The Plan:
I had a hard time deciding what to build. I wanted to build a nano-scale Medieval gonne, but the ones I liked would be too troublesome to build with my limited machining equipment.
I was inspired by a micro-gonne built by Terry C. in 2008, as well as Mike &Tracy's nano-Rodman project that was going on at the same time. My plan was to build a sort of "nano-Rodman-on-a-stick":
I sketched this while looking at a Rodman drawing from wikipedia.
I made no effort to accurately copy the Rodman proportions. I think of it as merely Rodman-esque.
The scary part of the plan was the rear of the barrel - I wasn't sure I would be able to make it look right.
Construction:
I was walking through the hardware store and found a 5/8" bolt that looked like it might have a nano-gonne inside. I took it home and cut the ends off before I drew the plan. Hindsight says that I could have gotten some extra length by keeping the threaded end on.
I'm making this on my mini-mill. This is definitely NOT a recommended cannon-making tool - it just happens to be the only machine tool I have at the moment!
One limitation of my mini-mill construction is that I need to have one end of the work turned to a diameter that fits one of my collets. I chose the 5/8" bolt because that was the size of my largest collet at the time (Note the "was" - I now have 3/4" and 1" collets, so I can finally move up into the micro scale soon). The end that attaches to the tiller is turned down to 1/2", which was the size of my 2nd largest collet.
The other limitation is that I'm putting my lathe tool in my milling vise, which is 3" high. That means I can't turn anything more than 3" in length with a single setup. However, if I can turn my project around and put it in a collet, my maximum length becomes 6".
I drilled the bore and vent first, and did a test firing with the rough barrel. I JUMPED when it fired, as it was much louder than I expected!
The next day I put the piece back in the mill and started turning the rear of the piece. The bolt metal turned very nicely:
However, there was more runout (wobble) in my setup than I would like. I couldn't resist building from a bolt like others have done, but if I make something this size again, I'll probably start with cold-rolled 1018 instead.
It ended up being much easier than I thought it would be to form the rear of the barrel with the lathe bit and files:
Now it's time to pull it out of the 5/8" collet
and switch to a 1/2" collet so I can work on the other end. Here's an odd picture of the barrel in progress:
The hardest part of the project ended up being the middle of the barrel where there is a gentle concave curve.
As you can see from the picture I did work on both the top and bottom first, saving the middle part for last.
I slowly realized that I hadn't really planned this out very well. I've been working with flat files on turning projects up till now, but I need curved files for this project!
I remembered that I had bought a cheap set of needle files from Harbor freight that I'd never used. They cut pretty slow, but got the job done.
(I'll be happy if anyone has suggestions on where to get a GOOD set of small files)
I actually spread out filing the barrel to shape over 3 days - I couldn't get it to look right. I quit when I decided it was about as good as it was gonna get.
Finished handgonne barrel in white (click on any of these pictures for larger images).
Test Fire:
(Why, yes I CAN hit the side of a barn!)
By the way, there's less energy escaping
through the touch hole than it would appear. I enlarged the top of the vent with a #1 60
o center drill so it would make a powder "pan". When you go through the movie frame-by frame, you see a big flare-up from those grains of powder outside first, and that flare is superimposed on top of the sparks flying out from the main charge (2 grains).
What's next?
A couple of things I liked about the Terry C. project I mentioned before were the internal threads for tiller attachment and the fact that he blued the barrel. It looks like getting the tiller attached so it looks nice is going to be harder than I'd imagined, so that's still in progress.
I think big steel cannons should be painted black in most cases, but I'm not sure I could do a nice job on a piece this small. Bluing is an attractive option. I did some tests with cold blues and rust bluing, and decided to do a rust blue on the gonne. In my tests it took about 2 days for each rust step, so it might take a couple of weeks before I get a finish I'm satisfied with.
I've never blued anything before, and I was surprised to find that for a small part, there's no more work rust bluing than there is in cold bluing - it just takes more time!
andy
