The CS:R NextGen Frame

Dry Fit & Assembly

 01/05/16, 01/20/16, 02/10/16, 07/23/18, 09/19/18

There is a lot of detail to assembling the NextGen Frame. What follows is an overview of the prep work for the frame.
There are separate sections, that you can jump to for the:
Frame Dry Fit
 05/16/20 Inner Core Assembly - the original PVC Inner Core has been replaced by the Tab Core - described separately (follow the link!).
Rear Door Assembly
Crash Test Dummy
Utility Arm Box Assembly
Utility Arm Motivators
Dome Motivator Assembly
Fixed Shoulder Hub Assembly  revised 09/19/18

First step is to familiarize yourself with all of the parts as you separate them from the panels they were machined from, removing the tabs and flash, if any. There is a set of .pdf files that describe all of the parts you can download here (with supplier information for extras, like the magnets). The .pdf files are organized & structured by the 'type' of part - ribs, rings, etc. The panels the parts are machined from do not share that organization!

Ring4, Core4, Utility Arm Ring (upper). Ring4 now has mounting holes for the Rockler bearing while the Core4 plate has holes for a dome motor and slip ring mount.

Core2 & Core3, Under Shoulder Rings, Door Ring (top), and Door Ring (middle)
 05/16/20 - The PVC Core 2,3,4 panels have been replaced by the Tab Core panels. The instructions that follow have not been updated. (follow the link!)

It turns out that Ring4 is symmetrical and can be installed upside down.

This is the MC variant of the Large Data Port. The lip on the upper part mates with the notch on Ring4.

here's a better view of the notch in ring4 shown above.
this feature should be facing down (into the body of the droid)
NOTE!! - you should hold off on installing your LDP until after you have mounted your skins to the frame. Otherwise the skin mount gets more complicated.

Left: top view of LDP installed on Ring4
Above: bottom view of LDP

Dome Motivator, door ring middle, rear door ring, inner door ribs

Ring1 Frame Bottom (the extra holes are for gluing to Ring0), Top Door Ring, Ankle Slice Panels, Utility Arm Box Ribs

Ring0 (also serves as the skirt bottom), Utility arm ring (lower). Rib slots end with Ring1 so it's not necessary to fill in the joints.
The two small parts are the rear door keys. See rear door frame assembly for more information.
[02/10/16] Do not Glue Ring0 in place until after you mount the skins. Having it removable will make the skin mounting easier!

Plates - shoulder (4), core mounting plates (1), and a rear door rib. The shoulder plates now have mounting holes for both 2-leg and 3-leg configurations. 
A Note about the Shoulder Plates shown above. The mounting holes are smaller, 1/8 inch, than what you will see in the assembly pictures. It was done to accommodate CS:R leg specifications that call for 1/2 inch bolts. But those were derived from designs done by builders of aluminum droids. Meanwhile there are lots of builders who used Dave Everett's Styrene Droid Plans. Dave used an entirely different bolt pattern. I chose to leave the decision up to the builder when I reduced the hole sizes. To follow the assembly instructions shown here you can drill out the holes at top/bottom/left/right to 1/4 inch and use 1/4-20 bolts to hold the plates together during dry fit and glue up. Leave drilling the remaining holes to when you are ready to mount legs.For more of the details on mounting legs, jump ahead to the section on Fixed Shoulder Hub assembly.

Ribs1 -
ankle slice rings and skin attachment points 

Ribs2 - and the second Core mounting plate.

Above: these are the skin attachment points. shown above in the Ribs1 panel they are not discussed here in the frame assembly.

Right: they are installed in the droid's "armpit" and are used to anchor the end joints of the 1/2 wrap engraved skins.

you'll find more information on the web pages that talk about mounting the engraved skins.

Here is how the skin attachment points work. Only one problem. They don't leave enough clearance around the Fixed Shoulder. [The large holes in the shoulder just happen to fit over the 1/4-20 bolts]

If you have already glued the attachment points in place you can use a dremel tool to grind off enough to give you clearance around the Fixed shoulders. Remember they get wrapped with a layer of .040, so you'll need that much on both top and bottom.

CS:R Shoulder Hub

NextGen Frame Utility Arm Box (.125 thick)

NextGen Frame Skirt Parts (.125 thick)

A couple of points to keep in mind about the parts the slots in the  rings look symmetrical but they are not! R2's panel spacing is different front to rear. The rings have a locater hole that marks the "FOD - front of Droid". Ring1 also carries a "Left of Droid" marker since the cutouts for the octagon ports are also not symmetrical. The Ribs have a similar hole that marks the "top of Droid". The Core panels are also not symmetrical since the guides the Core slides in on are on the inside edge of the ribs.

There is a lot of detail to assembling the NextGen Frame. What follows is an overview of the prep work for the frame.
There are separate sections, that you can jump to for the:
Frame Dry Fit
Inner Core Assembly - the original PVC Inner Core has been replaced by the Tab Core - described separately (follow the link!).
Rear Door Assembly
Crash Test Dummy
Utility Arm Box Assembly
Utility Arm Motivators
Dome Motivator Assembly
Fixed Shoulder Hub Assembly

Design Errors - 01/05/2016
As I was working on the instructions for installing the engraved skins I noticed two design errors in the Frame. They have been fixed in version 3. If you took delivery of a frame before 2016 then your frame has these problems. My apologies for not noticing sooner!

Ring1 (frame bottom) is cut to allow mounting of the Octagon Port. While the cut in the front lines up, the one in the rear does not!

I made the Assumption that the Rear Octagon Port was located in the same position as the front one, and simply reflected the cut from one side to the other. I should have checked.

To fix this problem, use your favorite cutting tool and follow the guide lines in the picture above. If you have already glued the Ring0 (skirt bottom) to Ring1 then use a Dremel with a sanding drum to reduce the thickness in the area shown.

Above: This is the space behind the Pocket Vents. The rib shown was notched for clearance. Just not enough.
Right: there are 4 ribs on the Ribs-1 panel, only 2 need to be notched but it was easier to notch all 4 on the panel.
Both ribs that need to be notched are on the Left hand side of the droid when viewed from either the Front, (Shown Above Left) or from the Rear (Shown Above Right)

Left: Again, use your favorite cutting tool to extend the notch upwards as shown.

Design Errors - 01/20/16
Someone told me a long long time ago to never tell visitors to your home "I have killed the cockroach in the kitchen." If you've never encountered cockroaches consider yourself lucky! They are among the sturdiest creatures in the world, difficult to kill and found in large numbers. The implication is that if you have one bug, it's a good chance that there are more. Sure enough, a second problem showed up

Malcolm M sent me photos of the middle door rib slots not lining up with the outer rib slots.

when I went back to the CAD design drawings I found my mistake.

you can just barely notice the difference in the rib position if you compare the middle of the rib to either end,
Now, I had assembled two rear doors and never noticed the problem. When I went and took a closer look at the rear door with skins on it I noticed that the center ring is bowed just a little. In practice, it's not enough to cause a problem. The CAD drawings have been fixed and all currently shipping frames have ribs with the slots in the correct places.

Once all of the parts are broken out and sorted here's what you should have

Ring 1 with FOD (front of Droid) and left of Droid markers

Ring 4 the LDP cutout serves as front of Droid marker

Ring 0 (this face has the slots for the skirt parts) the two oval cutouts are finger holes used to pop the rear panel open.
If you are not going to have a skirt simply turn the ring over and glue this face to ring 1.

From left to right: Utility Arm Ring Upper & Lower, Utility Arm Box Ribs (2), Rear Door Ring (note no FOD hole), Rear Door Ribs(2), Shoulder Ribs(4), Ankle Slice Ribs(4).

Note that the Utility Arm Box Ribs shown here have changed. See Below.
Left: In order to have a way to anchor the Utility Arm Box to the frame I've added holes and Thread-Serts (also called NutSerts) to the ribs. There will only be one on each side to correspond to the tip of the utility arm. To get to the screw you'll need to extend the arms and then reach in with a screwdriver to remove the screw. I'd use an Allen head since it will stay on the end of the driver when you go to insert the screw initially.
The NutSerts fit into a 1/4 inch hole and take an 8/32 screw.
Do Not Over Tighten the screw.
I got mine from they are
THREAD-SERT (ALUMINUM) Standard Thread Size: 8/32
YOU DO NOT HAVE TO BUY THESE> I Install them for you!
Thread-Serts/NutSerts are normally used where Blind Fasteners are required. Typically where you can't get to the back of the hole to hold a nut in position. To insert a Blind Fastener you usually need a special tool that pulls the fastener together expanding the barrel and locking it in place. However, that's not needed here! I simply insert the fastener in the plastic part and then compress it in a vise!

Under Shoulder Ring(2), Shoulder Plate(4)
Ankle Slice Ring(2), Ankle Slice Plate(2)

Rear Door Parts: Bottom Ring, Top Ring, Middle Ring(2), Inner Rib(2), Outer Rib(2)
For parts details on the Inner Core and the Utility Arm Box see the assembly details.

There is a lot of detail to assembling the NextGen Frame. What follows is an overview of the prep work for the frame.
There are separate sections, that you can jump to for the:
Frame Dry Fit
Inner Core Assembly - the original PVC Inner Core has been replaced by the Tab Core - described separately (follow the link!).
Rear Door Assembly
Crash Test Dummy
Utility Arm Box Assembly
Utility Arm Motivators
Dome Motivator Assembly
Fixed Shoulder Hub Assembly

Frame Preparation Work
Preparing the parts for assembly ahead of time rather than during the assembly process will make the assembly process go a little more smoothly. The material here should be considered suggestions as everyone has there own preferences. For all of the parts, removing them from the panels and removing the remaining edges of the tabs is a first step.

parts sometimes have a raised edge where the part was cut from the panel. there are two ways to remove it. sometimes I use the edge of a utility knife

and other times I use a file.

