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Soldered: My first pneumatic

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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Soldered: My first pneumatic

Unread postAuthor: boyntonstu » Sun Sep 20, 2009 8:20 am

After having to fight to retrieve it, I added a small 'eye' and also a bumper.

At the sealing end I used a pair of Home depot 1/2" flat washers and a piece of softer Neoprene rubber.

Trial and error lead me to this solution.


Image

I took it up to 210 psi in just a few seconds with my small a/c compressor.

I squirted some soapy water on the fittings and I found a few leaks on 2 screw threads.


Image


Completed gun.

Image

It fires with a huge bang!

I have the ball valve reversed.

When I reverse it, I will pull the lever towards the gauge instead of away from it.

The balance point at the chamber is a little front heavy, but it is not too unbalanced.

Notice that I soldered half of a 3/4" coupling at the muzzle to reinforce it.

It should be able to sustain a bang here and there without damage.


I do not know how high the compressor will go.

The quick disconnect retains pressure and I have to bleed off the pressure after each fill. (oily smoke comes out the intake side.)

I may add a T and a valve for bleeding.


BoyntonStu
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Last edited by boyntonstu on Sun Sep 20, 2009 9:29 am, edited 1 time in total.
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Unread postAuthor: spudtyrrant » Sun Sep 20, 2009 8:41 am

nice job on your fist one , yeah piston valves are fairly loud I'm sure everyone who has built one but not been warned was surprised on the first firing(including me).

Do you add air from the back to seal it and then add air to the front to equalize or are you using a spring?
Again nice job. :)
p.s. that a/c compressor could take you to at least 300-350psi with no problems so add MOAR POWER :twisted:
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 20, 2009 8:56 am

Looking good, bit better than a slingshot eh :)
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Unread postAuthor: boyntonstu » Sun Sep 20, 2009 9:28 am

jackssmirkingrevenge wrote:Looking good, bit better than a slingshot eh :)


Thanks,

A few comments:

I have not used the Schrader valve yet.

I may use it in the future; perhaps the discharge the chamber without firing a projectile.

There is no return spring.

It seals by applying the pressure from the rear.

I may have accidentally discovered a rear-sealing piston.

I believe that the bumper seals the pilot after the barrel seal is opened.

If this is true, very little compressed air escapes out the pilot.

I agree that a slingshot is not comparable for high power shots.

Joerge had to use his feet and arms to get close to 100 fpe.

My initial goal is to achieve 150 fpe.

If this piston holds up, I would recommend using 3/4" oak dowel instead of a cast piston for a 3/4" copper pipe. Oak dowel is inexpensive, the perfect size for an o ring, and very easy to work with.

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Unread postAuthor: qwerty » Sun Sep 20, 2009 9:59 am

looks nice! and powerful but hows performance um guessing very good but i still dont get how the piston got stuck into that wood.
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Unread postAuthor: spudtyrrant » Sun Sep 20, 2009 10:01 am

boyntonstu wrote:It seals by applying the pressure from the rear. BoyntonStu

i was just wondering because i didn't see an equalization hole or are those floating o-rings?
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Unread postAuthor: boyntonstu » Sun Sep 20, 2009 10:32 am

qwerty wrote:looks nice! and powerful but hows performance um guessing very good but i still dont get how the piston got stuck into that wood.


If I understand your question, the rubber is held to the oak with sheet metal screws.

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Unread postAuthor: boyntonstu » Sun Sep 20, 2009 10:36 am

spudtyrrant wrote:
boyntonstu wrote:It seals by applying the pressure from the rear. BoyntonStu

i was just wondering because i didn't see an equalization hole or are those floating o-rings?


Yes, they were designed to 'float'.

The O ring grooves were made in under 5 minutes.

Use a pipe cutter to cut a pair of lines into the wood and use a knife to remove the material between the lines.

A round Swiss needle file was used to smooth the base of each groove.

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Unread postAuthor: Technician1002 » Sun Sep 20, 2009 10:56 am

Well done. It look great and handles high pressure. I haven't gone high pressure yet, but I'm working on it. :D
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Unread postAuthor: qwerty » Sun Sep 20, 2009 11:34 am

the rubber is held to the oak with sheet metal screws.


No i ment in the first picture it looks like that the piston has been fired into some wood or is that the hole were you cut it out?
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Unread postAuthor: boyntonstu » Sun Sep 20, 2009 12:15 pm

qwerty wrote:
the rubber is held to the oak with sheet metal screws.


No i ment in the first picture it looks like that the piston has been fired into some wood or is that the hole were you cut it out?


Oh! Sorry.

Just a hole in a piece of scrap wood.
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