsion for maximum negative torque (pushing against the rotor to stop it). At 91 degrees it is in maximum positive torque, full repulsion.

It is apparent from Fig 2 & 3 that the stator is not aligned with the rotor during these transistions. Because of this the flux will be asymetrical in your sensor.

Cheers,

Harvey
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Fri Apr 04, 2008 9:22 pm PostPost subject:
Wunderland
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Harvey wrote:
But in Fig 2. & 3. The fields are in both attraction and repulsion simultaneously during AGW mode. Only at the transition between poles (equitorial pass) do all forces become zero. This very brief transition is dead center between negative torque and postive torque maximums. Normally we would expect phase 3 to be centered directly over this region but when comparing CH1 with CH2 timing we find the stator lagging the rotor. This is because the rotor is driving the stator in your tests. If you powered the stator instead of the rotor I think you would see phase 3 shift to the other side.



@Harvey

The tolerance of the "trip wire"/ is +/- 0.5 mm.
I've got some 'food' for your boys:
Some ASCII data from the scope - AGW mode while the rotor turns
1.: clockwise
2.: anti clockwise
There is stator-lagging in both cases.

The data is in mathcad format.
But I can not post this data on some nasty places like this photobucket.
Photobucket only accept pictures and no data files.
Does anybody know a better place to post anonymous data?

The stator is lagging - that is surely the reason for the asymmetry.
You can see this effect on the 3rd. video (stroboscopic) as well.
Al told in some older posts, that the stator magnet was marked wrong.
Is this the whole truth?
I'm not sure whether just only friction and magnetic losses are the reason for stator-lagging:
There is no lagging in the GW mode.

Could some kind of viscosity or other magnetic effects cause the lagging in AGW mode?
If the lagging is caused by some friction, why does it seems to cause positive torque?

@prof:
We all try to replicate Al's device, but it doesn't work.

There are two possibilities:
1.: The corresponding effect is too small to spin the device.
2.: The corresponding effect does not occur at all.

For case 1:
We may find the effect with our scopes and optimise it until the OC MPMM spins from alone.
If we understand the effect, we could construct powerful devices and we will be the king.

For case 2:
We will have no chances to find the effect at all and we are the losers.

You can try to replicate my measurements (I could help with an analog integrator).
I think it is important, that someone else is replicating my measurements.
You could find some other ways to make the OC MPMM transparent.
Do you know anything about 'rotor lagging' if you power the stator?
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Fri Apr 04, 2008 10:03 pm PostPost subject:
overconfident
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@Wunderland,

Due to rotational inertia the driven component will always lag behind the driving component. This happens with both GW and AGW stator rotation but is more pronounced in AGW because the magnetic forces change quicker, thus the rotation has less chance to catch up. If you power the stator, you will find lag from the rotor but it won't be as obvious because of the larger mass.

The positive torque you see on the rotor can actually be caused by friction or binding in the stator which prevents the stator from responding into a magnetically favorable (mechanically unfavorable) orientation quickly enough to establish the magnetic equilibrium it wants and allowing more torque to be extracted than would be if there was no lag.

This is what I have been trying to say about latches. We actually "want" to inhibit stator rotation at specific points in order to enhance the positive torque on the rotor in magnetic repulsion. The lag is our friend.

OC
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Sat Apr 05, 2008 4:54 pm PostPost subject:
MADPROF
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@ OC

Taken over 350 photos today of AGW, alot of goods ones do you want me to post them. I will seperate them into some kind of order?
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Sat Apr 05, 2008 5:42 pm PostPost subject:
overconfident
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MADPROF wrote:
@ OC

Taken over 350 photos today of AGW, alot of goods ones do you want me to post them. I will seperate them into some kind of order?


Are these using your drill press automation for more consistent movement?

I would select all the photos for 3 consecutive rotor magnet numbers (for example, 1, 2, and 3). Then I would sort them so they show the rotational movement as the rotor magnets approach and depart from the stator. Having pics that look identical is OK, it will confirm the synchronization.

FYI: I would also be interested in photos of GW sync, although I think this rotor is too small to get a realistic idea how that might work.

OC
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Sat Apr 05, 2008 6:15 pm PostPost subject:
MADPROF
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overconfident wrote:
MADPROF wrote:
@ OC

Taken over 350 photos today of AGW, alot of goods ones do you want me to post them. I will seperate them into some kind of order?


Are these using your drill press automation for more consistent movement?

I would select all the photos for 3 consecutive rotor magnet numbers (for example, 1, 2, and 3). Then I would sort them so they show the rotational movement as the rotor magnets approach and depart from the stator. Having pics that look identical is OK, it will confirm the synchronization.

FYI: I would also be interested in photos of GW sync, although I think this rotor is too small to get a realistic idea how that might work.

