The Comprehensive Guide to Building a Realistic R2-D2 Replica

BODY CONSTRUCTION

R2-D2 is defined by his unique dome, so that’s where we’ll start. Our styrene dome has two layers – inner and outer – and a base called the dome ring. The outer layer with the panels is laser-cut for us, but you’ll need to trim excess and cut the dome panels free from their retaining tabs.

TIP: Before you cut anything, label everything — many parts look similar once they’re all over the workbench. Also, use all the reference materials available on the Astromech.net wiki and forums. Read everything. Ask questions.

The dome base needs internal support, and a pair of floral rings from your local craft store work perfectly. For now, just trim them to fit in the bottom of the dome, on top of the dome ring. You’ll glue them later.

Mate the outer and inner dome and mark where you need to cut the holes for the 3 Holoprojectors. These can be stationary or servo-controlled. The front projector is what we see R2 use for the “Help me, Obi-Wan” hologram.

Next, cut out the holes for the Front Processor State Indicator (PSI), the Rear PSI, the Front Logic Displays, and the Rear Logic Displays.

Finally, make a cutout for the Magic Panel. This panel looks like it’s made of metal, but it lights up in some scenes and it opens in others. Because it does things that defy engineering, it has been dubbed “magic.”

Before you can glue the outer and inner dome together, you need to drill glue holes in the inner dome as shown, so you can flow solvent between the 2 layers.

Align the domes using the top, center dimple. Starting at the top of the dome and working downward, flow Weld-On #3 between the layers, through the holes you drilled. Clamp or tape in place until dry.

CAUTION: Weld-On is a solvent, not a glue; it works by actually melting the plastic parts together. It’s serious stuff, so wear gloves and eye protection, use good ventilation, and don’t get it on your skin. Weld-On #3 is water thin and near instant (use a syringe type applicator), while Weld-On #16 is thick and slower acting. Sometimes to prep parts I’ll use a brush or cotton swab with Weld-On #3 before I mate a part. If you’re not comfortable using Weld-On, there are other options; the forums are filled with advice on glues and cements to use.

Aluminum domes have a similar process, as they are 2-layer as well.

Another option is a single-layer, molded fiberglass dome from MARS Props, aka Austin Roghelia and Scott Murphy. All you need to do is mount the Radar Eye, Holoprojectors, Logic Displays, and PSIs, and then paint. If you want to see a complete R2 dome being built in only 2 days, the guys have an excellent video tutorial:

The Rockler Bearing connects the dome to the body frame and lets R2’s head spin 360 degrees. Years ago the club discovered that Rockler’s 17-3/8″ Lazy Susan bearing, which is used by woodworkers, happens to be a perfect fit for R2. Unfortunately it is loaded with grease, hard to turn, and noisy. By replacing the steel ball bearings with acetal bearings and cleaning and polishing the interior channels, the Rockler works beautifully.

TIP: The Rockler bearing isn’t cheap. Wait for a sale; they can be 50% off sometimes. You can also try similar-sized bearings, but the Rockler is consistent in quality, so it’s a known factor.

You’ll mount the outer ring of the Rockler bearing to R2’s Frame. The inner ring is what the Dome rests on. Drill matching holes in the Rockler, the Frame, and the Dome Ring. Do this before attaching the dome ring to the dome. When complete, the dome sits on bolts to hold it in place. Make a key mark, so you know which hole is for which mating hole on the dome ring.

When all the holes are drilled, you can now epoxy in the Dome Ring and the floral rings in the dome. Be generous with the epoxy as this will be the support for the whole dome.

You’re eventually going to make the dome panels operable, so you need to cut the inner dome to allow for that. For the “pie panels” on top, the inner lip’s top and sides should measure about 20mm, and its bottom, where the hinge goes, about 10mm, as shown here.

After cutting out all the panels and holes clean, gently sand the edges.

R2’s Radar Eye is the focal feature of R2’s “face.” If you compare movie to movie, that Radar Eye moves around quite a bit! Almost all builders will end up placing it by eye — pun intended. If it looks good to you, that’s where it goes. I placed mine in different locations for a week before settling on what looked good to me.

If desired, make a hole now in the dome underneath the radar lens, so later you can place sensors or a camera.

