Why do some silencers have springs in them?
What do they do?
PS I was going to ask why are there springs in moderators,but I could imagine
all those school boy humour replies aimed at the guys who look after this website
Diana 52.22 Vmach kit/short stroked.3-9x40 Airmax.AA S400.177+Hawke 4-12x40 EV
A pure guess, but using a spring is a cheap & easy way to hold internal components in place with no further fixings.
Well... This is a complete guess....
The springs and weights inbetween are there to dissipate energy from the air pushing the pellet. The pulse of air provides and a sharp force (impulse) to the weight, which starts it oscillating and the springs will bring the mass to a stop as quickly as possible.. There are several regions of damping, such as critical damping....
Just a pure guess
Most of the silencers with springs inside that I've had a look at, have fairly low rate springs, they don't need lots of force to compress them.
If you take the worst case, the air coming out of the muzzle fills the first compartment of the silencer (and slightly pressurises it) before going through the hole and into the next chamber, I can see there being a transient force on the baffle sufficient to cause the spring behind it to deflect.
They are just very convenient spacers to stop the baffle assembly from rattling or being required to be made to any accurate specs, i.e. design everything at least 1/2" too short so it will definitely fit, and let the spring take up the slack.
I don't like them because I don't like the idea of any movable objects in there, and a PCP's blast could very conceivably shift the baffle column forwards momentariily, and potentially a springer's recoil could jolt them too.
Again, this just a guess, however if the air coming out of the muzzle has a longer distance to go before exiting the silencer compared to the pellet, this will mean the pellet will leave behind the air pushing it therefor silencing the air-noise that would normally accompany the pellet leaving the muzzle, ie, it's holding back the air and quieting it down?
In my minds eye the coils of the springs make the air take longer to get out of the barrel, silencing it.
I suppose they serve both purposes of silencing it, and holding baffles in place.
As said, just a theory
What slows the air down is the fact that it expands into a given chamber and then has to find its way through a hole in a baffle into another chamber where it expands even further, and so on. Any friction due to the spring breaking up the smooth inner surface of the silencer can only be second order effect.
I have made loads of silencers and the most successful of these has no springs, no hair curlers, no pot scourers. Just baffles and spaces and orifices. Oh and a bit of engineering design.
springs are only fitted to make an annoying twang or boing when shot through. the idea is the pulse of air is hit by the baffle resonating back towards the pulse of air cancelling it out. active damping its called. i prefer the passive type described above.
The spring does nothing more than work similar to the cup shape baffles you get in a normal silencer such as a Parker Hale design. The word "baffle" gives a description of the effect of detouring the flow of high speed air that creates the noise.The simple one piece shape of a spring is a cheap way of creating the effect. When I made silencers in South Africa we used a spring shaped piece of nylon rod inside a tube for .22 rimfire and it works well. Still have one here in UK.Air rifles are very easy to silence and on some you can even use an empty tube as long as there is an end cap with a small diameter hole large enough for the pellet to exit.
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I have a 12 year old Tech Tronic silencer which has springs.
On my recent sound level comparisons it wasn't bettered.
And performed marginally better than a Daystate airstream.
Just think about what happens at the muzzle, or at the point where gun air meets outside air. The air coming out is at a higher pressure than the atmosphere.
In a badly behaved PCP, the firing valve is still open when the pellet reaches the muzzle, and so the pressure at that point could be close to the firing pressure, about 100 bar in a regged gun and maybe higher in a knock-open.
In a well mannered PCP, the firing valve shuts before the pellet leaves the barrel, and the maximum air pressure happens while the pellet is in transit. So the exit pressure is somewhat less, and of course no air is wasted.
In a spring gun, the maximum pressure happens - near enough - at the point when the pellet starts to move, and the pressure at the muzzle on exit will be typically 20 bar or thereabouts, much less than a PCP.
A typical PCP uses something like 150cc of air per shot. If you could have a silencer, just an empty can, of 150cc volume, and make the assumption that the exit hole is small enough to trap the air momentarily, then the exit pressure can only be 1 bar above atmospheric. Which is why volume helps.