OC


OC

O.K Give me a hour see what I can do.
These pics are of whipmag std in A.G.W Take a look and see what you think. I will then sort out G.W............ They are light years apart!!!!!!!!!!!!!
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Sat Apr 05, 2008 7:24 pm PostPost subject:
MADPROF
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@OC

Shots for Mag1 - Mag3

http://s258.photobucket.com/albums/hh279/madprof02/Magnetic%20Lag/

If you need more I have 4-8 as well.

A.G.W is a very weak interaction with the rotor, it seems to take the least path of resistance around the rotor field and as such has almost no effect on the rotor.....There is something big missing to relicate Al's setup.

Whilst spinning A.G.W I slow the stator with my finger, it drops out of sync with a very light touch and the rotor hardly see's it.


G.W If I slow the stator while spinning A.G Then I can apply such a force where by the stator will stop the ROTOR within seconds.

It's like A.G.W see's very little magnetic shear compared to A.G


Is there a reason why the stator drives the rotor, and not the other way round?
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Sat Apr 05, 2008 7:41 pm PostPost subject:
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@Wunderland

I would love to replicate your work, but I would need a brain transplant to pull that off.. sorry. If you need any engineering work to fine tune your set-up then give me a shout.

Magnetic lag you ask!! Well I am just starting to get my head round this at the momment ,so I know nothing. Embarassed The big problem is everybody else are using the WRONG WORDS. Laughing
Keep up your great work.
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Sat Apr 05, 2008 7:46 pm PostPost subject:
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@MADPROF,

I would expect AGW stator rotation to be weaker than GW but that doesn't mean the torque to the rotor would be less under ideal conditions. It's very possible there actually might be more torque transmitted.

As far as shear, AGW should actually experience twice the shear as GW rotation, but the field interactions may be more superficial because the field is varying more quickly and less naturally.

OC
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Sat Apr 05, 2008 7:50 pm PostPost subject:
overconfident
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MADPROF wrote:
@Wunderland

I would love to replicate your work, but I would need a brain transplant to pull that off.. sorry. If you need any engineering work to fine tune your set-up then give me a shout.

Magnetic lag you ask!! Well I am just starting to get my head round this at the momment ,so I know nothing. :oops: The big problem is everybody else are using the WRONG WORDS. :lol:
Keep up your great work.


FYI: When I was speaking about "lag" above, I was speaking of mechanical lag due to inertia, not magnetic lag (viscosity). I hope these are the RIGHT WORDS.
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Sat Apr 05, 2008 8:24 pm PostPost subject:
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MADPROF wrote:
@ OC

Taken over 350 photos today of AGW, alot of goods ones do you want me to post them. I will seperate them into some kind of order?


@MADPROF

Very nice work on the pics -- and lots of it. Looking at the photos, however, it's not clear to me that these are AGW.

... Q: In your AGW/GW photobucket presentation(s), how are you distinguishing between AG and AGW (I don't see "AGW" mentioned anywhere on current photobucket link).

(I know ... Everyone's a critic! Sad )

Cheers Very Happy
Yada ..
.
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Sat Apr 05, 2008 9:19 pm PostPost subject:
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Also to be clear the rig is turning clockwise?
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Sat Apr 05, 2008 9:38 pm PostPost subject:
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@All

Rolling Eyes What a complete prick, I've done it again..

ALL shots are A.G.W Rotor is spinning clockwise. I will shot G.W tomorow but will need to shoot twice with and without load on stator, because I think the timing will changea lot.

@OC Your words were fine, I was thinking back to magnetic shear. Taking about shear, I don't think it is in A.G.W. It's more like compressing the field going between the stator and rotor and then expanding out the other side, ying and yang.
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Sat Apr 05, 2008 11:41 pm PostPost subject:
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overconfident wrote:
@Wunderland,
Due to rotational inertia the driven component will always lag behind the driving component. This happens with both GW and AGW stator rotation but is more pronounced in AGW because the magnetic forces change quicker, thus the rotation has less chance to catch up. If you power the stator, you will find lag from the rotor but it won't be as obvious because of the larger mass.


@OC
I measured the lag of the stator in GW mode.
I was surprised to find a negative lag!
The maximum of the mag. field is reached before the rotor magnet is on the heigh of the stator magnet.

Fig. 4: Mag. field changes in the rotor magnet (the same as Fig. 1)


There are two plots combined: Clockwise and anti-clockwise rotor rotation.
I will prevent adjustment errors of the trip wire on this way.
- The two forked light barrier signals are at the top
- In the middle: one sensing coil (anti-clockwise)
- Bottom: the integrated magnetic field.

Fig. 5: Zooming into Fig. 4:



Both integrated traces are leading.

