shut-off valve suppressor

[Brian the brain]

Hahaha!
great first try!

But...remember to add some volume to the design next time.
You always advice integral suppressors covering the entire barrel and now look what you did...

I would have never thought of using a plugged hole to drop in the bb.
I was thinking more...inline, two part, dump in the bb before screwing the two parts together.
Your idea might have opened up a very cool option for tuning the thing.

a bigger diameter means a bigger jump for the blocker bb..wich could then be adjusted with your delrin bolt...If you had put it on the bottom side.
Start out with a long travel..then turn in the bolt and lift the restposition of the bb of it is still too noisy.
I recommend firing something a bit more forgiving than a lead slug...

What size was the exit port on this?
Was it perhaps a snug fit for the projectile and was the suppressor not perfectly centered perhaps?

Anyway...the fact that the bottom blew out means the concept works.
It held in the pressure....for a split second.
This also means stuff is happening VERY quickly in there.

I'm guessing this is the next best thing to a captive piston when it comes to silencing ..but with a lot more potential..
Clearing the bb from the muzzle could be mechanised to work in semi or even full auto as long as ROF isn't too high.
All very exciting and innovating...

[Fnord]

Haven't found the BB yet

Speaking of which, was it you who had suggested vaguely similar idea by PM a couple of years ago?

Yeah, here is the relevant part of the diagram.

You can basically ignore the red parts, since they're just gaskets and are not really necessary in this design. Pink is/are bolt holes

[jackssmirkingrevenge]

no idea if it was him but that's a rather obvious solution to the problem don't you think?

Yep, but I recall my objection being in the case of his design that the projectile actually had to strike part of the mechanism for it to work, not the best of ideas.

But...remember to add some volume to the design next time.
You always advice integral suppressors covering the entire barrel and now look what you did...

I never claimed not to be a hypocrite If the barrel is strong enough though, this isn't strictly necessary.

Was it perhaps a snug fit for the projectile and was the suppressor not perfectly centered perhaps?

5.5mm exactly, I couldn't make it any bigger because otherwise the airsoft BB would have popped out.

Of course it was perfectly centred, I machined it but yeah, it is a bit of a tight fit.

Anyway...the fact that the bottom blew out means the concept works.
It held in the pressure....for a split second.
This also means stuff is happening VERY quickly in there.

Yep and yep. The barrel got very hot, even for such a brief delay in gas exit.

I'm guessing this is the next best thing to a captive piston when it comes to silencing ..but with a lot more potential.

Captive pistons can be made to work, but they have their limitations and put significant stress on the system itself. This seems to offer the possibility of making a "conventional" system without the need for sabots or arresting devices.

Now, next step... I think I need a bigger ball, 0.5mm difference is a little too tight. Needs some thought, watch this space.

[Brian the brain]

Prototype curing

Of course it was perfectly centred, I machined it

You epoxied it on didn't you...

If the barrel is strong enough though, this isn't strictly necessary.

The barrel got very hot, even for such a brief delay in gas exit.

the emphasis is on strictly..
edit: BTW...the barrel IS strong enough LOL!!

watch this space.

Trust me..
I'll be back..

[jackssmirkingrevenge]

You epoxied it on didn't you...

Yes... but into machined holes, so it's all lined up

BTW...the barrel IS strong enough LOL!!

No doubt about that, I would be comfortable igniting a 30x mixture in a section of barrel tubing sealed at both ends.

I'll be back..

I bet you said that with lever action in hand and sunglasses on

Hmmm... I don't have many light balls around, plenty of ball bearings but I want something easier for the gasses to pick up. I have some 0.68" rubber balls, hmmm...

[jackssmirkingrevenge]

prototype v1.1, same concept but made a little differently.

- Instead of a screw, a collar keeps the BB in place and seals off the porting, this should resist the blast better.

- A brass inset is added to the exit end of the unit to ease the passage of the projectile.

[wyz2285]

The bb will drop naturally by gravity, so if the suppressor is accidently mounted with the bb housing tube pointing upwards, what will happen It´s crucial for me because I´d like to use it on my future hybrid rifles, not a steady base mounted hybrid.
I´m really interested now, all these parts looks possible for me to make, humm...
Have any video for us to "hear" it working?

