ROTATES FIELD | MODEL CONSTRUCTION

In a previous article under the heading “electronics for beginners” (see “M-K” № 8, 1979) we understand how magnetic field is formed it Turned out that, in particular, generates supplied to the coil (solenoid) electric current. The same field with a certain force acts on it carried to the magnet. But the magnet with the same force acts on the wire, which carries current. On the phenomenon of the interaction of electric current and magnet based electric motors (electric motors).

Any electric motor consists of two main parts. Creates a stationary magnetic field is the stator, which is a permanent magnet or a field winding, the rotating part — the rotor.

How does the motor? Between the poles of a permanent magnet (stator) is a rotor — a coil of wire: it flows an electric current. Such a coil with a current creates a magnetic field.

Interacting with a permanent magnet (stator), the North pole of the coil (rotor) is attracted to the South pole of the magnet and South to North. If you now change the direction of the current in the coil, the location of the poles of the rotor is also reversed. Near the North pole of the stator will be a North pole loop, near South — South. There’s a repulsive force, and the round will turn a half turn. A new change in the current direction will cause the turn another half turn, etc.

Changes the direction of the current in the rotor winding is a special device — the collector. The simplest collector is a metal ring divided into two halves. Each half ring is connected to one end of the rotor winding. The half-rings are pressed against the brush of a metal plate connected to a current source. The brushes pass from one half ring to the other, and the direction of the current in the rotor winding changes. So it rotates continuously. This is how the DC motor.

And now we offer ourselves to manufacture electric motor for moving models (Fig. 1). Start with the stator. In figure 2, cut out 18 plates of annealed steel (e.g., tin) with a thickness of 0.5—1 mm. In plates drill 4 holes Ø 2.5 mm: they will need for tightening bolts. Next bond all the plates together, treat yourself with a file the ends of the stator, focusing on its inner surface. Its diameter should be equal to 41 mm.

Fig. 1. Homemade electric motor.

In the package drill two holes Ø 2.5 mm for fastening of the front and rear plates. Then disassemble the stator, clean each plate from stripes, cover with a layer of shellac or glue BF-2 and re-assemble.

The excitation coil (coil on the stator) wind the wire in enamel insulation Ø 0,4—0,5 mm of PEL or PEV of 0.4—0.5. On the frame, glued from pressshpana put 150 turns.

The rotor core make stacked from 18 separate plates discs Ø 40 mm. In the center of each plate, drill a hole of Ø 4 mm. Then from sheet iron with a thickness of about 2 mm make two round template. A little away from the edge, drill them at an equal distance from each other five holes Ø 8 mm. Extend them using a round file to the size specified in figure 2 (POS. 7).

Fig. 2. Details of the motor:

1 — brush holder, 2 — spring, 3 — brush, 4 front panel, 5 — shim, 6 — collector, 7 — rotor, 8 — shaft, 9 — stator, 10 — ball, No. 3, 11 — solenoid, 12 — screw, 13 — rear panel.

Collect all the plates on a metal rod with thread, and the edges install the templates. With bite the package tight pull, attach the nuts and finish on a lathe or with a flat file, increasing the rotor diameter to 39 mm. Drill holes for winding a round file, enlarge the templates.

Disassemble the rotor, carefully clean each plate from stripes and rinse in acetone. Then cover each plate with shellac or glue BF-2. Finally, the rotor assemble with the order of the plates remained in place. Of the rotor plate put on a steel axle turned on a lathe. Pull them tight between templates with the nuts and place in a hot oven.

After that, wrap the coil wire of PEL or PEV of 0.4—0.5. Laying start from the longer end of the shaft, making the output length of 50 mm. the First 50 turns of the wrap through the first hole in the third (Fig. 3). The end of the wire don’t tear off, fold, slightly twisted, in the form of a loop. Then use the wire to wind 50 turns, but between the second and fourth grooves. Again make a loop again and continue winding in the same direction, but this time between the third and fifth grooves. Then between the fourth and the first, fifth and second.

Fig. 3. Scheme of winding the rotor windings.

The end of the last coil will connect with the beginning of the first. The grooves remaining after winding, insert the cardboard strips to protect the insulation from damage.

Now fabricate the manifold. It is a circle of insulating material on which are not touching each other, fortified FIVE conductive sectors. They are made of copper washers, sawn into five parts. Sectors glued to a circle of glue BF-2 so that the gaps between them were not more than 1 mm.

The finished manifold air dry for 1-2 days, then carefully scrub: when the rotor rotates, the brushes must slide along the surface of the plate without jamming.

Put the manifold on the axis of the rotor and secure it in this position to the middle of each sector was against the mid-groove of the rotor. Then to the collector plates solder the ends of the windings of the rotor.

The device of brushes and brush holders shown in figure 2.

A. VALENTINE’s

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