The rear door uses magnets to hold it in place. I get mine from K&J Magnetics. There are pockets in the mating door halves. The trick is to get the magnet polarities correctly when you are all done.

Take a moment to review the handling instructions on K&J's website.
It's easy to chip a magnet. Buy extra magnets as more than one flew off my workbench, attracted by a nearby piece of iron. If you drop one on the floor it may be difficult to locate!

the easiest way to separate a magnet from the stack is with a wiping/sliding motion. Make sure the pocket is clean and the magnet seats fully. If there's a problem pulling up on the stack will pop the magnet out. There's also a hole if you need to push from the other side.
Note: while you will see me installing 3 magnets in the door pockets I've determined that 3 is overkill and only 2 are needed. One at top, one at bottom.
Here's the 'trick' to making sure the magnets mate properly. stack a second magnet on top of the ones you just put in! They will mate by default.
Note: I had already put my rear door frame together before I realized it would be simpler to put the magnets in first. Do these steps before you assemble the door frame.
Now, press the mating door frame rib against the rear frame rib making sure the magnets seat into the pockets. separate the two pieces by sliding them apart otherwise the magnets will just come out again.
Once you've got mating magnets in both pieces you will have to be careful handling the parts around metal objects. Before a magnet files out of it's pocket put a drop of Cyanoacrylate adhesive (super glue) around the edge to hold them in place.

NextGen Frame Dry Fit
At this point, before starting to glue anything, you should build up the frame using masking tape to hold things together so you have a good idea of how the parts fit.
Tight fit is important to get good glue joints. Variations in the thickness of the plastic from suppliers sometimes makes the joints a little too tight. It's probably easier to make the slot slightly wider with a file than to reduce the thickness of the tab. Just don't over do it. If you run into the problem when trying to put ribs into slots on the rings [ie were there's an open end to the slot] try spreading the edges of the slot apart with a wedge (a large screw driver).

Above: Shoulder plates come in pairs. For now I'm using a 1/4-20 bolt to hold them together
Right: The plates fit into the Under Shoulder Rings

Assemble both sets

Then insert them into Ring4

Locate the 4 Shoulder Ribs. Install one on either side of the Under Shoulder Ring.

Since it's an end slot, put some tape on the rib to ring joint to hold the parts in place while you are doing the rest of the assembly.

Turn the assembly over. Making sure of the front of Droid orientation, insert the Shoulder Ribs into Ring1.

Now that the Frame is standing on it's own, we'll fill in all of the detail ribs, rings and panels.

At the front, install the two Utility Arm Ribs. Use tape to hold them in place at the top.

Install the Upper (with slots)  & Lower Utility Arm Rings.

Install the two Utility Arm Box Ribs. 

Note: there are now left/right versions with NutSerts installed.

Turn the frame around to the rear and put the two Rear Door Ribs in place. Note: there are now left/right versions. The Ribs have pockets for magnets that must face the door frame.

Add some tape to the bottom to hold the rim in place securely.
Note: the bottom slot has been made deeper to hold the rib.

Above: Insert the rear door ring.

Right: Turn the frame to one of the shoulders

Left: Insert the Ankle Slice Ribs using the top of Droid holes for orientation.

Insert the Ankle Slice Plate into the Ankle Slice Ring.
Left: Insert the Plate/Ring assembly into the Ankle Slice Ribs.

Frame Glue Up
While you can start your Frame Glue Up now, please read ahead to see what the rest of the assembly process involves. Because there are multiple sub-assemblies to the frame, and you'll have to wait for the glue to dry between assembly steps, if you have the shop space you might want to be assembling different parts at the same time.
For this frame, I've been using primarily the Weldon #3 (fast set, watery) cement. It relies on having a tight fit between the parts and is pulled into the joint by capillary action. Use with proper ventilation, or leave the area while the glue is drying.

Above: The Weldon #xx glue dries evaporates really quickly. Have your clamps and alignment bolts ready to go before you apply any glue.
Right: use 1/4 inch bolts to hold the plates in alignment.
The shoulder plates you get will not be drilled with full size holes. For hole alignment, to glue the plates together, you can drill the 4 holes that I have used for 1/4 inch bolts (top, bottom, left, right) while assembling the shoulder plates above. The remaining holes (see the parts.pdf drawing) are for: the legacy 3-leg fixed shoulders (the ones at 45 degrees - drill to 1/4 inch) or CS:R style legs (the ones at +/- 36 degrees - drill out to 1/2 inch).  For the CS:R legs Do NOT drill out BOTH holes. You only need to drill one set in each shoulder! Drilling both holes could weaken the shoulder plate as they are close together. You might want to wait till the frame is assembled to make sure you drill the correct set of holes!

Left: have your clamps pre-set for the thickness of the plates.

Above: I'm using a BIG applicator to make it easy to get a lot of glue applied quickly.

Yes, even though the slot is off center it is possible to put the shoulder plates in backwards. Make sure they fit between the rib slots!

Above: Once the glue dries you can turn the assembly over and add the Under Shoulder Rings (partial) and then glue them in place.
Right: turn the frame upside down again and now install the 4 shoulder ribs. Use the Under Shoulder Rings for alignment.

turn your frame so it's right side up with the front facing you.

install the utility arm ribs (note top of Droid holes in the ribs) they are trimmed on top to enable the utility arm box to slide out.

Turn the frame around so you are working on the back and install the rear door ribs. the magnets should be facing you. [ sorry, there are no magnets in this pix]

tape the bottom edges of the rear door frame to hold them in place.

when you the Weldon #3 on joints that are in the surface of the frame that's in contact with your workbench you should expect some leakage. make sure that the surface won't be harmed by the cement! [don't do this on your dining room table!]

At this point, the Frame Glue-Up and Dry Fit diverge. We won't put the rest of the Frame ribs & rings in place until we've test fit the sliders and the Inner Core.
The PVC Inner Core has been replaced by the Tab Core - described separately (follow the link!) - this section is obsolete.

Left: the Sliders on the bed of the 3D printer.
Above: sample Sliders

This is how the sliders fit in the Core PVC pipe.
The fit will be loose. That's OK since you need some clearance in order to be able to slide the Core in.

The slot in the slider needs to be a tight fit on the ribs in order to glue it in place. The inside corners of the channel are slightly rounded. Use a file to sharpen the corners of the slot.
Sliders are installed in a descending spiral pattern. This is done so that you need to engage only one slider at a time when you insert the Core. Note the red marker on the top of the rib for slider #1. There is a similar red marker on the Core pipe for that position.

Each of the first 6 sliders in the sequence shown to the right is 1/4 inch lower.

Slider #7 starts a new sequence (the front two ribs are shorter to allow clearance for the utility arm box)

The sliders are staggered in height, getting lower by 1/4 inch as you proceed around the top ring (first 6 sliders).

Above: Simply line up the two red markers and drop the Core into place.
Right: this Core was assembled with the dome motor on the Droid's Left side (your right in the picture). Turn the top Core plate over if you want it on the Droid's Right.
The next 4 pictures show the locations of the sliders with the core in place.  If the Core binds when you go to insert it simply identify the core that's too tight and sand down the surface slightly until it's easier to insert.
[02/10/16] DO NOT GLUE THE SLIDERS IN PLACE YET!!! Mounting the skins will change to fit of the core. Now that you know the process involved and have observed the slider locations with the skins off it will be easier to fit them after the skins are mounted . Wait until then to glue the sliders in!

With the fit of the sliders and the Inner Core tested, we now continue with the glue up of the rest of the Frame Ribs & Rings

Use tape to make sure the ribs are in close contact with the bottom shoulder rib

tape both front and back then glue the joints.

Left: insert the ankle ribs in the frame. Note the orientation of the ankle slice rib slots.
Above: It's your choice. you can assemble the ankle slice plates to the ankle slice rings and then insert the assembly into the frame, or you can insert the ankle slice rings into the frame and then put the ankle slice plates into position
Left: make sure the ankle slice plate is in good contact with the ankle slice ribs and then glue it in position.

Inner Core Assembly
The original PVC Inner Core has been replaced by the Tab Core - described separately (follow the link!) - this section is obsolete.
There are very few parts for the Core assembly. There are 3 Core circular rings (Core 4 - top, Core 3 - middle, Core 2 - bottom), 3 Core plates and 8 pieces of PVC pipe with an edge cut off. Before we start assembly, we'll take a moment to go over symmetry issues. The notches cut in the core rings line up with the ribs in the frame. While they are left/right symmetrical they are NOT front/back symmetrical. The Core rings, like the frame rings, have "Front of Droid" holes as markers. Here's an example!

Rings aligned

all of the notches line up

Rings deliberately mis-aligned

While some notches line up, some do NOT. It's a small amount and the PVC pipe will bend to fit, but then bind when inserted into the frame.

 First however a note about how the PVC pipe is cut.

Don't try cutting the PVC pipe without something to protect your hands! This was my first attempt at a fixture for cutting the pipe. However, PVC is tough stuff and I didn't like the results I was getting.

This was the fixture I eventually developed. I mounted a slitting saw on my CNC router and hand wrote G-code to cut the slots.
If you've decided to cut your own parts for the NextGen Frame let me know.
I can supply the PVC Core Pipes and the mating Sliders at nominal cost.

Start by inserting the Core Plates into the Core 4 and Core 3 rings. There are 4 slot locations. We supply 3 Plates, think about how you want to use the Core before you do the assembly. Turn the assembly upside down so that the top (Core 4) is face down on your work surface. This gives you a nice stable platform to start inserting PVC pipe into.

before you start the next step take a moment to check your ring alignment

make sure you can see BOTH "front of Droid" markers

Left & Above: put tape on the PVC pipe so that the cut edges stay slightly below the edges of the Core rings.

run a bead of cement around the edge of the PVC pipes in the Core 3 ring to hold them in place

transfer the tape to the Core 4 ring and then run a bead of cement on those joints as well. While you have the cement out you can also put a bead on the Core Panels where they join the Rings.

