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Brutal HPA BBMG idea

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Brutal HPA BBMG idea

Unread postAuthor: jackssmirkingrevenge » Wed Feb 17, 2010 1:35 am

I've recently got myself a couple of these 1/4" ball valves, low friction and with around 8.5mm porting.

Image

This got me thinking about making an HPA version of my ball valve strafer. The ball valve only needs to move around 45º for the BBs to pass through, and by gearing it down the travel can be made much less withough making the trigger too heavy so in terms of ergonomics it should be more feasible than my previous attempt.

The advantages of this setup are obvious, you have full pressure in the chamber already so there's no need for pesky detents to allow for pressure buildup - the BB already has whatever pressure you're putting in behind it. Rate of fire will be horrendous but hey, miniguns are cool :) besides, with 100 psi I was getting 350-400 fps with steel 0.177" BBs, heaven knows what 8 times the pressure will put out, so short bursts should be enough to shred pretty much anything :D
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Unread postAuthor: McCoytheGreater » Wed Feb 17, 2010 1:42 am

Could work. Should work. Keep us posted on the gearing. I think we have a couple of these laying around our shop.
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 17, 2010 1:45 am

I always figured this was the ultimate configuration for high performance in BBMGs but the awkward ergonomics put me off, it's only now (because of the sentry project :roll:) that I was thinking in terms of gearing it up to make it as practical as a blowgun trigger, watch this space ;)
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Unread postAuthor: McCoytheGreater » Wed Feb 17, 2010 1:56 am

Will do. How will you be gearing the trigger/valve assembly? Rather, what materials will you be using to gear the assembly.
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 17, 2010 2:50 am

I have a stock of suitable gears in my spares box - one of the items I look out for when cannibalising something before disposaly - and I think it's reasonably safe to say that copious amounts of epoxy will take care of the rest :D

Really though you don't actually need gears, it can be done with levers:
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Unread postAuthor: bradisfun » Wed Feb 17, 2010 4:26 am

this looks like it could make it to my pencel case as i have been looking for a small/compact gun tho i wanted a semi but oh-well the only thing is that i was gonna use like paper scrunched up or blue tack but this is still brotty cool and compact so... yea
but this looks like it would be perfict for the sentry gun project
good luck with it :)
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Unread postAuthor: django » Wed Feb 17, 2010 5:44 am

Looks great mate :D ,the rate of fire on this thing would be astonishing to say the least and power would be devestating!! your mag will empty as fast as you can blink I suspect?. Ive never used a HPA Bottle before = what pressure are these generally charged to?, there were guys on the BB MACHINEGUN OWNERS GROUP who ran home made BBMG's on straight Co2 and said they could easily eat a 4X2" peice of wood like butter and thats at 800 psi...
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Unread postAuthor: psycix » Wed Feb 17, 2010 6:43 am

Actually, a gear is nothing more than a wheel with a lot of levers.


What will you use as a chamber? A one meter cube full of epoxy? Or a thin plastic hull with an epoxy coating that will blow up?
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Unread postAuthor: POLAND_SPUD » Wed Feb 17, 2010 7:05 am

@psycix
heh good point...
It seems that this can be built with a 1/2" T, length of pipe and a few fittings. In this way he could build something that is both serviceable and strong enough to survive 800 psi

Though he has tendency to avoid the simplest solutions :D
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 17, 2010 7:05 am

bradisfun wrote:this looks like it would be perfect for the sentry gun project


Pretty much what I had in mind for the sentry, only that will be much smaller calibre and on a remote line.

your mag will empty as fast as you can blink I suspect?


Rate of fire should be similar to any other vortex BBMG. The beauty of the ball valve design is that no matter how big your chamber is, you always get the same power, unlike a conventional BBMG where increasing chamber size reduces pressure and therefore power.

Ive never used a HPA Bottle before = what pressure are these generally charged to?


I fill mine to 3000 psi from my SCUBA tank, output is adjustable by shimming the reg spring, it can do approximately 450 psi (no shims), 650 psi (one shim) and 850 psi (two shims).

What will you use as a chamber? A one meter cube full of epoxy? Or a thin plastic hull with an epoxy coating that will blow up?


Har har di har :P I think I'll use the printer cartridge aluminium tubing I've been using for my semi and cartridge experiments of late.

POLAND_SPUD wrote:It seems that this can be built with a 1/2" T, length of pipe and a few fittings.


Which is precisely why I WON'T do it :D

Edit, actually - this is rather embarassing :oops: - I had a bit of a quick rummage in the workshop, and look what it turned up :D 1/2" 316 stainless hehe
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Unread postAuthor: POLAND_SPUD » Wed Feb 17, 2010 12:05 pm

so... does it work?
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Unread postAuthor: Gippeto » Wed Feb 17, 2010 12:16 pm

Well at least that shouldn't blow up in your face.

Unlike TLAR engineered constructs of partially cured binary adhesives. :wink: :lol:
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Unread postAuthor: grock » Wed Feb 17, 2010 2:34 pm

Just out of curiosity, with a BBMG ROF, wouldn't there be a pretty good chance of a bb getting stuck partially in the ball valve, which would stop it from closing? If that is actually a problem, how would you fix it? Also, about how many shots you think you could get off that tank at 450 PSI?
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 17, 2010 3:53 pm

POLAND_SPUD wrote:so... does it work?


I don't know yet, first of all the tee needs to be modded in such a way that it opens the bottle by repressing the pin (as well as sealing against it) - either that or I'll use the ASA adapter you've seen before, currently serving as my schrader fill station (I have another that's fitted to the pressure washer handle, but I have yet another one on the way). Also, it turns out one of the sockets on the tee (where the ball valve is) is proper forked, no wonder it was lying around :roll:

Unlike TLAR engineered constructs of partially cured binary adhesives.


LOLOL I had no idea there was an acronym that described the manner in which I tend to work so exactly! :D

Just out of curiosity, with a BBMG ROF, wouldn't there be a pretty good chance of a bb getting stuck partially in the ball valve, which would stop it from closing?


I never had this problem with my 100 psi ball valve strafer, the thing is that the BBs are in motion and are highly unlikely to jam.

about how many shots you think you could get off that tank at 450 PSI?


I can only answer that after testing, I'm guessing short firing time but a lot of shots :)
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Unread postAuthor: USGF » Thu Feb 18, 2010 5:38 am

jackssmirkingrevenge wrote:I have a stock of suitable gears in my spares box - one of the items I look out for when cannibalising something before disposaly - and I think it's reasonably safe to say that copious amounts of epoxy will take care of the rest :D

Really though you don't actually need gears, it can be done with levers:


Levers are good, linkage might be better. Heim joints might be overkill, large model RC servo stuff should work well.

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