Magnets Behavior in Earth's Magnetic Field Some Surprises

I observed something that puzzled me.

I set up 10 neodymium magnets in a stack laid on a 5 inch Styrofoam disc floating in water.
This is simply a very large compass. As you would expect it pointed north/south to align with Earth's magnetic field.

Next I placed a normal compass on a wooden table and held a single magnet closer and closer to it until the compass pointed 45 degrees away from Earth's north. It was about 8 inches away.

Next I held the same magnet a little farther than 8 inches from the large compass I had made floating in water. As I moved it a little closer the large compass started to turn and then proceeded to attract to the magnet in a very direct way.

Why the difference? The difference I am referring to is that the large compass should move north from the attraction of the Earth's magnet but doesn't while it moves towards the single magnet with considerable enthusiasm.

My first guess was that the large compass floating in the water did not move north normally from just the Earth's magnetic field because it was attracted downward towards the Earth's magnet. This was wrong.

What I learned after making some inquiries was that while magnetic torque (what turns the compass needle to point north) is proportional to the strength of the magnetic field the force of magnetic attraction is not but rather proportional to the gradient of the magnetic field. Since the Earth is so much larger than my large compass the gradient (or slope) of the magnetic field is flat and the attraction is nearly zero.

This is relevant to my subject of magnetic field traction in Earth's magnetic field of course. As I already had observed you couldn't get a magnet to directly move a little boat from Earth's magnetic field but now I know why. But more importantly this means you could have one of my rotating or pendulum type magnetic devices in Low Earth Orbit and it would not exert a force or acceleration downward towards the Earth constantly. That is a very good thing.

(There are still other considerations. For example the effects of Lenz' Law which would slow down the magnet in orbit as it crossed Earth's magnetic field lines.)

Here are two experiments that I did related to this (be sure to turn the sound on and read the descriptions):

TESTING KNOWING THERE ARE MAGNETIC HOTSPOTS

Now that I have been a bit enlightened about the magnetic hot spots under the floor I have a strategy to continue testing the permanent magnet devices in spite of them.

Once I have identified a hot spot, whether it is a nail under the floor or a beam or some source of magnetism, I will try to start over it and see if I can maneuver away from it. Or I will start somewhere a little away from it if the attraction to the hot spot is too strong to maneuver away from and see how long I can avoid the model being drawn into the hot spot.

Identifying a hot spot isn't all that difficult. First of all the device works too well to be true but keeps going in the same direction. Granted that can be difficult since some of the devices can only go in one direction. Next use the magnetometer. In my latest informal experiment the magnetometer read over 10 uT higher on the Z axis over the hot spot. It is difficult to simply scan a whole area for a hot spot but it is possible with patience also.

A device with permanent magnets that are used to swing against a weight in the water tank in an aluminum pan should be able to go in any direction. I needed to identify which side of the device rotates with more mass. If the center of rotation is shorter on one side that is usually the side with the greater mass and where the most centrifugal force will be as it swings side to side like a pendulum.

So below is a 4 minute video of two trials. In the first 2 minutes of the video the model can be seen to drift without being maneuvered right into the hot spot from a standstill to a speed of 4 inches per minute approximately. This of course is a false positive result.

In the second 2 minutes of the video the water tank is in the exact same location with the hot spot in the same place as well. The model is starting from a standstill and then maneuvered in a pendulum motion and can be seen to not move into the hot spot. This shows that the maneuvering model has achieved a bit of thrust. Of course there are other factors that would remain to be ruled out for example slip stick effect.

Originally I tried to start in the hot spot and maneuver out of it but the model didn't have enough power to do so, hence I settled for simply staying away from the hot spot. The hot spot is in the north east part of the water tank or the lower left part of the screen. The model consists of a servo that controls the rotation of the stacks of neodymium magnets. It is actually an IR remote control toy robot with the magnets taped to some craft sticks to its top. When the north end of the stacks of magnets points east the aluminum pan rotates counterclockwise and vise a versa. The weight at the other end of the 10 inch aluminum pan is clay that is a blue color.

