Due to the way all the modern LEGO gears are perfectly quarter-turn symmetrical, there doesn't appear to be any way to assembly 2 opposing gears such that I get a 2 perfectly parallel axles.

This image illustrates the problem:

enter image description here

When one gear it perfectly centered, the other gear is rotated half a tooth.

How can I get 2 opposing gear's axles to be perfectly parallel? Are there any older or special gears that are useful here? Otherwise, are there any good workarounds?

  • 1
    Do you have any restrictions on the maximum distance of the gears or similar? – Wrzlprmft Dec 22 '18 at 7:05
  • @Wrzlprmft No necessarily, just that they turn in opposite directions. – Alexander O'Mara Dec 22 '18 at 7:06

If you use a crown gear or bevel gear to connect your gears twice perpendicularly, they are exactly opposing each other, turn in opposite directions, and are parallel (if the respective axle is aligned to the coordinate system of the construction). Like with all gear-to-gear connections, you have a little wiggle room that may exceed half a tooth.

illustration of construction

If you want the opposing gears next to each other, you can use further gears attached to these (coming with yet more wiggle room).


You could use a belt system to get a perfect, parallel rotation. The chain links used in this video are #3711 and the gears appear to be the same as the ones shown in your example.

enter image description here

There doesn't seem to be an easy way to get the gears to turn in opposite directions without the use of gears (without that half tooth lag).

Two high friction, Technic rubber wheels, placed directly against each other will rotate almost perfectly. Although they might de-synchronise after many revolutions.

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