Gravity Powered Walking LEGO Animals

Hey everyone, Jason here, today I’m excited to show you my latest LEGO creations, which are these gravity powered walking
animals. These are extremely simple mechanical
devices that are based off some traditional
wooden toys that I stumbled across online one night.
So how exactly do these work. We’ll take a look at the duck first, which
is basically just two hinged parts: the body and the front leg are rigidly connected and the rear leg is just allowed to swing freely on a hinge and if we pull the legs out you can see that it’s
just a basic Technic pin and a couple of Technic pieces, and that’s all there is to it. So we’ll take a closer look at this in action. I can actually take the side of the duck off and put the legs back in, and that way we can see exactly what’s going on as it walks. So there are three important
aspects to the design which make it all work together. The first is the curved feet, which allow the model to rock back and forth just like a rocking chair. The second is the swinging rear leg, and it’s actually important that it’s constrained in its path which is kind of built in to the design of the duck, but I’ll explain that a little bit more in the kangaroo model. Third is that the center of gravity of the
body needs to be at or just above the pivot point on the rear leg, and that’s so that when it rocks backwards onto the rear leg the body can tilt back, which actually kicks the front foot forward and that way when it comes back to the front it actually takes a step. So when you put it all together you get this cool little walking motion. So I’ll run it again and slow the video down and that way you can really see what’s going on. If we take a look at the kangaroo model, you can see that the legs are on either
side of the body which means there’s no built-in
constraints to where the legs can swing, and it just doesn’t work properly. You
need some way to constrain the legs so that the feet get planted in the
correct position for it to walk properly. So the way I
achieved that is by connecting the rear legs together using this Technic axle and it is allowed to swing through a gap at the bottom of the body. In that way the leg swing is constrained and the animal can walk properly. If you’d like to build either of these
models yourself I have created step-by-step building instructions which
you can find on my website at I’ll add a link in the
description and at the end of the video. One note, if you do build them yourself I am running them on
a piece of foam on top of a piece of cardboard, and that is because LEGO is extremely slippery. So without piece of foam or piece of cloth they’ll just slide more than walk down the slope. So that’s about all there is to it, I hope you enjoyed these models and the video. Thanks for watching, keep on building and I’ll see you next time.

100 thoughts on “Gravity Powered Walking LEGO Animals

  1. doesn't work don't build I was happy because I finished I bought foam and some of the bricks for nothing raged ??????

  2. I just built the duck and absolutely love it! Can't wait to surprise my daughters and my nephew with it! Thank you so much for the amazing build and easy to follow instructions!

  3. That's very good. In order to keep it as a lego pet, why not make a conveyor belt made to the speed of the model forced down by gravity, customization to the angle of the belt for the speed, and make it wide enough for the model to have some space for its own. Now let's see how far that little duckie can walk in a marathon.

  4. That walking duck is fascinating. It sort of acts like an escapement mechanism which slowly lowers the duck down the inclined surface.

  5. Alexis: This should be a real set, kids would love it. Like if you agree. So I will do the sale duck on Lego Digital Designer.

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