Spiral Magnetic Gradient Spiral Magnetic Gradient Motor Using Axial MagnetsMotor Using Axial Magnets

Thomas Valone, PhD, PEIntegrity Research Institute

SPESIF, Johns Hopkins Univ., February 24, 2010

http://www.ias-spes.org/SPESIF.html

Credit: Tom Schum for spiral stator construction

Gradients Are Used for All PowerGradients Are Used for All Power

• Thermal gradient is used for heat pump• Voltage gradient is used for electricity

“pumping” of current• Gravity gradient is used for hydroelectric

power• Pressure gradient used for natural gas and

water pumping• Magnetic gradient is used for nothing so far

The net Force created on the ball bearing = the magnetic field gradient multiplied by the induced magnetic moment, as with the Stern-Gerlach Experiment

Hartman Patent #4,215,330

Side View

10 degree incline

drop-off

--Modern Physics, Schaumm’s Outline Series, Gautreau et al., McGraw Hill, 1978

Their experimental setup: The magnetic field B is more intense near the pointed surface at the top than near the flat surface below, creating a slope in a graph of B vs. z , which is the gradient dB/dz.

Steel ball bearing #4

Top View

FFzz

zz

Inhomogeneous Magnetic Fields = Inhomogeneous Magnetic Fields = Magnetic GradientMagnetic Gradient

Two experimental examples that utilize the magnetic field gradient

Spiral Magnetic Motor (SMM) Spiral Magnetic Motor (SMM) Uses the Magnetic GradientUses the Magnetic Gradient

Popular Science, June 1979

Hartman Patent 4,215,330

θφθ d

dBMF cos=

dzdBFZ φμ cos= z

Spiral Magnetic Motor (SMM)Spiral Magnetic Motor (SMM)Archimedean spiral is used

for SMM stator magnets where r = 6 + θ/2 and B(r) is

linearly dependent on θ

6”

Creates a constant torque for 75% of each cycle

F = ∇U where U = M · B and

r rU M B M Bθ θ= +

r rU M B M Bθ θ= +

SMM Governing EquationsSMM Governing Equations

rBMB

rMF rr

∂∂

+∂∂

=θ θ∂

∂= rBMT

221 EU oE ε=

oB

BUμ

2

21=

For a maximum B field in air of 20 kG(2 Tesla), UB = 2 MJ/m3

For a maximum E field in air of 3 MV/m, UE = 40 J/m3

2,000,000 = 40 X 50,000 !

Maximize radial B field (Br) for maximum torque0

ENERGY DENSITY CONSIDERATIONS:ENERGY DENSITY CONSIDERATIONS: B-FIELD = 50K x E-FIELD

∫= θdTW

Experimental ResultsExperimental ResultsSix SMM designs were tested: 1, 3, 4, 6, 10” rotors

Rotor and Stator B Fields

01234567

1.25 3 4 6 10

R ot o r D iamet er ( in.)

kG

▲ = rotor, ♦ = stator magnetic flux density

Spiral Magnetic Motor Angular Velocity

0

2

4

6

8

10

12

14

16

18

0.4 0.8 1.6 2.4 3 3.8 4.6

Angular Displacement (radians)

Ang

ular

Vel

ocity

(rad

/sec

)

1" rotor

3" rotor

4" rotor

6" rotor

10" rotor

Poly. (4" rotor)

Polynomial Fit

0 90 180 270 degrees

- - -Data acquisition limit- - -

Peak KE, Back Torque, Mass, BPeak KE, Back Torque, Mass, B--FieldField

1.25 3 4 610

Kinetic Energy (J)Back Torque (N-m)

Rotor Mass (kg)Rotor B Field (T)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Rotor Diameter (in.)

Kinetic Energy (J)

Back Torque (N-m)

Rotor Mass (kg)

Rotor B Field (T)

5 Rotors Tested: 1.25”, 3”, 4”, 6”, 10”

10” rotor: 0.80 joules

Phototransistor detail

Peak Values:

-0.5

0

0.5

1

1.5

Angular Displacement (degrees)

10" R

otor

Tor

que

(N-m

)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

10"

Rot

or P

oten

tial E

nerg

y (J

)

0 90 180 270 360

Rotor Torque and Potential Energy for One Cycle

Torque Measurement T=rxF

∫= θdTW

Positive Work Region

Negative Work Region

315°

Positive net work required to move latched rotor at 315° to end (starting point) at 360° :

W = 0.52 Joules

when starting at 0.78 J KE

10” rotor tests

Prof. Eric Prof. Eric LaithwaiteLaithwaite’’ss Suggestion Suggestion for Increased Torquefor Increased Torque

Place metal plate of particular permeability underneath rotor in order to produce:

Favorable Hysteresis Currents

Laithwaite Eric, Propulsion Without Wheels, English Univ. Press, 1970

Hysteresis Depends on Hysteresis Depends on Permeability and Resistivity*Permeability and Resistivity*

teHB β

πμ−−= 2

81

Designing the Growth of Eddy Currents to Match Rotation Speed

teHB β

πμ−−= 2

81 )4/( 2μδπρβ =

*Bozorth, Ferromagnetism, J. Wiley & Sons, 2003

= resistivity, = permeability, = thickness of plate, H field is suddenly applied

Choosing aluminum or copper for example, the permeability will be the same as free space ( o = 4 x 10-7), which is very low and the resistivity is also low. Choosing an aluminum plate that is about a centimeter (1 cm) thick would also be a good choice since the thickness of the sheet "delta" is squared and also in the numerator. Altogether, the calculation shows a relatively slow build-up over a tenth of a second and only about 30% at a millisecond after the stator field magnet is applied to the rotating disk, which is in keeping with a delayed eddy current that would push instead of retard the changing flux as would be normally expected from Lenz’ Law.

Wiegand wires are FeCoV bistableVicalloy metal with 2 regions

US 1973 patent # 3,757,754

Used for years for auto ignitions

Provides repeatable magnetic pulse

Pop. ScienceWiegand causes Barkhausen jumps of magnetic domains that align quickly

Inverse magnetostrictive (MS) effect combined with a piezoelectric material

(PZT) and voltage

MS-PZT

Magnetic Switching for SMM Magnetic Switching for SMM

IRI V-Track Dual SMM with Radial Magnets

Switching can be applied to the top stator magnet

Piezoelectric Actuator that bends with very little voltage applied

MultiMulti--Stage SMMStage SMM