I would like to have a trebuchet design at the Minifigure scale and simple enough for kids 10+ to build.

enter image description here

Note 1: The counter weight can be any non-LEGO heavy object.

Note 2: On top of the standard LEGO bricks, we have a lot of LEGO Technics and my kids are using them all the time. So, Technics are OK in the design.

  • 2
    I assume you're happy with a non-LEGO weight? Most elements are quite light unless you've got a few weight bricks lying around? Commented Jan 14, 2013 at 22:04
  • 1
    @Zhaph-BenDuguid Good point. I'm adding this to the question. Thanks!
    – pcantin
    Commented Jan 14, 2013 at 22:11
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    Does it need to be functional?
    – Joubarc
    Commented Jan 15, 2013 at 12:07
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    Just as a bit of information, minifig scale isn't terribly restrictive as a trebuchet can be relatively massive compared to people. en.wikipedia.org/wiki/…
    – jncraton
    Commented Jan 15, 2013 at 12:30
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    @Joubarc Off course it needs to work. We have a castle to attack.
    – pcantin
    Commented Jan 15, 2013 at 14:52

1 Answer 1


There are a number of designs on the net that I found with a simple search. Google image search produces images from the merely functional ones like the instructions linked here through to quite realistic looking ones that appear likely to work.

Lego Trebuchet

or this big one

big Lego Trebuchet

The key for a simple, easy to build one is to use wheels on the base. It will shake back and forth when fired which means the structure does not need to be as strong. If you don't do that then the base will need to be similar in size to the arm, as in both pictures above. I am a little surprised that there's so little bracing on the arms of these models, as you can make a much stronger model using a tension member at least on the top of the arm, if not below.

But with Lego the main issue will be the density of the weight. Lego doesn't do high density part, so most people use non-Lego weights. Since you're willing to do that it's easy - the first picture shown has a lead weight, which is why it's hard to see that there's a weight at all.

  • You could probably still pull off an official-pieces counterweight with the right size battery piece; there are several in Lego's history that are rather hefty and would adequately fill that role, and many of the physics training aid sets I've seen include them for the purposes of training motor-based construction functions. Commented Apr 1, 2022 at 13:40

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