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pneumatic grenade?

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Picture time

Unread postAuthor: bobgengeskahn » Sat Mar 13, 2010 7:34 pm

ok so here they are, mind you this was a proof of concept, that went terribly wrong... but questions, comments and especially criticism is welcome! :lol:

This is the stuff we started with:
1 x bike tire
2 x schrader valves
1 x cock drain
3/4" PVC
2" ABS
2 x 2" ABS unions
1 x 2" ABS end cap
1 x 2"-3/4" PVC reducer
1 x 3/4" PVC end cap
Image



first we fit the seal to the end of the 2" ABS, I had bike tires laying around and spent most of the morning trying to find something more robust or neoprine like, but was unsuccessful, we attached it with shoe glue and then pushed one of the 2" unions right over it, as you can see in the third picture it pulled the material all the way down, this actually made a really really tight fit.
Image
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once this was done we just eye-balled how long we wanted it to be and cut and test fit the collar to the other end:
Image

Image

Once this was done I constructed the end cap. We placed the drain cock in the side since it needed to be threaded and that was the thickest area that we could tap into:
Image
Image
Image

after this was done we made the core out of PVC. we took a dremel and took out the rim of the reducer cap so we could fit the 3/4" pipe through and fit the end to the threaded cap (why we went with a threaded cap i have no idea, seemed like a good idea at the time, shoulda just gone with a normal cap), we test fitted it for depth before using the glue so that it was putting just a little bit of tension against the diaphragm. after we knew where it was on the diaphragm we punched a hole with a SMALL awl in the center of it.
Image
Image
At this point we attached the end cap and tested the diaphragm by blowing air through the schrader, the diaphragm held well and vented well, and expanded a LOT... so my first question: how much should a diaphragm stretch?


unfortunately this as close to an assembled picture as i have... (was NOT expecting it to blow apart) here we have the assembled outer body with the core in the background drying.
Image


After that picture we used the PVC-ABS cement and put the two together and didnt let the glue dry enough apparently, because when i pressurized it (i had the PVC section pointed away from me, thank G-d), the PVC section flew across my garage and did this to the diaphragm:
Image

Lessons learned so far:
1. let the glue dry
2. need to read a little more on diaphragm valves lol


well thats what happened, I hope this at least provided some amusement for some of you even if there was no real progress made, although the drain cock valve assembly did work rather well.
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Unread postAuthor: Marffy » Sat Mar 13, 2010 7:47 pm

cool idea. i like the look of them. have you seen davidvani's airsoft grenades? they are pretty cool. you should check those out.
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Unread postAuthor: bobgengeskahn » Sat Mar 13, 2010 8:25 pm

hmmmm, is that on this forum? i searched for the username and didnt come up with anything, and when i searched for grenade the only threads that came up were in the OP
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Unread postAuthor: iknowmy3tables » Mon Mar 15, 2010 6:18 pm

sorry for the late reply I've been having trouble posting replies from my home computer (I'm on spring break and I normally live on campus)
well the bust disk cartridges arn't very relevant but
here it is
ARGHH now that you mentioned cartridges I keep accidentally using the word cartridge instead of diaphragms

excellent work on the prototype, chamber sealing diaphragm valves much I've only seen it on certain commercial valves

well you know how on most barrel sealing diaphragms people typically put solid backings around the center because pressure tends to want to push the diaphragm out the barrel so typical barrel sealing diaphragms, well a chamber sealing is even more tricky because the area around the center has to be thick enough to endure the pressures, so typically diaphragms aren't supposed to stretch much at all

you ought to order some sheet neoprene or this purpose or layer up the diaphragm, here's another construction diagram that should help limit the stretchable area of the diaphragm (once I get it uploaded)

edit: here's the diagram, sorry I could get it sooner I was at home for spring break and the internet at home has been annoying
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