Robo-Rooter- 3lb Combat Robot




About: robots, machining, vintage mopeds, and other silly things....

Robo-Rooter is my latest combat robot. It is a 3lb horizontal disk spinner.

Step 1: Design and Concept

Over the summer a friend was selling some of his unused combat robot parts and I bought one of his hubmotor disks from one of his old robots. I bought the disk before I had any real plans for building a robot to use it. I originally wanted to do a vertical spinner like the robot it used to be in, but with the disk at 6" dia the robot would have had to be comically large to have any stability. I thought about it some more and decided to do a horizontal spinner. After looking at manyotherhorizontalspinners i settled on the fairly generic design that many horizontal spinners share. Which is a semi triangular shape with weapon at the front and wheels at the back.

Now that I had the weapon and general design of the robot I could begin work on designing everything else. I first determined what components I wanted to use. I went with two Fingertech TinyESC's and 1000rpm motors with 2 1/4" wheels for drive because the combination is fast enough for a weaponed robot.  I decided to run the robot at 3s or 11.1 v because I already had 3s lipo batteries and a charger left over from another project.

To actually design the robot I used Autodesk Inventor. I first modeled out the area needed by each robot component and then figured out how small I could make the robot and still fit everything. The other challenge was keeping it under weight.  Designing it in a CAD program made everything easier than the other design method I use which is to physically lay out each component and then draw an outline on cardboard.

Step 2: Making the Robot

After I finalized the CAD model I sent the drawing of the frame out for water jetting. After wating a couple of weeks, they magically appeared in the mail. I then got to work. All I had to do was make two UHMW motor mounts. Which involved cutting to size and drilling eight holes into two blocks of UHMW so I don't have any fun pictures of the process. (although the end result looks nice)

I also don't have any pictures of wiring the robot because soldering requires two hands and my camera can't levitate.

After assembling and weighing everything I discovered that my robot was 1/2lb under weight. so I decided to upgrade the back armor from 1/32 titanium to 1/16" spring steel and wrap it around the sides to act as wheel guards. I also added fender washers to the wheel hubs to hold the wheels on better because during testing the wheels got ripped off when the robot hit stuff with the weapon. These additions brought the weight up to a respectable 2lb, 13oz

Test video of the weapon vs 1/4" thick steel. (please excuse the one handed driving)


1/16" thick titanium frame
3s 1000mah lipo battery
custom hubmotor disk weapon, spins at 6000rpm giving it a 109mph tip speed
2 wheel drive with 1000rpm motors, tinyESC's and 2 1/4" wheels

Step 3: More Information

Robo-Rooter will be competing in the 3lb weight class at North East Robotics Club's event at the Motorama Carshow Febuary 16-17th in Harrisburg PA. More info about how the robot did will be added to this Instructable post event.

For info about competing check out

The Builders Database This is the place where you can find out about and register for competitions

North East Robotics Club The premier robot combat event host in the North East

Combots/Robogames The largest events on the West Coast. They run weight classes from 1lb all the way up to 220lbs.

For parts check out

The Robot Market Place  They sell everything and anything related to robots for competitive 3-12lb kits and parts for robots up to 30lbs

FingerTech Robotics for 1-3lb robot parts and an awesome 1lb bot kit.

HobbyKing for cheap stuff from China



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    16 Discussions


    2 years ago

    Hello AlexHrn,

    I am planning on building a combat robot and I really like your design. If you are able to send me the CAD files I would really appreciate it.

    Thank you so much,



    2 years ago

    Hello AlexHrn,

    My team and I are planning to build a robot similar to this. Could you please upload the CAD files?



    3 years ago

    Is it easy to make


    3 years ago

    IS there anyway to pay someone to make one for us? I dont care if materials are cheap it is for a school project. I am a single mom and just cant do this. I need a front spinning weapon and love this model. my email is

    If willing or know where I could get one made or a kit to build it with all parts that would rock.

    Michele Gorman


    5 years ago

    how much was the total cost?

    I'm curious to see how the 1/16" Ti holds up when the disc gets hit by a high KE vertical spinner. With the shaft mounted so far out it might tear out of the Ti. Also, is that a dead shaft setup where the main part of the hubmotor spins too adding to the moment of inertia? If it is that's a great idea and an excellent way to get more out of the weight of the motor.

    Thom Kouwen

    5 years ago on Introduction

    Getting beat up so badly, how long do the bearings in the evil spin thing last?


    Reply 6 years ago on Introduction

    For this robot, I used a friend who has access to a water jet but in the past I've used Whyachi

    and I've heard good things about the Big Blue Saw


    6 years ago on Introduction

    I saw a version of this at the Dragon Con Robot Battles several years ago. I'm pretty sure the thing did so well in the light weights division that they even jumped into the heavy weights Free For All and won! I think I even have a video of it somewhere on my home computer.

    1 reply

    Reply 6 years ago on Introduction

    ok nvm it was a different bot in the FFA match: but I found a vid of the bot I saw: