I'm looking for the best way to gear down a Power Function XL.

I need to achieve a very slow output RPM (less than 1-2 RPM). I've tried a 625:1 gear (trough 40:8 gear). Can someone link to a well done gearbox like that? Moreover, how I can make an axle more resistant at high torque (I've tried with brick round 2x2).

  • Do you mean less than 1-2 RPM? As written, you're indicating greater than 1-2 RPM.
    – Nick2253
    Oct 21, 2014 at 18:50
  • 1
    Yeah, I mean <1-2RPM (or around).
    – Imlach
    Oct 21, 2014 at 19:10

2 Answers 2


The XL motor runs at approximately 220 RPM. Therefore, the following gearbox from the ELEC 201 class LEGO Design module from Rice should be sufficient:

LEGO 243:1 Gearbox


You can use a worm gear for a compact, high ratio gearbox. By putting a worm gear on the motor shaft and using it to drive a 24 tooth gear you can achieve a 24:1 reduction.

For example

For high torque applications you could use multiple parallel axles held together by gears or wheel hubs.

  • Sadly, a 24:1 doesn't resolve my problem. Maybe i can add some other gear using worm gear as the input.
    – Imlach
    Oct 22, 2014 at 18:18
  • Then by using two of these assemblies you can achieve 576:1 reduction. Or if that is too much, you can get another gear either before or after this setup for an additional 2:1 or 3:1 reduction.
    – zovits
    Oct 22, 2014 at 18:43

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