The models introduced here are all motor-driven. Because speedboats, ships and other models require high running speed, electric locomotives, tanks and other models require high motor power, so we must first make high-speed and high-horsepower model motors. Most of the models introduced in the book use the same motor, which is convenient for us to make them uniformly. Due to special requirements, the electric aircraft model only introduces the motors used in the aircraft model and hydrofoil model respectively. We can see the appearance of the self-made three-pole motor in Figure 2- 1, and all parts are numbered for our reference.
(1) is the stator magnet in the motor, and there are coils around the enameled wire. When the current passes through the stator coil, there is magnetic force on the stator magnet, and it becomes an ordinary electromagnet. ② It is the rotor of the motor and the main rotating part of the motor. It is equipped with commutator ③, so that the motor rotor can continue to be electrified when rotating, and the commutator also plays the role of changing the direction of current in the motor rotor coil. (4) There are two brushes to deliver current to the commutator. ⑤ and ⑦ are rotor bearings, which support the rotor of the motor to rotate. ⑥ is the axis of the rotor, and the model is driven by the rotating power of the motor. Figure 2-L The left figure is the schematic diagram of the motor. In the future, only the schematic diagram of the motor will be drawn in the model electrical wiring diagram, so the marks and codes in the schematic diagram should be clearly seen first.
Let's start making motors. We need to make several models. First, we need to make the required motors. It is more convenient to do a few at a time than to do it by one person.
First of all, make the iron cores of the stator and rotor of the motor well. See Figure 2-2a for the size of stator core. First, cut out five thin iron sheets according to the size of Figure 2-2b (first cut out according to the size of the dotted line in the figure, and then file A and B to the specified size with a trowel during processing, so as to make the iron core tidy), fold the five iron sheets together and bend them into the shape of Figure 2-2a, clamp the uneven parts of A and B with needle-nosed pliers and file them into five pieces, and then weld them into hard pieces with tin. The most important thing in manufacturing is to make the inner circle of the stator core very smooth, so that the rotor will not collide with it when it rotates inside. After the stator core is processed, it should be coated with a layer of paint to prevent rust.
Next, manufacture the rotor core: firstly, cut out four pieces of iron with the width of 12mm, overlap them, and bend the iron pieces into one pole of the rotor according to Figure 2-2c, and one * * * needs to be bent into three poles. Attention when bending: the distance between the magnetic pole of each rotor and the welding axis should be the same. After bending, cut off the iron sheets at both ends of each pole, flatten them, weld some tin, and note tin at the place to be welded firmly on the drawing (that is, the place where the two halves merge). Finally, cut off the two ends with a big sewing needle, polish the two ends smoothly, then penetrate into the rotor core and weld it firmly as a rotating shaft.
Using quilting needle as motor shaft has an outstanding advantage, that is, it is very smooth and round, with very small resistance and fast rotation speed, which can reach 8000- 12000 rpm, and it is suitable for electric models introduced in books.
After the rotor is completed, it should be inspected. Whether the rotor is calibrated is one of the keys to whether the motor can generate the maximum power, so the calibration work should be done carefully. As shown in Figure 2-3, make an inspection rack to check the rotor, put the rotor on it and turn it slowly to see if the gap between each pole and the tip of the pointer is equal. If one gap is smaller than the other gaps, it means that this pole is longer than the other two poles. You can use a hammer to knock a few times on a pole that is too long, as shown in Figure 2-4 (you must pad the battens shown below, otherwise the angles between the three poles are not equal).
After the stator and rotor cores are completed, winding work will be carried out. In order to ensure that the enameled wires wound on different cores of the stator or rotor do not have short circuit (leakage), two layers of kraft paper should be wrapped around the windings of the stator and rotor before winding. First, wrap two layers of tough paper (such as kraft paper on the cover of an old exercise book) with a width of 18 mm in the middle of the stator core, and then wrap the prepared one with a diameter of 0. L ~ 0. 13 mm around kraft paper in the middle of stator core. Before winding, in order to prevent the thread end from loosening, the enameled thread end can be tied with silk thread. After winding a layer, cut a piece of 20 mm wide tissue paper and wrap it on the wound coil, and then wrap a layer of enameled wire neatly on the tissue paper. Each layer should be wrapped in a thin paper for insulation. The stator coil is wound in six layers. After winding, tie the enameled wire to the end of the coil with silk thread to prevent it from loosening. The coil is wrapped in kraft paper and coated with paint. Finally, polish off the paint of the enameled wire at both ends of the coil and wind the stator coil.
And then bypass the rotor coil. First, paste all the inner parts of the rotor core with tissue paper and dry glue. When the glue is dry, use enameled wire as thick as the stator coil to wind the wire. The winding starts from the center of the rotor (that is, near the rotating shaft) and is neatly and tightly wound. Wrap a layer of tissue paper around each circle for insulation. Six layers are wound on each rotor pole. After all the winding is finished, set aside a certain length to cut the wire, and tie the end of the wire tightly with the wire to prevent it from loosening.