Fig. 6:
I have displaced the forked light barrier (~3mm).
That should show the impact of the displacement:


------------------------------------------------------------------------------------------------------

You can see the leading stator on Fig. 1 as well (1st Post).
- Is this just an incorrect measurement - well, I don't think so.
- I this only a magnetic leading effect inside the rotor magnet and the stator is still lagging?

Harvey wrote:
It is apparent from Fig 2 & 3 that the stator is not aligned with the rotor during these transistions. Because of this the flux will be asymetrical in your sensor.


@Harvey:
I never make a trace if the stator spins instable.
I only stop the scope if there is a perfect sync.
I can get GW mode, AGW mode and sometimes GW*3 (three times faster than normal GW).


@MADPROF:
If you can't understand something, this could be my faulty English as well - sorry. Embarassed
You took some fantastic pictures.
I should also try to make some pictures in GW / AGW.
This could solve some leading/lagging questions.

http://s258.photobucket.com/albums/hh279/madprof02/Magnetic%20Lag/?action=view&current=RIMG0258.jpg
You are powering the stator in AGW mode at this picture?
I can't see any leading / lagging there....
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Sun Apr 06, 2008 2:09 am PostPost subject:
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@Wunderland,

If you are judging maximum magnetic field by the peak produced at the coil, that is actually the maximum "change" in the magnetic field, not the maximum force. There may be a phase shift between the peak changes sensed by the coil and the peak torque forces applied to the rotor.


@MADPROF,

I just got all the photos downloaded. I'll start sorting so I can more easily analyze them.
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Sun Apr 06, 2008 7:53 am PostPost subject:
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overconfident wrote:
@Wunderland,

If you are judging maximum magnetic field by the peak produced at the coil, that is actually the maximum "change" in the magnetic field, not the maximum force. There may be a phase shift between the peak changes sensed by the coil and the peak torque forces applied to the rotor.


The law of induction teach us this for the voltage. This is the case.
M1 (lower half of Fig. 4,5) is the integral of the voltage and is proportional to the magnetic flux.
That's the trick!
==> @Fig. 4,5: M1: 4.5mT/Div without a shift caused by the law of induction.

If your equipment can't integrate, you can take the zero-crossing of the voltage as the moment of maximum field intensity.

An asymmetrical placement of the magnets could cause some errors.
But my clockwise / anti-clockwise test should usually find this error.

I've forgotten to say:
I can't power the motor and adapt the scope to the rotor sensing coil at the same time.
I can only measure while the device is running down.
The run-down time of the stator is much shorter as the rotor run-down. Therefore, this fact should not affect the measurements (I think).

I will try to make some pictures later - they could help here...
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Sun Apr 06, 2008 12:09 pm PostPost subject:
MADPROF
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@Wunderland

I have been though the other five mag positions and there are more shots like this one (3).

http://s258.photobucket.com/albums/hh279/madprof02/Magnetic%20Lag/?action=view&current=RIMG0258.jpg

The rotor is spun by hand then A.G.W latched, then the shots are taken. I can only think I have a few shots just before A.G.W drops out, or it might be rotor speed related.
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Sun Apr 06, 2008 5:31 pm PostPost subject:
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@MADPROF,

I've been studying your photo exhibition. If you've read all my rants, you'll know that AGW stator rotation was not something I predicted, just something Al stumbled upon. So take anything I say about AGW with a grain of salt. (I still want to see what GW looks like. It should correspond much closer to what I see in my imagination.)

I'd like to suggest a small deviation from the experiments, introducing a bit of additional asymmetry. What happens if we slide the rotor north poles of the rotor magnets closer together and the south poles farther apart so the field alternates: intense between north poles, weaker between south poles?

Another option might be to advance all the magnets so the leading end is slightly closer to the stator than the trailing end, to give a stronger effect when approaching the stator than when retreating (or vice versa if you spin the opposite direction).


@Wunderland,

You obviously understand electronics and calculus much better than I do. I do not have any formal engineering training or background in higher mathematics. I just have some persistent, amorphous images in my head. I do not have any of the test equipment you use and wouldn't know how to use it if I did.

I'm just trying to describe what I see in my head. If it doesn't make sense, just ignore me.

Keep up the good work.

OC
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Mon Apr 07, 2008 7:54 pm PostPost subject:
MADPROF
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@OC

Hi mate,

Been up to my eyes sorting out this PC, Hard drive was shot so they fitted a new one, they told me it would be as good as new, They were right just how I brought it 5 years ago!!!!!!!!!!! I have spent the last two days putting all the software back and all the windows updates, anyway its working again.

I knew AGW was not intended to start off with, but I think it still needs taking further, more on that latter.

