While constructing the skeleton, this was the most challenging part of the project (by far). The time spent exploring possibilities that resulted in failure far outweighs the time I spent creating something that works.
But on the bright side, you can learn from my mistakes and skip straight to the good stuff. Let's get started!
Step 1: The Parts
You'll want all the vertebrae (including the upper cervical spine, which should already be completed), the ribs, the intervertebral discs, and the sternum/costal cartilages. You will also want to get a goose neck arm here...it's actually an iphone holder.
In addition you'll want a healthy supply of small and mid sized bungee cord, a couple of screws, and some heat shrink tubing, as described here.
Step 2: Prep the flexible arm
The arm is a mount for an iphone. When you get it it will have a clamp on one end as well as a rubberized coating (pictured).
Strip away the hardware clamp and rubberized coating, making sure to keep the washer and nut that brace the clamp to the arm (it will help anchor to the sacrum at the end).
Step 3: Create holes through the vertebral bodies, and widen the vertebral canals
Line up each disc with its corresponding vertebra and trace out a circle. After marking each side, use a dremel to drill a hole through each vertebral body. It should be large enough to permit a mid-sized bungee cord to pass through.
The disc itself should permit one of these cords, so it may need to be expanded with a drill bit.
The vertebral canal should be expanded with the dremel as necessary to allow for the goose neck arm to pass through, as pictured.
Continue to do this for all vertebrae, except for the C1, C2 which are already prepped during the upper cervical spine project.
At C2, direct the bit so that the cord can thread through the vertebral body and into the vertebral canal.
Step 4: Same thing for the sacrum
Bore a hole through the sacrum in such a way that the goose neck arm can be inserted through the sacrum (without the washer and nut in place). But make it small enough so that when the washer and nut are in place, the arm cannot be pulled back out.
Step 5: Prep the rib cage
Lay out the ribs with their corresponding vertebrae. You'll note that each rib makes contact with each vertebra at two places: the vertebral body and the transverse process.
Drill two holes into each side of the vertebra and two holes into each of the ribs to join these surfaces together.
The floating ribs are not pictured here, but you should be doing the same thing for them as well.
Note that the holes exit at the articulation points (the flat surfaces that interface with the ribs). You'll want the corresponding rib surfaces to also have holes drilled in them as pictured:
Continue with this until all true ribs are mounted to the vertebrae.
Step 6: Secure the sternum to the first ribs
Little to no movement is permitted at the junction of the first rib (and it's helpful to have a stable frame), so the next step is to anchor the first ribs to the sternum.
Drill pilot holes through the ribs and cartilage, anchoring them with a couple screws, as pictured.
Step 7: Thread the sacrum, discs, and vertebrae (with ribs) and disks onto the arm and bungee, starting at the skull.
There is a large ball and socket on one end of the arm, so you've got to keep that at the top and work your way down.
Note that there is a brief adjustment to be made to the cervical spine (Step 8 below)
Once you have it all together, it will look like something out of Aliens.
Step 8: Secure the cervical spine to the thoracic spine
From the previous upper cervical spine project, you have two bungees that run into the vertebral artery foramen, as shown here.
in order to better stabilize the cervical spine, readjust these to run through all of the transverse foramen of the cervical spine.
Drill a hole into the transverse process of T1 and use it as a new anchor point. Click on the picture below to have an expanded version of the image.
Step 9: Use heat shrink tubing to secure the ribs to the sternum
Heat shrink tubing is crazy stuff. Cut a little more than you need and make sure that you have your ends lined up appropriately. L2 here was just heated with a heat gun, and L3 is about to be.
Step 10: Secure the floating ribs
In order to keep the floating ribs from jutting out in odd ways, secure them with a strand of small bungee cord that doubles back around the ribs and anchors to the spine, as pictured here.
Step 11: Stabilize the spinous processses
Drill holes through each of the spinous processes and attach them one by one in series. Each hole will have two strings running through it. While a bit tedious, I found that this was a crucial step to keep the spine stable--unsurprising since this essentially duplicates the interspinous/supraspinous ligaments.
Step 12: Give the skeleton a convenient handle for carrying around.
It's helpful to be able to suspend the skeleton upright. Drill a hole into the skull and tie a large bungee to the top of the goose-neck arm. Thread this (along with the medium bungee that connects to the vertebral bodies) through the hole, pull it taught, and tie it to a hook. You now have a convenient way to display your skeleton.
This is a challenging and occasionally tedious portion of the project, but the end result is something unique. After completing the spine and the rib cage, you'll find that the upper extremity is a breeze.
Next time: the shoulder
By Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body, Gray's Anatomy, Plate 112, Public Domain