Following Frank Pirz’s instructions the Frame and the Skirt go together fast. It’s a slot A into slot B type design. Be sure to pay attention to orientation of the parts. Use Weld-On #3 to tack parts in place and then follow up with Weld-On #16 to add strength to the joints. You can flow Weld-On #3 between joints rather easily. The frame might seem a little flimsy but the skins will hold it all together.

Attach the skirt to the bottom of the frame. While the frame is hidden, the skirt is a visible component and will be painted later. Fill any gaps in the styrene joints with model putty or Bondo, and sand smooth.

The body has details that include the Large Data Port, Utility Arms, Data Ports, Coin Slots, Center Vents, Octagon Ports, Side Vents, Pocket Vents, and Coin Returns. Note that many of these names are not official, but rather came about because of what they seem to look like.

Before you attach the skin, test-mount the Rockler Bearing’s outer ring to the Frame. On the bearing’s inner ring, add upward guide bolts to match the holes in your Dome Ring and use nuts to adjust how the dome sits on the frame. You want enough of a gap to clear the frame and skins, but not too much so as to look awkward. Make sure the dome spins freely and the gap is even as it spins. R2 is coming to life!

Like the dome, the skins are also a 2-layer process. You can buy laser-cut skins or budget skins (scored lightly but you need to cut them out by hand), or download DIY plans to cut your own.

You’ll wrap R2’s frame with the first skin layer, check the fit, adjust, and let cure, and then repeat with the second layer. If you want the body doors to open, you need to cut them out before adding the second layer.

TIP: It might seem counterintuitive, but don’t cut the doors out before gluing the skin. It’ll make the skin flimsy and much harder to position and you’ll curse the day you did it. The skins are scored, so it’s just a light touch with a knife to get the doors out.

Tack the skin in place with Weld-On #3 and follow up with Weld-On #16. Secure the skins with straps, painter’s tape, or strong magnets, and let everything fully cure before moving on.

NOTE: Some builders have had better luck with glues instead of solvents when mounting the skins. The skins are thin, and too much solvent can cause ripples that need to be fixed later.

Once the skins are attached, trial-fit all your external components and adjust them if needed for final fit. For example, in the front of R2 are his two Utility Arms. If you’re going to make these arms move, they have a tendency to rub the skin as they arc outward. This can be fixed by sanding the backside of the arms at an angle. If you’re not making them movable, there’s a 3D-printed static arm and box set available in Astromech.net’s 3D file section.

Don’t glue any components in place yet.

We’re building a 3-legged R2, where his center foot is extended for easy cruising. In this mode, the left and right legs are at about a 36° angle, and that angle is set by the shoulder mounting plates you used in the frame. The shoulders are round at the top and have mounting bolts for the body on one side, and for the legs on the other.

Frank’s styrene legs incorporate the ankles and are extremely strong. The legs and shoulders bear all the stress of driving R2 around. In the early movies, when they used radio-controlled R2s you can sometimes see that they had a bar welded between his feet to strengthen the legs. Today our club-designed legs are stronger and need no additional support.

Like the body, the legs go together fast. Take your time, tack in place, and follow through and make sure all the joints have a good bond. When you complete the legs, fill any gaps with a plastic filler.

R2 will be driven by two Razor scooter 100W 24V motors, one in each foot. The drive system is probably the most challenging part of the build, but with a little patience you can do this in a simple workshop. I used the tools at my local makerspace, FUBAR Labs in New Jersey, to fabricate all the components.

The design calls for 2 wheels in each foot, driven by a chain. You’ll need to fabricate axles, attach the sprockets to the wheels, cut the chain to length, and assemble it all. This is a good rainy weekend project. For every part of the drive system, I made at least one spare, so if I ever need to replace a part I won’t have to start from scratch.

You can find more detail on the drive systems here.

The feet are covered with, of course, foot covers. This is where 3D printing meets styrene building. Frank’s foot shell design uses styrene for the flat sections and 3D printed half rounds for the curves under the battery boxes. Removable panels are held in place with magnets and allow access to the mechanicals in the foot. Often we think of 3D printing as a singular design choice, but in this case it’s combined with other materials to make a very practical and effective design.

Frank repeats this in the battery boxes. The flat components of the box are styrene, and the round sides are 3D printed. The battery box is strong and functional, with a removable rear and side panel that makes changing batteries very easy.

