cannon... a work in progress. Part 4

The back half has been turned down. You can also see the file mentioned earlier in the bottom left of the pic.








Here it is.









Just another view showing the button on the back. It didn't quite get rounded enough. Now that I did this one I've got some thoughts on how to make things go smoother.

As mentioned, use as large a spindle as you can. Reduce the epoxy use so that it's only as large as the smallest section. If possible, use wood caps or something that will not dig into the foam if the nuts tighten. Cut as close to the finished size as possible, make it "stair step" and cut the sections round as this balances it and reduces wobble and the mess.

The biggest thing that would help is to use a wood lathe with a support would be much better suited to turning foam then a metal lathe set up like this.

The only thing left is to drill a hole in the barrel, add the trunions, and the vent hole. After that it's all a matter of skinning it over. Wood glue works well, then you can apply polyester resin or bondo to form a hard shell. Smooth that, spot putty and then make a mold.

I'm debating if I should do another with the changes I mentioned above to improve the shape. Some sections are slightly out of round due to the wobble in the thin shaft.

more to come...

cannon... a work in progress. Part 3

The front half of the cannon is turned down. Basically it was just long boring work. Something I found out along the way, USE THE LARGEST DIAMETER SPINDLE AS YOU CAN. There were some vibration issues and "flop" at higher speeds, due to the length of the rod as well as it's thin 3/8" diameter. 1/2" would probably have been better, 3/4" better still. I think that's as thick as I could do without boring the headstock on the lathe out.




A little bit further along in the process. No, no action photos since I only have two hands. Another thing I realized is that I should have only used epoxy to the smallest diameter of the foam...that is, it doesn't shape as well with file cards so you'll have to use the file on it. If less is used in the only the center you can turn it quicker.





A close up of the end. if you look closely at the seams between the discs you can see they're raised, the result of the epoxy.








Here's some of the tools used, as well as a huge mess.










More to come...

cannon... a work in progress. Part 2

This is the basic plan, scaled up plans for a "miniature eighteen pounder" to what I felt would make a nice small cannon. Nothing too fancy here. In the background you can see the beginning of the shaping of the foam.








Here's a shot showing the initial smoothing out of all the rough cuts. You can also see that doing this makes a huge mess of very fine foam dust and chunks, depending on what kind of tools you're using. I guess I should mention what I'm using, huh? Primary tools are an auto body file, or a horse shoe file. It has large arched teeth and you'll be able to see it better in another pic later. Also a rasp, a file card and some drywall sandpaper. Open window screen type since it doesn't clog nearly as much. I said there was a bit of static, it's actually pretty cool to see the foam spinning and the small bits orbiting it, not flying off, but orbiting. It gets old fast since as soon as you touch them they stick to you instead.


More to come...

cannon... a work in progress. Part 1

So, as promised, the cannon build ....

I've turned foam before, back when I had no lathe. I did it with a large "U" shaped setup built out of 2x10. There was a large flat base with two uprights, one upright had a hole for a drill. I chucked up the threaded rod after fitting the drill into the large hole, the other end sat in a bearing. It worked OK, but not great as the drill kept falling out of the hole.

Now that I've got the lathe, I might as well use it right? If this cannon was an inch smaller in diameter I think I could have pulled it off over the bed. How can you turn a foam cannon that is larger then the mini lathe you have? Since you could turn several sections and glue them together, the real problem is how do you overcome the swing over the bed issue? You could build something like this.


Here we have the extended rear bed for a 7x12 mini lathe. It's just a piece of 2x10 with a piece cut off to form the support. Some shelf brackets and another piece of wood hold it in place. A hole was drilled to fit a small bearing that the threaded rod rides in. Yes, bench space has been exceeded. It's not really a smart idea to have it overhanging the bench like that. This will be fixed with the expansion of the shop in the somewhat near future.







The cannon itself is 21 discs cut out of pink insulation foam held together with 5 minute epoxy. A hole was drilled at the center of each disc to hold it onto a long piece of threaded rod. At the ends two nuts and as large a washer as I had on hand was used to clamp it together while the epoxy hardened.







You can see the washer here as well as the rough cutting of the foam.











More to come...

Cannon: step 0, err, -1

For some reason I can't get any pics uploaded here right now...so I'll hold off on adding cannon stuff.

I will say that there were a few issues that came up, but nothing too serious, and if anything it was a learning experience.

stay tuned.