Motor, assembled from kit #13

Difficulty level: 1 (simple, no special tools required)

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pdficon_smallKit contents: Kit #13, Kit #14

If you want to purchase one of these simple inexpensive kits, click here.

If you want to understand how they work, click here.

Read all instructions carefully and check the Safety Rules before you start!


  1. Glue together two 2×2 rotor pieces as shown*. Pay attention to their alignment.


  2. Insert the motor shaft through the holes. Short end of the shaft should stick out about 1/8” (3 mm) above the surface of the knobs.

    Rotor with shaft

  3. Add plastic sleeves (washers) to both ends of the shaft. They fit tightly and require some effort. You may put the sleeve on the table and push the shaft in with the negative end of the battery. Leave a small gap so the sleeves are slightly above the surface of the knobs.
    Left sleeveRight sleeve

    If you notice burrs on the plastic sleeves remove them with a sharp knife.

    BurrBurr removed

  4. Glue magnets to the rotor with the letter ‘S’ facing outside.

    Magnets on rotor

  5. If you want your rotor look better you may cut out the white glossy round labels that are provided and paste them to the magnets. It is recommended to use regular white glue or a glue stick on the labels for better results. This step is optional and may be done after you finish your motor.

    Magnets with labels

  6. Make the second rotor with two magnets if you plan to compare them during your experiments. This step is also optional and may be done later.

    Two rotors

  7. Assemble the motor base plate.

    Base plate assembly

  8. Assemble rotor on the base plate. Try to spin it by hand. If it does not spin freely you might need to squeeze blue bricks slightly together to push plastic shaft sleeves in. There should be a tiny gap between sleeves and inner sides of the bricks with holes.

    Rotor on base plate

  9. If you purchased the kit #14 with ready to use electromagnet, skip steps 7 – 10. Otherwise slide the 1×2 brick with two holes on the electromagnet core to the mark as shown.

    Electromagnet core

    If the brick is loose you may use super glue to prevent it from sliding while making the electromagnet.

    The position of the brick is important. It defines the length of the electromagnet. If it is too long it will not fit; if it is short the motor will be less powerful or will not work at all. Mark on the core should be OK but you may find more precise position by checking it on the board as shown below. Smaller gap makes faster and more powerful motor.

    Spin the rotor and make sure that none of the magnets hits the electromagnet!

    Check electromagnet position

  10. Measure at least 5” (13 cm) of the wire and fold it.

    Leave open end at least 5" (13 cm) long

  11. Tape the folded end and wind all the wire in one rotational direction (either clockwise or counterclockwise) moving back and forth along the core. All spool wire should be used.

    First wraps

  12. When there is about 5” (13 cm) of wire left, secure it with a cable tie.

    Assembled electromagnet

  13. Remove the insulation from the wire tips with fine sandpaper (included) or a sharp knife.

    Remove insulation from wire tips

  14. Assemble electromagnet on the base plate.

    Electromagnet on base plate

  15. Attach the battery holder to the base plate.

    Battery holder on base plate

  16. Insert the batteries and briefly connect electromagnet wires to the battery holder wires. If nothing happens switch the wires. With the correct connection electromagnet repels the permanent magnets and the rotor stops in the position shown.

    Electromagnet test

  17. After you found the correct connection trim red (positive) wire from the battery holder and corresponding electromagnet wire. Remove the insulation from the wire tips and twist them together. You may tack this connection under the battery holder.

    Connect positive (red) wire

  18. Fasten the reed switch to 1×2 brick with side holes using cable ties. Trim them with scissors.
    Attaching reed switch - step1Attaching reed switch - step2Attaching reed switch - step3
  19. Assemble the reed switch on the base plate. Trim the wires as necessary and remove at least 1” (2.5 cm) of insulation.

    Reed switch on base plate

  20. Form ZNR contacts as shown.

    Bent ZNR pins

  21. Wind bare wire ends tightly around the reed switch / ZNR contacts.

    Connected reed switch and ZNR

  22. Screw twist-on connectors. Do not over tighten as you may break the reed switch!

    Twist-on connectors

  23. If the head of the electromagnet is lower than the rotor axle you may add small 1×1 brick as shown to have a better alignment. It also provides additional support for the electromagnet.

    You may tape the electromagnet wire that is connected to the reed switch to the side of the rotor stand (clear tape is shown). Make sure the tape is below the axle hole.

    Taped wire and supported electromagnet

    Spin the rotor by hand. Make sure it does not hit the electromagnet, reed switch or wires. You should hear the click every time the magnet passes the reed switch.

    Your motor is ready to check. It should work on 1, 2, 3, or 4 batteries. On one battery it may require a slight push if your electromagnet is not aligned with the motor axle or the permanent magnets are not perfectly centered on the rotor.

  24. The included jumper wire allows you to experiment with 4 different voltage settings (1.5, 3, 4.5, and 6 V DC). You will need 4 AA size batteries.

    Insert bare ends of the jumper wire between the spring and plastic case to make a good contact and hold them in place.

    The following pictures show typical usage of the jumper wire for 1, 2, or 3 batteries.

    1.5 Volts:

    1.5 Volts

    3 Volts:

    3 Volts

    4.5 Volts:

    4.5 Volts

    Please note that some battery holders may have different connections inside. If your battery holder design is different you can still use the jumper wire in the same manner to get all 4 voltages, but you need to find appropriate connection points for each voltage setting.

  25. You may add speed control knob that allows changing the speed of the motor from maximum to full stop. It may also increase the rotational speed 10-25%.

    Assemble the speed control as shown and glue the magnet with the letter ‘S’ facing outside.

    Speed control knob

  26. Speed control knob should be located as shown below and it provides the following speed changes (positions are approximate, experiment with it yourself).

    Full stop:

    Full stop

    Slow speed:

    Slow speed

    Regular speed (same as without speed control knob):

    Regular speed

    Maximum speed (may be 15-20% faster than regular):

    Maximum speed

    Speed control magnet counteracts with the magnets on the rotor (that is why it is important to have the same pole to face a reed switch). It changes the gap between the reed switch contacts.

    The phenomenon of increasing the speed is based on making the gap smaller allowing the reed switch to work faster.

  27. If you plan to add a generator from the generator kit to your motor you need to add 1×2 plate under the motor shaft.

    Plate for generator experiments

    Using the speed control knob as a switch is possible but not advisable (removing one of the batteries is a better option).

    Here is the normal situation when the motor stops. There is no current going through the circuit.

    Speed control - correct stop

    However if you accidentally move the rotor it may also stop in this position:

    Speed control - incorrect stop

    In this case the reed switch is activated by the speed control magnet but the rotor magnets are out of reach. Motor looks like it is in a complete stop but in reality there is a big current going through the circuit (it may exceed 1 A on 4 batteries). This current will quickly deplete the batteries and can overheat and destroy the electromagnet.

    Be aware of this possible scenario if you use the speed control as a switch.

You may glue bricks together and to the base plate if you do not plan to disassemble it. Do not glue the speed control knob!

Visit our site at for principles of this motor operation, troubleshooting, speed measurement, and other experiments.

Enjoy your motor! We hope you had fun building it.

* Colors of the parts may vary.

This is not a Lego® product even if it contains Lego® bricks and plates. All warranties provided by Simple Motors.

LEGO® is a trademark of the LEGO Group of companies which does not sponsor, authorize or endorse this product or these assembly instructions.

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