How do they work?

The drawing that shows a curved "arcuate" armature magnet in three successive positions over a line of fixed stator magnets provides at least highly simplified insights into the theory of permanent magnet motive power generation. Johnson says curved magnets with sharp leading and trailing edges are important because they focus and concentrate the magnetic energy much more effectively than do blunt-end magnets. These arcuate magnets are made slightly longer than the lengths of two stator magnets plus the intervening space, in Johnson's setups about 3-1/8 inches long.

bote that the stator magnets all have their North faces upward, and that they are resting on a high magnetic permeability support plate that helps concentrate the force fields. The best gap between the end poles of the armature magnet and the stator magnets appears to be about 3/8 inch.

As the armature north pole passes over a magnet, it is repelled by the stator north pole; and there's an attraction when the north pole is passing over a space between the stator magnets. The exact opposite is of course true with respect to the armature South pole. It is attracted when passing over a stator magnet, repelled when passing over a space.

The various magnetic forces that come into play are extremely complex, but the drawing shows some of the fundamental relationships. Solid lines represent attraction forces, dashed lines represent repulsion forces, and double lines in each case indicate the more dominant forces.

As the top drawing indicates, the leading (N) pole of the armature is repelled by the north poles of the two adjacent magnets. But, at the indicated position of the armature magnet, these two repulsive forces .(which obviously work against each other), are not identical; the stronger of the two forces (double dashed line) overpowers the other force and tends to move the armature to the left. This left movement is enhanced by the attraction force between the armature north pole and the stator south pole at the bottom of the space between the stator magnets.

But that's not all! Let's see what is happening simultaneously at the other end (S) of the armature magnet. The length of this magnet (about 3-1/8 inches) is chosen, in relation to the pairs of stator in magnets plus the space between them, so that once again the attraction/repulsion forces work to move the armature magnet to the left. In this case the armature pole (S) is attracted by the north surfaces of the adjacent stator magnets but, because of the critical armature dimensioning, more strongly by the magnet (double solid line) that tends to "pull" the armature to the left. It overpowers the lesser "drag" effect of the stator magnet to the right. Here also there is the added advantage of, in this case, repulsion force between the south pole of the armature and the south pole in the space between the stator magnets.

The importance of correct dimensioning of the armature magnet cannot be over-emphasized. If it is either too long or too short, it could achieve an undesirable equilibrium condition that would stall movement. The objective is to optimize all force conditions to develop the greatest possible off-balance condition, but always' in the same direction as the armature magnet moves along the row of stator magnets. However, if the armature is rotated 180 degrees and started at the opposite end of the track, it would behave in exactly the same manner except that it would, in this example, move from left to right. Also note that once the armature is in motion, it has momentum that helps carry it into the sphere of influence of the next pair of magnets where it gets another push and pull, and additional momentum.

Complex Forces

Some very complex magnetic forces are obviously at play in this deceptively simple magnetic system, and at this time it is impossible to develop a mathematical model of what actually occurs. However, computer analysis of the system, conducted by Professor William Harrison and his associates at Virginia Polytechnic Institute (Blacksburg, VA), provide vital feedback information that greatly helps in the effort to optimize these complex forces to achieve the most efficient possible operating design.

As Professor Harrison points out, in addition to the obvious interaction between the two poles of the armature magnet and the stator magnets, many other interactions are in play. The stator magnets affect each other and the support plate. Magnet distances and their strengths vary despite best efforts of manufacturers to exercise quality controls. In the assembly of the working model, there are inevitable differences between horizontal and vertical air spaces. All these interrelated factors must be optimized, which is why computer analysis in this refinement stage is vital. It's a kind of information feedback system. As changes are made in the physical design, fast dynamic measurements are made to see whether the expected results have actually been achieved. The 'new computer data is then used to develop new changes in the design of the experimental model. And so on, and on.

That very different magnetic conditions exist at the two ends of the armature is shown by the actual experimental data displayed in the table and associated graph. To obtain this information, the researchers first passed the probe of an instrument used to measure magnetic field strengths over the stator magnets and the intervening spaces. We shall call this the "Zero" level although there is a very tiny gap between the probe and the tops of the stator magnets. These measurements in effect indicate what each pole of the armature magnet "sees" below as it passes over. the stator magnets.

Next the probe is moved to a position just beneath one of the armature poles, at the top of the 3/8-inch armature-to-stator air gap. Another set of magnetic flux measurements is made. The procedure is repeated with the probe positioned just beneath the other armature pole.

Now "Instinct" might suggest, and correctly so, that the flux measurements at the top and bottom of the air gap will differ. But if "instinct" also suggests that these differences are pretty much the same at the two armature pole positions, you would be very much in error!

First study the two tables that show actual flux density measurements. Note that in this particular experiment the total magnetic flux amounted to 30,700 Gauss (the unit of magnetic strength) when the probe was held at the "Zero" level under the north pole of the magnet, and a total of 28,700 Gauss when the probe was moved to the top of the 3/8-inch air gap. The difference between these total 'measurements is 2,000 Gauss.

Similar readings made at the air gap between the south pole of the armature and the stator magnets indicates a total flux at "Zero" level of 33,725 Gauss, and 24,700 Gauss at the top of the air gap. This time the difference is a much larger 9,025 Gauss, or four and one half times greater than for the north pole! Clearly, the magnetic force conditions are far from identical at the two ends of the armature magnet.

The middle five pairs of figures from each table hive been plotted in graphic form to make these differences more obvious. In the top "South Pole" graph the dashed line connects, the "Zero" level readings made over the stator magnets and over the intervening air spaces. Points along the solid line indicate comparable readings made with the probe just beneath the armature south pole. It is easy to see that there is an average 43% reduction of the attraction between the armature and stator magnets created by the air gap. Equally true, but perhaps not so obvious, is the fact that there is an average 36% increase of repulsion when the south pole of the armature passes over the spaces between the stator magnets. The percentage increase only seems smaller because it applies to a much smaller "Zero" level value.

The second graph shows that the changes are much less dramatic at the north pole of the armature. In this case there's an average 11.7% decrease of attraction over the spaces, and a 2.4% increase, of repulsion when the armature north pole passes over the stator magnets.

As you study the data, be sure to note that the columns are labeled differently. In the case of the north pole data, the stator magnet areas repulse the armature north pole while the spaces between the stator magnets attract. The conditions are exactly the opposite for the south pole of the armature magnet. When the south pole passes over a magnet, there is strong attraction; when it passes over a space, there is repulsion.

The Ultimate Motor

A motor based on Johnson's findings would be of extremely simple design compared to conventional motors. As shown in the diagrams developed from Johnson’s patent literature, the stator/base unit would contain a ring of spaced magnets backed by a high magnetic permeability sleeve. Three arcuate armature magnets would be mounted in the armature which has a belt groove for power transmission. The armature is supported on ball bearings on a shaft that either screws or slides into the stator unit. Speed control and start/stop action would be achieved by the simple means of moving the armature toward and away from the stator section.

There is a noticeable pulsing action in the simple prototype units that may be undesirable in a practical motor. The movement can be smoothed, the inventor believes, by simply using two or more staggered armature magnets as shown in another drawing.