2x Studio Scale Falcon Gun Turret- Scratchbuild

[Bondo Fett]

Yep, new pictures needed, for technical/stupid reasons. I had lots of BTS pics of modeling up the gun muzzle, but I can't get to them so I will just describe it.
The laser cannon is a quad barrel, so I plan to model up one and cast it four times. I will do this in two sections: the barrel shaft and the muzzle. If my plan works out the barrels will be cast around a brass tube so the muzzle can mount to the end, and the whole piece can mount to the gun body with a nice solid rod.
The muzzle is designed around a 1/4" brass tube, some flat styrene sheet, a couple of tank wheels, and some bondo (polyester fuller putty). It's about 1" by 1" by 3/8". Here are some pics:

I never figured out what the ILM guys used as the original piece on the 5-footer- I guess it is the engine pod from a jet powered bomber?

The barrel shaft model will have to be turned somehow. I don't have a lathe, so maybe I'll use a drill press? Working on it...

 

[joberg]

Wow...that's really good

 

[Bondo Fett]

Got some rubber on this thing. Looking forward to tomorrow.

Smooth-On Mold Max 30 that was lying around. I hope it is still good.

 

[Bondo Fett]

Wow, I see I have been ignoring this build for a long time. Decided to get on the barrels as planned, turning them using a drill press. Turned out to be easier than I expected.

I sandwiched a .25" tube with balsa wood slabs using wood glue. I probably should have used CA as the slightly harder glued areas gave me some difficulty with the shaping.

I cut a profile out of aluminum shim stock, not for shaping, but as a guide. I did all the shaping with sandpaper.

Not entirely sure what I was doing so I went slowly, with lots of stopping to check the shape. I gave up on absolute screen accuracy and am just trying to make the proportions look good, with a nice crisp finish. Remains to be seen if I pull that off.

Well, I was surprised how finely the balsa could be shaped and surfaced. I had been expecting it to rip to shreds as soon as the sandpaper touched it. I had to build up a section on the base because I cut it down too far. I used bondo, and later wished I had just coated the whole thing with it- it is slightly harder and denser, giving an even finer finish. This will probably work for what I'm trying to do.

Drenched the whole thing in primer which raised all the fuzz and some bubbles, too, weirdly. Thought about using polyester sanding primer, then decided that was overkill for something this size. I'll know in a few days.

 

[joberg]

Normal that your balsa is fuzzing/bubbling. A light sanding with 320 grit will do the trick Glad to hear that the project is still on.
Eager to see how that mold turns-out

 

[Bondo Fett]

Normal that your balsa is fuzzing/bubbling. A light sanding with 320 grit will do the trick Glad to hear that the project is still on.
Eager to see how that mold turns-out

Thank you! I ran the muzzle pieces too, I'll post some pics later.

 

[Bondo Fett]

Chucked this thing back in the drill press and sanded it out, zapped it with another light coat of primer, and I think this will work for what I'm trying to do. Still much work- the base of the barrel has a lot of detail to build before I can mold this.

Here are the muzzle tips rough castings. The rubber I used wasn't entirely appropriate for this small of a mold and even though I brushed a face coat of rubber over the form, tiny bubbles from mixing still managed to land on or near the surface. The bubbles are invisible, but when I cast these in my pressure pot I got these blobs that look like one of those squeeze toys where the eyes bulge out, times 100. Not hard to sand off, though.

Even though I cast about 10 of these tips, none of them came out perfect. They all have an air bubble in one of the 'emitter rings'. An easy fill with glazing putty. Also some of these have positive bubbles in the resin down inside the center rings, you can sorta see them. I'll knock those out with a pin vice and these will be finished parts.

 

[Bondo Fett]

A little bit of movement on this barrel model. Added some more to the back of the body and added a 90 degree wedge along one side with a quick molded glob of bondo. Also added the large flutes and sanded the whole thing down a bit. A few more fine detail geegaws and then primer.

I'll try to have better pictures soon.