At this point jump ahead to the section labeled Crash Test Dummy. It describes the results when my frame fell off a 30in stool. As a consequence, I've changed my recommendation for the cements to use for gluing the PVC pipe sections in the Core.  I'm recommending plumbers 2 part PVC cement (Purple primer and Cement). Use it in place of the SciGrip #3 and #16 I used here. The other alternative would be SciGrip #10 but I don't have any experience with it.  The Crash Test Dummy section illustrates my technique for applying the cement. Your mileage may vary.

Once the glue is dry on the upper portion of the core insert, we'll add the lower ring. Since the bolts that hold on the Center Ankle protrude threw the frame bottom rings we'll space the lower core ring up 1 inch to provide clearance. The pvc pipe will act as 'legs' to provide the spacing.

Left: place the core upside down

Above: make a set of marks on the pvc pipes 1 inch up from the bottom

Above: mark all of the legs

Right: wrap tape around the pipe ends at your marks. The tape will hold the lower core ring in place while it's glued.

The reason we do this is to allow space under the core for the bolts that hold the center ankle in place.

Take a moment before gluing to verify the "front of Droid" holes line up!

then run a bead of glue around the joint.

Rear Door Dry Fit & Glue Up
Next we'll work on the Rear Door Frame Assembly. This section starts with pictures of the 1st generation prototype and then adds information on the door "keys" at the end. There's also some detail about the minor error in the middle door ribs.

Insert one of the Middle Door Rings in the slots of the two Middle Door Ribs.

Left: tape the Top & Bottom Door Rings to one of the Outer Door Ribs. Note the Top of Droid marker in the Rib. Then Tape the other Rib in place.

Above. Insert the previously assembled Middle Ribs & Middle Ring into the door frame. If you look closely you'll notice the middle ribs extend beyond the bottom of the door frame. 

Above: Insert the remaining Middle Door Rib into the Frame Assembly and tape in place.

Finished rear Door assembly. The tape up, done this way, is a little tedious. There is another way that relies on having the magnets already in place on the frame & door ribs.
Rear Door Alternate Assembly method.
First, note that I've bolted the ring0, skirt bottom, onto the bottom of the frame. with the magnets holding the two outside ribs in place, insert the top and bottom rings of the door frame and tape in position.
Then add the center ribs and rings.

Next, add just a drop of Weldon #16, the syrupy cement, to the joint on the rear edge

Above: Just a drop of glue.
Right: Turn the frame upside down and again, using just a drop of glue, glue the top door ring to the top edge of the door frame. Use just enough to hold the joint together and in alignment.

Once the glue has dries, carefully remove the door frame from the body and glue the joints with Weldon #3. Do Not use the #3 with the door in the frame or you won't be able to remove it!

Check Rear Door for fit in the Frame.
Adding the Door Keys. So far you've seen the door & the magnets to hold it in place. Here's how you'll get it open

Above: the door key's mount in two slots cut into the bottom door frame ring.
Right: There
are two oval holes cut into the bottom two frame rings. 

The holes are cut back from the edge of the frame to clear the skirt.To use, insert your finger up under the skirt, find the hole, reach threw and push back on the key. The bottom of the door will pop open.

Crash Test (Dummy)

My NextGen frame traveled into NYC for Maker Faire 2015 thanks to Paul Gentile who was working the FUBAR hackerspace booth and decided to host a booth for NYC area R2 builders. I wasn't paying much attention when I brought it back down to the basement workshop. I put it on top of a 30in stool with a padded top without  making sure it would be stable. Later in the evening I was upstairs when I heard a crash from the basement. Sure enough the frame had fallen off of the stool. Here's the post mortem on the crash.

Left: That's the 30in stool the frame fell from.

Above: The major damage was to the center core, where the glue joints to the pvc pipe failed. The frame joints were made using SciGrip #3 which is a solvent cement that fuses the two pieces into one. All of those frame joints, and the one's in the rear door were still intact.

Left: the bearings in the utility arm box unseated themselves. I never put the screw in that would hold it in place.

Above: Since the SciGrip cements I had available don't bond to the PVC pipe I'm going to try using Plumbers PVC Pipe cement.

Above: I tried it out on a spare piece of core using some shorter pieces of pipe. Be careful with the 'purple primer' it will stain just about anything it comes into contact with.

Right: as in the earlier assembly, the core is upside down. The flat surface insures the top edges will all be even. The tape keeps the pipe segments from rotating while glue is applied. Note the glass plates. They are to keep the work bench clean.

Working space is tight. Only glue two pieces at a time. I applied the primer and cement using Q-tips. Gently roll the Q-tip so the primer is squeezed out and runs down into the joint. I did 1/2 a pipe at a time then got more primer on the Q-tip for the second 1/2. Do two halves of one application, then do the second pipe. I applied primer twice to each pipe (it evaporates quickly) then followed up immediately with the clear cement. Then move onto the next pair of pipes.
When all 8 are glued let the glue harden overnight before going onto the next set of joints.

