Introduction: Steampowered Mechnical Arm (with Flamethrower!)

About: I enjoy making things of all sorts, with an emphasis on bicycles, tiny/useful/just plain nifty devices, cartoonish arch-villany, and not destroying the planet we live on. If those last two thing sound contradi…

The other day, I was reading delightful instructable by V-Man373, regarding the process of making my very own Gatling Gun Prosthetic arm. I briefly considered following those instructions very closely, but it then occurred to me that for an invidual who uses his hands as much as I do, and much of the time uses them in tandem, having only one functional hand would be a burden on my sanity, no matter how incredible the replacement was.

So I took the basic idea of putting my arm inside a length of PVC, and building upon that platform; however, instead of its sole purpose being weaponry, I set out to build a working mechanical hand on the end.

The following steps might be a tad confusing to some of you, but I reccomend reading the Gatling Gun instructable first, and this one will make a great deal more sense.
The seeming disorder of my process eminates from only loosely following the logical progression of Mockup, Prototype, Final Product.

In fact, what I intended to be my final product became my Mockup/Prototype after considering what Seattle weather would do to a cardboard shipping tube!

Step 1: Conceptualizing

In my father's chaotic assortment of garage-junk, I found a length of cardboard shipping tube that fit my arm quite well; cut in half and shoved inside itself, it was quite sturdy.

More rummaging turned up all manner of metal bits: hinges, plumbing parts, mounds of nuts/bolts/washers, and the like. The most time consuming part of the construction process was drilling, bending, and bolting it all together in the right combination so it fit, and worked to my liking.

Step 2: Gathering Materials

At about the time when I had attached to the end of the tube, a rigid metal nub (the thumb, if you will) and a curved, hinged finger that closed around it, I realized that I live in Western Washington, which is a rather wet place. Cardboard does not enjoy being rained on, not at all.
Eventually, practicality triumphed over frugality, and I bicycled to my local hardware store and bought a length of 4" diameter PVC.

Thus, the Final product became the Mockup!

All the while, more ideas for attachments occurred to me: a brass valve was purchased along with the PVC;  I thoroughly raided our box of random plumbing bits, adding a flowsensor, some ribbed tubing, more pipe, wires, and various brackets to hold it all onto the main device.

Step 3: Aesthetics

After much, much fiddling with the attachments along the main tube, I began painting the small items made of unsightly white plastic, i.e. the flow sensor and the small pipe junctions, in a more pleasing brass color. Here I learned the value of a subsequent clearcoat: metallic spraypaint is, unfortunately, very prone to chipping!

While waiting for parts to dry, I was holding a 1/2" PVC cross junction in my [working] hand, and, like a waterballoon dropped from a zeppelin, the idea of mating the flowsensor assembly to that junction, which would then branch out into hoses, towards... firepower.

My arm would a "business end" in more ways that one!

Step 4: More Aesthetics

At last, I had everything fitted and arranged to my satisfaction, and it was time to prime and paint the main tube.

I gave it a thorough sanding, inside and out, to help the primer stick, rammed small chunks of scrap PVC into the unneeded holes, and began spraying.

Step 5: Aesthetics Headaches

At some point, I deduced that the brass-colored PVC bits would not be brass-colored for very long, as simply touching them seemed to rub the stuff off.
Clearcoat was in order!

However, one problem arose: the clearcoat reacted with the metallic paint underneath, and blistered it in places. The can stated "dries in 15 minutes or less", but that must not include "stops emmiting fumes". In the end, it looks rather like the inconsistancies and flaws inherent in cast brass. Bully!


At long last, a good 4 days after the project's beginnings, everything was drilled, filed, hammered, sawed, cut, whittled, tapped, bolted, sanded, painted and assembled!!!

Much maniachal cackling was enjoyed.

Step 7: Afterthoughts

As an afterthought (which I should have done at the start) I took that ring-thingy from the PVC crosspiece and put it inside, on the lever that my fingers grip.... rather than simply wrapping my fingers around a bar, I can put my index finger through that ring, which feels much more intuitive.

If I make another one of these, I might take a length of 4" pipe, put a PVC reducer coupling on the end, and have the grabber assembly mounted on that, with the control lever running through the smaller pipe hole; a somewhat more elegant solution, which would conceal my stump more effectively. Getting tools inside the pipe to tighten all those bolts would become even more difficult, though.

Also, I did not light this device at all. At some point, I will probably wire red LEDs inside the flamethrowing assembly... perhaps a flashlight mounted inside the main tube, to illuminate what I am grabbing.....