Please observe:

Measurements with cellphone Magnetometer and scale and observations of large compass floating in water

Measurements with cellphone Magnetometer and digital kitchen food scale and observations of large compass floating in water

      I got a few cellphone Magnetometer apps to make some rough measurements.

      The units of measure of magnetism are microTesla or uT. One uT equals 0.01 Gauss.
At my location in the state of NY the Earth's field is 52 uT. However this is the entire force referred to as F and its vector mostly points into the ground at about a 66 degree angle. So the actual force pointing north is 19 uT or what is referred to as the X measurement.

      Before I go into farther detail let me give my results. The results were that the Earth's magnetic field was powerful enough to push or pull a magnet by attraction or repulsion with enough force to make a little boat travel in a water tank.

      Why this is not immediately obvious is because the magnet must be oriented in such a direction that it does not turn freely like a compass and align with Earth's magnetic poles at which position it will have no push or pull.

      Let me use the Levitron toy as an example of this. The top on the classic version of the Levitron weighs 60 grams approximately. Because due to the gyroscope effect of the top spinning it is able to push away from the magnet in the base with enough force against gravity to hover over 1 inch high. But if it is not spinning than it will simply line up with the north and south poles of the magnet in the base and sit on its side with no evident sign of propulsion against gravity.

      I took one N42 0.5 inch diameter by 0.25 inch length neodymium magnet and measured from various distances in uT on the Magnetometer. At 12 inches it measured approximately 2 uT. At 3 inches it measured 225 uT.

      Next I set up a scale with a similar magnet on it and held the N42 over it to see when it would repel at 1 gram approximately. That distance was 3 inches approximately.

      Next I set up an aluminum pan filled with water with a Styrofoam disc floating in it. I placed a stack of 14 of the N42 magnets along a diameter of the Styrofoam disc in effect creating a giant compass. This pointed north. I measured a rough estimate of when the Styrofoam disc would move as I moved an N42 magnet towards it from various points around it.

      The Styrofoam disc floating in the water with the 14 N42 magnets on it rotated a little and then either moved towards the magnet I held or away from it very visibly from distances over 12 inches.

      So for starters we can conclude that a magnetic force of only 2 uT is enough to move the magnetic boat through the water.

      Next we can conclude that Earth's magnetic force since it is 10 times that amount of course can move a properly designed boat.

      I won't say how fast or slowly but will state that it will apply a force that causes continuous acceleration taking into account other factors such as friction in the water and nearby magnetic or ferrous objects.

      Now since we have observed that 225 uT presses 1 gram force to the magnet on the scale we need to somehow extrapolate what that gram force is at 19 uT. (Earth's magnetism at my location)

      I am just going to take a guess that the relationship between microTesla and gram force is directly proportional. So since 19/225 is approximately 0.1 or a little less that is the amount of gram force the Earth's magnet (magnetic field) is pushing against the Styrofoam magnetic boat which is constructed with 14 stacked N42 0.5 inch diameter by 0.25 inch neodymium magnets.

PERMANENT MAGNETS IN CIRCLE OR PENDULUM PROPULSION

PERMANENT MAGNETS IN CIRCLE OR PENDULUM PROPULSION JUST AS GOOD AS ELECTROMAGNETS AND REQUIRE ALMOST NO ELECTRICITY

      There is no doubt in my mind now that this principle works. A permanent magnet or an electromagnet rotating off center like a compass in Earth's Magnetic Field will work in LOE (Low Earth Orbit) and would have practical applications for at least de-orbiting small satellites at the end of their life cycles if not as well for adjusting orbits.

     The video above is a small model made from a 12 inch aluminum pan, some N42 half inch diameter Neodymium magnets and a toy robot that rotates and is used for a servo. Clay is used for weight. The clay is blue colored. 

