SpudFiles

Ragnarok wrote:I hadn't. In any case, it's not quite the same as I had in mind; I am naturally reluctant to produce something that has the potential for blocking the barrel.

That is a valid point, maybe a floating ball was not the best way to go about it. Still, the fact that it seems like an obvious solution which no one has yet successfully implemented makes it sound like there is no easy implementation of the idea, as attractive as it looks on paper.

I looked at the idea, but I'm somewhat torn on the choice between this baffle shape (which isn't trivial to produce) and being able to extend the 22mm pipe through the suppressor (which has its own advantages*), as these aren't hugely compatible

A drill press can be sufficient to produce a complex and effective baffle stack:

Ultimately yes, but the 30cm planned length is about as long as I'm up for stomaching. Longer would make the launcher unpleasantly long and front heavy.

Yup, it's always a compromise between suppression and size.

Unless you're Russian. In which case, there is no compromise.

jackssmirkingrevenge wrote:A drill press can be sufficient to produce a complex and effective baffle stack

While very pretty, I think you're underestimating the difference in size here.

Scaled up for 20mm calibre, that's less trivial to create. Also, it's not so suited for the off-centre design I want - I'd rather the thing didn't block the line of sight over the barrel!

The fact that it seems like an obvious solution which no one has yet successfully implemented makes it sound like there is no easy implementation of the idea, as attractive as it looks on paper.

What I had in mind initially was crudely this:
Black is barrel, grey is an extension of it and red is the main structure of the suppressor.

The ports marked in green would be the ones covered by reed valves - allowing flow into the cavity, but not out. Only the rear most port in each cavity would be uncovered (or perhaps partially covered).
This doesn't seal off the air in the barrel or chamber, of course*, but it is still dramatically reducing the rate at which a large portion of the gas volume can rapidly vent to atmosphere.

*That said, the jets of air from the rear ports will provide some degree of slowing turbulence.

Ragnarok wrote:While very pretty, I think you're underestimating the difference in size here.

Scaled up for 20mm calibre, that's less trivial to create. Also, it's not so suited for the off-centre design I want - I'd rather the thing didn't block the line of sight over the barrel!

Here's the solution I had found for larger bores:



Not shown in the diagram are the ports in the chamber closest to the muzzle connecting the grey inner tube to the black outer tube. This gives you the possibility of creating a series of effective baffles within a relatively small diameter tube coupled with an unobstructed line of sight, while still giving you a large volume for pressure to drop via expansion (and heat loss of course )

You might want to look at the Silencerco Osprey:



[youtube][/youtube]

No doubt the design works, almost 30 dB reduction on a 1911 and better than more conventional competing designs.

Something like that could be fabricated out of sheet metal or even properly reinforced plywood with relative ease and without the need for specialist tools. Heck for a pneumatic you could make it out of balsa. and then...



http://www.cfsnet.co.uk/acatalog/CFS_Ca ... e_378.html

That and a splash of epoxy and you'd be golden, and it would be extremely light to boot!

jackssmirkingrevenge wrote:Here's the solution I had found for larger bores

I do like that hybrid approach to the problem. Perhaps modified slightly, to capitalise on the potential gains of muzzle venting: (Probably with more numerous and sophisticated baffles than that, but I just hacked apart the picture I did earlier).

I guess it is possible to omit any extension of the barrel if needs be, but the muzzle fitting as I've built/designed it at the moment will align and support weight better if used that way.

I don't know whether I'd try incorporating reed valves into this design though.

You might want to look at the Silencerco Osprey:

It's possibly what got the idea of eccentric suppressors in my head in the first place.

Ragnarok wrote:I guess it is possible to omit any extension of the barrel if needs be, but the muzzle fitting as I've built/designed it at the moment will align and support weight better if used that way.

For a smoothbore, go with a full length perforated barrel extending to the tip of the suppressor. It's the only way to guarantee prevention of baffle strikes with unrotated projectiles - as used on shotgun suppressors:

It's possibly what got the idea of eccentric suppressors in my head in the first place.

And not the work of your fellow countryman? Philistine!



