My Sumos

For your viewing, here is my current site:
Exhume uses a Pololu Micro Dual Serial Control.
Both Expendable and Flaming D’nut use the Dual Serial Motor Control.


Those are some great robots! I especially like seeing all of the details of construction. How much range do you get on Expendable’s IR sensors? I’d like to know how building them that way compares to using something like the Sony IR distance sensors, which I have in general been quite happy with. Also, what kind of strategy does a robot like that use? Just drive straight toward the opponent, or try to sneak around to his back side or something? It seems like with those big flat red lips it would be hard to hide…

I don’t really know the maximum range of Expendable’s IR sensors. I found out that having an adjustable range is better. Our local events do not restrict competitors much, so we may get someone within a foot of the sumo ring’s egde. Because of that, I limit the range to about a foot. The adjustable voltage regulator normally comes out about 2.5 to 3 volts (that includes the 1.7 volt drop for the IR LED). It can go up to about 8 volts max, so there is plenty of spare range capability.

The big advantage of these sensors is the limited “Emission” angle of 15 degrees. Once I “see” the other robot, I know exactly were he is. This is particulaly handy when pushing on the other robot. My robots make minor drive changes so that the other robot is always exactly centered in front of my robot.

My standard strategy is to spin in place until the other robot is seen, then push forever. I can not identify the front from the rear of the other robot and I don’t have enough speed to do much else. There are normally six to eight starting alternatives that may be selected. Some of them include circling the other robot.

The big flat red lips were a croud and announcer favorite. The red feather boa did get caught in one of the wheels causing Expendable to loose one match. If I had won that match, I would have had to run against my son with “Sticky” and he would have killed poor Expendable.

The purpose of Expendable was to have some fun. Things were just getting too serious around here.

Rick Brooks

Well, it sounds like your robot worked pretty well and was a lot of fun - it’s best not to be too serious about these things. Maybe I’ll post a message about my own Sheepbot some time…

Wow, i was impressed with your robots, especially Mighty Man. I am very involved with Lego robotics, but I have not seen very many combat robots. I have a question abouth the Mighty Man: what is lego battery box under the RCX was for.

The battey boxes in Mighty Man are there just for weight. I’m affraid that Mighty Man is no longer competitive on a local basis. There are three Lego builder that have dominated the class recebtkt and I can see no way of upsetting that domination.


It’s been two years since I posted my web site and sumo projects on this forum. In that time I ran out of free server space, so had to get another site. So you can now see my projects on:
In the last major update of the site, I added several videos of a variety of sumo contests that I have entered.
We did replace the Pololu Dual Serial Motor controller in the 150 pound sumo with the Roboteq AX2500 (at $500, it is slightly more expensive that the Pololu product), but I am still using the Dual Serial Motor controllers in all of my other robots.

Rick Brooks

Hi Richard:

I really like the tutorial you made for the “ExSpurt Tires”. Are these available commercially? (Do you sell them?)

Thanks in advance,



Sorry, I don’t plan on selling any tires.

Actually, I am still working on the design. The tires on the web site still bounce a little when pushing hard. I’ve tried to reduce the bounce by making the tires thinner (less to flex). Keeping the outside diameter at one inch, the wheels are now up to .850" which give a tire thickness of .075". That seems to help, but I am still testing them. Also, they are a little harder to make, so I’m also working on the molding technique.

I have tried to describe the construction of the wheels and tires so that they could be duplicated by anyone with a lathe and a mill. If there is some area of construction that is not sufficiently described, please ask for specific details.

Robotics for me is all about learning skills. I have no experience with lathe/mill operation, but I’m picking it up as I work on pieces like the ExSpurt tires.

It is all a lot of fun.

Thanks for asking!


Thanks Richard!

If you want to make rubber more rigid, I would consider adding things to the mix. Remember also that you could use pure rubber (latex) and then vulcanize it by exposing the tire to smoke. I’ve seen locals do it in an artesanal fashion, and their results were amazing. You could also add some fibers to the matrix. Chop a few and mix them in.

All the best! -Migs

Very cool bots you have there on your site!

On May 1, 2008 ExSpurt won the Third Mini-Sumo Robotics Challenge at The University of Northern Iowa. You may watch the three hour video at this link:

Two days later, on May 3, 2008, ExSpurt won the Spring Chibotica 2008 Mini Sumo event. A new robot, Extra Parts, won the Racing Line Following event.

All of these robots still use the Pololu Dial Serial Motor Control to take the Serial Out from a Parallax Basic Stamp and create the PWM to drive the motors.

Extra Parts is just a collection of left over and previously used parts from my junk box. It was built two years ago but, until this contest, it could not follow a straight line. The PID didn’t stabilize it enough to keep it from oscillating off of the line. The breakthrough was replacing the MINH battery pack with LiPo cells to cut the mass of the robot. With less to control, the PID allowed stable running of the course. Extra Parts appears to run about the same speed as 3pi (but I have not yet measured the straight line speed). That brings up an obvious question: I wonder what 3pi could do with 2 LiPo cells instead of the four AA cells? And that leads to another question: Should we be hacking a product before it becomes available?

Rick Brooks


And congratulations.