Sumo 3K - Post 01 - The Origin

Every engineering project begins with a problem. For us, it arrived as a competition brief of an inter-school design-and-technology robotics challenge. The brief was simple - build a robot that pushes the opposing robot out of a circular arena, 1 to 1.5 metres in diameter. Weight limit: 3 kg.

That open-ended constraint is both exciting and terrifying. There are a hundred ways to build a combat robot. What we needed was a principled approach to making decisions — not just one that worked, but one that worked best within the constraints.























Before touching any hardware, we spent time thinking about what "winning" actually requires. To push an opponent out of the arena, the robot must:


  • Generate enough pushing force to overcome the opponent's resistance.

  • Maintain enough traction to not spin its own wheels while doing so.

  • Be controllable precisely enough to manoeuvre in a 1.5-metre ring.

  • Survive mechanical impacts without falling apart.

  • Do all of this within a 3 kg budget.


Each of these requirements maps directly to an engineering decision. 

  • Pushing force → motor torque. 

  • Traction → tyre material and drive configuration. 

  • Control → microcontroller and connectivity. 

  • Durability → chassis material and fastening method. 

  • Weight → materials selection and component choices.


The competition isn't about speed — it's about force and friction. A slower robot with more torque and grip will almost always beat a faster one with less traction. This framing shaped every design decision that followed.


We could have purchased a pre-made robot chassis kit and modified it, or we could have 3D printed using plastic material. But we wanted to think through and justify every component we were using. Building from scratch was the decision.


That decision meant sourcing individual components, coordinating with a fabricator for the metal chassis, actually soldering, writing the WiFi control firmware from scratch, and debugging. It was harder, but far more rewarding.


The next few posts document the complete build journey of Sumo 3K — the physics behind the design, the chassis fabrication, the electronics - including a circuit that failed and why, the WiFi firmware, and what we learned from the process.

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