Author Topic: Fuel filter silencer  (Read 1610 times)

0 Members and 1 Guest are viewing this topic.

Offline airgunnut

  • Hero Member
  • *****
  • Posts: 3831
  • Karma: +1204/-1148
  • I aim to please, but usually miss!
    • Doncaster
Re: Fuel filter silencer
« Reply #20 on: February 04, 2021, 08:18:55 AM »
taken from my post on airgun bbs in 2014
i had a gun power stealth for which i bought a massive silencer, looked fantastic, i thought that with the size of the silencer it would be more than capable of trapping the blast of air and quietening the stealth, it did not work! the internal volume of the (so called) silencer was that big it caused an echo, increasing the blast sound rather than muffling it!!!
on the other hand a former work mate made a silencer for his air gun, at first i didn't notice it on the gun, on a closer look it looked like a barrel weight, until he pulled the trigger, all you could hear was the faint click of the action, he said that the hole in the baffles was just (and he did mean just) bigger than the pellet.
in ww2 the welrod pistol had rubber washers with the central hole smaller than the bullet http://www.timelapse.dk/thesilencer.php to keep as much gas in the silencer for as long as possible

things to think about when building a silencer
have a stiff rod the internal size of the barrel (.177 or .22) to aid the lining up of the baffles
build the silencer on the gun, this will insure the baffles are aligned correctly when using the rod
work out how much air the gun releases in to the barrel, then you can use this to work out the volume the silencer has to be (too small and the silencer will be overwhelmed and could be dangerous, too large and it will echo) it also means that the silencer is as small as possible
make the holes in the baffles as small as possible
you will have to experiment with how many baffles you need for your gun

To further my statement about findind out how much air is released in to the barrel, (this is an eg as every gun is different) say your gun is regulated at 80bar and injects 3cc of air in to the barrel, the air expands as it wants to be at atmospheric pressure, so that 3cc of 80bar air will expand to 240cc, if you made a silencer that's only 150cc then it will be overwhelmed and could blow apart if not made "beefy" enough
"Men occasionally stumble on the truth, but most of them pick themselves up and hurry off as if nothing had happened"
Winston Churchill
尼尔·菲奥里

Offline Baggawind

  • Hero Member
  • *****
  • Posts: 1778
  • Karma: +1191/-4
  • Planet Airgun's Pied Piper
Re: Fuel filter silencer
« Reply #21 on: February 04, 2021, 10:45:39 AM »
Knowing how much air is released is the problem. That depends on so many variables it is , to me at least , impossible to work out. For instance , the size of the valve , hammer weight and hammer spring strength , how far the valve opens . Too much for my simple mind.
As a footnote however , my lightweight ratter has always sounded a bit " snappy " when fired . It is fitted with one of my silencers , built to the same dimensions as a Weihrauch . Even fitting an HW unit didn,t cure the problem. But , yesterday when testing the rifle i felt a small puff of air coming from around the breech area. So i pulled it apart and found out where the air was coming from. I made a new brass insert that holds the probe o ring and also contains the tp. Now no leaking and , more importantly , it,s as quiet as a Weihrauch. Chuffed to bits.

Offline airgunnut

  • Hero Member
  • *****
  • Posts: 3831
  • Karma: +1204/-1148
  • I aim to please, but usually miss!
    • Doncaster
Re: Fuel filter silencer
« Reply #22 on: February 04, 2021, 12:05:36 PM »
Too much for my simple mind.
Bollocks, you are designing and building trigger and valving systems for air guns, this should be a walk in the ratting pen for you!
take the barrel you want to use, plug one end, fill with water, then pour into a cup on a weighing scale (cup pre zeroed on the scale) this will give you so many grams of water, 1 gram = 1 cc. unplug and dry the barrel, replace on gun, fit a pressure gauge on the muzzle end, cock the gun (no pellet for obvious reasons) pull the trigger and read off the psi, now you have every thing you need to work out how much air is released.
plastic hair curlers holding lightly packed coarse wire wool as the "packing" baffles with a hole size just bigger than the pellet and a tube of the size are all you need to produce a silencer.

