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silencers

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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silencers

Unread postAuthor: POLAND_SPUD » Sun Jan 20, 2008 5:04 pm

I am currently building a silencer for my QEV cannon (it isn't semi yet, it seems that it would take me some time to make several upgrades on this but since I am using threaded steel and iron fittings it shouldn't be any problem).

The silencer is a 2L bottle that fits nicely on the muzzle of 1/2" steel barreland it seems that the size/volume is appropriate as wel (is it really.......... ???)

I am going to test several versions: with baffels, w/o baffels, with holes and w/o holes in the outher casing.. I'll post some results and maybe some pics in one or two weeks time...

now if anyone has some theories or did some research or tests you are free to post here about them
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Unread postAuthor: ALIHISGREAT » Sun Jan 20, 2008 5:26 pm

i wouldn't bother testing with hole in the outside because do you see any firearm silencers with holes in the outside?

but the difference in effectiveness between the with and without baffles silencers would be good to know.

oh and what size will your chamber be? and what pressure will you use it at?

i will also be constructing a silencer for my 400psi piston cannon as i don't want to scare the neigbours :D and i'm thinging of useing a muzzle brake style attachment to redirect the air back into the silencer which won't be sticking off the front of the barrel as the best will already be 150cm+ long how well do you thnk this would work? if it fails i will just make it removable.
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Unread postAuthor: POLAND_SPUD » Sun Jan 20, 2008 7:40 pm

I've already build the gun. Currently it is all metal, other specs
barrel - 115 cm 1/2"
chamber - 70 cm 1/2"
firing valve - 1/2 QEV
pilot valve - 1/2 ballvalve
pressures tested 0 - 320 psi ( above 300 psi the noise is unbearable)

the gun is way too loud... I even tested with 30 cm chamber but it was still loud

well I would try the version with holes - just to be sure whether it really works or not...

"useing a muzzle brake style attachment" - ALI could you elaborate on that, I don't really understand that... ?

as far as the problem of lenght is concerned I am also thinking of the testing how much the performance of silencer is affected by the overal lenght of barrel + silencer.... so in other words how well it would work when the muzzle is at the back of the silencer vs. in the middle of the silencer.... possibly it would be better idea to drill several small holes on the last 10 - 15 cm of barrel and then just put a bottle over the muzzle and the holes.... but I am going to do that only if the current designs fail do their job satisfactory
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 20, 2008 7:42 pm

Volume is your friend in this case, make it as big as you can. you've seen this design, if you can get creative with the baffles it will be even more effective.
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Unread postAuthor: POLAND_SPUD » Sun Jan 20, 2008 7:56 pm

is 2 L enough ? the silencer is already something big and I am trying to keep it as light and compact as possible... possibly I could increase the volume even more by adding another 2L bottle under the barrel or on the barrel and connect it withe the proper silencer - so that it would work as a kind of additional expansion chamber (?)
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 20, 2008 7:59 pm

It should be enough for a reasonably quiet shot, but bigger is always better. I would start with one bottle and see how it goes.
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Unread postAuthor: ALIHISGREAT » Mon Jan 21, 2008 2:33 am

"useing a muzzle brake style attachment" - ALI could you elaborate on that, I don't really understand that... ?


well muzzle brakes direct the gases from the muzzle backwards... so i was thinking of instead of just using holes in the barrel i would use a brake to direct the gas.

It should be enough for a reasonably quiet shot, but bigger is always better. I would start with one bottle and see how it goes.


i don't think bigger will be much better because his sliencer will already be 2000cc. another thing to silence it more is to add a silencer to the pilot, as you will be closer to it than the muzzle (i'm guessing) it can sometimes be quite loud. i will have to silence the QEV pilot on my cannon if i want to use it without ear protection.
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Unread postAuthor: jackssmirkingrevenge » Mon Jan 21, 2008 2:45 am

ALIHISGREAT wrote:i don't think bigger will be much better because his sliencer will already be 2000cc.


silencers are like engines, there's simply no substitute for cubic capacity ;)
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Unread postAuthor: ALIHISGREAT » Mon Jan 21, 2008 2:49 am

silencers are like engines, there's simply no substitute for cubic capacity


but its also about practicality and gain, not every supercar manufacututer put a massive 16L W16 in their cars because its super big and powerful :wink:
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Unread postAuthor: POLAND_SPUD » Mon Jan 21, 2008 1:22 pm

yeah silencer on the pilot would be needed to silence it... i was thinking about adding a muffler but i have no idea how this would affect the flow of the pilot valve...

