This post originally featured at Tested.com
Last year, I was talking with a friend of mine about some of our
"holy grail" projects. I told him that it was one of my dream builds to
make a T-800 Endo Arm, as an actual prosthetic for an amputee. You know
the scene: in Terminator 2, Arnold cuts off the skin of his left arm to
expose his robotic endoskeleton.
I told him how it would be a
dream project to build an Endo Arm like in this scene, for someone who
is missing a limb. I've met or been made aware of a few people over the
years who used their unique body attributes in their costumes, but I
never had the chance to connect with someone.
He said he wanted to introduce me to someone. This is Laura.
Laura
is a left arm transradial amputee, meaning that she is missing her left
arm below the elbow since birth. She's also really into cosplay, and
living in Atlanta, she has been a "featured zombie" on The Walking Dead.
You've probably seen her in the shambling hordes.
We met and I
told her about my idea and what we could do, and she was enthusiastic. I
felt really lucky because this really was one of my dream projects! She
said she had done a few costumes in the past that incorporated her arm,
but nothing really to the scale of what we planned. The idea was to 3D
print a CAD design for the Endo Arm and possibly wire it up to an
Arduino and some sensors and servos to make the fingers open and close.
It was going to be a fun and really challenging build, and I was really
looking forward to getting it started.
And then, Mad Max: Fury Road came out and changed
everything.
You might have read
Laura's blog post
on her Tumblr that went viral a couple weeks after Fury Road hit
theaters. To quote Laura's blog post, "If I don't cosplay this character
immediately I'm pretty sure all my friends will riot."
We
had a short conversation at MomoCon here in Atlanta and I asked her
permission to build her the Furiosa arm as a real actual prosthetic,
much like we were going to do for the T-800 Endo Arm and she couldn't
have been more thrilled. Our plan was to finish it for Dragon*Con 2015,
and we both couldn't wait to get started.
During our planning for the Terminator Endo Arm project, I took a 3D scan of her using an Xbox Kinnect and a software called
Skanect.
It allows you to easily get a rough 3D scan of a person or an object.
It's not high enough detail to look photo realistic, but it's enough to
get basic proportions. I use this myself to scale Pepakura files and do
other digital sculpting where I need to have the proportions of a person
or a thing. We tried getting a 3D scan of Laura's arm and the results
were all right. It was just enough to use for scaling and "subtracting"
her arm from the Endo Arm model.
When we shifted gears to Furiosa,
I decided the first thing to do was to get a plaster cast of her arm,
because the prosthetic would have to actually fit her, and there was no
way for me to "try on" the prop myself while building it. After an
afternoon at the shop, I had one of the weirdest casts I've ever made,
but it was exactly what we needed!
At this point I got a lot of help from Adam Greene of
Pixelbash Props,
who took a higher detail 3D scan of the plaster cast, and assisted by
creating the 3D model used for the build. Laura and I agreed that we
should 3D print the arm to cut down on as much weight as possible. I was
worried that if it was too heavy that she wouldn't be able to lift it,
or she would become fatigued after wearing it for a short period.
The pieces were 3D printed on my home 3D printer, as well as the printers at
Freeside Atlanta,
the non-profit hackerspace that I work from. After a few long prints--a
total of about 30 hours print time--everything was ready to be cleaned
up and assembled.
The
process of cleaning up a 3D printed prop is pretty simple: Rough sand
the surface to get rid of some of the print lines, then (in the case of
an ABS print) use "ABS sludge"--a thick mixture of acetone and ABS--to
coat the surface. This acts like a body filler and will help fill in the
remaining gaps, but as the acetone evaporates, the ABS bonds to itself,
so you have a single rigid object. The part is then sanded again with a
finer grit sandpaper, and coated in a thin layer of spot putty to fill
in any remaining pits or print lines. After that dries, the excess is
sanded off, and then primed for painting.
Once
the 3D printed parts were cleaned and roughed together, I designed and
laser cut the mesh screen for the fingers. It was cut out of 3mm acrylic
and heated with a heat gun, and then bent to shape around the fingers.
Since building this I've discovered the actual prop likely used a
motorcycle exhaust baffle, but the acrylic worked out great for us as it
was lightweight and readily accessible.
There are two wrenches in
the arm, one attached to the "pinky" finger and one lashed to one of
the forearm pistons, that needed to be fabricated. I rummaged through
the autobay in the shop to find a couple of wrenches that were of
suitable size, and then molded them in Mold Max 30, one of the molding
silicones that Smooth-On produces. I wound up casting these out of
Smooth Cast 320,
but my original plan was to use a light and flexible foam. That turned
out to be unnecessary since the resin ones were small and light enough
to not cause issues.
The
hand and the finger grilles were hit with a primer, and then a base
coat of matte silver. I then did a light dusting with a darker metallic
paint for the the lowlights and to bring down the "shiny and chrome"
factor. After all, Furiosa's arm is a functional piece of equipment and
has a lot of wear and tear from being out in the Wastelands!
Laura
came in for a test fitting, and for us to size and finish the strapping
system for the arm. Scrap leather and spare belts were cut down to size
and riveted together for the harness. Laura sewed the shoulder pad
which goes underneath the pauldron, and we attached those together.
For
the support pistons, I used some 6mm fiberglass rod laying around the
shop, and 3D printed connecting joints for them. Those were then bolted
on to the 3D printed arm, giving the wrist a range of motion. In other
words, Laura will be able to pose the wrist.
The two wrenches came
out really well. The small one was attached to the pinky finger, and
the other was wrapped tightly to one of the support rods with some
leather cord. Fun fact: I believe the leather cord is there to cover up
the manufacturer of whatever wrench the prop crew cast off of, because
it's placement is exactly where you would expect to read "SNAP-ON" or
something. So, I followed suit and covered up the name with the leather.
Then
it was on to weathering, which is my favorite part of any project. I
did a few light washes in black and various tones of yellow, orange, and
brown, but I wiped most of it away to keep it looking metallic. The
movie has an orange filter applied to most of it, so I relied on B-roll
and behind the scenes photos for true to life colors. The arm isn't
rusted as much as it is worn down and dirty, but I did apply some light
rust around the bolts that connect the finger grilles and the other
hardware attachments.
The
shoulder was designed in CAD from looking at stills from the film, then
laser cut out of EVA foam. There is what appears to be a model plane
engine on the front, so I grabbed a random DC motor from the shelf and
glued that in. The pull strap I quickly 3D printed based off of product
photos for a weed wacker. Then the whole pauldron was weathered as well.
There
are three cables connecting the shoulder to the arm: a braided metal
hose, a clear/yellow tinted tube, and a brake cable. I got similar
looking things of each and bolted them on to the arm, and attached them
on to the shoulder end.
She also wanted me to make the belt buckle
emblem, which I quickly 3D printed up, and cleaned and weathered. I
grabbed this model off of Thingiverse, which you can
download here.
I
met up with Laura at Dragon*Con and delivered the prop to her in her
hotel room. We did some final fitting of the prop on Saturday so she
could wear it to the costume contest, and to make sure everything was
100% for the big Fury Road photo shoot on Sunday afternoon.
That
about wraps it up! It was an incredibly fun and rewarding build and I'm
happy I can scratch one of my dream projects off of my list.
