LEGO Technic 42099 X-Treme Off-Roader Power Functions mod with SBrick

The LEGO Technic 42099 4X4 X-treme Off-Roader is a very fun set to drive around, but it’s even better if we have company! I created this Power Functions mod to match the look and performance of the original.

This Power Functions mod uses 2 PF XL motors for driving, 1 PF Servo motor for steering, 2 SBricks for control, 4 PF lights and a PF AA battery box.

The aim of this modification was to create a Power Functions version of the original set. It could be done in many different ways even with better performance, but I wanted to create a demo set to compare the real-life abilities of the Powered Up and Power Functions motors and also to match their performance so they can be played together.

Because of the different base speed of the PU and PF XL motors I had to use a different gearing but they can be matched to be in a similar range. The two set of gears used for both motors can be set up the following way:

Powered Up ~550 RPM – 20T/12T + 16T/16T
Power Functions ~530 RPM – 20T/12T + 20T/12T

Powered Up ~330 RPM – 20T/12T + 12T/20T
Power Functions ~320 RPM – 20T/12T + 16T/16T

Powered Up ~200 RPM – 12T/20T + 16T/16T
Power Functions ~190 RPM – 20T/12T + 12T/20T


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