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Pete Zaria's Over/Under Combustion

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: SpudBlaster15 » Sat Jan 13, 2007 4:32 pm

I would attach the strip near the center, slightly favoring the rear (ball valve end) of the chamber. A rearward ignition site enables faster flame propogation as opposed to a central/frontal site.
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Unread postAuthor: PVC Arsenal 17 » Sat Jan 13, 2007 4:42 pm

Excellent job. Especially great breech design. You could try making it with a saddle tee on the chamber and a snap tee on the barrel as a guide.

Overall though- great, clean work.
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Unread postAuthor: Kenny_McCormic » Sat Jan 13, 2007 9:59 pm

i would use two 45 degree elbows instead of a u bend it should fit your shoulder better that or some sort of wood block on the back of the gun.
other than that it looks good. and i would make a better barrel support also. and are you goint to use a chamber fan?
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Unread postAuthor: Pete Zaria » Sat Jan 13, 2007 11:55 pm

OK, heres the pics with the second barrel support and the jurry-rigged shoulder pad.

Whole gun dry fit:
Image
Image

Closeup of barrel supports. Note how the 2" pipe is sanded to fit the chamber. You can see the chamber through it. It's also sanded to fit that ring on top of it. There's a groove filed in the "ring" for the zip tie to sit in, so it can't slip out. The zip ties are strapped down pretty damn tight, but not tight enough to flex the pipe.
Image

Breech open:
Image

Shoulder pad:
Image

Chamber fan:
Image

I'm taking these pics on a 7.2mp Canon camera but resizing them down to 400x300 for quick loading. If for any reason you want me to post higher res pics, just ask.

@Kenny_McCormic,
The shoulder pad works pretty well as-is, and I already have this fitting, so I think I'll stick with it. If I was building it scratch (without using spare parts) I'd probably use double 90's. Yes, I have a chamber fan.

I'm just curious, what would you guys suggest for barrel supports? These seem pretty sturdy.

Thanks a bunch for the input.

Peace,
Pete Zaria.
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Unread postAuthor: MrCrowley » Sun Jan 14, 2007 1:35 am

Me, Personally, I Love them :P
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Unread postAuthor: Pete Zaria » Mon Jan 15, 2007 10:33 pm

OK, update:

Built the second handle. I'm rigging up the electronics in the handles now.

Finished the spark strip. Made one out of copper clad circuit board with grooves in it. My BBQ sparker will jump all six gaps, and will be used until a stun gun is acquired (next paycheck).

I soldered the wires for the spark strip and fan to nuts that will go on the inside of the chamber to line up with the bolts, like this:
Image

I decided to attach the ball-valve side reducer with 6 bolts. I'm using big 3/8" steel bolts with nuts and washers. I had measured out for 8 bolts, and decided they were too close together, and that I didn't need that many. With six bolts, I have one every 2 and 2/3rds inches. I drilled the holes for the bolts, tapped the holes, and glued the nuts with wires soldered to them to the inside of the chamber, lining up with the holes as in the pic above.

I'm waiting for the glue to dry. I have to glue the nuts one at a time (no room for more clamps) and Gorilla Glue takes 3-4 hours to dry, x 6 bolts is going to take a while.

I'll post pics of the spark strip, handles, and bolt assembly tomorrow.

Peace,
Pete Zaria.
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Unread postAuthor: Pete Zaria » Tue Jan 16, 2007 2:32 pm

OK, problem.

The nuts I glued to the inside of the chamber won't hold when I try to thread a bolt into them. So I'm going to have to figure out a new way to run the wires for the spark strip and fan into the chamber.

So far, I'm thinking that I'll just bolt on the valve-end reducer, then reach up inside from the other end and alligator clip the wires onto the bolts. This will work, but would be difficult to service later.

Any ideas on how to pass the wires for the spark strip and fan into the chamber without drilling holes?

Peace,
Pete Zaria.

