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diaphram/piston coaxial

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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???

good
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you should make a larger launcher that has interchangeable valves too
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ok... and could need some improvement
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ok... and could need some improvement
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diaphram/piston coaxial

Unread postAuthor: origin unknown » Thu Jul 05, 2007 1:23 am

This started out as a diaphram cannon, but later on I decided to create a piston for it to see if it would perform any better. Now I have a gun that can be used as a diaphram or a piston gun using the benifits of both valves, and I believe I am the first to do this.

SPECS
chamber: 1.5" sch40 pvc
barrel: 0.5" sch40 pvc
valve: selectable; diaphram or piston
pilot valve: modded blowgun w/ ball valve safety
fill valve: screw-in schrader or a check valve attached to coupler nipple

My diaphram is made of 1/8" sheet rubber, and it fits between a male adaptor and a female adaptor. My piston, which fits inside the male adapter, is made of hot glue and it has a neoprene sealing face. My diaphram works great, it shot a medium weight projectile about 100 ft upwards pointing the launcher straight up. The piston did work, It just didn't open fast enough to let a sufficient amount of air come out the barrel. This problem could easily be fixed, by using a larger pilot opposed to my smaller modded blowgun. This is my first gun with a completely homade valve, and I am very proud of it. I plan to be making a barrel sealing piston valve with 1.5" porting all housed in a 2" T, but it won't be started for a while.
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Attachments
coax5.JPG
Hot glue piston
coax4.JPG
diaphram
coax3.JPG
schrader valve, and pilot valve assembly close-up
coax2.JPG
me holding the launcher in the firing position
coax1.JPG
I know... I tapped the hole for my pilot valve assembly kinda crooked.
Last edited by origin unknown on Thu Jul 05, 2007 2:34 am, edited 1 time in total.
Ecclesiastes 1:9 - What has been will be again, what has been done will be done again; there is nothing new under the sun.
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Unread postAuthor: spud yeti » Thu Jul 05, 2007 2:14 am

That looks like a really cool little cannon you have there! I love how it is interchangeable too! As I was looking at your gun, I thought of something... What if you had both the piston and the diaphram in?? You would have the sealing power of the piston and opening speed of the diaphram! Just a thought though, so why dont you try it and see!? :D
Really good work though!
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really good quote/phrase here
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Unread postAuthor: Mitchza89 » Thu Jul 05, 2007 2:17 am

Thats a great looking Coax there.
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Unread postAuthor: origin unknown » Thu Jul 05, 2007 2:32 am

spud yeti wrote:That looks like a really cool little cannon you have there! I love how it is interchangeable too! As I was looking at your gun, I thought of something... What if you had both the piston and the diaphram in?? You would have the sealing power of the piston and opening speed of the diaphram! Just a thought though, so why dont you try it and see!? :D
Really good work though!


The only way to combine the two would have one piloting the other. I would have to build a different gun to test that. Maybe a homemade diaphram piloting a piston... that would be interesting because most people use sprinkler valves or QEVs to pilot their piston, not anything homemade.
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Unread postAuthor: spud yeti » Thu Jul 05, 2007 3:08 am

Yeah, thats a really good idea, and could be fun to experiment with! Maybe you could sketch a few plans and I'll do like wise and we'll see what comes out! I have loads of time (school holidays).
back on topic though: nice cannon! (Im trying not to hijack threads :D )
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really good quote/phrase here
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Unread postAuthor: noname » Thu Jul 05, 2007 10:39 am

A couple months ago I made a coaxial that used either a piston or a diaphragm, along with a combination of both, that allowed it to open extremely fast and then slam back and allow full flow.
Nice gun. :D
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Unread postAuthor: spud yeti » Thu Jul 05, 2007 11:04 am

Sounds logical. So you think it works the best then? (to have both piston and diaphram)
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really good quote/phrase here
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Unread postAuthor: noname » Thu Jul 05, 2007 11:16 am

I don't have a chrony, but in order, damage-wise, the piston was worst (shot through one side of a can), diaphragm was second, (shot through one side and split open the other side), and the combination shot through both sides and dented my shed.
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Unread postAuthor: hi » Thu Jul 05, 2007 11:48 am

nice. what did you get the rubber from and what did you cut it with? its a great looking gun you got.
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: noname » Thu Jul 05, 2007 1:03 pm

I just get 1/8" and 1/16" sheet rubber from Ace Hardware. I can usually cut it with huge scissors, but I need an exacto knife sometimes.
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Unread postAuthor: origin unknown » Thu Jul 05, 2007 2:31 pm

I used these nice Fiskars scissors that are used to cut thicker materials, especially bushes and small branches.
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Unread postAuthor: e1337 » Thu Jul 19, 2007 8:20 pm

I like the cannon, but how did you melt and mold the piston?
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Unread postAuthor: origin unknown » Sun Jul 22, 2007 4:28 pm

I sprayed the inside of the pipe my piston was in with cooking spray and squirted the hot glue in. It is quite simple...
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Unread postAuthor: spud yeti » Wed Jul 25, 2007 2:31 pm

Another method: cooking oil works well, but if you having trouble with it you can also use greased up baking paper around the inside of the pipe, this increases flow quite nicely too.
Did you melt the glue through the gun or microwave it or what though?
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really good quote/phrase here
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Unread postAuthor: origin unknown » Fri Jul 27, 2007 6:00 pm

I melted it through the glue gun.
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