Motor, assembled from kit #12 (without safety ring)

Difficulty level: 1 (the simplest, no special tools required)

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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. Insert the motor shaft through the holes in two 2×2 rotor pieces as shown*. Center the shaft.

    Rotor with shaft

  2. 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

  3. Attach double sided sticky pads to the magnets. It does not matter to which side you attach them as long as you use the same pole for all magnets. This is very important! If you do not use the same pole for all magnets your motor will not work.

    The easiest way to achieve it is to attach the pad to the top of the stack and then move top magnet to the bottom; after you attach all four pads your stack should look as shown. Do not remove the second liner from the pads yet.

    Single magnetFour magnets

    Neodymium magnets used in this motor are very strong! Be very careful – if they are allowed to fly to each other they may shatter.

  4. Attach all four magnets to the rotor. Try to be accurate and center them on each side. Make sure there is no gap between the plastic halves.

    Magnets on rotor

  5. If you assembled the motor properly and lubricated the axle this motor on 1.5 Volts battery may rotate with the speed up to 2600 RPM or even faster. This is really fast but may not be fast enough for the magnets to lose the adhesion and break the reed switch or fly off the rotor. However as a precaution you may add a safety ring that completely eliminates this possibility. This step is optional for your first experiments with the motor, but we strongly recommend adding the ring later.

    The ring fits tightly and requires some effort. After centering the ring squeeze the rotor halves together to make sure that there is no gap between them.

    Rotor with safety ring

  6. 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

    We strongly recommend lubricating the shaft ends. It allows the motor to run smoother and faster. You may use a drop of oil from your car dipstick, WD-40, or even vegetable oil.

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

    Remove insulation from wire tips

  8. Assemble electromagnet on the base plate.

    Electromagnet on base plate

  9. Attach the battery holder to the base plate.

    Battery holder on base plate

  10. Insert the battery and briefly connect electromagnet wires to the battery. If nothing happens switch the wires. With the correct connection electromagnet repels the permanent magnets and the rotor stops in the position shown. This is a perfect test for the electromagnet and the magnets orientation: rotate rotor quarter turn four times – if all permanent magnets are oriented properly rotor should always stay in the position shown.

    Electromagnet test

  11. 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

  12. 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
  13. 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

  14. Wind bare wire ends tightly around the reed switch contacts.

    Connect wires to reed switch

  15. You may tape the electromagnet wire that is connected to the reed switch to the side of the rotor stand (clear tape is shown).

    Taped wire

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! If it does not start on its own you may need to give it a slight push. Generally if your battery is fresh it should start rotating without the push if you find the correct position of the electromagnet and the magnets on the rotor sides are centered.

It spins fast!

If you have not done it already add the safety ring as shown in step 5.

You may glue bricks together and to the plate if you do not plan to disassemble it.

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

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

* Colors of the parts may vary.

You may try to build similar motor from the parts you could find yourself. However please be advised that the precision of our modifications on this motor kit matches the precision of original parts with tolerances up to +/-0.03 mm (this is 1/10 of human hair thickness!). You need such accuracy to achieve stated speed and power.

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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