The Fixed 3-Leg Shoulder Assembly

(Original Design)

First step is to separate all of the parts from the sheets they were machined from, remove the tabs and flash, if any.
Left: There are 24 shoulder risers and 4 shoulder plates
[8 if cut from .125 thick styrene]

below: there are 2 .040 edge strips (3 shown here)

Actual assembly starts with the shoulder plates and the shoulder risers.

Each shoulder plate has a locater hole that marks the
top of the droid's shoulder. while the plates have a
symmetry it's convenient to orient them all the same
direction.
test fit the shoulder risers in the plates.  once happy with
fit apply glue to top & bottom of risers and finish the
assembly.
make sure the locater holes are lined up

clamp while the glue dries. 4 clamps would be better
than the two shown.
At this point you've finished gluing two shoulder hubs.

For the next step we'll drill out the countersink holes that make the two identical hubs into left and right.

line up the hubs so that the locater holes are in the
same directions
mark the edges o (outer) - i (inner) - i - o

Transfer the marks from the edges to the surface
and then circle either the inner or outer set of holes
Turn the hubs over and do the same to the other side

Use a piece of 1/4 inch scrap styrene on top of the hub.
Drill the countersink till the head is below the surface

Using the scrap as a guide, set the drill press depth
gauge to the depth of the countersink
With the scrap now under the hub, drill out the
holes you marked on each side of the hubs.

The shoulder risers might stick up slightly. Since you
want all of the hub surface in contact sand them down.
left: I use a 1/4 sheet palm sander to sand my hubs

below: edges are now smooth.

Next steps will be to install the bolts, washers and nuts from both sides of the hubs and then glue on the edge strip.

install a pair of washers & nuts on each edge. Start from the inside.
If you don't have a Jr Jedi with small fingers to help
a pair of needle nose pliers can be useful.

Don't forget to use something to lock the nuts in place.
(Loctite is only a suggestion)

redo the marking for top, add a mark for bottom
add a third mark about 1/3 of the way around from
the bottom.

glue a piece of scrap styrene at the bottom point
to double the thickness where the edge joint will be
Wrap the edge strip around. It's deliberately oversize.
start in the middle of the double thick rib you just made.

glue the edge strip on up to the 1/3 point marked earlier.
put glue on both the edges and the ribs
Once the glue on the first 1/3 is set trim the end of the
edge strip so it fits tightly. glue the remaining 2/3 of the
edge striip in place.
the joint will be on the underside of the shoulder hub
and hidden behind the leg

I used a flat file to trim off the excess width on the edge.

It's been suggested that foil tape makes a good finish.
Shown here is a roll of tape used for sealing HVAC
joints.

Don't want to cut your own? You can try this parts source.

Congratulations, you've got a completed set of shoulder hubs for your R2!

Shown here is a mock up of a leg placed on the shoulder hub mounted on the frame
posed with a familiar friend.

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