After winding the rotor and stator coil, conduct electrical inspection as shown in Figure 2-5 to see if the stator or rotor coil is short-circuited with the iron core. Find a dry battery, weld a wire from the negative electrode (battery bottom) and connect it to a terminal of the stator; In addition, a small electric ball is used to wind a piece of enameled wire with both ends polished and painted around the threaded part. When checking, contact the tail tip of the small electric bead with the small copper cap (positive electrode) on the battery, and contact the stator core with the enameled wire on the small electric bead to see if the small electric bead is bright. If the small electric bead is not bright, it means that the insulation between the coil and the iron core is good and can be applied; If the small electric bead glows, it means that the stator coil and stator core are charged, that is, short circuit, and the coil must be removed and bypassed again.
In addition, connect the two lead wires of the stator to a 3-volt battery (two batteries in series 1.5 volt dry battery) to see if a big nail can be installed. If the suction force is not large, it may be a short circuit inside the coil, so it should be removed and rewound.
Check the three coils of the rotor in the same way. If a coil is found to be short-circuited with the rotor core, or the power-on test results show that the suction force is not great, then the coil on this pole should be removed and rewound. We should strictly check the quality of the coil. If a short-circuited coil is used carelessly, not only will the model not start normally, but it will also consume a lot of power. Therefore, all coils should be qualified before the next assembly work.
Where the commutator is installed on the rotor shaft, wrap a thin paper coated with glue around a cylinder with a diameter of 4 mm (Figure 2-6a). When the glue is dry, cut one end of it flat with a blade to make its length equal to 8 mm.
Commutator is 0.3-0.6mm thick copper skin. According to the shape in Figure 2-6b, a motor needs three pieces. In order to bend the commutator copper sheet into an arc, a mold should be made. The mold is made of a small piece of iron, copper, aluminum and other metals, and a semicircular groove with a diameter of 4.5 mm is cut on it. Then find an iron wire with a diameter of 4 mm as the upper die, put the cut commutator copper sheet into the groove and hammer it into the die (Figure 2-6c) to make the circular commutator segment. Then bend the narrower part at the back up by 90 degrees to make the commutator as shown in Figure 2-6B.
When installing three commutators on the small paper tube of the rotor shaft, there should be a small gap (about 0.5 mm) between every two commutators. The gap should be aligned with the rotor pole (Figure 2-2D). Then the three commutator segments are tightly tied to the small paper tube with silk thread dipped in glue. Then scrape off the paint on the six wire ends of the rotor coil, and weld the wire ends to the three commutator segments according to the connection method in Figure 2-2D, and the three commutator segments shall not contact each other for short circuit.
After the rotor is completed, it must be checked for balance. According to Figure 2-7, erect two blades on the table and put the motor rotor on the blades to see if the weights of the three electrodes are the same; If a pole is heavy, it will automatically turn to the bottom. At this time, it is necessary to stick several layers of kraft paper on the two lighter poles to make the three poles equally heavy. If three rotors with different weights are assembled on the motor, the motor will vibrate badly when it rotates, which will affect the normal work.
Next, make the front and rear support frames of the motor. Its function is to support the rotating shaft of the motor. First, according to the size of Figure 2-8a, bend a copper sheet with a thickness of 0.5 mm into the shape shown in the figure; Punch a small hole in the middle, which is just the size to allow the large seam as the rotating shaft to rotate flexibly in the middle. This is the front support frame. At its two bends, four or five layers of thin paper dipped in glue wrapped it as insulation material. Find two small pieces of copper skin, cut them into strips with a width of 6 mm, wrap them with tissue paper, as shown in Figure 2-8b, and clamp them hard with needle-nosed pliers as insulation supports for welding brushes on them in the future. Check the stator and rotor coils in the same way as before to see if the two brush holders are short-circuited with the front holder.
The rear support frame is only a piece of brass with a width of 6 mm and a length of 16 mm (Figure 2-8c), and there is no need to drill holes in the middle. Bearings shall be welded on the front and rear support frames. The method is as follows: a section of enameled wire with a diameter of 0.5 mm is tightly wound on the needle to form a spring-shaped copper spiral pipe, which is cut into three sections with scissors and welded to the places where the bearings are welded on the front and rear support frames to form the bearings. Be careful when welding the bearing, so as not to block the hole in the bearing with tin. After welding, be sure to wash the residual welding oil in the bearing hole with kerosene or alcohol to prevent the shaft from rusting.
After the bearing is completed, the motor rotor should be able to rotate flexibly without clamping, but it should not be too loose, because too loose bearings will make the motor rotor jump when rotating.
As shown in Figure 2- 1, the rear support frame can be bonded with wires and tightly tied to the coils of the stator core ... It should be noted that the bearing should face the middle of the stator, otherwise the rotor and stator will collide with each other and cannot operate after installing the rotor.
The practice of brush is very simple. As shown in Figure 2-9, a brush spring is bent from a copper wire with a diameter of 0.5 mm and good elasticity, and then two small brush pieces are cut from a copper sheet with a thickness of 0.5 mm, and welded on the spring according to the shape shown in the figure to make a pair of brushes for model motors.