The Senna wood frame plans are a tried and proven design that many builders have used for quite some time. The horizontal supports of the frame are comprised of a circular top and base plate using 3/4" plywood, and five rings (one full ring and four quarter rings), which serves as the "ribs" of R2-D2. The rings were made using 1/2" plywood and form an interlocking pattern with the vertical supports. There are ten of these vertical supports (also called "uprights") which also uses 1/2" plywood, and are strategically spaced around the frame. On both right and left sides of the frame, a vertical plate made from 3/4" plywood, serves as a support system for Artoo's legs. The uprights and plates are connected together via dado joints and the rings and uprights are connected with notch joints. Got all that? :)
Because the plans contained large circular drawings, printing the plans spanned on several 8.5" x 11" paper and then joining them like I did with the construction of the skins, would be very difficult. Therefore, I decided just to use the completed skins as a guide for the placement of the uprights and the spacing of the rings, keeping the Senna design in mind.
Materials & Tools:
Frame:
1 -3/4" x 4' x '8 Birch Plywood*
1 -1/2" x 4' x 8' Birch Plywood*
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Jig(s):
1 -1/4" x 4' x 4' MDF
1 - 1" x 2" x 8' Furring strip
1 - 2" x 4" x 4' Scrap Lumber
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1 -1 pound box 1 1/4" Deck Screws
1 -bottle of Wood Glue
Router and Router Table
1/2" Straight Router Bit
Hand Held Power Jig Saw
Assortment of Clamps
Table Saw
150 Grit Sandpaper
Hand held Power Drill
5/8" Countersink Drill Bit
1/8" Drill Bit
Pencil
Ruler
2 -Cans of Cheap Flat Black Spray Paint
* Having a full sized truck to carry those 4'x8' sheets of plywood from the Home Depot really helped! The amount of wood from these sheets is enough to make one frame and a set of legs (which will be covered later).
Cutting the top and base plates was a straight forward process using a makeshift jig for routing out circles. The jig was simply made by using a small section of MDF board with a hole on one end for the router and a hole on the opposite end, for the screw, which acted as a pivoting point.
After making sure both circles equaled exactly 18.0" in diameter, I then taped the completed skins around the bottom circle as shown:
Using the skins as a guide, the location of the 10 uprights were established, indicated by the red arrows. According to the plans, these locations were strategically placed where hinges would be installed for doors and around areas where they would not obstruct openings where greeblies such as center vents, utility arms, large data ports, etc. would be installed. In order for the coin returns, pocket vents, power couplings, and octagon ports to fit, "pockets" needed to be created. These areas were also marked for routing.
Cutting out the dadoes accurately to install the uprights was in need of jig, so I created another one out of MDF. The jig was nothing more than a board with a screw that attaches to the center of the circle which allowed it to rotate around. The jig also had one edge for the router to follow and second one that served as a stop. This made the process very simple: Rotate, Clamp, and Route.
In order for the uprights to align correctly, the top plate must be a mirrored copy (this excludes the routered pockets) of the bottom circle. To accomplish this, all I did was place the top circle on top of the completed bottom circle and used the routed area to mark the top circle.
Please note that the key word here is "mirror," and not duplicate! If all you did was duplicate another bottom base plate, you will definitely run into major alignment problems. All dadoes and pockets were routed 1/2" deep using a 1/2" straight bit.
Cutting the ten equally sized uprights was also a straight forward process using the table saw. According to the plans, the uprights varied in length, but since I was figuring out the spacing of the notches myself, I thought it would be more appropriate to cut the uprights to the correct length once its all put together. The side plates were also cut the same length as the uprights and using the ring cutting jig once again, two 18" diameter rings were cut.
Because the rings and uprights were designed to interlock each other, they both needed to be notched out at the right points. Again, using the base plate as a template, I placed the a ring on top of it and marked the routed sections. This was done again for the second ring.
Because the rings and uprights were designed to interlock each other, they both needed to be notched out at the right points. Again, using the base plate as a template, I placed the a ring on top of it and marked the routed sections. This was done again for the second ring.
To notch the rings, I then used the router table using another clamping jig. The jig was created from two pieces of furring strip screwed to a small 2" x 4" piece of lumber. A few clamps simply held the whole thing in place and ensured a straight alignment, but most of all, a safe cut.
The uprights also needed to be notched to interlock with the rings. Using the completed skins as a guide, I verified the locations of notches, which also determined the the spacing between the rings. The spacing was extremely important because the rings should not be placed where it would obstruct potential doors. Moroever, the rings should be placed at the right level to serve as a shelf or holder for the greeblies. Clear as mud? ..thought so.
Once again, I sought the help of the mighty router table to notch the uprights. For the sake of reproducibility, I taped and clamped a few of them together, and then routed them as one unit.
The last pair of items cut is called "shoulder wings." (see the picture below). These are attached to the side plates and act as a structural support to keep the skins cylindrically shaped. For a more specific information, please obtain a copy of the plans yourself through the R2 Builders Club as this article is not a step by step procedure.
PUTTING IT ALL TOGETHER
There were alot of modifications I had to make in order to be consistent with the wood plans such as shortening some of the uprights to accomodate the legs, utility arms and large data port. Also, a rectangular opening was cut out on the base plate to accomodate his front foot and a circular opening was cut out on the top plate to allow access to his droid "guts."
Most builders glue the frame, which makes a permanent bond, but I decided instead to use a mixture of 1 1/4" and 2" deck screws to hold everything in place. I went this route because just in case I messed something up along way, anything that needed replacement would be simple. To accept the screws without splitting the plywood layers, the frame was carefully predrilled and the screws were counter-sunk so it did not interfere with the skins.
...and here it is with a fresh coat of flat black paint! Ain't she a "beaut!"
After few weekends and many week nights of annoying the neighbors with the whining sound of power tools and the smell of freshly routed saw dust in the air, they finally got a break. ...that was until I started working on R2-D2's legs...muahaha!.
Coming up next... Leg Construction