     Rotating the magnets as opposed to using fixed electromagnets gives great control of the little "boat" floating in a tank of water. It makes the boat turn in the low friction of the water pretty responsively. (Remember however the video is time lapsed at 6X)

     Here is how and why it works. 

*    When the head of the toy robot is turned the magnet turns and then the whole aluminum pan model turns as the magnets act like a compass seeking to point north and south.

*    As the aluminum pan turns it does not turn around the center of the torque from the magnet nor does it turn at the center of its mass but at a third point. Magnetic torque is extremely powerful compared to magnetic attraction of opposite poles at a distance. (Someone help me with the math and engineering.)

*    The aluminum pan since it turns at a point not its center of mass has one part of it turning that is more massive than the other (The part on the side of the magnet). That creates centrifugal force. There is no claim here this defies any laws of physics since the magnetic interaction with Earth is an external force applied to the model)

*    The centrifugal force pulls the aluminum boat in a line.

*     This invention translates rotation from magnetic torque from a powerful compass into linear motion. (or force to be technical)

3 Electromagnets Turned On Off Rapidly Works But Some Issues with Static

      To pick up from the last blog post I made some changes and had some success.
    
      The first change was to reverse the polarity of the upper pointing electromagnet. I did this by loosening the nuts that hold the second foam board to the first and turning around the electromagnet rather than reverse the wires. Now when the electromagnets are powered on they don't oppose each other. Now they will make the top of the device be inclined to move towards one of Earth's magnetic poles and the bottom two towards the opposite pole.
   
     The second change was to add permanent magnets at a right angle to the foam board near the top. Now when the electromagnets are off the permanent magnets are inclined to point north/south with Earth's magnetic poles.
  
     The third change was to alter the Arduino sketch (program) so that the electromagnets only go on and off several times a second instead of reversing polarity.
 
      Now it is set up as an earlier model that I somewhat understand. The device will oscillate as the electromagnets and the permanent magnets interact with Earth's magnetic field. Since the point where they oscillate is not the center of the mass of the whole device and neither at the center of the point of magnetic torque from the magnets acting like a compass and rotating, the device will go in a line.
  
     As can be seen in the below (time lapse 6x) video this works.

     The red cardboard 3 fold boards are reducing the effect of air draft and you can see the device accelerate a little over the several minutes it is on. Note that it is only turned on after some period of time to establish that it is standing still in the water.

     Below is a second trial. (Also at 6x time lapse.)

                                      


     This worked several times but then a problem with what I am almost certain is static electric charge occurred.

     Here is what happens.

     The 10 inch aluminum pan is used specifically as opposed to Styrofoam. In previous experiments Styrofoam caused this problem but now it happened anyway. I am not really sure exactly how it works but the static prevents the device from moving in the water, even when deliberately physically pushed. It will go for a short time then come to a perfect standstill. (My experience is that in any of the previous experiments a small push would make the model drift quite a bit.)

    The thrust generated by this device is not powerful enough to overcome the resistance to motion from the electrostatic charge.

    One thing that seemed to work in the past was to empty the container of water completely and refill it. I am now waiting for warmer weather to empty the water and try again. Also it may be that the choice of foam board for the structure of the model was not the best one.


20180125 Thursday - I did some math and realized that turning the magnets on and off at short intervals is not as effective as doing so at longer intervals. (Not necessarily with this exact model but it explains why this model is weak.)

     To get a centrifugal force from a pendulum the speed of the pendulum's motion is important. The faster it moves the more centrifugal force. To show that it will move faster in one longer motion than in many shorter motions we only need to show that any velocity will be greater in one continuous acceleration from 0 than many small accelerations each from 0 and to do that we need to do some Calculus. But is it pretty easy Calculus.

Velocity = Acceleration * Time

So for our example we will compare a 10 second continuous acceleration from 0 verses 10 1 second accelerations from 0 and show that the 10 second continuous acceleration amounts to much greater velocity.

