Disney Tech on a DIY Budget

People who want to get into robotics face some pretty high hurdles that often discourage them before they even tighten their first bolt. For starters, complex robots are very expensive. They require actuators, sensors, and computing platforms for operation that can easily cost tens of thousands of dollars. Beyond the cost, there is also a lot of expertise that goes into building a robot. Experience in software engineering, mechanical engineering, electronics, and complex mathematics is required, for instance.

Kayden Knapik is a budding robotics engineer who doesn’t have a big budget or extensive background knowledge in the area. Yet he still is determined to build a BDX droid like the ones that roam around Disney parks. Copying Disney’s work was too difficult and costly, so Knapik came up with another approach. Using his methods, he saved many thousands of dollars and greatly simplified the build to make it more approachable.

Instead of relying on exotic industrial hardware, Knapik built his robot around a set of 16 Robstride quasi-direct drive motors. These actuators offered a better balance between cost, durability, and performance, while still delivering enough torque to support a fully walking bipedal machine. The complete motor setup cost around $2,800, dramatically less than the estimated $7,500 Disney reportedly spends on actuators alone for its own BDX platform.

The robot’s onboard computer is an NVIDIA Jetson Orin Nano, the same portable AI computer used in Disney’s version. Combined with an inertial measurement unit and built-in joint encoders, the system continuously monitors balance, orientation, and motor position in real time. Power comes from a standard 40-volt lithium-ion lawn mower battery, chosen because it was affordable, widely available, and safer than assembling a custom battery pack.

Most of the chassis was 3D printed from PETG plastic with high infill settings to improve strength. But the robot quickly exposed the limits of plastic construction. During testing, the powerful hip motors repeatedly shattered the hip roll joints. To solve the issue, Knapik redesigned the stressed components and upgraded them to CNC-machined aluminum parts.

Another major challenge is teaching the robot to walk. To simplify this task, Knapik let the computer figure out how to do it on its own. He used reinforcement learning in simulation software, including NVIDIA Isaac Lab and MuJoCo. Inside the virtual environment, the robot performed millions of training attempts while being rewarded for staying upright and moving forward. The simulations also included randomized friction, mass changes, and motor delays so the trained AI could better survive the transition from simulation to the real world.

The finished droid can walk, turn, and express emotion using moving antennas, lights, and sound effects. Knapik has made the entire project open source, so you can build a BDX droid of your own. If the price tag is still too high for your tastes, hang in there a little longer. In the future, Knapik plans to create a much smaller version that can be built for under $400.