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Valveless launcher

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: POLAND_SPUD » Thu Jun 10, 2010 7:03 am

lol it works :D
I haven't achieved semi auto yet but at full auto the ROF seems to be close to 8-10 RPS

I am really surprised that no used this before to build a full sized BBMG
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Unread postAuthor: spudtyrrant » Thu Jun 10, 2010 7:12 am

Well don't just sit there, we need video :P
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Unread postAuthor: POLAND_SPUD » Thu Jun 10, 2010 8:27 am

[youtube]http://www.youtube.com/watch?v=Y6UfEmoyQ7k[/youtube]
damn something tells me I've got to order at least 20 000 BBs

this detent opens at ~200 psi
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Unread postAuthor: jackssmirkingrevenge » Thu Jun 10, 2010 9:08 am

POLAND_SPUD wrote:I am really surprised that no used this before to build a full sized BBMG


Oh come on!

Well, looks like it works :) but your aiming skills haven't changed, you really need to stand closer to your target (and put the camera much closer!)

What's the input pressure?
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Unread postAuthor: POLAND_SPUD » Thu Jun 10, 2010 9:30 am

slightly above 200 psi...
earlier I tested it with a smaller washer but it didn't work (meaning that I got past 500 psi but it did not release the BB) so I replaced it with one that has the largest hole that I could find)

but your aiming skills haven't changed
lol you put your targets 2 meters from the gun and yet you manage to miss a couple of shots... :D
anyway this thing has some very sharp recoil (not something I'd expect from a gun firing .12g bbs) and it isn't finished yet.. I put together all the fitting that were not used on anything else and I built the gun and then tested it
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Unread postAuthor: ramses » Thu Jun 10, 2010 2:52 pm

that has quite the sound to it. something like a .22.

do you know what's causing the feeding issues?
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Unread postAuthor: POLAND_SPUD » Thu Jun 10, 2010 3:28 pm

in fact this version had very little problems with feeding... in a previous test I used a vertical pipe as a mag and it was much worse... I think that a larger valve should help to eliminate this completely.
right now I am using one of those all aluminium valves that you can see here
Image
(it has 60L/m @ 6bar of flow... the idea was that the low flow would help to achieve single shots but right now I am leaning towards using just a plain blowgun becasue I want to test a proportional valve (ohh BTW blowguns are proportional valves, right ?))

in this test I was mostly trying to get as low ROF as possible and the 'pshhhh' sound that you hear is just venting the gun via the 3 way... when the bbs don't load you hear more of a continuous 'shhh' but IIRC it happend just a few times in this vid

also notice that at ~00:17 you can hear that the round gets 'chambered' right after the shot but it does not fire so I release the trigger and the 3 way vented the gun at ~00:20
the bb was 'loaded' but due to slightly lower pressure it failed to fire... surprisingly, once I vented the gun and pressed the trigger again everything worked
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Unread postAuthor: jackssmirkingrevenge » Thu Jun 10, 2010 3:42 pm

Ah, so it's 6mm? With heavier projectiles (say steel 6mm bearings, which you'd want for reasonable damage) you'll probably have less projectile agitation for the same flow and much more feed failures. Never bothered seriously with airsoft BBs, I want what I shoot to be harder than what I'm shooting at :)

In my experience, low flow is ideal for semi-auto or low rate of fire but if your feed system relies on the BBs being agitated, this leads to feeding problems. Perhaps the solution is to have a tube magazine likethis one. I've proposed the idea before but never did any serious work on it, if I could reliably coil the 4.5mm copper tubing I use as a BB barrel it might just be workable.
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Unread postAuthor: POLAND_SPUD » Thu Jun 10, 2010 4:40 pm

6mm

yeah, .12g to be more precise...
but I've just ordered 2000 of .30g bbs

you are probably right - I'll try to improve feeding in this design but if it fails with heavier ammo then I'll try that one

you should build one as well.. with your filling station and 0.8g bbs 30J per round is achievable
damn... you might as well build one in 3/8" calibre
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Unread postAuthor: jackssmirkingrevenge » Fri Jun 11, 2010 2:31 am

you might as well build one in 3/8" calibre


I thought I did already :P

The mag was unreliable but the performance was there had I tinkered with it...

[youtube]http://youtube.com/watch?v=arhnaUwQFgs[/youtube]

I was thinking of maybe going with heavier calibre but semi-auto for the sentry gun, a servo operated ball valve would provide a predictable burst of air that would allow for consistent performance... but hit probability falls drastically if you're just firing single shots.

I definitely want to see if i can coil the copper tube I have without distorting it...
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Unread postAuthor: POLAND_SPUD » Fri Jun 11, 2010 3:45 am

lol sorry I have spent too much time in the sun

I definitely want to see if i can coil the copper tube I have without distorting i

who said you have to do it yourself?? have it done for you... I am sure that some service stations have the equipment for bending brake lines but even a straight tube mag would be enough for 3/8" ammo


also I think it is possible to build a simple loading mech similar to the one used on semiauto MKIII, which could be useful as it would allow to use stuff such as airsoft mags...
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Unread postAuthor: urgle the danish cow » Fri Jun 11, 2010 9:35 am

i suggest buying an airsoft hop up bucking to substitute for the o-ring to prevent wear-and-tear and to increase performance
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Unread postAuthor: POLAND_SPUD » Sun Jun 13, 2010 4:41 am

this version uses a rubber washer not an o-ring... but you are right to some extent, a hop-up might be a good idea.... I've noticed that the bbs don't fly in a straight line...I am guessing that the rubber washer induces spin on them but it is 100% random
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Unread postAuthor: jackssmirkingrevenge » Sun Jun 13, 2010 5:24 am

I tried my hand at bending some copper tubing myself, filled it with BBs to keep it from kinking... using the same steel BBs that you intend to use as ammo isn't the best idea, pretty much jammed up :roll: maybe some 6mm I/D tubing will make a better magazine for 4.4mm BBs...
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Unread postAuthor: inonickname » Sun Jun 13, 2010 5:38 am

Sand will most likely work better than BB's.
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