This page will detail my attempt to build an R4 astromech droid. I call it an attempt, since its my first one and I'm really going off the beaten path for the materials and methods used. If it does work then I'll have a nifty page on how it was done in case anyone else cares to try. 

Current Status: Need to build an inner frame for the dome and need to create the rear panel for the dome before moving forward.

Posterboard! What? No. Really? Yes. Posterboard. R4-F7 will be my first droid. I'm on a really tight budget so I'm going to try building an R4 dome out of posterboard. I have plans to make it sturdy and whatnot, but it's still a work in progress.

But I'm getting ahead of myself. The droid I'm after is an R4 unit - prequel style, with a paint style likened to R4-T8 (the droid to the left). Prequel era R4 units seem to be different in at least two distinct ways that I can tell. First off, the holo projector protrudes from the dome "flush". With the original trilogy, R4 units had their holo projectors mounted in a box-like housing. Check out the picture of R4-M9 to the right. You can see the difference in how the holo projector is mounted between the two droids. The second difference is in the utility arms. In the original trilogy, R4 units had two, just like any other astromech. In the prequels, R4 units had one and a rectangular plate underneath. So in short, I'm after the look of the droid on the left, right down to the paint style. When I finally decided on what I wanted, I began work on the dome...

The R2 Builders club has a lot of measurements for astromechs already. Currently, the have domes and bodies that are 18.25" in diameter. From the research I did, that seems to be ballpark for the right size. I needed to build this dome in a conical shape by creating triangles that taper together along the length of the dome. An 18.25" diameter needed a 57.3" circumference. Unfortunately, posterboard only comes in 28" length sheets, so I needed two full sheets and a thin strip (1.3") from a third sheet.

Next, I got a little daring. I used an action figure of an R4 unit to measure how tall the dome was. I knew the base of the dome was 18.25", so the first thing I did was measure the base of the dome on the action figure. Once I had my ratio, I could calculate all the measurements of the full size droid, proportional to the action figure. Yes, I am taking for granted that the action figure is an accurate scale model of the ones in the movies.

So to create the conical shape, there are six large triangles about 14.25" high and 9.5" long at the base that curve around the dome. These don't lay flat. Then there are six smaller triangles that fill in the gaps as the larger triangles taper upwards. The very top of the "dome" is a hexagon with each side at 4.5" long.

I measured the triangles out on the posterboard, giving myself a 2.25" strip for the base of the dome (which may or may not remain, depending on how I end up mounting it to the body), and cut the triangles out. Then I taped the three posterboard cutouts together with duct tape.

Posterboard isn't very thick. If I were to make the dome out of one ply of posterboard, its going to be weak and flimsy. i decided to go with three ply of posterboard. But to give it that etched look, I wanted to cut out the panels. The picture above of R4-T8 doesn't really show etchings, and it seems like the designs are just painted on. However, someone once said something on the Astromech.net boards in that the droids we see buzzing past in the movies for maybe 2 seconds (like R4-T8) really only need to look good from a distance. All evidence shows that astromechs have nice, etched out panels in their domes. Others have made this conclusion, and I'm on board with it. I think the R4 should have nice etched out panels.

The first thing I do is work on the front panel, where the radar eye will go. Now here, I haven't reinvented the wheel. Previous makers of R4 units in the R2 Builders club have come up with the measurements. I am using the measurements as posted by Doug on Astromech.net. There is one etched panel for this side, in the shape of a trapezoid with a little "tail" at the bottom.

Front Panel (etching over Radar Eye)
distance in from side 3/8"
length of top of trapezoid 4.5"
height of trapezoid 2.25"
distance of trapezoid to eye 1/2"
width of "tail" at trapezoid bottom 1/2"
"etching" width 2mm

I use a large triangle template and cut out the trapezoid from the pattern. This gives me the outer trapezoid to trace on my existing dome triangles and my inner trapezoid to show the etched out panel. I'm doing two ply of this, leaving the etching down to the first ply so that it gives the illusion of being carved out.

I glue the two ply triangles to each other and the two ply trapezoids to each other. These will eventually be glued on to one of the triangles in the "first layer". Now I need to make the small triangles that will fill in the gaps when the large triangles taper together when the flat dome pattern is rolled up into its conical shape. Below are pictures of the new small triangles traced onto posterboard. Like the larger triangles, these will be two ply. Like the larger triangles, the smaller ones are six in number. two of the three sides are 14.25" long and the bottom side is 4.5" long

The etching pattern for these smaller triangles are the same for all six. Again, Doug from the R2 Builders club measured these out for his R4 unit so I went off his specs. the cut out makes two trapezoid shapes stacked one over the other, with a small 1/2" passage connecting the two (shown in the pictures below).

Small Triangle etchings (six in number)
distance in from side 3/8"
Bottom line of the 1st trapezoid 3 3/4"
Top line of the 2nd trapezoid 4"
Bottom line of the 2nd trapezoid 7 3/4"
width gap of passage between the two 1/2"
"etching" width 2mm

Since I had never done this before, I had a quandary over weather I should glue the panels to the flat pattern or roll the flat pattern into the dome and then glue the panels afterwards. Really, I just wanted to see my dome put together, so I rolled it up, inserting the smaller triangles as I went - using duct tape to hold each triangle to the next. I also cut out a hexagon (4.5" sides) and duct taped that on top. Right away I noticed that the flimsy posterboard was folding in on itself from the strain of the neighboring triangles and duct tape. I was hoping the 2 ply panels, once glued on, would give it more durability and keep it from buckling. 

R4-T8's side panel

Now I needed to start making the larger triangles for the remaining five panels. Using the paint pattern from the R4-T8 droid, I had to sort of use a combination of eyeballing and taking some proportional measurements from my action figure. There are four shapes within this paint pattern. The first is a bit of a trapezoid with a small rectangle cut out at the bottom. The second is that small, silver rectangle mounted on the trapezoid. The third shape is that small rectangle that is cut out of the bottom of the trapezoid. And the fourth shape is that .. well, I'm not sure what that, geometrically speaking. But its that box below the trapezoid.

For large panels to the right and left of the radar eye, shape #4 faces front of the dome. Four the large panels flanking the rear large triangle, shape #4 faces away from the front of the dome. The rear panel itself is a bit of a mystery, how I'm going to "etch" that out, but I'll get to that later. 

Large Side Triangle etches (four in number)
distance in from side 3/8"
Shape #1 length 4 1/16" with 1" X 1/2" rectangle cut out of bottom center
Shape #2 length 1" X 1/2" rectangle (2 ply glued over trapezoid for a raised look)
Shape #3 length 1" (minus 2mm) X 1/2" (minus 2mm) for etching 
Shape #4 length 4 1/8" long and 5.75" in from opposite triangle side. (1" in from center)
"etching" width 2mm

Now I have all but the rear panel cut out and glued together. These two ply shapes are ready to glue unto the dome. First, I glue the the outer triangle on, let it dry, the carefully insert any inner shape(s) so that its centered and I have that nice "etching" effect around the inner shape(s). This was not an exact science for me, and I found I had to take a razor to the shapes a lot. I'm hoping I can do some finishing work "in post". 

Yikes. I have two problems. The first is that I'm not sure what the paint job looks like on the very rear panel (opposite the radar eye) on this brand of R4 unit. To keep it canon, I'm loath to just make something up. But that's the least of my worries. Even with the full 3 ply of posterboard, I still have a buckling problem.

I'm going to need to build a frame for the inside to round out the dome and provide stability.