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gun for sister

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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which one should i make?

the bazookasish one
6
55%
or the waist shot one
5
45%
 
Total votes : 11
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Unread postAuthor: Juicey » Wed Apr 25, 2007 11:32 pm

Close-quarter, dual sprinkler valve assemblies

How to make two sprinkler valves VERY close together.

Requires a few special tools but makes for a very compact double 1" valve system. The idea of this assembly is to minimize the linear length taken for extra fittings, and have a compact unit with two valves, more or less doubling the performance of a sprinkler valve based launcher.

Above are all the parts you need, two of everything. Teflon tape also required, for sealing of threaded components. Not-so-common tools required are a lathe for cutting the plugs down to size, and removing the ridge, and a 1" NPT pipe tap. To use a tap this large an appropriate and significant restraint is required to tap the 1 1/8" holes precisely and parallel to each other. (See pics below for a close up of a tapped plug.) Tapped hole spacing is dependent on the specific brand and geometry of the in-line valve you might use; in some cases using a 3" plug may not even be possible due to an excessive center/center distance with the valves touching.

When you have all the parts in order, put an appropriate amount of Teflon tape on all threaded parts (5-6 turns), and begin assembly of the two halves. First assemble the nipple and sprinkler valve, without the female adapter yet, so you are able to turn the valve around to torque it. After the valve is tightened, then you can attach the female adapter, as it can be turned with channel-lock pliers or a small pipe wrench. Make sure the flow directions on the sprinkler valves will both be going in the same direction on a completed unit, so in opposite directions on each half made now. Picture with all of the threads just started, (shown below) but cannot tighten the valves to the plug with the female part in the way (I should have one more picture I suppose). Tighten each system so each half is of the same effective length.

Now that everything is tightened....and you are pretty (VERY) sure due to your skilled craftsmanship it will not leak, proceed with the final [IRREVERSIBLE] part of the assembly: gluing the two halves together. Make sure the end of the spigot adapter 'pipe' has been broken off and smoothed nicely, as you will not be able to give the standard 1/4 turn upon assembly. Prime all four surfaces, then small amount of cement on female part, bunches on the spigot part, and push it together....viola! (3rd pic below) Make sure to keep it level to prevent glue from running into the sprinkler valves. A slight rotation may be necessary to square up both halves, taking out a little twist, but don't move it too much from the position it took by itself...as this is the most 'relaxed' and least stressful on the pipe fittings. If the holes were drilled and tapped precisely this should not be a problem.

Please note, if you ever need to take this apart, your best bet is to cut through the adapters, as they are the cheapest/most expendable parts so you can salvage the other parts.

Another method for getting two 1" sprinkler valves close together. Just some pictures. Made from a 1 1/2 x 1 1/2 x 1 1/2 three-way elbow and a 1 1/2 tee, 4 1 1/2 x 1 bushings, and 4 1" spigot adapters.

More pics below. (4 and 5)


That's the article from spudtech. And if u need some pic's they have some listed here

Also if u are curious on how the mythbusters cannon looked, there are some pics on the thread here
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Unread postAuthor: iknowmy3tables » Thu Apr 26, 2007 3:45 pm

:o yeah thats it I looked all over and couldn't find it, , I don't think you need the lathe , but anyway you can also use this method to get all 4 barrels attached really close on a end cap
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Unread postAuthor: cdheller » Thu Apr 26, 2007 8:51 pm

pyromaniac wrote:I will but i don't know how to move the barrels out. A 45 would be to much and theres no like 20 degree one.

post on the poll.



Although 20 degree fittings are not made they do make 22 1/2 or 1/16 bend fittings.

You will not find them in pressure fittings (dwv only)


2 other ways to do what I think you are trying to do involves making offsets and/or swing joints.

I'm hoping the crappy paint drawing shows the concepts of the design well enough.

The offset with 45's will resist the force of recoil a little better.

You can also rotate the top 45(or 90 on a swing joint) to make the outlet not parallel with the inlet. (giving your barrels spread)

You can also lay the bottom 45 at a 45 degree angle from level and glue your top 45 into it (saves 1 fitting).

If these concepts seem like they would work out your problems a trip to your plumbing supply store to get a bunch of small fittings to make a little model ofyour design would make it easy to get your final parts list

After you assemble your rig dry and unglued marking the fittings with a pencil or magic marker helps to assembly them lined up correctly.

Grey glue has a slower set and cure time, that might help you make some final adjustments easier .

Maybe canting the barrels to induce net spin would keep the net open and flat?

Maybe plugging up the individual barrels and measuring the water it takes to fill them up would get you close enough on the synchronized firing time thing.


I'm guessing this will not be a shoulder fired rig?


I hope this helps
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