My setup at present will not allow me to move the rotor magnets position, but this is something you must try. Now the pc is up and running I will shoot A.G for you to look at, I have done a small video to look at.

http://s258.photobucket.com/albums/hh279/madprof02/GW%20vs%20AGW/

Back to A.G.W I have shown to myself that this is a very weak magnetic interaction between rotor and stator, and in present form it has no chance of turning the rotor, never mind 2 other stators in G.W.

This leads me to think that Al's first video is the real thing, the only differance is we have something BIG MISSING.

Ping said a few days ago that the dampers could house batteries, True they could and I could build one to run no problem, but powering the stator.

From the video you will see how much stronger A,G is compared to A.G.W, but Al shows his stator spinning A.G.W, the big problem here is it will not spin the rotor like this, there is not enough magnetic coupling there, A.G no problem, you could do that.

So we are back to the Ball in the Bowl with A.G.W, it's evading capture ( taking the least path of resistance) Now if we could produce a path, be it eletrical,magnetic or what ever else to form a connection then we would have Al'S whipmag.

Hope this makes some sence.
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Mon Apr 07, 2008 8:21 pm PostPost subject:
Wunderland
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Here are some pictures in GW / AGW mode (clockwise rotor):

http://s295.photobucket.com/albums/mm122/Imwunderland/Blitzbilder/

Result:
Significant stator lagging in AGW mode.
In GW mode there is a jitter - some pictures are leading, some are lagging.
I should check the arrangement of my magnets, but there is a small lagging by the magnet with the senor coil (GW34).

==> I can't explain my measurement in Fig. 5 at the moment.
Some other effects are responsible for this phase shift...
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Tue Apr 08, 2008 8:36 am PostPost subject:
Harvey
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Wunderland wrote:
overconfident wrote:
@Wunderland,

If you are judging maximum magnetic field by the peak produced at the coil, that is actually the maximum "change" in the magnetic field, not the maximum force. There may be a phase shift between the peak changes sensed by the coil and the peak torque forces applied to the rotor.


The law of induction teach us this for the voltage. This is the case.
M1 (lower half of Fig. 4,5) is the integral of the voltage and is proportional to the magnetic flux.
That's the trick!
==> @Fig. 4,5: M1: 4.5mT/Div without a shift caused by the law of induction.

If your equipment can't integrate, you can take the zero-crossing of the voltage as the moment of maximum field intensity.

An asymmetrical placement of the magnets could cause some errors.
But my clockwise / anti-clockwise test should usually find this error.

I've forgotten to say:
I can't power the motor and adapt the scope to the rotor sensing coil at the same time.
I can only measure while the device is running down.
The run-down time of the stator is much shorter as the rotor run-down. Therefore, this fact should not affect the measurements (I think).

I will try to make some pictures later - they could help here...


The voltage should be proportional to the rate of change of Flux B. The faster the rate of change the higher the voltage. I am still not sure what function you are using for your integral in M1. It may be beyond my scope of understanding. Looking at Faraday's equations...

http://en.wikipedia.org/wiki/Faraday%27s_law_of_induction

...I don't find the relationship that results in positve Y values for M1 for a CH1 value of negative y. Is it possible your integral is including an 'absolute' modifier?

Thanx
Harvey
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Tue Apr 08, 2008 9:10 pm PostPost subject:
Wunderland
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Harvey wrote:
The voltage should be proportional to the rate of change of Flux B. The faster the rate of change the higher the voltage. I am still not sure what function you are using for your integral in M1. It may be beyond my scope of understanding. Looking at Faraday's equations...


Yes, thats right!
If the voltage is zero, there will be no change of the Flux M.
OK?
This means, there is a maximum or minimum Flux at this moment.
You can see so on Fig 1 .. 5

Harvey wrote:
...I don't find the relationship that results in positve Y values for M1 for a CH1 value of negative y. Is it possible your integral is including an 'absolute' modifier?



==> Positive voltage: rising Flux
==> Negative voltage: falling Flux

Ch1 is the voltage - M1 the Flux.
Have a look on Fig. 2.
You will find that M1 is a perfect integral of Ch1.

The scope can integrate because there is a computer inside. Wink
It is an integrated MATH function - look at Fig. 4 / "Math1/Intg(Ch1)"

-----------------------------------------------------------

I was checking my rotor magnets.
One became loose (shifting approx. 3mm!)

This affect my measurements.
==> Fig. 4 + 5 could be wrong - but I need more time to check this out...

I have no milling machine at home and an inaccuracy of 1mm is affecting the leading / lagging effects very strong!
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Tue Apr 08, 2008 11:32 pm PostPost subject:
overconfident
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Wunderland wrote:

... an inaccuracy of 1mm is affecting the leading / lagging effects very strong!


Excellent work Wunderland. See my previous post about modifying the distance or position of the rotor magnets. If 1mm can make that much difference, maybe 2mm can make even more difference. Asymmetry is our friend.

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