Really though, the first Maxim silencers at the turn of the last century were mostly eccentric

http://www.aacblog.com/the-maxim-silenc ... to-use-it/

jackssmirkingrevenge wrote:For a smoothbore, go with a full length perforated barrel extending to the tip of the suppressor.

The downside is that's obviously going to affect gas and sound diffraction, and will thus reduce the effectiveness of the baffles. Well spaced ports can be made pretty large and high flow, but it's never going to be flawless.
Hmm. Maybe there could be something in angled ports.

The other question when it comes to baffles is phase cancellation. I know there's distinct limits to this, as a report is not a pure tone... but the stage technician and trumpet player in me wonder if a set of baffles, all differently spaced, could be used to focus the sound reduction on the 4000-9000 Hz region where human hearing is most sensitive.

Sound recordings show a lot of HEAL's report is pitched in this region, so it's not implausible to assume that Timberwolf would do the same.

Really though, the first Maxim silencers at the turn of the last century were mostly eccentric

In both senses. There's a certain wackiness to "There is a very strong tendency for the silencer to be blown off the front of the gun" being portrayed as a positive point.

Short answer: No, I'd need more resonators than I can meaningfully fit into the space to suppress that range of frequencies.

It may be worth having some other form of acoustic absorption in those cavities though.

A simple and effective solution would be to trap the gas.

Imagine adding a T to the barrel, a one way valve and an airtank large enough to create a sufficient drop in pressure..
A second valve could be used to drain the airtank slowly.
This bleedvalve could then be set to release the trapped gas to atmosphere through a industrial muffler, or a nozzle at a desired rate of flow.

Another way to achieve the same in an offset coaxial design would be to drill holes in the barrel, covered by some very light tubing.( cut into rings)
This will act like the one-way valve.

yet another way would be to use a reducer over the barrel.
Drill the holes in the barrel end set the reducer over them, porting into the larger diameter side of the reducer.

Then springload a ringchaped piston so it seals against the edge of the reducer.
You'll have a coaxial oneway valve around the barrel.
place this inside of a coaxial tank or container.

Wich ever method you choose-> this is the way a regular suppressor works, but executed in an extreme way.
Dropping the pressure and release it slower.
An additional baffle on the end would eliminate whatever noise is left.

On top of that:
After the projectile clears the muzzle...why is your valve still dumping pressure?
restricting the pilot exhaust ( timewise) would already reduce the noise by a significant factor.
Without bulk.
I frequently used a hammervalve to pilot the pistonvalve and set the hammerblow to meet my needs.

Or bottle the pilot exhaust ...it would do the same.The trick however is to adjust the volume of that "bottle"
I'm thinking...a section of pipe with an adjustable plunger?
Cut down afterwards, once you find that sweetspot.

Don't forget bleeding off the trapped pressure.

An added benefit would be multishot capacity..

The QEV is theoretically only 10 bar rated as well, but I'm fairly sure I recall that similar valves have been tested a good way past 40 bar by others. It's probably the "piston" that's the limiting factor here, although I'm not immediately well off for a way to upgrade it.

Aluminium piston with a neoprene seal...shouldn't be to hard to produce.
I see you have a checkvalve problem aswell.

A spring behind the piston of a QEV turns it into a checkvalve if you fill from the "barrel" side.

Perhaps you could adapt one already incorperated in the setup?

Brian the brain wrote:After the projectile clears the muzzle...why is your valve still dumping pressure?

The short version is that the valve design has performance, not air economy, in mind.

The longer version is that ratio of seat to piston diameter means pilot pressure in Timberwolf needs to fall to below about 30% for the valve to fire. But the valve is also made to ignore the idea of D/4*, and instead opens by about D, in order to ensure that it's as much out of the flow as possible, minimising any flow restriction.
* Because I think the "a chain is only as strong as its weakest link" logic that spawned this idea is flawed. Flow across any restriction causes a pressure drop, so it's more like electrical resistances in series.

Unless I cook up a system that actively repressurises the pilot (insert Airplane gag here) mid-firing, the valve isn't going to close until the chamber is almost completely empty. There's not a lot of air to be trapped that way.

