Who Knew Replicating a Functional BB-8 Would Be So Hard?
Roopinder Tara posted on March 24, 2016 |
Firefighter Ed Zarick has released the designs for a 3D printed, functioning and full-scale model of...

Most moviegoers leave the special effects to the professionals. Firefighter Ed Zarick, however, was not content with seeing BB-8 rolling around the silver screen of Star Wars: The Force Awakens. Instead, he had to build his own working replica of the iconic droid. As you might imagine, doing so was no easy task, as Zarick had to overcome a number of engineering hurdles to bring BB-8 to life. Fortunately for other fans of the film, he’s not only pulled it off, but Zarick has also made the project open source, providing all of the details for constructing his remote-controlled BB-8 bot online.

The completed BB-8 replica by Ed Zarick. (All images courtesy of Ed Zarick.)

Since BB-8 made its debut in the very first trailer for The Force Awakens, there have actually been numerous attempts to recreate it, most notably by a Facebook group called the BB-8 Builders Club. Inspired by the efforts of the group’s 10,000+ members, Zarick sought to improve upon their designs to make his own model of the droid as functional and accurate as possible. The end result is nothing short of amazing, filled with all of the flashing lights, whistling sounds, and even BB-8’s signature rolling movement that’s made him so popular among moviegoers. But how did he manage to get to this end result?

The outer shell for the head of the BB-8 replica was 3D printed in ABS plastic on a MakerBot Replicator 2X 3D printer.
The outer shell for the head of the BB-8 replica was 3D printed in ABS plastic on a MakerBot Replicator 2X 3D printer.

To begin with, Zarick was standing on the shoulders of giants, as the BB-8 Builders Club had already designed 3D-printable CAD files for building the bot’s head. When it came to making thisfloating dome, all he had to do was set his infill to 100 percent and click “print” so that one of his MakerBot Replicator 2X 3D printers could fabricate the parts in ABS plastic.The body, however, is a 20-in. polycarbonate sphere, sourced from California Quality Plastics and priced at roughly USD$500.

The mechanics of BB-8, housed within a polycarbonate sphere.
The mechanics of BB-8, housed within a polycarbonate sphere.

To those more interested in the interpersonal dynamics of (possible) Star Wars couple Rey and Finn, the mechanics of how BB-8 moves may not be fully appreciated at first, but, upon further consideration, it really is amazing to see a robot whose body rolls in every direction while its head moves with it. Attaching the head to the body, Zarick points out, is not the most difficult part of making BB-8 move. The dome-shaped head is simply connected to the body with magnets, one at the base of the dome and another attached to a column within the sphere below.

Zarick’s BB-8 replica moves with a single axel and counterweight.
Zarick’s BB-8 replica moves with a single axel and counterweight.

Zarick’s biggest contribution to the BB-8 project is the drive train, which is a simple and elegant solution to what could potentially be a complex problem. While other BB-8 builders have implemented a “hamster wheel” design, as Zarick calls it, for moving the bot, this builder has used a single axel with a counterweight. The hamster ball setup, he explains, would see a motor drive a set of wheels inside of the sphere, pushing the body the same way a hamster pilots a hamster ball.

In fact, this is how the Disney BB-8 toy designed by Sphero operates. Two wheels, attached to a hefty set of electronics, drive the small remote-controlled gizmo forward. A weight at the base keeps the ball level, while a mast, jutting out of the axel joining those two wheels, is connected to the head by magnets.Scaling that design up to the size of the actual BB-8, however, is much more difficult than one might think, according to Zarick. He says that there is too much weight for the hamster wheel setup to handle.

The mechanics of Zarick’s BB-8 replica in action.

When BB-8 made its first public appearance at Star Wars Celebration 2015 in Anaheim, California, ahead of the film’s release, Zarick was sure that he could see an invisible single axel driving within the body of the bot, with a counterweight hanging below it. At the other end of that weight is the magnet, attracting BB-8’s head to its body.

This whole design results in a system in which, as a motor spins the counterweight in one direction, the ball rolls in the other, with the head exactly opposite to the counterweight.In this way, Zarick’s system is much simpler than the hamster wheel setup pursued by other builders or even the Sphero toy. It also left him with plenty of room to embed lights within the sphere, without the risk of a robotic hamster-equivalent running them over.


Building BB-8’s Mechanics

The internal mechanics of Zarick’s BB-8 are made up of a handful of motors, mounts, bearings, shafts and pulleys. Just about everything else was custom milled in quarter-inch aluminum with the firefighter’s own CNC machine. To support the necessary weight to drive the BB-8 forward, he milled braces that run parallel to the main mast of the system. A spin motor at the center of the mast spins the pendulum one direction, so that the ball moves in the opposite direction. All of this is connected to the main carriage of the droid, another component Zarick cut from aluminum himself.

Many of the internal structural components of Zarick’s BB-8 were milled from aluminum.
Many of the internal structural components of Zarick’s BB-8 were milled from aluminum.

The head of BB-8 slides along its spherical body thanks to the counterweight pendulum within, but to really give it life, it needs to spin on its own. To provide BB-8 with a magnetic neck, a continuous servo motor is attached to the magnet within the droid’s body. As this motor rotates, so does the magnet, which causes BB-8’s head to rotate on the other side of its big polycarbonate body.


Remote-Controlled Puppetry

Anyone who’s been to the movies knows that Hollywood is full of deceit. Elijah Wood wasn’t really as short as he looked while playing Frodo, and the Ewoks were only actors in suits. This same Hollywood deception applies to BB-8. As it turns out, the droid that appeared on stage in Anaheim was not the same bot that won our hearts in Episode VII. In actuality, BB-8’s presence in the film was made possible by a variety of computer-generated special effects, static props and expert puppetry on the part of puppeteers Dave Chapman and Brian Herring. Though there were a few radio-controlled versions made for the set, the BB-8 that makes public appearances was not constructed until after the film was shot.

Zarick’s 3D-printed remote for his BB-8 replica, with three small buttons on the side for controlling BB-8’s sounds and an analog stick for controlling its motion.
Zarick’s 3D-printed remote for his BB-8 replica, with three small buttons on the side for controlling BB-8’s sounds and an analog stick for controlling its motion.

If you’re no puppeteer, the next best thing you can do is to create your own remote control. Where better to turn than the folks at Adafruit, who have more than enough DIY supplies for a given electronics project such as this. Zarick purchased an XBee Module with wire antenna for wireless data exchange. Hooked up to an Arduino Pro Mini, a lithium battery, a few other electronics adapters and a couple of analog sticks, the firefighter had himself the perfect recipe for a one-handed controller—his own open source Arduino code being the secret ingredient to make the whole thing work. All of these components were then housed within a 3D printed shell. Of course, BB-8 wouldn’t be complete without the ability to whistle and beep, code for which Zarick has linked with several buttons on his remote. 

Designing, building and programming the BB-8 replica—not to mention finessing the system to get the counterbalance set just right—took a total of about two months, or a few hundred hours of pure build time. Being a firefighter has its perks, other than saving people from burning buildings and cats from growing trees. Zarick’s schedule has him spending twenty-four hours on-duty and forty-eight hours off, giving him ample downtime between shifts to spend on his hobby.

Zarick with his completed BB-8 replica.
Zarick with his completed BB-8 replica.
The total cost of the project was somewhere around $3,000, though he admits that some of this was spent on parts that either broke or weren’t used in the final product. In actuality, the cost of building your own BB-8 might be closer to $1,500-2,000. Obviously, then, doing so is not for the faint of heart. And while you may not need to be a professional engineer, you do need to have a serious love of Star Wars.

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