Hydro-Pnumatic

[sergeantspud2]

This gun came to me when i was day dreaming in english (lol go figure) we were studying prefixes and suffixes and one of them was hydro. Then I began to think hmmm hydro... thats like hydro-mining that the gold miners used... hmm it shot high pressure water from a hose... hmm it looked like a spud gun... So thats where it started. It has changed designes 4 times from when it was a 4 foot long pipe to a 5 foot long pipe to an over and under design (which I built but had a problem talk more about it later) to an over and under with bumpers on each side of the piston, which i found is a critical part. I guess I could call it a hybrid but intead of propane and air its air and water.

Basically how it works is theres a piston on the side with the PVC valve and I push the piston back to where it gets to the T, then fill up the side twards the valve with water, then fill up the other side with around 80 psi of air and that compresses the water. But since water has low kenetic energy unlike air, once the valve is open there is an intial "POP" from the compressed water but also the 80 psi on the other side of the piston will push the piston forward and force all the water out which in turn propels the projectile. My begining plans were to fill up the entire area of that side of the piston but after my test i found out that that is too much water for the piston to push fast enough so if I put only 1/3 (approximately) that it works way better. There is also a GIF of my old design of how it would work the only mod i made from that is that i extended the area where i put the air so it wont lose pressure as quickly.

Ok now my story about how important it is to put bumpers. With my last design I put the piston in then let it the glue all dry and pushed it back. It seemed to be working so I did it a few times untill i pushed it to far back and it got caught in the T. I kept bouncing it on the ground (softly) and it wouldnt come out so i put around 40 psi in it and started hitting it on the ground (pretty violently) untill I heard a WHOOOOM!! The piston aligned itself and came rushing down the chamber, hit the 1/4" nipple which i put in there to be a make shift stoper tore all the pvc apart and shrapnel went all over the place. Now remember this all happend instantly and with only 40 psi!

Ok one more thing before I get to the pics...
I know most of you guys skip the description and look at the pics first and decide if you want to read the description so ill put this question in bold so you guys wont miss it.
What kind of valve do you think I should put on it? I know the ball valve is choking it but im afraid that a sprinkler valve will have to much friction and slow the water down and a piston valve will still have to make a U turn. So what do you think?

Ok now for the pics...
I also have a video at the bottom

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This is the second design, I got rid of the hose hookup. I just use a funnel.


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Heres the broken pics before I put on the bumpers

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<a href='http://media.putfile.com/Hydro-pnumatic-1'>Click here to watch 'Hydro-pnumatic-1'</a>

Thanks for lookin

[FiveseveN]

Wow... I'm surprised it ever worked, mainly because there is no such thing as "compressed water". All the energy is stored in the compressed air and is passed to the water through the piston. Same thing as firing water in a regular pneumatic with a sabot.
It's a good idea, though. Perhaps one could make a piston valve with liquid pilot.

[sergeantspud2]

Well I know theres no such thing as "compressed water" hence the piston which when mixed with air created the boom that pushed the projectile out.

EDIT: Dont know what happend to the pics look like the picture hosting site when down for now. Ive been using them for a little over 1 1/2 years so they might come back

[sam_516]

i must say that it is a good idea to trust murphy's law caz if you don't then you will get hurt crap that thing must have some kick... i shot my combustion cannon with water as the projectile (well my friend...rna_duler...shot it i was too much of a wimp) and it blew straight out of his hands and stuffed his kneee up...

nice thought tho and english is the best place to think up of cannon designs...well skool is the best place caz wat else do you go to skool for but learn

[sergeantspud2]

Oh yeah there's major kick i cant hold it I have to put it up against the ground. Im thinking of some kind of stand for it.

I guess not many people are looking at it but theres a question in there also. What kind of valve do you guys think I should put on it because im getting tired of turning the ball valve. And with a sprinkler valve im afraid that it will produce to much friction with the water having to go up then back down with the diaphram.

[rna_duelers]

there isnt really another valve you could use maybe a butterfly valve?but thats basicly the same,try making a pneumatic ram for the ball valve maybe.

[FiveseveN]

Your best option is probably to rig a spring and trigger to the valve you have now.

[drac]

Burst disks all the way.

[sergeantspud2]

Ok so maybe if I get a metal ball valve because the pvc one is really hard to turn then do the pnumatic ram idea. Would a ram off of an autococker paintball gun have enough pressure to open it do you think?

[Flinchy]

thats an interesting concept you have going there, although id rather go with compressed air than water.

[sergeantspud2]

Yeah, theres pretty much no benefit for using water. I just wanted to make a gun that no one has made before and its cool because you can fill it all the way up with water and fill the barrel with water, shoot it in the air and get drenched with water

[rna_duelers]

Well i dont think a ram off a paintball gu would do,you could make one from pvc it wouldnt be to hard to design.A piston inside some pipe with a rod attachet to it would work fine i would think but make sure it can swivle and has some give.There is a cannon on this site that uses a pneumatic ram just get some ideas off it.

[Darkside 6ix]

i like it. especially the fact that you thought it up in english class.

[sergeantspud2]

Ok I think instead of making a piston Ill just but one from mcmaster they're like $20 for a 7/16 bore and a 3" stroke. The only thing I need to think of is how im going to mount it. I was thinking get a 4x6 piece of wood and cut it down to 4x6x7 and cut a half a hole down the middle so I can lay the valve inside of it then I can mount the ram on the piece of wood. I think that would make it heavy though. Got any ideas?

[GhostMonkey]

oooo ... really good idea ... can't believe it blew everything apart with just 40 psi ...