When I glued the bottom core plate on originally I used tape to create an edge for the core plate to rest against while the glue was setting. This time I used C-Clamps since I didn't think the tape would stand up to the primer and it would be difficult to clean up if the plate slipped while the glue was setting.

Utility Arm Box Assembly
Unlike the rest of the frame components, the Utility Arm Box is cut from .125 thick plastic since it's a functional component rather than a structural one. This section describes both the Arm Box Assembly, The Utility Arm Assembly and installing the Utility Arm Motivators (servos).
Arm Box Assembly

Left: The Arm Box consists of 2 side pieces, a center piece where the servo mounts are (with tabs), 2 top/bottom pieces (with notches), and 2 sets of  bearing mounts rings (one set with 3 holes, one set with just one hole in the middle).

Above: Start by putting the sides into one of the top/bottom pieces and (below left) taping it in place

with the tape holding the bottom in place insert the center servo mount. again tape the edges to hold it in place.

Tape the remaining top/bottom piece in place. Glue the arm box joints.

Above: The bearing mount plates with the three holes mount to the top & bottom rings of the arm box (note the matching 3 holes in the arm box top & bottom)

Right: file off any excess glue that might be on the inside edges of the joint. It will prevent the bearing rings from bonding to the top/bottom rings.

Above: top (& bottom bearing ring in position)

Right: I used spring clips to clamp the pieces together for gluing

bearing ring glued in position

the FR188-ZZ bearings fit snugly into the bearing rings.
Utility Arm Assembly & Mounting the LDP (lower part)

The utility arms have 3 pins, made from 3mm filament, to hold them in alignment while they are being glued together. If you are going to put a LED at the arm tip  extend the channel threw the tip.

The arms that I ship to customers are already drilled for the filament.

cut the pieces short as there's not much depth in the arm halves.

make sure all 3 pins line up and that the edges are together before you clamp them

Above: clamp the halves together, insert a 1/4 in shaft (or a bolt) to act as a fourth alignment point
Right: there's a hole for an anchor screw to hold the Utility arm in place but still permit some up/down adjustment
note! for better access move the hole

Cut a piece of Plastruct 1/4 in tubing to length
I've shown a tubing cutter here, the last time I tried mine it was too dull to cut the plastic. You can use a sharp knife!

Center the Utility arm and tighten the screw to hold in position.
DO NOT Over Tighten the screw.

The CS:R Large Data Port pieces have no visible means of Support. The three holes in the top/bottom arm box rings are for 4/40 screws that fit into tapped holes in the LDP bottom part.

Above: To make it easier to remove the screws I used allen head screws (and only 2 of them)
Right: arm box in the NextGen Frame with LDP upper  part in position. My version of the LDP has an extension on the rear edge that fits into the pocket in the underside of the top ring.
Utility Arm Motivators
My original design for the arm motivator called for the use of GT3 timing belt loops. I was going to 3D print utility arms with the GT3 sprocket attached and print a separate sprocket to be attached to one of the servo 'horns' supplied with the servo. It was going to be difficult to attach the sprocket to the horn and then there was still the problem of tensioning the timing belt. I was searching for sprockets, for a different application, when I came across sprockets that could be mounted directly onto a servo from Servo City. They make a line of .1277 in plain bore sprockets, servo sprockets and plastic chain. While SDP-SI also carries .1277 sprockets and chain, they do not have servo mount sprockets. I used an 18 tooth servo socket and a 20 tooth plain bore sprocket on the utility arm shaft (it's a TIGHT fit). It takes less than 6 in of chain to form the loop (it's sold in 1 ft increments).
While this approach looks good, there is one fatal flaw that I overlooked. The plastic chain is a 'snap-together' design, but it's only rated for a 4lb tension. Just about any obstacle is sufficient to cause the chain to pop open. given the design of the arm box, it's not possible to re-string the chain without removing the arm box from the droid.
[7/22/18] The Utility arm motivator project was dormant until I encountered a new product development. Servo City began offering MXL sprockets designed to attach directly to R/C servos. [They offer both Futaba and HiTec versions!]. While I was attempting to 3D print mating sprockets to attach to the Utility Arms my good friend PaulG (aka The Hobby Guy) came up with a more elegant solution! Simply drill out the R/C sprocket with a .25 drill! All that remained to do was to come up with a way to provide tension for the belt drive. What follows is the design that I've worked out,

Utility Arm Motivators V3.1
below: The Arm Box panel itself is mostly unchanged

Right: the changes were made to the servo mounting cutout and the bolt holes used to hold the servo in place.

above: The general assumption is that servos, under normal conditions, are more or less indestructible. When you work on your Arm Boxes, make sure you are over a work surface, this is what can happen when you drop one on the floor!

right: if this happens to you, you can get (from Hitec, in any case) replacement case parts to make repairs!

for those of you who read Mad Magazine (I haven't in a long time!) this step is usually the one that's accompanied by the Sproing! sound and parts flying all over the place! - fortunately that didn't happen!

