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Turning a Model Cannon - Trunnions and Cascable

Thinking about turning a model cannon barrel on my mini-lathe. Something like an ACW Napoleon. Most seems fairly straight forward, but I'm baffled by the trunnions (bits that the carriage holds on to) and the convex curve of the cascable (breech end). I've heard that people turn these things, but:

- for trunnions, I can only come up with either leaving an untapered "slice" of the barrel and cutting the trunnions by hand, or boring holes and inserting a round bar. Neither seems very elegant.

- for cascable curve, I guess I could maybe grind a tool bit that would cut convex curve, but I think it would come out pretty small. I've seen ball turning attachments, could they be persuaded to only cut half a ball?

Any suggestions welcome.

Thanks, Chris

Reply to
Chris
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The trunnion design depends on whether this will be a firing model or not. If not, then I suggest just drilling and tapping holes in the side and making trunnions to thread in. That's the way they are in the plans for the Parrot Field Rifle that was published way back in the early '80s in HSM.

If you want integral trunnions then yes, leave a ring and use an annular cutter on a mill to cut away straight down leaving a trunnion, and saw away most of the waste and turn the rest on a vertical mounted rotary table with a tailstock. Get it real close and then blend the lines and then polish. It's painful but it will work. They're supposed to be cast on, of course.

To form slightly weird things like the cascable you might have to resort to roughing away as much as you can and then using a form tool. Guys use a "graving tool" which is handheld using a rest like on a wood lathe, but that's an advanced technique.

GWE

Chris wrote:

Reply to
Grant Erwin

For finish machining the cast-in-place trunnions, use a hollow mill in a drill press if you don't have a milling machine. Dave

Reply to
David Anderson

Silly thought. Make the bit where the trunnions sit a slightly larger diameter. Thread this. Take a plate of suitable size. Make a hole in the middle to be threaded for the cannon. At two corners, flat the edges, drill a hole. This will be used to put a collet in, and work the trunnions between centers. Now, simply cut away all that is not a ring plus two bars. Attach to collet through the middle, and then put a radius on the sharp edges.

Oh dear, I seem to have missed the 'mini' above.

Reply to
Ian Stirling

Reply to
Grant Erwin

ai carramba!! 1 semester machine shop at the local college, 1 chinese mini-lathe, 1 drill press, 0 mill, about 6 months "experience". This seems a bit beyond me - I had to draw a picture to figure it out!

Guess I'll use screw in trunnions for version 1, rough the cascabel on the lathe and file the rest.

Thanks for the suggestions.

Chris

Reply to
Chris

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