 

[joberg]

Yes, I always put baby powder in my silicone molds (I don't have a pressure pot) and brush the excess off. I use Alumilite for most of my stuff.
No bubbles and no fuss It's looking good; now you know how to sand/paint balsa to a fine finish. It's just that sanding, painting and doing it again and again until there isn't any "fuzz" on the wood

 

[Bondo Fett]

Yes, I always put baby powder in my silicone molds (I don't have a pressure pot) and brush the excess off. I use Alumilite for most of my stuff.
No bubbles and no fuss It's looking good; now you know how to sand/paint balsa to a fine finish. It's just that sanding, painting and doing it again and again until there isn't any "fuzz" on the wood

Thank you, yeah, this was my first try with balsa and I'm pretty pleased with it, it turned really nicely. The fuzz aspect was handled with the first coat of primer. I will definitely be adding it to my bag of tricks.

I've started powdering my molds, too. Its a noticeable improvement. I think it also makes it easier to wash the finished parts, unless I'm imagining that part.

 

[joberg]

Thank you, yeah, this was my first try with balsa and I'm pretty pleased with it, it turned really nicely. The fuzz aspect was handled with the first coat of primer. I will definitely be adding it to my bag of tricks.

I've started powdering my molds, too. Its a noticeable improvement. I think it also makes it easier to wash the finished parts, unless I'm imagining that part.

Yes; it's easier to wash the parts.

 

[Bondo Fett]

Finally finished modeling the barrel master for the quad gun. A quick shot of Mr. Surfacer 1500 ties it all together.

The nurnies are a little overkill maybe. On the original there is a small facetted square, not much detail, that I was never able to identify. But, I told myself when I started this project that I would not duplicate any simple squares or rectangles and embellish those in some way.

Now I have to figure out how to mold this thing- it barely fits in my pressure pot already.

 

[joberg]

Love it; the greeblies are good and it adds a "Je ne sais quoi" with the whole look Eager to see it all coming together.

 

[TazMan2000]

Whenever ILM enlarges a model, they always change the greeblies, so I wouldn't worry. I don't think you'll have the Studio Scale police after you.

TazMan2000

 

[Bondo Fett]

Finally done fooling with the window frame. A little primer to bring it all together.

The photos really make it look flatter than it is, its actually quite dished. Also, the primer shows up all the tiny bubbles I had never noticed before.

 

[Bondo Fett]

Got a lot done on the quad barrels. Set the model up in a frame for molding. It seems a little over designed, but I need to be able to get at both ends of the mold, and I just couldn't figure out how to do that in a simple box mold. Besides, this is how I build baluster molds for my day job, and I'm using materials I already have to hand.

That aluminum strip holds some registration pins as well as providing a small gap under the back of the barrel so that the rubber doesn't go to a knife edge. Makes a more precise edge in the casting and preserves the detail.

This is Smooth-On Rebound 25 silicone. Very time consuming to control all the runs and drips, but it is what I have to work with. If I can work it right this will work as a glove mold and the parts won't have a molding seam cast into them. Will know later.

Trimmed and ready for the mother mold.

Epoxy/glass laminated mold, in two halves. I'm letting it cure over the weekend before I tear it all apart and get to see the results.

 

[joberg]

Great updateLove that window frame and the mold making!

 

[Bondo Fett]

Ready to rock! New resin just showed up, so tomorrow I can cast up the barrels. Stoked!

 

[Bondo Fett]

So...some pretty significant setbacks. I did not photo document much of this part of the adventure; I'll try to describe things as best as I can.

My brushed rubber mold ended up having a lot of bubbles sandwiched between the layers. This was not apparent to me when I built the mold, in fact, I was very impressed with my handiwork! The rubber was slit up the long side and fit into the mother mold perfectly.

I used Smooth-On's Smoothcast ONYX for the castings, with a brass tube captured inside. I have been pressure casting resin lately which has been a huge improvement in quality. The bubbles in the rubber didn't reveal themselves until I ran the first cast. All I can figure is the bubbles inside the rubber layers were collapsed down by the pressure (60+psi), yet didn't re-expand when exposed to atmospheric pressure. This gave me castings with hundred if pimples like these:

Here can be seen the bubbles in the rubber. None of this was visible until I ran the first casting.

I've used brushed-up rubber molds for many projects, but only for larges scale pieces, like laminated fiberglass for props and such. I've never used it for small part resin castings. Okay, live and learn.

 

[joberg]

Wow...that's bizarre for sure.