Ali how is muzzle brake going to silence the gun ? It makes sense if you are going to build sometineg like that butinside the silencer... just a muzzle brake wouldn't help much AFAIK
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Unread postAuthor: ALIHISGREAT » Mon Jan 21, 2008 1:30 pm

Ali how is muzzle brake going to silence the gun ? It makes sense if you are going to build sometineg like that butinside the silencer... just a muzzle brake wouldn't help much AFAIK


yeah thats what i meant, let me draw a diagram :P the reason i would do this is to cut down on any extra barrel length.
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Unread postAuthor: POLAND_SPUD » Mon Jan 21, 2008 4:19 pm

I just tested a silencer built with a 2L bottle only.... there is some reduction in the level of sound but I was expecting something better - well at least I can still hear after a shot at 300 psi... so to sum up - it is not a great improvment but at least I am not going to get deaf....

hmmm also I noticed that the bottle dents after every shot.... after replacing it with more rigid bottle everything is ok...

so my next steep is either: 2 X 2L bottles, baffles or additional expansion chamber (maybe just another bottle that would be connected with the silencer by a garden hose or something

I'll post pics later
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Unread postAuthor: ALIHISGREAT » Mon Jan 21, 2008 4:43 pm

hope it workes better with the baffles, what size hole do you have in the end of the 2L bottle or is it over the barrel?
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Unread postAuthor: Ragnarok » Mon Jan 21, 2008 4:59 pm

POLAND_SPUD wrote:( above 300 psi the noise is unbearable)
the gun is way too loud... I even tested with 30 cm chamber but it was still loud

Why are you not using ear defenders? There should be at least one set of ear defenders in any spudder's collection, and a set of goggles too. Preferably two of each, that way you're less likely to be unable to find a pair when you need them.

Noise dies off with distance quicker than you might think, so other people are not as much of a concern as you'd believe. If you measure 90 dB a metre from the muzzle (I recorded slightly more with HEAL, but that was dumping a volume of air a full order of magnitude larger than yours with a higher C:B ratio), it will have fallen to just 70 dB ten metres from it.
Another 22 metres, it's just 60 dB - and that's a no louder than a quiet conversation.
Add in an outer house wall and background noise, people in houses 30 metres away are going to be completely oblivious to your activities. It's only the people that live right next to you that you need to be concerned about, and I find that if you tell them that you've got a fairly noisy "air rifle" that you'd like to use occasionally, but only at reasonable times of the day, they'll be fine with it.

It's worth bringing the volume down a bit, but you don't need to be too worried. I'll have to create a new suppressor when HEAL goes to 30 bar, but until then, it's not a problem.
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Unread postAuthor: POLAND_SPUD » Mon Jan 21, 2008 5:22 pm

Ragnarok wrote:Why are you not using ear defenders?


Acctually I am usually using them - but even when I have them on is quite loud above 300 psi
anyway the problem is that I fire close to my house so my parents are not really happy about the level of noise and my dog doesn't like that neither...
besides - it would be nice to have an almost silent gun.....

lowering the chamber volume is possible - I suppose that the gun would be much more silent with my current silencer if I was using half the chamber volume I use now.... the problem is that it affect performance and I still want to use this gun with my 170 cm 3/4" barrel..... possibly I could add a ballvalve between to sections of chamber that could be closed to cut the volume volume when needed

ALI - the hole is ~20mm... maybe the smaller hole I have little time this week......I hope I would have more during this weekend..... :?
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