there used to be a silencer that you could increase/decrease the length to tune it
not the one i was thinking of but......
https://www.allcocksoutdoorstore.co.uk/item/Swift/Flatback-Stumpy-Sound-Moderator/Q0Y
"Men occasionally stumble on the truth, but most of them pick themselves up and hurry off as if nothing had happened"
Winston Churchill
尼尔·菲奥里

Offline Baggawind

  • Hero Member
  • *****
  • Posts: 1778
  • Karma: +1191/-4
  • Planet Airgun's Pied Piper
Re: Fuel filter silencer
« Reply #23 on: February 05, 2021, 11:14:50 AM »
Not bollocks exactly. I,m really am not that clever. Any damn fool with knowledge of how to use a lathe and milling machine can do what i do. You just need to know how a pcp works really.  There,s no science or mathmatics goes into making any of my creations. I did,t know that 1cc of water weighs 1 gram.  And it wouldn,t have occured to me in using that to calculate the volume of a silencer.  I just come up with an idea , make it and hope it works. When i made my first pcp there were no technical papers or drawings available then. So i had to work out for myself how they worked. That chap Ford of Sportsmatch fame wouldn,t even talk to me when i asked what material i should use. The late , great , Gerald Cardew on the other hand told me what to use and even offered to test the tube for me. I used to send him plastic and ptfe offcuts and even a load of cutting tools . What a nice man he was. Ken Galway even offered to send me the drawings of one of his Fieldmaster rifles , but i turned the offer down.  I just wanted to work it out for myself. Anyway the first pcp was a pistol , back in ,89 . Bloody heavy it was too , I,d over built it. When i described my valve design to Barry McGraw he said it would never work. It did and still is working.  ???  After making the pistol i had by then bought a Titan Manitou which, after a year or so, i stripped down to see how it worked. It was plain sailing after that , it taught me all i needed to know. I can,t finish this post without mentioning my very good friend Dave Whelham who has helped me more than i care to mention.  Oh and by the way, this morning i compared my silencer against the Weihrauch when fitted to the Ratter. To my ears , mine is actually quieter . Once again though, not exactly a scientific test.  :)

Online Gambo

  • Administrator
  • SuperHero Member
  • *****
  • Posts: 29610
  • Karma: +218/-50
  • Pellet Porn Queen
    • Cardiff, South Wales.
Re: Fuel filter silencer
« Reply #24 on: February 05, 2021, 06:39:18 PM »
You,re probably right about the harmonics thing.  Another thing might be something to do with wether the rifle is regualted or not . Lower pressure being released perhaps. I don,t know. 

Certainly reg'd rifles do seem to benefit more than unreg'd ones when fitted with identical silencers. However, two of my fave rifles,  the FX2000 and the AA 310/410 are both unreg'd, yet the Weihrauch is much more effective on the FX. Both are doing the same velocity with the same pellets, both have similar fill pressures so I think it's safe to assume that both rifles are expelling a very similar amount and pressure of air......yet the FX is noticeably quieter at the muzzle. The only difference I can think of between the two is the FX has a floating hammer......so maybe there is less hammer bounce onto the exhaust valve..........compared to the AA valve which is under constant pressure from the hammer spring.

 

EDIT...... Not really fully convinced about the silencer volume theory.....and here's why.....

I've bleated on a number of times in this thread how much I rate the Weihrauch silencer, and how I've fitted them to as many of my PCP's a possible, as they are the absolute dog's at reducing muzzle report.

If that effectiveness was all down to the internal volume being perfectly matched to the rifle's air output, then why are they just as effective on sub 6ftlb pistols, right up to FAC rated rifles throwing out in excess of 35ftlbs?

Thinking about it logically, Weihrauch designed that silencer for their HW100, which in their home market only legally produces 6ftlbs....yet it works fantastically at the UK limit of 12ftlbs too. Up the puff to 30ftlbs+ and it's still doing the beans....and working at a power and air volume output I would doubt it was ever intended for. All varying air pressures and volumes....but still the best IMHO.

I can see the idea behind that perfectly matching the internal volume is a sound one (pun intended), but whether it is actually the most important thing I'm not so convinced. I will however concede that a silencer with too small a volume will not be effective if the rifle expels more puff than it can handle....but too much volume is equally as bad? Hmmmm?!?! Dunno. ???

