The Beest


After the Sphero Strandbeest I wanted to build a new smaller version with motors and remote control. The Sphero Strandbeest was only able to walk in a straight line and it was not an easy task to mod it into something else. I decided to leave it like it was and move on to this new project. It was something Roxanna and I had talked about making for a while and she had already made the GlowStrand and started on Deca. I therefore got some good ideas from her earlier and ongoing builds. When I started modelling The Beest I had already settled on mounting small yellow geared motors in modules of two legs to make the build modular. This was also something Roxanna had worked out during her prototyping, but I wanted to redesign everythng and make the build slightly different.

I started by setting up the correct measurements for the Theo Jansen linkage in Inventor . I had the Sphero Strandbeest in Inventor and used this model as a starting point for the legs measurement ratio as this is crucial for a smooth walk. I then started modelling the motor to exact measurements.

The motor model I made for precise modelling.

The final leg and motor enclosure design.

After a lot of small design changes and many failed prints and tests...

I ended up with a working design, and a box of "spare" parts.

The final design with a temporary middle part. I have still not decided how the middle part will look but since this design is modular now it is easy to swap it(4 nuts). I'm working on a middle part with a latch that opens by servo power but I haven't finished it yet. I will share the final middle as soon as I have finished designing it.

Check out the 3D print tab for build instructions and ask in the comments if something is unclear.

The first walk test
Leg parts w/support material162.21 KB
Leg parts147.34 KB
Frame and spur gears202.86 KB


For the legs I made a design to keep down the number of parts. This means that it is necessary with support material to print it. Download the zip file with support(I modelled it in Inventor) if you want to print without support material on your printer or the zip without support if you want to add the support material in your slicer software.

Step 1:

You need:

  • 3mm filament( or M3 bolts and nuts)
  • Scissors or pliers(to clean up parts)
  • M3 and M6 drill bits
  • Drill

Print the following quantity of parts:

  • 8 pcs - Arm large
  • 8 pcs - Arm medium
  • 8 pcs - Arm mini
  • 8 pcs - Arm small
  • 4 pcs - Major tri R
  • 4 pcs - Major tri L
  • 4 pcs - Minor tri R
  • 4 pcs - Minor tri L

Step 2:

Remove all support material and clean up the parts. Drill out all the holes. Small holes M3 and big holes M6.

Step 3:

Assemble each leg module. One module consists of six parts.

I used 3mm filament to fix the joints. Cut it to suitable lenghts, heat the end with a lighter and press it gently with the side of the lighter to make it into a rivet.

It is important to fix the large and medium arms on top so that the flat sides are facing outwards.

Make 8 sets of leg modules. Remember to use left and right parts on the same modules to get the filet on the outside.

Motor frames

You need:

  • M6 threaded rod
  • M6 nuts and lock nuts
  • M3 bolt and nuts
  • M6 ball bearings (Available here)
  • 2 geared motors with dual shaft
  • Wire
  • Soldering iron

Print the following quantity of parts:

  • 4 pcs - Spur gear large
  • 4 pcs - Spur gear small
  • 2 pcs - Minor frame part 1
  • 2 pcs - Minor frame part 2


Clean up the parts and drill out the holes. Solder wires onto the geared motor and feed them through the lower hole on the frame.

Add nuts like in the image below. Add a M3 bolt to each of the large gears and 4 nuts. Add ball bearings to all the big gears. Remember that when you fit the small gears to the motors the bolts on the large gears should be opposite of each other.

If you have problems with clearance on the gears drill out the top hole for the large gear with a M7 drill bit to and tighten it a bit higher up.


Main base

I have not finished the base yet but you can print the temporary base until it's done if you want to test it.


fhareide's picture
Last updated: 
30 Mar 2017 - 16:55
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