The motors actually extend into the battery boxes, but there’s still room for the batteries. Many builders put the batteries inside the body of R2. Instead, you’re going to use LiPo batteries, one in each battery box. Also mount the electronic motor controllers in the battery box. Then all you need to run up into the body is a low-voltage PWM signal and ground.

The center foot and ankle are next. The center foot has a swivel caster that allows R2 to move in any direction. The center ankle attaches to the middle of the skirt. The whole setup will let R2 turn in a very tight radius. This completes all the major body components.

For our R2 we’re keeping it simple: radio control for movement, Bluetooth audio for sound, a Teeces lighting system, and Pololu motor to turn the dome.

Connect your scooter motors to two Pololu 18v25 motor controllers, one in each battery box. You’re using two 11.1V 4000mAh LiPo batteries, again one in each battery box. This should give you several hours of run time. With this setup, 12 volts is plenty of power.

For the Dome Motivator, we’re using a 30:1 metal gearmotor 37Dx52L mm from Pololu, with the same 18v25 motor controller, and a Pololu 80mm×10mm wheel with high-traction sticky tire. This wheel will ride on the inside of the Rockler bearing to move the dome, using a spring mount to maintain tension. You could go with a gear drive here, but the wheel works fine and keeps it simple.

All 3 motor controllers can be connected to a typical R/C receiver. Drive and steering are on my right stick, and the dome control is on my left stick. If you have an R/C setup already, this is a great choice.

Since R2 can weigh in at 100+ pounds and a loose droid is never good thing around people, I suggest a 2.4GHz system with a failsafe that returns all controllers to neutral if signal is lost. You can buy these off-the-shelf at most R/C hobby suppliers.

NOTE: An alternative to a R/C setup is the ServoShock system which pairs a Sony PS3 game controller via Bluetooth (or USB) to a receiver module that has the same outputs as an R/C reciever. The ServoShock module can connect to 10 servos, has 17 digital outputs, and automatically returns to neutral if signal is lost. And it’s got the added benefit of an optional shield that plugs into Arduino; in the future you could leverage that for additional functionality. The PS3 controller works at a range of 10 to 20 meters; you’ll never be that far from R2 at an event, so range is more than adequate. A used PS3 controller is about $30 and the ServoShock module is $40, without the shield.

The optional shield has been out of stock recently, but the project is open source and I was able to order a shield PCB from OSHPark and build it myself from the documentation.

R2’s dome electronics as seen in the movies include 2 big round PSI lights, front and rear logic displays, and 3 holoprojectors that light up too. The easiest way to handle all of these is with the Teeces V3 Dome Lighting System available through the club. It’s an older system, but an easy DIY kit that includes an Arduino Pro Mini to run the lights. (Soldering the Teeces kit together is what led me to seek out FUBAR Labs, become interested in the whole Maker Movement, and create soldering kits to teach others how to solder. So, I am a little partial to this kit!)

Once the kit is built, mount the logic lights to your logic frames. The PSI mounts are a homebrew solution from the club using 1½” PVC pipe fittings from the local home superstore.

You need to power the Dome Motivator, your R/C receiver (or ServoShock unit), and the dome lights. The ESCs from Pololu provide an option for 5V out to receiver. Add another 3,000–4000mAh, 11.1V LiPo battery for the dome motor and controller. Connect it to the ESC and use the 5V out to power your receiver. For the lights in the dome, you could put a smaller battery inside the dome, but I prefer using a slip ring to move power from inside R2’s body up to the dome. Use a 24-wire slip ring with a slip ring adapter from fellow R2 Builder, Michael Erwin. This adapter uses a DB25 connector on each end to allow you to remove the dome easily. It also pairs wires to allow up to 2 amps of power per channel to be sent through the slip ring. Again, you don’t need it now, but it will be there when you’re ready for it.

TIP: Use R2’s doors to access the electronics so you don’t have to remove his dome all the time!

Additional electronics in the dome could include servos to move the holoprojectors (you can see my holo servos here) and to open panels, or accessories like the Life Form Scanner or Periscope that rise out of R2’s dome. You have prepped your dome for these, but you’ll tackle them at a later date. (There are 6 more movies due out — you have some time!)

