Let's Make Robots!

4P - Quadruped prototype

moves around

4P is a small quadruped robot designed to teach more complex mobility functions with the use of inverse kinematics and stabilization algorithms.


The concept behind 4P is that it has to be build with the resource of a CNC and some other basic tools and be cheap enough to be used as a disposable platform for teaching and learning. Based on the original design we arrived at the following specifications:

  • 3mm Acrylic parts
  • 12 mini servos for 3DOF per leg
  • small arduino based board
  • light weight battery (lithium or equivalent)
  • RF communication for debug and basic sensor feedback

It is still at a very early design stage, since we are working on another major project, but we are happy with our development so far to share it with the community.

leg movement



Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

I noticed you said "mini servos" above. That and the blue colour in the graphics makes me feel you are thinking of using 9g servos (SG90).  While they may hold up the robot with all legs helping it stand up, if you do use 9g servos, I doubt you will get much speed out of it, and may not be happy with the outcome.

Checkout OddBot's description of his first build of his Chopsticks robot. He tried 9G servos at first.

They are cheap ($1 to $3 each) and they are indeed fine for some jobs. It is going to depend mostly on the robot's total weight. It won't be able to carry much (or any) extra load.

—Of course that may be moot if the servos being coloured blue was just coincidence.


A Side Story: No "I" in "Team"...  Reminds of job I had a number of years ago... One of the bosses (a fellow Scot and a lad I could joke with...) used that phrase, that 'there is no I in TEAM'...

I looked pensive as though I were thinking that over, and said, "No I in TEAM? ——Oh, I is not in yer team...???  So that being the case, why are ya makin' me wear this damned TEAM button...?" and made a show of taking it off. Another boss was nearby and did not think that the least bit funny.

My boss called me to his desk later and said, "I'm supposed to be giving you a talk about team-spirit an all that...  You know I'm not going to, so instead, let's go have a coffee...  I'll put it on expenses."

9G servos were in fact used for modeling because they are fairly common standard, but we know their limitations. However we do want to use them in the less stressfull parts of the leg (hence the simulations in 3D), so probably we will be using 2 or  even 3 diferent types of servos per leg (different in torque but not in shape). I will check the OddBot version to see his solution.

That is why is important that we share this design early so it can be discussed as we progress. 

Liked your story too. "Oh, I is not in yer team???" that just cracked me...


Ok, so far this is just a "concept" advertisement from some company. You entered this as a Robot -Work in Progress, so I want to see robot parts and construction happening, ok?

  I notice you keep saying "We", so are you this company? Are you building one, or what is the story? One reply said you are "trying to make the mechanics work", so I for one would like to see that...

So far it just looks like spam, so this is your chance to explain

         ----- (before I vote for it to be considered "spam" to be deleted :-)  Even though we are a hobbiest group, there is nothing really wrong with a commercial venture as long as you let us watch you building it as you go...

I am all for good graphics, but

[Begins Chanting:] "I want a robot." — "I want a robot."  — "I want a robot." — ................... (chanting fades in the distance.)

Hello Dan M

I'm the other part of the We.

I'm the guy responsible for the mechanical part of the process and usually I don't cut any part before triple checking it in 3D.

I think it's ok if the first interactions are all about 3D Cad graphics before we fire up the cnc and start assembling the 4P.

Hello Dan.

The whole idea behind 4P is to design and build a cheap platform for quadruped movement which will be open source, that means you can have the plans for free and that is why we started this Robot Project under development. Because it is just that, a robot platform under development.

The term "we" is because  I'm not working alone on this project, which is just one of our open source projects, and is not fair to say I'm doing it all. "There is no I in team". 

This post here for the community has also the purpose of making us work harder not to disappoint people like you, that really wants to see this become a reality. Peer pressure you might say. 

DroneTech is a startup, and I presented it already in the appropriate area. (http://letsmakerobots.com/node/33226)

The tl;dr; version:

We are a team, doing a robot project which will be fully open source, which wanted to share the full development from design phase to production with this community which has inspired me from the start to enter the robot world.


Very nice looking platform, it would be great if it was printable too!

Hi Ossipee

3D Print will not be forgoten like MarvinPT said but we are in a very early functional design, trying to make the mechanics  work before starting to shrink/replace the structure with the final designs.

We will try to keep the robot updated.

Thank You

Thank you. It's at a very early design stage, 3D printing will not be forgoten. Now we are aiming at CNC cut because is what we have at our place to prototype, but I believe that most of the parts are 3D print compatible so I'm not leaving that off the table.