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My first Cannnon

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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My first Cannnon

Unread postAuthor: scatman » Wed Mar 07, 2007 7:51 pm

Here is my first cannon. 4 in. compression chamber, 2 in. barrel. I extended the handle to give more leverage when turning the valve. The cannon is bolted down to make it easier to turn the valve. The only concern I have is the ball valve. They didn't have any solvent valves, so I bought a threaded valve and dremelled out the threads then sanded it down, it isn't as tight as it would be with a solvent valve. I tried to fix this, or alleviate the stress that would normally be on the joints by putting two pipe brackets over the valve. Let me know what you think.
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Attachments
100_1412.jpg
Finished
100_1418.jpg
the 2" PVC ball valve with an extension. The two pipe brackets take all the stress of turning the valve, versus putting stress on the joints.
100_1414.jpg
another view of the valve and handle
100_1415.jpg
0-300 PSI gauge, and valve stem. I used "seal-all" to get them sealed and adheared to the PVC cap.
100_1422.jpg
cannon and me

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Unread postAuthor: jrrdw » Wed Mar 07, 2007 7:59 pm

Good thinking strapping down the valve to keep the stress off the joints. What is Seal-All? Some kind of epoxy? Have you fired it yet? Looks like it will shoot good, if you can get that valve open fast enough. Iv'e used these types of valves on pool pumps, they are a [female doggy] to open!
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Unread postAuthor: imablackskater » Wed Mar 07, 2007 8:02 pm

nice it is mostly the same as my first gun except bigger and has a gauage
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Unread postAuthor: Pete Zaria » Wed Mar 07, 2007 8:25 pm

The reducers and end cap you used are DWV (NOT pressure rated) and should not be taken over 60-80psi regularly. I've pressurized DWV to 125psi and it's held it, but this does not mean it's safe or a good idea to do.

It's a pretty good first attempt, nice clean construction, but please don't use it over about 80psi, for safety sake. We don't like reading stories in the news about "Teen looses hand to 'potato gun' accident" or "Teen hospitalized with shrapnel from failed 'spud gun'". These stories contribute to making spud guns illegal....

For your next gun, if it's a pneumatic, use SCH40 NSF-PW fittings. They have to say NSF-PW and a PSI rating on them or they're not pressure rated.

If it matters, it took me 4 or 5 tries before I built a "high-quality", nicely finished gun. And yours is much better than my first attempt. Keep it up.

Peace,
Pete Zaria.
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Unread postAuthor: itwentboom » Wed Mar 07, 2007 8:43 pm

Good first cannon use a Mauler Valve next time they kick A**.
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Unread postAuthor: risto » Wed Mar 07, 2007 9:02 pm

what does it say on the chamber? "BE AMERICAN" and something else?

do you fire it at 300 PSI? that seems dangerous to run such high pressure on those fittings.
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Unread postAuthor: scatman » Wed Mar 07, 2007 9:22 pm

I have not fired it yet, well with anything in it anyway. I took it up to 20 psi and fired some air, sounds pretty sweet. The reducers say NSF-DWV on them, but now pressure rating. I'm planning on starting low and working my way up. I'll also probably put a blanket or something over the pressure chamber in case it does blow up.
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Unread postAuthor: scatman » Wed Mar 07, 2007 9:26 pm

seal all is a super duper kinda of glue. It is a little like epoxy and a little like silicone.
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Unread postAuthor: Pete Zaria » Wed Mar 07, 2007 9:29 pm

@scatman

DWV stands for Drain-Waste-Vent. Those reducers are not made to take more than about 20psi. As I said, I've pressure tested DWV parts to 125psi and they didn't blow up - that does NOT mean it's safe to do so, or a good idea. Also, since your ball valve is kind of jurry-rigged, I wouldn't trust it over about 60-80psi either.

A blanket won't do much good for shrapnel protection. Use thick fabric (denim, canvas, etc...) or wood if you really want to make a shrapnel barrier.

I wouldn't take that gun over 60-80psi max. If you were planning on going over that, I'd consider re-building it (or building another one) with all nsf-pw parts, and a modified sprinkler valve.

Don't get discouraged.

Peace,
Pete Zaria.
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Unread postAuthor: jjjd » Wed Mar 07, 2007 9:31 pm

very nice, i like how you added a handle to the valve. i have one of those valves to vent my combustion and its hard as hell sometimes
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Unread postAuthor: scatman » Wed Mar 07, 2007 9:48 pm

Pete,

Thanks for letting me know about that, I looked up the pressure ratings for dw, here

http://www.northernpipe.com/NPP_PVC_Hom ... _vent.html

and it was pretty descent, but I don't know if that is for what I have, because it is the same as SCH 40 and I don't have that. Do you know where I can find the pressure ratings? I know you said you tested it to 125, but I like to see the actual ratings. I was planning on runnin it up to 45 psi, then increasing by 10's. Yea I will definatly have something thick over it.
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Unread postAuthor: Pete Zaria » Wed Mar 07, 2007 10:23 pm

@scatman (where'd you get that SN anyway? Do I want to know?)

Schedule is just a measurement of wall thickness, not a pressure rating.
See:
http://en.wikipedia.org/wiki/Nominal_Pipe_Size
http://www.engineersedge.com/pipe_schedules.htm

Two different sch40 pipes of the same size could have two very different pressure ratings - for instance, NSF-DWV PVC SCH40 2" and NSF-PW PVC SCH40 2" and NSF-DWV ABS SCH40 2" all have different ratings. Therefore, schedule hardly matters (unless you're looking into a hybrid, for which sch80 or 120/160 are preferred for their thicker walls). What you really want to look for is the "NSF-PW" mark, and a pressure rating (xxxPSI @xx degrees F).

Look, if you really want to be safe, buy an extra 4"-2" reducer, a 4" end cap, and a 2" end cap. Install a schrader and cheap pressure gauge (which you can reuse after this anyway...) Solvent weld it together (using a short section of scrap 4" and 2" pipe, as needed), and intentionally over pressurize it til it fails. Dig a big hole, put it in it, with some thick-ass boards on top. Stand as far away as your compressor hose will let you get, and pump it up. If it doesn't burst when you've reached your compressor's max pressure, leave it pressurized overnight. If it doesn't blow, I'd say you're safe.

Personally, if I were you, I would not want to stand next to / hold a cannon made of NSF-DWV over about 60psi. If I wanted to go over that pressure, I'd build another gun using NSF-PW parts and a modified sprinkler :wink:

Peace,
Pete Zaria.
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Unread postAuthor: scatman » Sun Mar 11, 2007 5:43 pm

Pete,

I went to Home Depot a few days ago and the only reducers and end caps they have are the ones I bought. I asked him about pressure, and he didn't really know. Where would I get reducers and end caps that are pressure rated that high??

Thanks again,
A.J.
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Unread postAuthor: pyrogeek » Thu May 03, 2007 2:51 pm

If you put some glycering on the O-ring in the valve and work it back and forth, it will loosen up. Don't get it too loose, just loose enough to be able to turn it easily.
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Unread postAuthor: paaiyan » Thu May 03, 2007 3:14 pm

Nice looking, but like they said, try pressure rated parts next time. And what does the rest of the lettering on the gun say? I can only read be American.
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