An added benefit would be multishot capacity.

I'd prefer to achieve it from a regulated external source, as I'm more interested in consistent shots.

The external source is kind of essential anyway, seeing as the air in the chamber just isn't going to meaningfully stretch to six shots when I do get around to adding the magazine.

I see you have a checkvalve problem as well.

It's not really a problem. More of a musing on the suitability of hydraulic components.

Are you speaking from experience or are you just dismissing the idea based on your theory?

If you run Timberwolf through GGDT you will most likely find that the pressure left in the reservoir after ammo cleared the muzzle.
That is..unless you intentionally went with a very small reservoir.

My experience is that once you find that sweet spot, performance won't sufer while report is significantly reduced.

It's not very hard to test it.
And to correct me afterwards.

how about the suppressor suggestions?

God mode: install a decent sampling rate pressure sensor and cut off main valve after projectile leaves muzzle. Then you can use as inefficient a C:B ratio as you desire.

Or use a hammer valve.

Brian the brain wrote:If you run Timberwolf through GGDT you will most likely find that the pressure left in the reservoir after ammo cleared the muzzle.

Given the high valve efficiency, it's easy enough to estimate as just an adiabatic decompression. A C:B ratio of 1.5:1 means that the chamber tends to fall no further than about half pressure, although it will warm up slightly after firing.

The problem is not that the reservoir is too small. The problem is the valve.

The piston diameter is 26.2mm, with a seat diameter of 22mm. This means that at the point the forces are balanced on the piston, the pilot pressure is about 30% of the chamber pressure.
Now, in practice, the valve is going to start leaking air through the seal at a slightly higher pilot pressure than this (and can thus trigger the valve due to the force on the seat area), as some force differential is needed to seal the valve.
Still, I can get pistons to seal down to very low pressures, so the margin to create an airtight seal on the valve is fairly small.

So, the pilot pressure is inevitably lower than the chamber pressure as the projectile leaves the barrel. (So I guess, if you are saying things about the chamber size, you could say that it's too large relative to the valve dimensions).
The net force on the valve is still strongly in the red.

Thus, getting the valve to reseal at this point will require re-pressurising the pilot volume.

I actually did think up a way to do that a few years ago - build a piston valve tuned to that ratio of 50% pressure, give it a small reservoir, then hitch its pilot up to Timberwolf's chamber and its output to Timberwolf's pilot.
When chamber pressure falls below 50% - Bam, the piston valve opens and empties its reservoir into the pilot.

There's even a possibility to make the gas reservoir one side of the pneumatic cylinder for the semi-automatic magazine.

There were four issues I saw with it though.
1) Extra complexity, which may affect reliability.
2) If the main piston is be sealed up against its rear bumper, it may refuse to re-pressurise properly.
3) Sealing that fast may damage the piston face.
4) It's tuned for a specific C:B ratio, so may have a detrimental effect if barrel length is changed.

It does of course have the upsides of better air efficiency and a reduced report, but there's enough drawbacks to make me think twice or thrice about it.

how about the suppressor suggestions?

- #1 seems like it'll be really ugly.
- #2 is a lot like I already had in mind, just with a different way to make the reed valves.
- #3 sounds cool, but seems like it'll be heavier than other approaches.

mark.f wrote:Or use a hammer valve.

Not for this job, thank you very much.

mark.f wrote:God mode: install a decent sampling rate pressure sensor and cut off main valve after projectile leaves muzzle. Then you can use as inefficient a C:B ratio as you desire.

Currently this is god mode: http://www.daystate.com/images/reviews/ ... -SS-01.pdf

I know I'm a little late to the party here, but hopefully you haven't completely abandoned your project - it looks really promising. Have you considered using high pressure hose in place of the copper s-kink part of your chamber? That might be one way of getting smoother air flow in that portion of your chamber without the hassle of modifying copper components internally. Here's something I found. Rated to 500 psi and comes in steel:

http://www.summersrubber.com/prodsearch ... o+500+PSI)