Edit: A friend has suggested I use jbweld to secure the nuts to the inside of the chamber. I'll try this. Any ideas for a Plan B if jbweld doesn't work?
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Unread postAuthor: mark.f » Tue Jan 16, 2007 4:09 pm

Just tighten the nut and the bolt at the same time, from the inside and outside?

Also, are you gonna use gaskets to seal the fittings where they hit that pipe? A little like this?:

<img src="http://www.spudfiles.com/forums/album_pic.php?pic_id=315&full=true&">
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Unread postAuthor: Pete Zaria » Tue Jan 16, 2007 4:14 pm

Mark,
Thanks a ton for taking the time there.

I'm not going to use a gasket, just a bead of silicone caulk afterwards to prevent leaks.

I can't hold the nut on the inside of the chamber; the chamber will be closed.
The idea of this is to allow access to the inside of the chamber for future maintenance/upgrades. I'm going to try JBwelding the nuts to the inside of the chamber. If that doesn't work, I'll just use a 1/4" brass threaded nipple for the wires and forget about the nuts (the bolts will stay in place, I'm not worried about that).

Peace,
Pete Zaria.
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Unread postAuthor: Legendpilot » Tue Jan 16, 2007 4:52 pm

J.B. Weld is good stuff, just make sure you mix the correct amounts, I'm pretty sure it's 1 to 1, and sand your plastic for the best results. It ought to work for you. -Lp
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Unread postAuthor: Pete Zaria » Tue Jan 16, 2007 4:56 pm

Yep, that's what I'm thinking. Thanks, legendpilot. I always sand surfaces before soldering/gluing/epoxying/etc...

I'm going to JBweld the nuts to the inside of the chamber (one at a time, cause it drys fast), cover a bolt in crisco, and thread it in (to hold the nut against the chamber while the jbweld dries). I'm just hoping that the bolts come back out of the nuts. I'll see tomorrow when I can get some JBweld. There's too much snow/ice to get out today :x

Peace,
Pete Zaria.
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Unread postAuthor: Legendpilot » Tue Jan 16, 2007 5:10 pm

It's dries pretty quickly, but I would let it cure for at least a day. Also, and I know this may seem obvious, make certain to get no JBW on any part of the threads when you set the nut. -Lp

BTW - I think your snow may be headed my way!! :shock: (East Coast)
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Unread postAuthor: mark.f » Tue Jan 16, 2007 5:24 pm

Pete, I just realized with your ball valve vent and barrel connections, you wouldn't be able to reach the screws. Just another instance of me thinking too fast.

If only they made "bushings" for screws and bolts, and other straight threads. I'm pretty sure you could fabricate your own with the right tools, but the JB weld idea might be the best bet for now.


EDIT: ah, they do. They're called "helical inserts", and their more for repairing stripped threads, but they would work.

Gotta leave for work now, but a picture might be in order when I get home. (~9:30).

EDIT: phew, couldn't get this picture done last night. It was around 10:00 when I got here and I was tired.

Anyways, here's what I'm talking about.

<img src="http://www.spudfiles.com/forums/album_pic.php?pic_id=316&full=true&">

There is a helical insert threaded into both the pipe and fitting, and the bolt or machine screw goes through them to secure.
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Unread postAuthor: Pete Zaria » Mon Jan 22, 2007 11:45 pm

Mark, your idea saved my ass.

I found something similar to a helical insert. Basically a sleeve, threaded inside and out, with a washer attached to one side, with teeth on the washer that dig into the pipe. They've solved the problem.

I've just assembled and glued the cannon. I still have to install the propane meter. Pics tomorrow. Video soon after. :P


THANK YOU SO MUCH TO EVERYONE THAT HELPED MAKE THIS A SUCCESSFUL BUILD!

Peace,
Pete Zaria.

Edit: 300th post. Awesome.
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Unread postAuthor: squeaks » Tue Jan 23, 2007 12:00 am

One thing I can suggest is to do the stoichiometry to find the exact pressure that should be put into your meter pipe before injecting the propane into the gun. The only other thing that could suggest is a bolt or cam lock breach. Very nice gun. Should be rather powerful.
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