Yes Uggs, I too had a Stealth (brand new) with their own (un)stealth(y) silencer. The whole gun was a pig, completely unrefined and nasty. I sold it almost immediately.....but a few years later I wondered if I'd just been unfortunate and had a duff one, so I bought a secondhand one. That was just as crap. Just to make sure I then bought a 3rd one. Same.

Just like those immortal words in that song..........You're once, twice, three times a lady idiot!!!



« Last Edit: February 05, 2021, 07:25:31 PM by Gambo »

Offline airgunnut

  • Hero Member
  • *****
  • Posts: 3831
  • Karma: +1204/-1148
  • I aim to please, but usually miss!
    • Doncaster
Re: Fuel filter silencer
« Reply #25 on: February 07, 2021, 12:12:26 PM »
Gambo the reason for the correct volume of the silencer is to slow and hold the rapidly expanding gas and release it in a controlled manner which reduces the noise, with the exit hole been as small as possible to hold the gas in and reduce the turbulent air flow trying to overtake the pellet, the silencer can become a pressure vessel if its volume is too small and if its  not made correctly or made of materials too thin or cannot hold the pressure that builds up, it can undergo a catastrophic self disassembly. silencer manufacturers that make firearm silencers are now making them calibre specific to increase the effectiveness while keeping the baffles as simple as possible (reducing the cost) if the silencer is too big it can course an echo and make the gun louder(which is what happened to my stealth when i fitted a huge silencer which had just 2 baffles and nothing else.
the reason why airgun silencers are affective over a range of power limits is due to a compromise of size, baffles and cost (it will cost hell of a lot to produce a dedicated silencer for every gun and calibre in there range). 
with precharged pistols, they can use almost as much air as a rifle, pistols have at most an 8 inch barrel (most of the time a lot shorter) they have less barrel to accelerate the pellet down, while the air is expanding in the barrel you could say the pellet is extracting energy from it, soon as the pellet leaves the barrel its free wheeling to the target as the compressed air that was pushing it can now expand in all directions, with a short barrel you have to extract more energy in a shorter distance, the only ways of achieving this is to increase the pressure of the air behind the pellet or to increase the amount of air, (.177 uses more air as there is less surface area to push on) in regulated rifles and pistols with regulators they let more air in at regulated pressure (valve been left open a fraction of a second longer.

take a deep breath and exhale fast, not that loud, take another deep breath and blow it into a balloon, now pop that balloon, loud isn't it, both have the same amount of air but the balloon is at a higher pressure, a reg'ed air gun releases a big pulse of air at a exact pressure, un-reg'ed guns release a smaller pulse of air but at a higher pressure, both pulses of air might have the same volume at atmospheric pressure. as the un-reg'ed pulse of air is moving faster the silencer has to work harder to slow the air down (now you see why the silencer can be classed as a pressure vessel) if the silencer has the same volume as the pulse of air the baffle dont need to be a fancy design, the exit hole just has to be slightly bigger than the pellet. if the pulse of air is bigger than the volume, you have to have more/fancy design baffles to slow down the air giving the pellet time to exit the silencer before the air. if the silencer is bigger than the pulse of air then the air can bounce around in the silencer and echo.

sorry if it sounds like I'm insulting your knowledge of airguns but i'm trying to enplane as fully as i can.
"Men occasionally stumble on the truth, but most of them pick themselves up and hurry off as if nothing had happened"
Winston Churchill
尼尔·菲奥里

Online Gambo

  • Administrator
  • SuperHero Member
  • *****
  • Posts: 29610
  • Karma: +218/-50
  • Pellet Porn Queen
    • Cardiff, South Wales.
Re: Fuel filter silencer
« Reply #26 on: February 07, 2021, 07:01:07 PM »
Yes Uggs, I already previously knew and understood all of what you've posted above. ;)

It still doesn't fully answer why the same brand of silencer can work differently on different airguns of the same type and power. I've even seen the exact same silencer perform differently on identical rifles. How the hell can that happen? I can only hazard an educated guess at that. :-\

There have been past instances of airgun silencers coming in .177 or .22 calibres....but those were not that effective IMHO. If that was the answer to making quieter silencers then every manufacturer would have cottoned on and be using the technology, but the fact they aren't speaks volumes (no pun intended) to my mind.

I think one thing that can be agreed on this is that making an effective silencer is a black art.......there is no definitive as to what will work, and what won't.