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[help] So basically..is this how it works?

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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[help] So basically..is this how it works?

Unread postAuthor: stoj » Mon Oct 24, 2011 10:52 pm

I've been looking into making a marshmallow cannon lately and I've come to a standstill. I'm having trouble visualising/grasping the concept of the components. Help me out here..but is this how it works? (see attachment)

1. So the chamber connects to the QEV, which then connects to the trigger (pilot valve i think the technical name is?) and also to the barrel, and on activation of the trigger, the QEV allows air flow?

2. Also, if this IS how it works...will this method dump the entire chamber or can it be 'pulsed', depending on the length of time the trigger is held down? (effectively giving me a couple of shots before having to reload the canister, provided I reload the barrel?)

3. What sized chamber would you recommend for shooting marshmallows a significant distance, (i have a small fire extinguisher downstairs that could be utilized...which could handle a small/large amount of PSI I think)

Thanks in advance..also, first post! :) Great community.

EDIT: End result wanting to look (mechanically) like this...http://www.spudfiles.com/forums/psg-1-s ... 21786.html

(Aesthetically not possible, I'm not talented enough to shape wood that well)

Could I get pointed in the right direction too? Thanks!
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Unread postAuthor: Technician1002 » Tue Oct 25, 2011 12:01 am

General advice on the chamber is based on if this is designed for marshmallow plinking or if you are going for record marshmallow velocity. A huge chamber can be used for multi-shot, but the slow recovery of the valve will use huge amounts of air. The best design is generally designing the chamber size to be for one shot, and then use a second air accumulator tank for multi shot. A smaller chamber limits air usage and provides consistent high pressure shots.
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Unread postAuthor: jazzman56 » Tue Oct 25, 2011 12:03 am

Firstly WELCOME TO SPUDFILES :D

Yes, the first (1) question is correct, all though you need to add a fill valve (air compressor) to the Pilot (TRIGGER) of you QEV such as a quick release fitting found on a air compressor (make sure is a male one so it can pilot).

2, A QEV cannot be pulsed once piloted it will dump all of the air in the chamber out the barrel. To get multiple shots you can (These are only a few ways)

Have a Slide/Qev combo.

Or a ball valved one (it's easier but has less performance).


3, What size chamber do you already have, If it's larger than 500cm3 it's better off used as a multishot as pumping a 1 liter tank to 160 PSI takes about 45-50 pumps.



What type is it (Foam, powder, co2 etc.) Some extinguishers are rated less (look for the sticker/gauge with PSI/ MPA on it) ?

What pressure do you want to use it at?

Are you going to fill it via a bike pump or compressor?


(note in the current configuration you will only get one shot if a fill valve is added on the pilot side)


Hope this helps :)
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Unread postAuthor: stoj » Tue Oct 25, 2011 1:39 am

Both are extremely helpful posts...thanks alot!

The extinguisher (my little one has a net mass of 0.9kg, as read from the label) is powder, however I was planning to empty it and then use it for compressed air.

So what I'm looking at now is this. (attachment) (EDIT 2: meant to be ball valve not paddle valve :P) And the process of firing would be; Fire > open up fill valve to fill up air in the canister (from a secondary tank or portable compressor) > close off fill valve when at desired pressure > reload barrel > fire.

(JUMP TO MY EDIT1 IF YOU TLDR THE NEXT SECTION)

Would a better option with the air chamber to use PVC, then connect the fill valve, PSI gauge and PSI pop off valve to that? However I detracted the use of PVC as dropping it on occasions would increase the chance of it shattering and causing injury. Would it be possible to add a fill valve, psi gauge and psi pop off valve to a heavy duty canister such as the extinguisher to simplify the process? (Fire > connect external air compressor to tank > reload barrel > fire) Would this will also increase the simplicity of the design?

Also could you explain the slide/qev combo? Sorry for all the questions!