If there are 3 things that make R2-D2 R2-D2, they’re his dome, his Radar Eye, and his sounds. R2’s chirps and beeps strike a chord in people. When you start showing off your R2, you’ll be asked if R2 can make certain specific sounds. Sounds that people love. You’ll be amazed how they remember these from their childhood. Of course the club has a whole library of R2 sounds. If you want to really dive deep, pick up the book The Sounds of Star Wars by J.W. Rinzler. It covers the sound design of the movies and comes with an audio player so you can hear the sounds as you read along.

The easiest way to add sound to your R2 is with a Bluetooth speaker and your smartphone. Download a soundboard app that you like. Add your R2 sounds to it and place your speaker inside of R2. Bluetooth speakers today are very powerful — my little speaker cost around $35 and is very loud, even in a crowd. (When time and money permit, you can upgrade: now I’m using a Bluetooth receiver and local audio amp with twin 100W speakers!)

Assemble the major components of your droid. Test all your electronics and the settings of your motor controllers. When it’s all to your liking, take it all apart again. It’s time to paint.

First, read everything you can on R2 color selection and paint techniques. You don’t need a professional spray gun or booth — you can use ordinary spray paints for plastic, from the local home superstore or auto parts store. Choose a dry and warm, not hot, day to paint, but don’t paint in the sun, it will make the paint dry too fast.

Which parts should be which color? Check the reference photos in the Club’s wiki and you’ll see that R2-D2, like any character, has changed his looks over the years. While the changes may not be as dramatic as, say, 1950s Elvis and 1970s Elvis, each movie has some differences. For example, in the original Star Wars film (Episode IV: A New Hope) R2-D2’s holoprojectors have a black ring around the edge, while in other episodes they’re all silver. The R2 we know from the original trilogy looks different in the “prequels” (and even more different in the Clone Wars animated series). There are dozens of details that change like this. Paint R2 to the scheme you’re happy with. Some builders mix it up. It is all your choice. I’ve never had a kid run up to R2, throw his arms around him, and say, “R2, your holoprojector is the wrong color.”

For white parts I went with a flat white and for R2’s signature “blurple” color (aka “Hypo Blue”), I alternated between metallic blue and gloss purple. While the blue coat was wet, I sprayed a quick dusting coat of purple. For the “aluminum”-colored parts I used Eastwood “Almost Chrome” spray paint. Do your research and test your colors. Some builders like to clear coat; I do not. Other builders have taken their R2 to the local automotive body shop to be painted; that works too.

For R2’s shoulder joints, instead of paint I used aluminum tape. The tape has a sharp, bright look that works with the other aluminum colors to make R2’s appearance pop.
The 4 battery cables (Foot Hoses) are made from braided faucet hoses I found in my local home improvement store. I used BrassCraft’s polymer braided flexible water supply hoses. I started with two 30″ hoses, cut them into 4 pieces, painted with bronze craft paint, and glued them into knurled resin knobs. You can use stainless steel braided hoses, but they’re more expensive and harder to cut.

The last detailing choice is weathering. I hate this conversation because I still cannot decide — I love the weathered R2s, but I want the pristine, ready-for-the-big-ceremony R2. Except, then there are times I want a weathered, just-back-from-battle R2. I might need to build a second droid.

You might be wondering how builders get the dome, which is painted, to look even more like milled aluminum. You want Rub and Buff, a wax paste with metal in it. You can find it at your local craft shop. A little dab can do a whole dome. It’s like a shoe polish. Once you use it though, you cannot paint over it. I opted not to use it yet. But you can add it anytime. Just search YouTube for techniques to apply it. It takes a lot of elbow grease, but it’s worth it.

Painting tips

• Prep all your parts. Make sure you clean them of any grease or mold release, sand them smooth if needed, and remove all dust. Your spray paint will only look as good as your preparation.
• No matter how you paint, use a top quality painter’s masking tape. It makes the difference.
• Primer is a good idea. It may not be strictly necessary for say, white Krylon on white styrene. But many metallic paints are paired with a special primer you should apply first, to reflect more light through the paint coat. And on 3D-printed parts, use several coats of a self-filling plastic primer to smooth the texture.
• Paint in several light coats — don’t try to paint it all at once.
• Make sure you use paints of the same chemical family. Most problems occur when builders mix enamel with acrylics without realizing it. Let everything cure as directed and don’t rush.

After all the paint is dry, you can begin final assembly of R2. Welcome to the fleet! You have joined an elite few who have a showable, operational droid. We have thousands of members, but there are less than 500 operational droids, and less than 200 screen-showable droids worldwide.