THE MYSTERIOUS BACKPACK
01/16/18- I've looked at lots of pictures of Beru Sejin's backpack
thingie-- many from models and toys-- and judging from the variety,
it looks like nobody really knows exactly what it looks like! Some
are interpretations with features that appear to match those partially
visible in the production photo above and screen caps of the show,
and some take liberties that look cool but don't match anything
from the show that I've seen... so in a sense, they're all approximations!
Everyone seems to agree that it's covered by a transparent plastic
shell, with what look like insect wings at the bottom. Underneath
that, there's an insect-like abdomen, and a thorax with a radial
pattern: Vid captures from the show corroborate that. The part that's
open to speculation is the top part, or "head": The show
doesn't give any clear views of it. If it's a copy of parts from
or the actual Gumonga puppet, it doesn't necessarily follow that
it's meant to be Gumonga with parts decorated the same way (with
eyes). [For what it's worth, the creature Gumonga that attacks the
Ultra-Keibitai squad is human-sized, so would be flyspeck-sized
when mounted on the giant sized Beru Seijin. In fact, the wings
and lack of Gumonga's segmented legs suggests that it's supposed
to be different. It's possible that they needed something
to put there, and used the basic body shape of Gumonga because it
was easier than constructing something new from scratch (I've done
stuff like that before). They modified it with lights and who knows
So what does this mean? For me, not much! I've already accepted
that I'm making an approximation so I can embrace the notion of
doing what I think looks good.
The obvious question is... what is it, and why does Beru Seijin
have such a contraption stuck to its back? Only its designers know
for sure, but I see it as a good place to hide electronics. Maybe
the designers did too?
Hiding Electronics: For my purposes, the backpack needed
to be hollow and lightweight so the electronics, battery, and wiring
could be hidden inside. The battery needed to be fairly easy to
access. The backpack should be removeable so I could work on it
separately. It should be as lightweight as possible to avoid making
the doll more top-heavy and so it could be securely held in place
by a pair of neodymium magnets (I'd installed a matching pair of
magnets in the suit).
As the design evolved, I decided that it should be just a cover
for the circuit board, battery and wiring: Those components were
all lightweight and could be safely dangled within the cover by
the wiring. There wasn't any benefit in securing the components
to the backpack shell. If the backpack were to separate from the
back, the total weight pulling at the wires would be much greater
than the components alone; there would be more "give"
if the components were dangling inside. It also made the backpack
shell a totally separate assembly that could be worked on by itself.
Two wires from the neck lights came from the shoulder of the body
and terminated with an ultra-micro female socket; the male plug
was soldered to pin 11 of the circuit board. Four thin wires came
from the neck/head and were soldered to the Beetle circuit board
(eyes- pin 9, cheeks- pin 10) to make the head w/circuit board separate
from the body. An ultra-micro female socket was soldered to the
circuit board to get power from a lightweight 3.7v 150mAh Lipo battery.
The Backpack Shell: There were a number of ways to make
a lightweight shell. A slush-cast resin casting would have been
the most detailed, but would also require a fair amount of work.
I didn't have enough molding compound to do this (it's fairly large),
so I chose an easier way: Worbla. The shell was designed to be four
pieces: The baseplate (with magnets to secure to the back), the
head, thorax, and abdomen. The center thorax would be glued to the
baseplate, and the head and abdomen shells would slide into it,
each secured by magnets to the thorax. The removeable upper/head
shell would allow easy access to the circuit board and the removeable
abdomen shell would allow easy access to the battery.
The sketch (top) is a to-size template for
the baseplate. The polymer clay forms were sculpted using the
baseplate for size and shape, then used to heat-shape the black
Worbla. The thorax (midsection) disintegrated while removing it
from the Worbla.
Polymer clay forms were made of the three parts and the Worbla
was heat-shaped around them. I didn't spend much time sculpting
details in polyclay-- Worbla captures even less detail than vacuforming
styrene. I considered sculpting the details in epoxy putty on the
shaped Worbla, knowing that this would make the shells heavier.
However, I reasoned that it wasn't necessary since the shells would
be covered by an outer transparent shell: Since the sculpted 3D
effect would be obscured by the cover, details could be simulated
The LEDs are mounted on the inside of the
shell, visible through drilled holes. They look like sharp points
of light: I didn't diffuse them, although in retrospect, it probably
would have looked better. At first, they were blindingly bright.
