Disclaimer: The following has been edited to preserve the delicate flower sensibilities held by potential readers. Where the narrative seems disjointed please mentally insert your most depraved and disgusting epithet. It's not quite the same thing, but it's as close as you'll get.
So I wanted to build a steampunk hand. Every Steampunk maker, at one time or another, gets it into his head that he needs to make a steampunk hand. Go google 'Steampunk Hand' or 'Steampunk Arm"; I'll wait.
I'm not going to pick apart the workmanship of everyone else who has attempted this project in earnest. But, broadly speaking they are all ~sherbet~. Yes that's a matter of personal opinion; mine. If the goal is to represent a Pseudo-Victorian Era mechanical limb as might be employed to replace a hand that has been blown to pieces, then all of the results I have seen so far suffer from one fatal flaw. Some of them suffer from two. Most are made out of trash materials (plastic, leather in a structural role, etc...) and all of them have a living hand tucked up in there somewhere. By necessity then, the hand built will not look anything like a hand built to replace a lost hand. It just can't. It might be grossly over-sized, or it might simply be a decoration for the living hand with bits and pieces of the real hand or a glove showing through.
I solved the first problem by using only appropriate materials; for metalwork, this means I use metal.
The second problem is even easier to fix. I just found an amputee.
In the second photo is myself (wearing the apron) and Kyle Earl. Kyle is a retired Marine who lost his hand to an IED in Iraq. He was featured on Yahoo! News' 'Remake America' video program. I noticed that it had been about 2 years since his hand was removed but he went about his daily routine without one.
This got me wondering why? Maybe the basic prosthesis didn't offer enough utility to justify the hassle. Maybe.
Maybe he's a ~firetrucking~ Marine. When a Marine loses a hand do you pour some jelly into a mold and let it set up into his new one? Not on my watch.
So I offered to build him a golden mechanical hand. Not to replace the hand he lost so much as to replace the empty air that occupied that space now. The VA has already hooked Kyle up with the Darth Vader robot hand but even while that will help in his everyday activities, it's not a golden hand.
Kyle does a lot of outreach work and plays on the Wounded Warrior Amputee Softball team, so we got together and worked through my plan to build him an exhibition hand. Something to get people's attention. The first stage is winding down and it's really turning out well.
What follows is some of the process I used to build this hand.
Step 1: Making the Bones
I'm building this thing from the inside out, which means ... bones.
I'll let the Great Artificer take credit for the rudiments of this part of the design; it was inspired by nature.
But I added a creative element that I am quite proud of. All of the brass used in this project began as military surplus spent ammunition casings. The bulk of it is cartridge brass from .223 Remington (5.56 NATO). The knuckles, that we will see later, are the bases of 50 BMG Machinegun shells. The skin of the palm is actually the casing of a 90mm artillery shell.
Like Kyle, these things began their lives as weapons, they were used, and when empty they were returned home to be remade into something constructive.
One picture below shows one of the methods I used to melt and pour the bar ingots of brass. It is a basic clay pot charcoal foundry. It was under powered but quite exciting. After that I found my old melting torch.
The ingot mold I used is an inexpensive cast iron mold with 2 cavities on one side for 1/4" X 3/8"X8" bars and a single cavity on the opposite side to cast 5/8"X3/8"X8" bars.
Once the bars were cast I hammered them flatter to give me pretty uniform 1/2"X3/16"X8" bars. Some variation of course but I allow it because it adds a nice organic imprecision to the final result.
Step 2: Metacarpals
From a tracing of Kyle's left hand (then reversed) I created this angulation diagram by plotting the position of the knuckles and how the 'bones' would have to rout to them if I wanted the bones to be attached to the knuckles straight on.
Alternatively I could have cut the metacarpal bones to length and then mitered the joint so that the knuckles point straight. I'm glad I didn't. that would have been insane.
In the third picture you can see the two disks at each end of the wrist. those disks are the base on 50 cal machine gun cartridges. The brass to be between them is the body of one of those same cartridges that had been compressed in a way to remove the taper (it was slightly cone shaped).
Step 3: Knuckles
Now you can see it with the knuckle joints attached.
While the wrist is centered on the metacarpal bones, every other finger joint is laid out so the the bottom edge of the bone is at the same level as the bottom edge of the disk..
It's hard to explain just in writing but the bottom edge of each finger bone will lay flat to a table top even though the diameter of each knuckle joint is wider than the width of the finger bone.
Just have a close look and you'll see.
Also present in this pic is the first thumb segment. The thumb was actually one of the last things done to the hand.
Step 4: Phalanges
The first picture shows the hand with the Proximal Phalanges attached (or at least in the right spot.
The second two might give an idea as to the shape of the fingers that I was aiming for, where the roundness of the knuckle rides on top of the fingers.
In the second pic the fingers are not quite complete. I change the shape of the last two fingers and segment and partially articulate the index and middle fingers.
Step 5: Wrist
The basic idea for this joint is to create a yoke that the wrist barrel of the hand will set into and then secure it with an axial pin or bolt.
I actually drilled the narrow part of the joint and pressed a brass rod through to create a place to attach springs or servos or actuators if such things are added later.
The back-plate for the wrist is some light plate (or heavy sheet) brass and some sheet copper. The wrist bones were drilled and tapped and threaded rod set into it and then the copper plate was bolted on and brazed with a nice low-silver solder. That plate is then bolted to the heavier brass 'cup' which will be attached to the socket when the project is done.
Step 6: Thumb
The thumb on this hand is the part least like it's human inspiration, but has turned out to be my favorite feature.
Step 7: Complete Skeleton
All the pieces of the skeleton are here at this point.
All of the hardware gets changed out in favor of something with adjustable tension on each joint.
Step 8: Skin
A part of my original conception of this was to have a lighter 'skeletal' infrastructure that supports a brass 'skin' on the palm side of the hand and each finger.
What actually happened is that I completed the skeleton and it looked so badass that everyone told me not to cover it up with a skin,
Also, the bones ended up being thicker than I had originally imagined so they lent a bit of the 'roundness' to the overall theme that I was relying on the skin to provide.
But I still wanted the skin. I think it adds a human or living character to the piece that a mere skeletal hand could not. My goal was to create a hand that from the back screamed "CONSTRUCT", but from the other side it was smooth and rounded and organic. So I compromised a little and just put the skin on the palm.
To make the skin. I started with a vintage 90mm artillery shell casing. I cut the bottom off of it and then cut it long ways. After that I had to anneal it so that it would let me flatten it out.
Because the taper of the shell is very drastic at the shoulder (near where the projectile would set) I had to cut that part off and flatten the brass as two parts.
The final picture for this step shows my setting the lines on the palm with a dull chisel and hammer.
With the lines properly set I alternately sunk or raised portions of the skin with a small ball-peen hammer and a large pine stump to create the roundness.
Finally I drilled and tapped the metacarpals at points where they intersected the crease lines of the skin and attached one to the other with a half dozen screws.
Now go check out this project and others at my website http://www.ArtificerMade.com
Step 9: Some More Photos
Just some extra pics.