SpudFiles

slide valve & 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

that's the biggest disadvantage of slide valves - they don't have threaded exhaust ports
so forget about perfectly silenced pneumatics if you can't attach another one to the exhaust[/quote]

that's the biggest disadvantage of slide valves - they don't have threaded exhaust ports
so forget about perfectly silenced pneumatics if you can't attach another one to the exhaust

My semi system does not have this problem, the quantity of exhaust air is too small and can be effectively suppressed by the handle with a slight modification
I´m gonna build my own once I got time

POLAND_SPUD wrote:forget about perfectly silenced pneumatics if you can't attach another one to the exhaust

A detent pop-off or QDV style valve would not have the exhaust problem, and be more efficient

In fact this design promises to work best with elongated projectiles, are you there Petitlu

Hybrid test at 8x, fail. The BB lodged in the insert tube and blew it out. Clearly I'm going about this the wrong way in terms of the usual underengineering, as well as not incorporating an expansion chamber in order to lower stress on the BB.

Looking at the high speed footage though, I have one niggling doubt. I filmed it originally at 420 fps and then slowed it down even further:

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You can definitely see something going into the hole after the paper is blown away, and to me it looks much more like a lead pellet than a brass tube with a BB embedded it. As well as that, the pellet simply bounced off the wooden backstop so nowhere near the penetration I would have expected.

I'm forced to conclude that the BB/tube combination blew out before the pellet. Thoughts?

Here's the aftermath, note the discolouration on the paper:

I'm forced to conclude that the BB/tube combination blew out before the pellet.

If that happened, it´s obvious that the bb is blew out.
Maybe because the barrel isn´t tight enough comparing to the lead pellet, also the pellet maybe too heave and a considerable quantity of gas were able to passed though it and shut-off the suppressor.

I'm forced to conclude that the BB/tube combination blew out before the pellet. Thoughts?

Possible.
So far we have learned that it needs to be stronger or the pressure acting on it should be lowered.

We won't know if it's any good unless you add an expansion chamber to it.

Brian the brain wrote:We won't know if it's any good unless you add an expansion chamber to it.

A major problem I'm seeing aside from the strength of the system is that the exit hole is identical to projectile diameter, and there is only 0.5mm difference between ball and projectile.

I'm thinking the next step should be a smaller diameter version, say 3 or 4.5mm, if I'm stuck with a 6mm BB as a blocker.

Sounds like a plan!

Another option would be to try a metal bb.
Won't hurt to try.
Won't hurt me anyway...
It certainly won't clog up the exit too soon.

Dang!
You should've muffled the slide valve earlier.

I hope this doesn't turn out to be another long time quest like the full-auto-valve

Brian the brain wrote:Another option would be to try a metal bb.
Won't hurt to try.
Won't hurt me anyway...
It certainly won't clog up the exit too soon.

That's a good point, if the BB is indeed being picked up too early then a heavier BB will certainly help to mitigate this. My worry is that it would not be picked up by the gasses at all.

Dang!
You should've muffled the slide valve earlier.

Well if it doesn't work for high mix hybrids then it's not worth trying

I hope this doesn't turn out to be another long time quest like the full-auto-valve

Not really, as discussed in private I have made other systems work very well, so this is just an interesting alternative. Also, these days thanks to my machine investments prototyping is a lot less painful

edit: going for a prototype with an expansion chamber and an 8mm steel BB as a blocker, keep watching this space

edit II: done, testing tomorrow.

if the BB is indeed being picked up too early then a heavier BB will certainly help to mitigate this

lol can't you machine it out of acrylic and see for yourself if it's being picked up earlier or not?

Unfortunately the only place I can buy acrylic here only opens in the mornings so I haven't yet been able to stock up. Also it will be interesting to see if being exposed to a hybrid mix will actually reduce its transparency. Certainly in the clear tennis ball launcher the combustion mix didn't affect it.

Here's what the current prototype looks like inside, with a 5.5mm barrel, 8mm ball bearing blocker and 7mm muzzle opening. Instead of being in a tube, the ball rests between the two front baffles like this.

No joy with this one, as suspected the heavy steel bearing wasn't picked up by the gasses...

I'm calling this one plausible, but it needs tweaking.

Jack, you can order plastic 8mm airsoft bbs. They are made for the larger bore airsoft guns, not as common, but they are available.

I said it needs tweaking, not that I'd be doing the tweaking

Haha, I may give it a try. It looks like it is possible, considering your video of the qev slide combo with the suppressor. I think what you were hearing was the exhaust of the slide valve, try it with a silenced pilot valve.