Single Servo Walker

20 Oct 2015

I've updated the design of the Single Servo Walker to make him walk better and also to make him easier to build.

The STL files are now included in this post! :D There are also detailed build instructions there.

The main updates are:

  • A front guard piece has been added to keep the legs moving where they should
  • The rear body has been lengthened to help with balance

As you can see in the latest video, this robot is able to walk forwards and turn using just one servo!! (The software needs more refinement as he turns quite aggressively at the moment!)

I'm still in love with this simple design. I guess I have a thing quirky robots! :) Will post again as he develops!


12 Oct 2015

After getting inspired by the amazing single-servo walking and rolling robots built by erco at, I decided to have a go at designing my own version of the single-servo walker.

This is my initial attempt at this design. I managed to get it to walk, but it took some fiddling around with weight distribution, etc... However, I learnt a lot from this build, and will be refining the design to make an updated version. (I'll post the 3D printable files to Thingiverse after I get it right! :) )

Here's a closer look at the four 3D-printed parts:


The parts are pretty simple. The front legs just snap in using the pegs. Also, note that the front legs are passive! They move back and forth using to gravity.

Here are some assembly photos so you can see how the parts fit together.


In the video, I'm just using a basic test program to get it to walk forwards.

It should be possible to get this robot to turn left and right as well! I'll update the software to demonstrate that soon. :D

The passive legs in this design are based on the passive legs in erco's single servo walker. See a video of erco's fantastic design on YouTube here:

I'm really impressed and amazed at these one servo walkers!! I'll be doing more work on my design (both software and hardware). I want to get it walker better, and also want to demonstrate turning!

Initial test of my single servo walker
Video of the current version in action! He can turn!

Here are the 3D-printed parts that you will need. The files are attached on this page.

OSW2-01 3D Printed Parts - Sml

And here is the complete set of parts used in this build, including non-3D printed parts.

OSW2-05 All Parts - Sml

It consists of:

  • The 5 3D-printed parts
  • 2 small O-rings
  • 1 9g Micro Servo (and its screws and servo horn)
  • 1 Mobile phone booster battery
  • 1 hacked USB cable that we can use as a power cable
  • 1 Arduino Micro on a small breadboard
  • 3 zip ties

Here are the assembly steps!

1. Attach the Servo to the Front Body

OSW2-06 Assembly01 - Attach Servo - Sml

Secure it with a zip tie.

2.  Attach the O-Rings to the Legs

OSW2-07 Assembly02 - Attach O-Rings - Sml

Super easy! :)

3. Attach the Legs to the Front Body

OSW2-08 Assembly03 - Attach Legs - Sml

They just snap onto the pegs!

4. Attach the Front Guard

OSW2-09 Assembly04 - Fit on Front Guard - Sml

It fits like this, and it is secured into position using 2 zip ties.

OSW2-10 Assembly05 - Secure Front Guard - Sml

5. Attach a Servo Horn onto the Rear Body

OSW2-11 Assembly06 - Attach Servo Horn - Sml

There are holes in the rear body for the screws.

6. Attach the Front and Back body sections

OSW2-12 Assembly07 - Attach Rear Body - Sml

Secure using the screw that goes into the servo axel.

You are done!

You will need to add the electronics, but I'll leave it to you to choose your controller and power source!


Submitted by Roxanna77 on Sun, 2015-10-11 14:02

Roxanna77's picture
Really nice build, love the 3d printed parts! What tool are you designing in? Another awesome write up too! Thanks!
Submitted by cevinius on Sun, 2015-10-11 20:26

cevinius's picture
@Rox, I did the designing using Blender. It's not the best tool for CAD stuff... but I'm getting used to it now! @bdk. Thanks. I'm fascinated with these 1 servo robots at the moment. Erco has a cool wheeled one too! I'll do more tweaks on this design and then share it with people. It's a fun and easy build!! :D
Submitted by CKRadmin_fh on Wed, 2015-10-14 07:14

CKRadmin_fh's picture
Love this little fella! Will try to make one when you get it right. Feel free to post the 3d print files here too if you want to.. I have added that possibility now.
Submitted by cevinius on Wed, 2015-10-14 08:30

cevinius's picture
I'll try to finish him off this weekend. I'll put the STLs here for sure. :D
Submitted by fhareide on Mon, 2015-10-19 12:08

fhareide's picture
Love the update! Just makes me want to build it even more. I also like that you are using the new features at the site and write such detailed building instructions! Thank you, Cev!
Submitted by cevinius on Wed, 2015-10-21 03:28

cevinius's picture
The 3D model feature is very cool, FH! :D I'll do more work on the software to show some interesting behaviours!
cevinius's picture
Last updated: 
19 Oct 2015 - 09:42
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