To complete the repair, transfer the ball bearing to the replacement case lid and reverse the dis-assembly process.

Because we are going to mount using the top of the mounting ears you have to file off the piece of molded in  case reinforcement.
Above, Left & Right:
There's a lot of symmetry in the Arm Box parts. It's convenient to label the center piece where the servos mount with top/bottom designations and also note where the sprocket (top of servo) and body (bottom of servo) will be mounted.

take a moment to remove any rough edges in the servo mounting slots. You will only be using one slot, the one closest to the ball bearing,
Mounting the Servo Hardware
Left: for the next steps of the assembly a small bench vise will be helpful. You are going to be installing nylon lock nuts. You will find a 5/16 open end wrench helpful and an appropriate screwdriver. And a third hand if you don't have a vise!

NOTE: although Phillips head screws are shown here that's only because I have an assortment of them. Socket screws would be easier to install since the driver won't slip off of the head.

In addition to the Servos & Bearings, there are a number of small hardware parts that are needed for the assembly. I've made a list that you can download here: Parts List.

Install a #6-32 x 5/8 screw where shown. It will be the fixed anchor for the spring.
For this screw you can tighten the nut all the way.

Install a #6-32 x 5/8 screw in the single hole on the opposite end of the Servo. This will be the pivot for the Servo. Tighten all the way and then back off ~ 1/4 of a turn. The Servo should pivot freely.

Above: For the final screw you need to modify a #6-32 nylon nut by drilling out the threads. We'll be using it as a low friction pad. Use a #28 drill (#6 clearance). You will need 2, one for each Servo.
Right: hold the nut with a pair of pliers. If it 'grabs' on the drill bit it will hurt your fingers!

Install a #6-32 x 3/4 screw, with the drilled out nylon nut under the head, in the mounting hole the farthest away from the fixed anchor (the first one you installed). Tighten all the way and then back off ~ 1/4 of a turn. The Servo should pivot freely.
Install the spring between the two screws. I would suggest a small pair of needle nose pliers (jewelers pliers) for this step, Avoid unbending the loop at the end of the spring.

Do this step in a location where you'll be able to find the spring if it slips out of the pliers grasp and gets loose.
You might want to consider buying extra springs to cover that eventuality.

The Screw threads act as natural 'detentes' to hold the spring in place.

Not shown: When you have completed mounting your servos, you can attach the MXL sprockets to them.
Attaching Sprockets to Utility Arms

In order to use the MXL sprockets on the Utility Arms you need to drill out the servo mounting hole using a 1/4 in drill.
Right: I preferred to do that using my drill press to make sure the hole is square to the sprocket.

and pliers to keep my fingers attached to my hand!

Slide the sprocket onto the tubing and like up one of the holes in the center of the utility arm. It should be a tight fit.

using the sprocket as a guide, drill a hole into the utility arm using a #43 drill (tap drill for a #4 screw)

I'm using a #4-40 x 3/4 screw to keep the sprocket from rotating. You can tap the hole to cut threads into the plastic.
Installing Utility Arms in the Arm Box
There's a 'trick' to getting the utility arm with sprocket and shaft attached into the arm box.

First, remove the outer bearing. Second make sure the flange side of the inner bearing is facing the Utility Arm. Loop the drive belt over the servo sprocket, then rotate the arm so that the shaft enters the inner bearing by about 1/2 inch.
align the outer end of the shaft with the center of the  bearing hold and slide the shaft  into the hole. Replace the bearing and you are almost done! Screw two #6-32 x 1/4 screws into the ends of the tube to hold it in place.

Dome Motivator
Here's a look at what you need to do to set up the Dome Motivator. We'll also show a mounting method for the upper part of the LDP. Once we install the Rockler bearing it will be harder to mount the LDP so you may want to do it first.

There is a pocket cut into the underside of the top ring. The upper half of my 3D printed LDP has a matching extension on the back.

While you can drill threw the LDP's extension and the top ring and tap the holes in the ring so you can bolt the LDP upper half How often do you think you'll need to remove the LDP and/or replace it? I'd just glued mine in place.
NOTE!! - you should hold off on installing your LDP until after you have mounted your skins to the frame.
Otherwise the skin mount gets more complicated. Believe Me. It's easier to remove the Rockler!!!
I'd seen the Commando Eight's Instructions on "preparing" a Rockler in several Forum posting threads:
anybdy-know-size-of-the-long-screws-that-poke-through-the-rockler-and-up-to-dome  - post #3
possible-answer-to-rockler  -  post #5

As well as instructions for removing the Steel balls and replacing them with Acetal balls to make the bearing quieter.
So review that material before proceeding.
I also (will) have a web page for Rockler Bearing Prep.

With the Rockler prepared, bolt the Internal Gear of the Dome Motivator to the inner race. Extended length bolts give something for your Dome to mount to

With the internal gear installed you're ready to mount the Rockler to the Frame.

While there are 7 bolt holes for mounting the rockler, only 4 are reasonable to use.