I changed the resistor, but they were still too bright. Painting
over them helped dim them a bit.
The backpack lights were relatively straightforward: four SMD
LEDs wired in parallel with a resistor on an ultra micro plug set
soldered to the battery power of the circuit board. The only difficulty
was that three of the four were positioned in the thorax, but the
fourth LED needed to be positioned in the head section. I could
have used a separate plug with the LED installed in the head section,
but that would have been a hassle. Since both sections would be
covered by a transparent shell, I "cheated" and added a finger extension
to the thorax, reaching over the head section.
I did a very basic chestnut paint job on
the backpack. I liked the look of black Worbla, but most models/toys
paint it a fleshy beige/brown color, so I followed their lead
(it's loosely in the tradition of the Alien movies' chestburster,
minus the gore).
The Transparent Shell: The transparent shell was a pain-in-the-ass
to make. I had some transparent Worbla so I was determined to use
that. First of all, transparent Worbla isn't like black Worbla at
all. Besides the name, the only similarity is that they're both
thermoplastics, bendy, and relatively tear resistant. However, it's
nearly impossible to work, bare-handed. It requires a painfully
high temperature to work, and it cools (and becomes unworkable)
in a fraction of the time of black Worbla. I was totally unsuccessful
in my attempts to form an acceptable transparent shell of the backpack
by hand. The only part that was able to do was the lower wing; I'd
cut a separate piece of transparent Worbla for it and only needed
to form it with a curvature.
I then used my vacuformer to shape the head/thorax section. The
entire head/thorax/abdomen was slightly too long for my vacuforming
area, so I left out the abdomen, which would have needed a new form
with wings anyway. Even with vacuforming, the clear Worbla shell
wasn't quite what I'd hoped for. I may not have heated it enough,
but it failed to pull under the edges as cleanly as styrene.
Nevertheless, it had captured the main contours and was usable
(it didn't fit quite as well after I did some slight reshaping of
the black Worbla for the lighting). I glued the wing section to
the shell; unfortunately, the seam between the two pieces is obvious
and probably would have been better vacuformed as as single piece
with clear PET plastic.
I THINK WE'RE DONE?
01/21/18- It's gratifying when I finally get to show staged pics
of the completed project: It's taken 6 pages to get to where my
other articles start on page 1! That proves it's much easier and
faster to press the "Buy" button than it is to DIY (especially since
I omit article updates about deciding whether to buy, waiting for
the package to arrive, and unboxing pics).
The antenna were the last thing I installed and were one of many
things that I couldn't figure out how to make to my satisfaction.
The pics don't show it, but they're thin tubes of clear wire insulation
filled with a coil of wire removed from the core of a guitar string.
They were the only thing I could think of that had a repeating pattern
that were tiny enough to fit inside. I wanted to fill the tubes
with tiny spheres, but I didn't have any small enough to fit inside
the tubes. Cylinders would have been even better, but same problem...
and how would I adjust their positions within the tubes?
One of the great things about DIY is that there are usually many
different ways to do things, including the obvious (painted rings
on a clear tube) and solutions not yet though of (hey, I just remembered
that I have some really, really tiny jewelry beads...). When you're
doing it for yourself, it's not just about doing it the quickest,
easiest, and most practical way. It's actually fun to think
of different ways of doing stuff (even if it takes 6 pages)!
(Damn... I just noticed that I forgot to finish the ends of the wrap-around torso tubes. Once again showing that nothing I make is ever finished!)
Recap: This has been an interesting project to work on!
One of the most valuable revelations for me was learning about Arduino
and electronics stuff-- I learned that a hobbyist could do programmed
lighting and sound effects, and that it wasn't very difficult. I
still consider it "frippery", but it's a fun addition
to the dollmaker's toolkit, and super gratifying when you test it
and it actually works! As I was learning about it, I thought of
other places to apply it, like Medicom's Zetton & King Joe,
and the Billiken Gomess kit. The Ultra-series creatures are a natural
showcase for it, but it would be very cool to play sound samples
in the Mass Effect FemShep doll...