Lost Wax concept gun

I've been playing with the "lost wax" approach to carbon fiber molding for a little while on a small scale, and I finally have something to show for my efforts. There's still lots of work to do, but with the stock complete, I feel like the hardest work is behind me. So here are a few progress shots of my first attempt at a gun. It will end up as a small cross section, 52" long enclosed track gun for two bands and a 9/32" or 5/16" shaft. It's intended to be sort of an enclosed track CF euro design, with a butt extension for easy hip loading. I'm trying not to get too carried away with the actual design, while I work the bugs out of the construction process.

I found that the easiest way to cast the wax was to cast it into an oversized brick, let it shrink on top like it wants to, and then cut it to shape. The steel rod in the center reinforces the wax, so it doesn't crack during handling. It will also support the gun later when I'm melting out the wax.

This gun will be about 52" long when done. the rear 22" is carbon fiber over teak, so I have a solid core for mounting the trigger mech, handle, etc. The forward 30" is CF around wax, and will be hollow when everything is done. The two pieces are joined with a short CF sleeve.

Next post, getting the wax out . . .

Of course, once the carbon fiber is molded around the wax core, you have to get the wax out. So here's how I finally approached it. I used a $7 piece of stove pipe from Home Depot, and cut a plywood circle to plug each end. The plywood circles also supported the gun so that it wasn't touching the heated stove pipe. A small slot in one of the plywood discs allows melted wax to drain.

And here's the elaborate setup . . .

A thermometer in the uphill end allowed me to keep the temperature at about 160°F. Plenty hot enough to melt the wax, but no danger to the cured carbon fiber or teak inside.

Success!

Next, a few shots of the finished barrel . . .

The finished barrel is still a little long, so that I can trim both the muzzle and butt ends to their final dimensions. It's about 1-7/16" square, with a wall that is just under 1/8" thick, and an enclosed track cut for a 5/16" shaft. My hope is that it will be very maneuverable and easy to swim with, like a euro, but with an 8" butt extension for hip loading. The high mount handle area will get the modified Neptonics trigger that I posted a while back.

And strong? :thumbsup2:

That's where the raised handle will be, to get the grip as much in line with the shaft as possible

Here's a couple more pictures for a size comparison. The barrel on the left is a typical 28mm barrel, and the one on the right is a 30mm barrel.

It was pretty heavy with the wax in. I didn't check it, but I think it would have been seriously negative, even without the shaft.

Quote from Dan

Would it be possible to make the carbon tube more rounded on the bottom same as the top? Bring it down in overall diameter a little?

Certainly. The current shape was really driven by only three factors, and they are flexible:

1. I kept the bottom relatively flat, so that the handle attachment could be a simple "screwed plate" design similar to a typical handle. But this really applies only in the handle area. An if you wanted to go with a mortised handle, as you have done before, then the bottom could certainly be more rounded.

2. I didn't show pics, but there is an intermediate step where I clamp it from top and bottom to push a Delrin "dummy" piece down from the top to force the carbon fiber down into the track recess. I learned from the tube on my hybrid that clamping from above will tend to produce a slight flat spot on the bottom of a fully rounded shape. But the flat area is only 1/4" to 3/8" wide, so the bottom could certainly be more rounded then I made it in this case.

3. Squarish sides and bottom make it a little easier to hold the wax in a vise repeatably when cutting the wax "ingot" to the final shape. But again, only a small flat spot is really required.

I did calculations before I started to make sure that this gun would balance well with a 5/16" shaft, 10" of overhang, and a full 1/8" wall thickness. I think it would certainly be possible to make the tube a little smaller, especially if intended primarily for a 9/32" shaft. And 3/32" would probably be plenty of wall thickness.

Quote from LunkerBuster

amazing...and along those lines...couldnt you move freely between the round profile and the flat bottom only on the places where it was needed (ie just where the clamps go and just for the handle?) the benefit of the wax being that it doesnt have to be pulled out...just a thought

:thumbsup5: Yup. No reason why that wouldn't be possible. The process is mostly limited by whatever tools you have available to shape the wax core.

You da man!! That thing is saweeeet!