Mechanical Engineering

In late 2024, I started learning Blender, making projects and modeling designs I could print. For about a month I worked on which servo motors would be perfect for Spookey's legs, how the servos would fit in the legs, and what the weight of the printed parts and the components should be ideally. The first leg model I made was kind of rough, but it gave me a real starting point. Once I saw how the pieces actually fit together, it felt like, okay, this can actually turn into a working robot.

The first design of the legs was pretty simple. However, the shoes are designed to store FSR pressure sensors and HCSR04 Sensors in it to aid movements, balance, and obstacle detection.

The hip joint is the one of the most marvelous piece of mechanical tech I have worked on. It includes 6 parts including 2 servo motors. Hips have two rotational degrees of freedom: Pitch and roll.

The bottom piece is attached to the thigh motor, acting as part of the leg itself. A 65×65 bearing (with a 50×50 inner circumference) sits on top.
This same bearing fits perfectly, almost hugging the inside of the Top Part, creating a setup that allows smooth roll motion from Servo 1 while preventing any loose or unwanted yaw movement.
Servo 2 simply connects to the upper leg, handling the pitch movement.

Before I dive into the specific components, here’s an overview of Spookey’s current build.

Four 80 kg·cm torque servo motors: one dedicated to the knee and one to the ankle, with two additional servos at the hip joint providing pitch and roll rotation.
One FSR pressure sensor integrated into the sole. Among its functions, it detects whether the leg is in contact with the ground, serving as a boolean check before the opposite leg is lifted.
One HC-SR04 ultrasonic sensor mounted near the ankle to detect nearby obstacles at ground level.

Each leg consists of the following components:

All physical components of the body are 3D printed using standard PLA filament in either white or black. Each thigh, shin, and shoe weighs approximately 250 grams. Including all internal components and servos, a single leg has a total weight of about 1 kilogram.