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silencer volume

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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silencer volume

Unread postAuthor: ALIHISGREAT » Thu Sep 27, 2007 12:42 pm

would a volume of 423cm3 be alright compared to a 368cm3 barrel and a 1000cm3 (roughly) chamber.
p.s. i may have done the calculations wrong its pi*(r*r)*height right?
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 27, 2007 12:48 pm

nope, for a pneumatic it should be at least as big as your chamber - bigger is better and there's no substitute for cubic capacity.
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Re: silencer volume

Unread postAuthor: Hubb » Thu Sep 27, 2007 12:50 pm

ALIHISGREAT wrote:its pi*(r*r)*height right?


Yes.

As far as the answer to the question, if those are your numbers, it will work to silence your cannon, however, the bigger you went, the quieter it will be.
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Unread postAuthor: williamfeldmann » Thu Sep 27, 2007 12:56 pm

Your formulas are correct and you have the right idea, but not enough volume in the silencer for a "silent" shot. However, you are around half the chamber volume now which make a big difference in the loudness of your shot.

You will never get a truely silent shot. Movies and TV make it seem that way but it isn't true. However you can greatly lower the volume of the shot with enough of a silencer chamber.
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Unread postAuthor: ALIHISGREAT » Thu Sep 27, 2007 1:09 pm

jackssmirkingrevenge wrote:nope, for a pneumatic it should be at least as big as your chamber - bigger is better and there's no substitute for cubic capacity.

yes but my barrel is 130cm and my chamber is 85 cm long + the volume of some fittings and i want to make the silencer detachable to make the cannon smaller for storage etc. so a 1m+ silencer (when you take into account the barrel inside the silencer ruducing volume) is just not realistic.
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Re: silencer volume

Unread postAuthor: ALIHISGREAT » Thu Sep 27, 2007 1:10 pm

hubb017 wrote:
ALIHISGREAT wrote:its pi*(r*r)*height right?


Yes.

As far as the answer to the question, if those are your numbers, it will work to silence your cannon, however, the bigger you went, the quieter it will be.


woo i got the formula right! anyone who says maths is a waste of time is wrong :lol:
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 27, 2007 1:21 pm

ALIHISGREAT wrote:i want to make the silencer detachable to make the cannon smaller for storage etc. so a 1m+ silencer (when you take into account the barrel inside the silencer ruducing volume) is just not realistic.


Why not have silencer integral over the whole barrel like this - it doesn't increase your overall length at all and allows you maximum volume.
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Unread postAuthor: williamfeldmann » Thu Sep 27, 2007 1:36 pm

So now you have me wondering Jack...

Lets say I wanted to do this do an existing gun that has roughly the same length of barrel, 4 foot, and I have previously used a muzzle-mount silencer(of your rough design) with muzzle portings (around 2 inches in from muzzle). Assume my chamber is the same size.

If I wanted to run an itegral to cut down on length, do I use the same porting at the muzzle and just have silencer chamber running back toward the valve, or do I need new portings closer to the muzzle, or do I need porting every foot or what not. I know holes are more effective than slits.
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Unread postAuthor: ALIHISGREAT » Thu Sep 27, 2007 1:39 pm

jackssmirkingrevenge wrote:
ALIHISGREAT wrote:i want to make the silencer detachable to make the cannon smaller for storage etc. so a 1m+ silencer (when you take into account the barrel inside the silencer ruducing volume) is just not realistic.


Why not have silencer integral over the whole barrel like this - it doesn't increase your overall length at all and allows you maximum volume.


i would but i want power :twisted: and surely the full barrel silencer would reduce power by quite alot because the air pressure behind the projectile would drop significantly more earlier in the barrel an reduce performance. it would work better as a silencer though and i will probably use it ona future cannon to see how quiet i can make one, a pnuematic could probably be almost completely silenced by a fell barrel silencer
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Unread postAuthor: Hubb » Thu Sep 27, 2007 1:42 pm

A removable silencer?!?! Oh, no!!! :pale:


jk :D
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 27, 2007 1:51 pm

If you're using the same barrel length, be prepared to lose out on some performance. The ideal (within the real of home workshop craftsmanship) integral suppressor should look something like the attached diagram, and stuffing sound absorbing material into the chambers should increase its effectiveness.

i would but i want power and surely the full barrel silencer would reduce power by quite alot because the air pressure behind the projectile would drop significantly more earlier in the barrel an reduce performance. it would work better as a silencer though and i will probably use it ona future cannon to see how quiet i can make one, a pnuematic could probably be almost completely silenced by a fell barrel silencer


The thing with compressed air as a propellant is that the air pressure doesn't derive from heated gas as with firearms so it's more difficult to silence, particularly when using large volumes. A 0.22 rimfire rifle with a good silencer can be practically inaudible, but an air rifle producing similar ft/lbs would require a massive silencer by comparison.
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Unread postAuthor: williamfeldmann » Thu Sep 27, 2007 2:49 pm

I assume the "action" or valve is to the left in your picture close to the holes. Correct me if I am wrong.

Would it work to move the ports closer to halfway up the barrel with larger baffles toward the ends and smaller baffles in the middle? Would this be less effective?

It seems to me the farther I can get my projectile in the barrel before stealing its propulsion, the more power I harness. I know that only ports in the end of the barrel will be useless because the air won't have time to dissipate into the silencer, but at halfway there is still time to capture the majority of the air. Then a set of ports at the end of the barrel to catch the last little bit. Does this make sense?
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Unread postAuthor: ALIHISGREAT » Thu Sep 27, 2007 3:40 pm

williamfeldmann wrote:I assume the "action" or valve is to the left in your picture close to the holes. Correct me if I am wrong.

Would it work to move the ports closer to halfway up the barrel with larger baffles toward the ends and smaller baffles in the middle? Would this be less effective?

It seems to me the farther I can get my projectile in the barrel before stealing its propulsion, the more power I harness. I know that only ports in the end of the barrel will be useless because the air won't have time to dissipate into the silencer, but at halfway there is still time to capture the majority of the air. Then a set of ports at the end of the barrel to catch the last little bit. Does this make sense?


yes it does, another way could be to use shaped baffles to redirect the air back wards and have the holes near the muzzle but have a full length silencer.

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kind of like my crude punctuation drawing! excempt obviously the shaped baffles would not stick into the barrel they would just redirect the air back into the silencer chamber. and if that was a whole barrel the holes would start wher the astrix is.
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 27, 2007 4:11 pm

I assume the "action" or valve is to the left in your picture close to the holes. Correct me if I am wrong.


No, the valve is actually on the right in this case - the idea is to let the projectile pick up speed before as you rightly pointed out robbing it of its motive power.

There are some integral firearm silencers where the porting starts at the breech as in the case of the HK MP5SD but the intention of this is to deliberately reduce the performance of standard supersonic 9mm ammunition in order to keep the bullets subsonic.
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Unread postAuthor: ALIHISGREAT » Thu Sep 27, 2007 4:33 pm

ahh i still could not do a full length one because of my breech loading setup
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