Since Acceleration will be considered a constant we will remove it from the equation or just call it 1.
For 10 separate accelerations of 1 second each from 0 the definite integral is:

10 Sum Time from 0 to 1

equals:

10 Time^2/2 where Time is 1 or 10 * 1/2 = 5 in lets say inches per second.

For one continuous acceleration for 10 seconds it is:

1 Sum Time from 0 to 10

equals:

1 Time^2/2 where Time is 10 or 1 *100/2 = 50 inches per second.

The difference between 5 inches per second maximum speed over 10 seconds and 50 inches per second maximum speed over 10 seconds is enormous.

      Now when we consider earlier experiments where the device rotates completely in a circle it makes sense that it is a much more efficient use of energy to produce linear motion since the acceleration takes place continuously for at least several rotations until a terminal speed is reached due to factors such as friction.

Look Ma' No Moving Parts- Electromagnet Propulsion with Three Electromagnets

THIS VERSION SEEMS TO WORK AND HAS NO MOVING PARTS

(IT DOES VIBRATE PROBABLY A BIT)

20180106 Saturday
     Last night I used foam board for two sides to hold 3 electromagnets in place so they are 120 degrees apart and close together at the center. I want to use bolts and washers to hold it all together. It will stand straight up so will need some support pieces.I have all the electronics needed. The electromagnets will all have like polarity pointing outward and inward. The polarity will reverse 10 times a second in the hope that this will drive the smaller aluminum pan as it floats in water. Some small steering magnets will also be added.

     The electromagnets will be wired in series and batteries will be used to provide 1 to 1.5 amps so not to overheat our H-bridge controller.

     I have it mostly set up with the L298n, Arduino, 8 AA NIHM batteries, a 9 volt battery and a quick little sketch (Arduino program).
The 8 batteries are 9.6 volts and I measured 1 amp so the 3 electromagnets are 9.6 ohms in series.

20180107 Sunday
     I've decided to use metal bolts as opposed to nylon bolts with consideration for static electricity, a problem that keeps occurring in the water tank and causes the boats to resist motion.

     All ready to test after batteries are recharged.

20180108 Monday
     Batteries are charged.going to use a fresh 9volt battery to. Seems the magnets weren't getting power.

It works. It moved towards Earth's magnetic North Pole. The batteries have to be fully charged then it will work for about 10 minutes. It moved about an inches per minute slightly accelerating for a few minutes.

20180110 Wednesday
     So far I noticed when the rechargeable batteries became drained the device didn't go so I considered that a reasonable control for these tests or experiments but I felt I should make a more formal control test with no power.

     I placed the device in the water tank without the power connected to see how long it would stay in one place.  

     The results were for a time humbling. I noticed that in the first control trial while I stood behind the camera the boat drifted north very much like it did under power. OK, I'm not that skeptical so I tried some more and was able to get the boat to stay in one place for six minutes and catch that on video.  I was able to do this several times while not always on video. The video was shortened to a minute by the video editor from Magisto.
  
     To get an accurate indication I need to stand away from the water tank when I do the experiment with the power on and come back to check on it several minutes later to see if it worked.

     I will soon do more experiments. In the meantime here is a control trial for six minutes shortened down to one minute for your approval.

     My lesson learned is that I know that this may be important work in magnetic field propulsion near Earth's magnetic field so I want to be sure to take my time and not rush through it.

    Also with this particular instance of magnetic propulsion the top speed was clocked at no faster the 1 1/2 inches per minute while other versions were much more powerful doing at least 2 or 3 or even 4 inches per minute. As I have learned 1 inch or 1 1/2 inches per minute is also the speed this particular device will go propelled by only the draft in my home.

    I decided to get some of those science project cardboard fold out boards with three sides and surround the tank completely with them and I was able to get the device to stay still for close to a half hour. (That is it did not to move all the way to either end or to either side and more or less stay within about 4 inches of its starting position.)

    This was a very nice project with the electromagnets and Arduino and working with foam board but I am afraid it isn't going to get me to outer space any time soon.:)