Access to lathe...what should I make?

[shardbearer]

I haven't been on spudfiles or worked on any my cannons in over a year, but I have access to a small and underpowered Unimat 3 lathe for the next 3 weeks, and figured I should make a new cannon. First time using a lathe yesterday I tried turning some scrap material, the motor kept stalling on 1-1/2" copper but 5/16" steel machined fairly nicely.


I ordered some aluminum and delrin, they should be here tomorrow. I'm definitely going to make some projectiles for my 1/2" QEV gun, unfortunately it doesn't have a compound slide so I can't really do any kind of taper, and doesn't have power feed to do threads, but I'll see what I can do.

As for a new gun, I was thinking of getting my fridge compressor working and then making a high pressure 1/2" copper gun, based off the PACA MK II with a delrin QDV. Is there an easy pen gun design I can make without threading? Should I attempt to machine a replacement piston for the leaky one in my 2" golfball cannon? Any other ideas?

[Gippeto]

A lathe opens all sorts of doors for creativity to bloom, and it seems like you already have some ideas of your own.

Common round parts are valve parts and projectiles. Due to your limited time, would suggest you do the projects you already thought about, and then if time permits... hammer valve.. toolies piston...balanced or partially balanced valve...bullet mold...higher pressure stirrup pump...list could get pretty long.

[shardbearer]

Ooh, a hammer valve and stirrup pump would be fun too... but I have so many projects

Here's some CAD drawings of the 1/2" copper gun I was thinking about, 24" barrel, 3/4" x 45" chamber that can be reduced to 18" if I don't want to pump as much. At 800psi, GGDT predicts ~800fps with a 1/2" ball bearing Debating whether to step the valve body up to 3/4"...



No, I did not model all those copper fittings by hand. McMaster has CAD models of almost everything they sell

Valve cross section, before firing. There will be a spring behind the trigger to push it back to this position, and some felt behind the piston to cushion it.


Valve actuation point


Valve after firing


EDIT: Shrunk the images to a reasonable size, click on one to see the high res version.

[dart guy]

why not spring load the trigger? it may make it a little larger and more complicated, but it would push the valve open pretty fast helping achieve greater accuracy. also i agree with gippeto, make some bullet molds while you can. Hot glue bullets seem to be popular(also weighting the tip is possible by putting a piece of nail into the mold), But unless you rifle your barrels they will have to have a front heavy design with some rear drag.