EDIT: I've realised using a secondary tank is far better...as it is portable. Would a worthy 'ammo' tank be something like this? http://www.ebay.com.au/itm/Air-Tank-9lt ... 4aafa129d3

And then I connect the hose to a valve, to another hose to the pilot valve?
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Unread postAuthor: Crna Legija » Tue Oct 25, 2011 2:23 am

more like this
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Unread postAuthor: wyz2285 » Tue Oct 25, 2011 2:29 am

Well for me one chamber is possible for semi, with a slightly moded blowgun :D but my way isn't very popular around here :roll:
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: jazzman56 » Tue Oct 25, 2011 3:58 am

wyz2285

Is there any chance of a how to for that modded blow gun as i still don't understand how it works :)
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 25, 2011 4:22 am

jazzman56 wrote:Is there any chance of a how to for that modded blow gun as i still don't understand how it works :)


Image

It's basically a pop-off valve at the pilot exit.
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Unread postAuthor: wyz2285 » Tue Oct 25, 2011 4:23 am

i'm using my phone right now so i can't send you a link, you can ask around or i send you a link when i get home
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: stoj » Tue Oct 25, 2011 4:35 am

Crna Legija wrote:more like this


from the slide valves i've looked at on ebay..are they all manually operated? if you could explain how this design works that'd be much appreciated..

EDIT: are they similar/exactly the same as piston valves?
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Last edited by stoj on Tue Oct 25, 2011 4:41 am, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 25, 2011 4:39 am

stoj wrote:from the slide valves i've looked at on ebay..are they all manually operated? if you could explain how this design works that'd be much appreciated..


Have a read through this post, should explain everything ;)
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Unread postAuthor: stoj » Tue Oct 25, 2011 4:54 am

that clears up a lot of minsunderstandings, thanks jackssmirkingrevenge. one more Q however; after releasing the trigger, this will stop the air flow to the barrel and the process will be repeated, however what does the 'manual' part of the name have to do with the product?

source from the link in that post; Deltrol SL35 3/4" Slide Valve NEW IN BOX Manual valve

does this mean that to cut off the air flow i'll have to pull it back or something?

thanks :)
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 25, 2011 5:06 am

stoj wrote:does this mean that to cut off the air flow i'll have to pull it back or something?


Did you imagine that you just had to mentally conjure up the concept of "valve open" and it would slide though telekinesis ;)

Naturally you have to pull it back to activate it, same as you would any trigger.

One small mod you have to make is a small spring to return it to the closed position if you intent to use it like a semi auto trigger.
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Unread postAuthor: stoj » Tue Oct 25, 2011 5:14 am

jackssmirkingrevenge wrote:
stoj wrote:does this mean that to cut off the air flow i'll have to pull it back or something?


Did you imagine that you just had to mentally conjure up the concept of "valve open" and it would slide though telekinesis ;)

Naturally you have to pull it back to activate it, same as you would any trigger.

One small mod you have to make is a small spring to return it to the closed position if you intent to use it like a semi auto trigger.


haha not entirely :P

SO will the air stop flowing when i pull the slide valve BACK, or when i release the trigger?

Plus what are the parts used in this creation? (I see a ball valve, chamber, trigger, etc but i can't see how the trigger works)
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 25, 2011 5:33 am

A slide valve has two positions, for the purposes of this conversation we will call them "unfired" and "fired"

A standard slide valve has no bias towards any particular position. In order to be used as a "conventional" trigger it needs some modification.

You basically need a return mechanism (coil spring, rubbar band, trained beetles etc.) that will keep the valve in the "unfired" position when you're not touching it.

You also need to attach some sort of... well, trigger - to the slide part, otherwise it's quite inconvenient to use.

Have a look at this fine example by Lockednloaded.

Plus what are the parts used in this creation? (I see a ball valve, chamber, trigger, etc but i can't see how the trigger works)


All you need is QEV and slide valve. The slide valve is the trigger, but as I said it needs some sort of trigger mechanism fabricated in order to have it function ergonomically.

You obviously also need to connect a chamber to one side of the QEV and barrel to another, and an air supply to the slide valve.

edit: pictoral guide :D
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