[jackssmirkingrevenge]

The bb will drop naturally by gravity, so if the suppressor is accidently mounted with the bb housing tube pointing upwards, what will happen

The housing is drilled straight through so the BB will drop into one side or another. I tried turning it around and the BB will always fall to one end. To be extra sure, another hole drilled at 90 degrees will make it virtually certain that the BB will not be in the way.

It´s crucial for me because I´d like to use it on my future hybrid rifles, not a steady base mounted hybrid.
I´m really interested now, all these parts looks possible for me to make, humm...

It should be possible to make this using a pillar drill, or at worst, epoxy casting

Have any video for us to "hear" it working?

I haven't tested it yet, epoxy is still curing, give it a couple of hours. If I blow hard enough down the barrel it seals up pretty well.

[wyz2285]

I haven't tested it yet, epoxy is still curing, give it a couple of hours. If I blow hard enough down the barrel it seals up pretty well.

Sounds very promising

The housing is drilled straight through so the BB will drop into one side or another. I tried turning it around and the BB will always fall to one end. To be extra sure, another hole drilled at 90 degrees will make it virtually certain that the BB will not be in the way.

I was thinking about mod a little bit your piston shut-off valve design by adding a light spring...

[Brian the brain]

Looks swell.

Please be a bit more methodical this time in stead of your signiature "KaBoom...woops"


I should know my place when mocking you.
You're doing the community a big time favour with this.
I feel I'm part of the idea but I haven't done any of the work so thanks again.


Since failure is always an option..
Start out with a 1x mix, no ammo.
2nd shot, 1x mix with ammo.

Then build up the mixes.

If it would fail at , perhaps, a 3x times mix..you will have learned a great deal from the earlier firings.
For instance, if and by how much it reduces the sound.
Does a higher mix mean more noise..?
... or will the faster moving gasses shut the valve faster leading to less increase in noise than you would normally expect?
Will it be sufficient for higher mix hybrids?

I can't wait!!

[jackssmirkingrevenge]

Please be a bit more methodical this time in stead of your signiature "KaBoom...woops"

hehe yep, I know I usually document my experiments with a lot more data but in this case I was so keen to try it out I didn't even set up the camera

I should know my place when mocking you.
You're doing the community a big time favour with this.
I feel I'm part of the idea but I haven't done any of the work so thanks again.

Again, not my usual MO. High speed footage for the next test, promise

Since failure is always an option..
Start out with a 1x mix, no ammo.
2nd shot, 1x mix with ammo.

Not really possible with this setup. The small spark gap a hybrid needs means that igniting a 1x mix even with a high voltage ignitor doesn't work. Before the BANG test shot I tried at 4x and 6x first, the mix ignited but it didn't break the disk (single layer of photo paper!) - hence the 8x test.

Point taken though, let me see if I can rig it up to the QEV/slide valve setup before going hybrid

I was thinking about mod a little bit your piston shut-off valve design by adding a light spring...

Too complex for its own right. If you're so worried, why not have a continuous groove like so, easily made by adding endcaps to a pipe:

[wyz2285]

I was thinking about mod a little bit your piston shut-off valve design by adding a light spring...

Too complex for its own right. If you're so worried, why not have a continuous groove like so, easily made by adding endcaps to a pipe:

Great Idea I will try it out!

[jackssmirkingrevenge]

Here's a tentative first test:

[youtube][/youtube]

Firing at 120 psi using my QEV/slide valve combo.

You can't really hear the difference between shut off removed (first shot) and added (second shot). The shut off is clearly working though, you can hear the "fshhhhhh" sound of the air leaking out after the second shot. At such low pressure the the pilot being vented also makes a bit of noise which could explain the lack of audible difference between shots.

[al-xg]

I like where this is going, it may also be a nice way to make gas piston blowback more effective, which would in turn be a neat way to dissipate energy.

[jackssmirkingrevenge]

a nice way to make gas piston blowback more effective

Yup, that's one benefit I hadn't considered - you can make a system cycle even with very low pressures.

Bit late for noise in case of a catastrophic failure and the epoxy hasn't fully cured anyway so I'm going to delay hybrid testing for tomorrow.