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LAY it down, turn it over, stand it up,raise it high, turn it around, move itback, push it forwardbut the AmazingMystery Motor keeps on going.

Astounding? It sure is. Especiallywhen you consider the way most othermotors work. Get their armatures theslightest bit out of whack and everythingstops. They just sit there and growl. Notso with the mystery motor. It runs whenheld in virtually any position over thepower coil,

Ever disassemble your electric drillsmotor? You end up with a pi le of washers, bolts, screws, bearings,brushes, springs, dirt and oil. Its prettycomplicated. A motor need not be,though.

The mystery motor has only fiveparts! With less effort than it takes toreplace the brushes in a hand drillsmotor youll have a mystery motor spin-ning up a real breeze.

Want your own? Wind the mystery

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ABMATURE ring (below) is plastic.Be sure to drill hole for shaftthrough center of piece of mag-netic strip to prevent vibration.

motors power coil on a plastic form,such as a 100-ft., 16mm movie film reel.The coil is 3,600 feet of No. 38 enameledwire. Inside the hub insert a ring of softiron. Cut a slit in the ring as shown.After winding the coil, remove theenamel insulation from the wires andsolder an AC cord to them. Then put thecoil in a soft-iron case, leaving the topopen.

The armatures plastic ring is 3/8 in.thick and has an inside diameter of 11/4

in. The l 3/16-in.-long armature is madefrom a piece of flexible magnetic strip,available from Lafayette Radio Corp.,Ill Jericho Turnpike, Syosset, N.Y., 11791.The price for a minimum length of 3 ft.is $1.69 plus postage. The stockNo. is 14 C 3307K.

Drill a l/16-in.-dia. hole through thelong axis for the shaft. Then drill holesin the ring and slip a piece of wirethrough the ring and armature. Lubri-cate the shaft.

MOTORS coil (left) is wound on plastic film reel.Solder AC cord to wires and cover with tape. Insertsoft-iron ring with a slit cut in it (below) in the hub.

FINISHED and ready to spin (above). Install coil insoft-iron cover and use rubber grommet to protect ACcord. Armature in holder is at right. Be sure it spinsfreely and does not rub against ring. Use a longershaft if armature is to drive a cardboard fan blade.

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A A

AXIS OF

ROTATION

TOP OF

COIL

MAGNETIC

STRIP

BEST POSITION FOR

SELF STARTINGS

N

SNNNS

NSSN

NSSS N SNSN

POS 1POS 7

POS 2POS 3

POS 4

POS 5

SECTION A-A

POS 6

117 VAC.

SOFT-IRON POLE

SOFTIRON

COVERCOIL

WINDING

MAGNETICFIELD

MAGNETIC FIELD

DIRECTION OFROTATION TOEQUILIBRIUMPOSITION

AXIS OF ROTATION(PERPENDICULAR

TO PAGE)

N

S

COILCOVER

+

Plug in the coil. Hold the ring near the coils edge withthe armatures axis parallel with the coils top. If thearmature doesnt turn, start it manually. How does it work?In mysterious ways, for sure.

Take a look at the lower half of the top diagram whichshows the magnetic field above the motors coil. Note thatthe lines of force (for the moment well assume theyreproduced by DC) con- centrate around the edges of thecoil.

Put a piece of magnetized iron in this field and it willturn so its N-S axis is in the same direction as the lines of force. It turns to establish equilibrium with the coils linesof force.

Consider the armature and coil shown in the bottomsketch. When the armature is oriented as shown, everytime the field reverses, a pole (arbitrarily, S, here) of thearmature tries to turn to follow. You might think that the

armature would move back and forth in step with the ACfield reversals. It doesnt because the S pole tends to moveto an area of greater magnetic flux density. Therefore, itmoves counterclockwise toward the coils edge andassumes an equilibrium position.

What you have just seen is the armature turning to providea position of equilibrium for the coils lines of force as thearmature is moved across the top of the coil to Pos. 7.

To get the armature to turn, we feed AC to the coil. Nowthe mystery motors armature is not just an ordinary pieceof iron. It has a strong magnetic field of its own.

Feeding AC to the coil causes the coil poles to change

from N to S. If the armature is free to spin and is startedmanually it will try to lock onto the rapidly-changing fieldand turn in synchronism with the AC frequency.

Plug the coil into anAC outlet and place the armature inPos. 1 as shown in our drawing. Try to turn the armatureaway from the position it first assumes. Note that it tendsto lock itself in this position. When turned too far it snaps180 to the next position. Now move the armature acrossthe coil face as shown and notice how it turns.

Why does it keep spinning? Because the armature hasmass and, therefore, inertia and it continues spinning oncestarted.

When turning to a new position (or with some help fromyour fingers), the armature picks up enough speed andmomentum to keep it going. It then continues to turn instep with the alternating field. The things which causespontaneous starting are vibrations and normal armatureunbalance. By the way, Pos, 3 is best for self-starting.Vemon J. David *

NOTE in sketch in upper left comer (hot Nand S poles are on sides of magnetic strip.Profile diagram shows how armatureturns to provide position of equilibrium tolines of force. At bottom, as armaturestarts to turn to line axis up with lines offorce, the momentum keeps the armatureturning.