Drill or Ream out the holes so that the 1/4 inch bolts are a smooth fit.

Then bolt the rockler bearing to the frame

Mount the Pololu Motor to the Core. Note Pololu's warning and use the correct length bolts. Mount the hub to the Spur Gear.

Insert the Core into your frame and verify the height of the top of the Internal Gear. Mine was about 3/4 inch.

With the Core removed from the frame, install the Spur Gear onto the motor shaft. Block it up while you tighten the setscrew so that it's on the flat of the motor shaft.

When you install the Core in the Frame make sure that the gear teeth line up properly. You can rotate the Rockler to do that.
DON'T Just Drop the Core and hope for the best!

Fixed Shoulder Hub
First, some observations about Legs, and the files that document them:

CS:L Legs had no mounting documentation.
See: Downloads->01-Official->CS-L Blueprints->Legs->Leg - Leg & Ankle.pdf
It's my understanding that they were considered internal details and left up to the individual builder.

Compare that to the corresponding CS:R documentation.
Downloads->01-Official->CS-R Blueprints->CSR PDF Drawings->CSR - PDF
look for the CSR LEG - 20140520.PDF file.
You will find there is now a bolt pattern for mounting the Legs.
But there is no documentation for the Shoulder Hub, or the corresponding shoulder plate that is part of the frame.

The closest that I could come to any part drawings is Jerry Greene's R2-R9 website.     Look for

I believe this is also the pattern used for the COM8 series of frames based on the pictures in the website gallery.

Finally, consider the fixed shoulder designs provided by Dave Everett for styrene droids.
Downloads->01-Official->Dave Everett Styrene Files
05 - Fixed 3 Leg
06 -

Where does that leave us when trying to design a Fixed Shoulder Hub?
My first pass at a fixed shoulder hub for the NextGen frame focused on the CS:R spec. It produced a shoulder hub that is similar to the Jag and Comm-8 hubs: A spacer with 4 bolt holes.

Unfortunately that ignores the fact that this is a styrene frame design and there are builders with Dave Everett versions of Droids using a different bolt mounting pattern.

Indeed there were folks ordering the CS:R NextGen Frame and my CS:L Legs. I think they were assuming that they would be able to use this shoulder hub to mount the legs to the frame.

Since I was providing a Fixed Shoulder Hub with the NextGen CS:R Frame "bundle" why not design it to serve both types of legs?

The image serves as a link to a 3D.pdf file.
Here is the result. It's a compromise in that the center hole in the shoulder hub is smaller than the mating hole in a CS:R leg. That had to be done to accommodate the holes for the  inner bolt pattern of the CS:L legs. To add strength to the design there is a piece of PVC pipe in the center of the hub.

This design works for CS:R legs since the risers are located on either side of the 1/2-inch bolt holes. It works for the CS:L Dave Everett & Media Conversions Legs since the 1/4 inch bolts also serve as spacers

The image serves as a link to a 3D.pdf file.

Here are the assembly details for the NextGen Fixed Shoulder Hub. You should also first review the instructions for my 3-Leg Fixed Shoulder. Finally, don't build your shoulder hub until you know what kind of leg you are going to use!
Revised 09/19/18 - be aware that for a CS:L droid the bolt length of the fixed shoulders was 2.25 in. it used a .25 in shoulder plate (later reduced to .22 in)
But the CS:R frame it uses a thicker shoulder plate at .375 (3/8) so it needs 2.5in bolts for the inner bolts.

Above: Parts in the panel plus the 2 pieces of PVC pipe.

Right: The left hand pair of  hub pieces have been turned over so you can see the countersunk holes. Note the single and double holes (circled) that denote which set the parts belong to.

Above: not all of the ribs are shown. The smaller rib is a filler so the skin has something to glue to. Make sure the pocket for the pipe is on the inside.
Right: typical parts placement.

Left: line up the two marker holes and fit the upper half of the hub in place.

Above: A rib has been left out so you can get a better view. The Pipe should just fit the space available.

Left: If the pipe is oversize, you can reduce it's height by rubbing it against a piece of sandpaper on a flat surface.

For CS:R Shoulder Hubs

Above: check the fit using 1/2 in bolts.
Right: Filler rib provides glue point for skins.
For Media Conversions (Dave Everett Styrene Droid) style shoulder hubs (read the note above again about bolt lengths!)

Left: start out with the alternating bolt/nut pattern. Make sure the bolts going into the frame are long enough to go threw the 3/8 shoulder plate.
Above: nuts on the outside serve to hold thing together.

Above: Once all of the hardware is in place you can add the filler rib

Right: don't forget you'll want to use a thread locker to make sure the nuts don't work themselves free.
For instructions on Wrapping the shoulder skins see the instructions for my 3-Leg Fixed Shoulder

Congratulations, you've got a completed CS:R ANH frame for your R2!

Front View with Utility Arm Box in place.

Utility Arm Box (only partially assembled) with a servo shown. 

Side (Shoulder) View

Rear View with Rear Door in place.

Rear View with Rear Door Removed.