I would like to use a subtractor in my next RC LEGO tank, as it enables the vehicle to turn on the move, as opposed to stopping and then turning.

Unfortunately, the subtractors I have tested so far cannot withstand the torque of heavy vehicles, which either causes the subtractor to break apart, or the differentials/gears to grind.

Does anyone know any subtractor designs which are able to deal with high tension/torque/stress levels so that enormous vehicles can still use them? 3kg-5kg tolerance would be ideal.

1 Answer 1


It sounds like you need a stronger differential.

Might I suggest this design by Nazgarot:

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If you make two, you can build a big and sturdy subtractor like this (probably customizing the gear ratios to your requirements, the right gearing could also remove the need for a PF switch):

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Here's a video of it in action:

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  • 3
    Very nice answer. You deserve to get the six-sided hat for this. :)
    – jncraton
    Commented Dec 13, 2018 at 2:58
  • Excellent. I've come back to this question like 4 times hoping someone had finally figured out a decent answer.
    – MindS1
    Commented Dec 13, 2018 at 15:06

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