A Life-Size FNaF Springtrap Animatronic That Actually Walks

The Five Nights at Freddy’s franchise is all about animatronic characters that have come to life, so it lends itself pretty naturally to animatronics projects in the real world. But building an animatronic on a man-sized scale is no small feat and the projects we’ve seen in the past have all been stationary. That makes them a bit less scary, so James Bruton used his robotics skills to build a life-size FNaF Springtrap animatronic that actually walks, just in time for Halloween.

Making bipedal humanoid robots that are capable of walking is still a massive challenge, which is why companies like Tesla and Boston Dynamics have garnered so much attention in recent years. But Bruton didn’t need his Springtrap animatronic to move with the grace and dexterity of a person, he just needed it to shuffle forward menacingly. While still difficult, that is a much easier challenge to overcome.

Bruton took his inspiration for the design from a little clockwork walking toy that uses a single actuator (a wound-up spring) to produce bipedal motion. It does that with a simple, but clever, mechanism that resembles a bicycle’s crankset. As it rotates, the mechanism lifts a leg and moves it forward, then back down. Next, it repeats that with the opposite side. Bruton’s Springtrap animatronic does the same thing, but with a big ODrive S1 motor instead of a spring. A Teensy 4.1 controls that motor’s integrated driver and a gear reduction increases the torque.

That works, but it is very unstable. The toy design didn’t scale very well, especially with the weight up high. To address that issue, Bruton used a whole pile of Dynamixel servos to actuate arms that can act as counterweights. In response to motion data coming from an IMU (Inertial Measurement Unit), the animatronic will move its arms to avoid falling over.

Several more servo motors (these controlled by a Teensy 3.6) handle the movement of the head, mouth, and eyes. Bruton can pilot the robot using his universal remote, which transmits via OrangeRX DSM2 modules.

The final step was to give Springtrap his skin, which Bruton crafted by hand from EVA foam. That’s a material popular among cosplayers, because it is easy to cut, form, and glue together. That then received a coat of yellow paint, with the appropriate weathering to create a sense of age.

Even if you’ve never played a game in the Five Nights at Freddy’s series, this would terrify you if you saw it coming towards you in the dark this Halloween.