Lego Technic Subtractor Racer MOC

As the name implies, this MOC features a “subtractor mechanism”. If you don’t know what it is, a quick search online will answer your questions, show various versions and what it is used for, but in a nutshell, it allows tracked vehicles to take on curves very smoothly and be remotely controlled the same way as any regular RC car: one lever to go forward/backward, and another to steer (check the picture below for reference).

I decided to do this MOC because there are plenty of subtractor mechanism examples and variations on the internet, but not many MOCs actually taking advantage of it, so here’s my contribution.

The set 42095 was the primary source for parts, so you’re up to a good start if you have it, only needing additional liftarms, gears and some miscellaneous pieces.

Keep in mind it’s only one l-motor driving the vehicle as the second l-motor is dedicated to steering (unlike conventional tracked vehicles in which both motors push the vehicle). This means I had to reduce the motor-to-wheels gear ratio (which is 1,667:1) to give it some extra torque.

Control scheme:

Digital building instructions sample:

Photos:

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Keywords:

Lego Technic, MOC, AFOL, building instructions, toy, building blocks, racing, subtractor, tracked racer, tracks