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adjustable rate of fire for BBMGs?

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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adjustable rate of fire for BBMGs?

Unread postAuthor: jackssmirkingrevenge » Tue Jan 29, 2008 1:40 pm

Following these ideas, here's a theory on how to make a device that would allow you to adjust the rate of fire of an ordinary cloud/vortex BBMG. The idea is pretty much self explanatory, the spring loaded ball detent resists the motion of the BB until it's pushed down, allowing the BB to escape and catching the next one, allowing the cycle to continue. Altering the spring compression would change the force on the BB and thus change the rate of fire (more compression -> slower ROF).

The added benefit would be that the flow restriction while the BB is "caught" would allow pressure to build up in the chamber, meaning the BB would be released at higher velocity which would compensate for the slower fire rate.

There is one problem I forsee, blocking off the flow might cause feeding problems in the case of unassisted cloud or vortex BBMGs.
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Unread postAuthor: judgment_arms » Tue Jan 29, 2008 1:53 pm

I saw a something similar once, except it used a magnet with steel BBs
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 29, 2008 1:58 pm

Ah, but this is adjustable ;)
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Unread postAuthor: Antonio » Tue Jan 29, 2008 2:11 pm

This could work very well when the airsource has a small opening to the barrel tube'' This would make a build up of pressure everytime a bb is shot. The thing is you need a seal just before the spring loaded pin to seal of the bb from the airsource.
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Unread postAuthor: Mr. Beaver » Tue Jan 29, 2008 2:11 pm

I saw a something similar once, except it used a magnet with steel BBs



i don't think a magnet would be reliable enough also like jack said it's not really adjustable.

and jack i think it's a great design only i think you should put two, one each sid of the barrel to give you more adjustability :lol:
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Unread postAuthor: al-xg » Tue Jan 29, 2008 2:12 pm

I found that with my vortex strafer when using a hop up (it wasn't ajustable but could have been) it made more of a plop plop plop sound instead of the usual whirring.

If the ball detent was replaced by(or coated with, or...) something with a little more friction you get the hop up effect too :)


Arrrg Ant it winked at me ;) :lol: did it always do that or is this new ?
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Unread postAuthor: judgment_arms » Tue Jan 29, 2008 2:14 pm

If you stick with one detent I’d suggest you put it at the top of the barrel that way the backspin doesn’t throw it into the ground.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 29, 2008 2:18 pm

ant wrote:The thing is you need a seal just before the spring loaded pin to seal of the bb from the airsource.


you don't really need a perfect seal, just a tight fit - after all, the main valve will be a blowgun valve to the chamber, with a much higher flow than any tiny leaks you might have.

Nice one with the user pic :D

Thanks for the hopup suggestions guys, hadn't though about it that way.
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Unread postAuthor: Antonio » Tue Jan 29, 2008 2:19 pm

al-xg wrote:I found that with my vortex strafer when using a hop up (it wasn't ajustable but could have been) it made more of a plop plop plop sound instead of the usual whirring.

If the ball detent was replaced by(or coated with, or...) something with a little more friction you get the hop up effect too :)


Arrrg Ant it winked at me ;) :lol: did it always do that or is this new ?


Ah nice one man! So it does even work with a simple hopup oring.
haha Al-xg, its pretty cool right. I first didnt notice we could add gifs as a profile picture, so when I saw someones profile pick (a walking stick figure) I made this. So it new since a couple of days or so. I was curious if anybody would notice it. I tried makin a longer delay for the wink, but that made the gif too big. Anyways nice to hear someone saw it lol.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 29, 2008 2:33 pm

It sucks that the size limit is so small though, I have a whole lot of cool animated gifs, less than 70k in size, and less than 100x100 pixels but too big for this forum.

PCGUY, perhaps we could trade spudbux (since I have enough to purchase a small village in Kurdistan) for larger (say up to 100kB) avatars?
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Unread postAuthor: Antonio » Tue Jan 29, 2008 2:39 pm

jackssmirkingrevenge wrote:It sucks that the size limit is so small though, I have a whole lot of cool animated gifs, less than 70k in size, and less than 100x100 pixels but too big for this forum.

PCGUY, perhaps we could trade spudbux (since I have enough to purchase a small village in Kurdistan) for larger (say up to 100kB) avatars?


LOl, yeah it took me some time to make this gif. I think I made about 10 until I had the right size, resolution and quality.
PCGUY, I have just a question, when I enter spudfiles at around 7 -8 oclock (gmt time) I cant open the webpage and its says there is an error. Whats this problem?
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Unread postAuthor: Ragnarok » Tue Jan 29, 2008 3:39 pm

Hmm. I've just put a blanket block using Firefox's adblocker on animated avatars, most just distract (or in some cases, just plain irritate) me - usually because of the way they repeat, or some are just jerky.
Some avatars have completely destroyed my chain of thought.

Any file that's is a ".gif" and has "avatar" anywhere in the filename just doesn't get loaded, no matter what site it's from. I may miss the occasional worthwhile one, but it saves me needing to block each one that gets to me in some way individually, which is the very vast majority.

That's part of having Asperger syndrome, things can affect you in weird ways. I have seen some good animated avatars in my time, but as some can totally throw my chain of thought (really inconvenient, believe me), I just have to block them completely.

Odd question: If I just say Adbl0ck without the er (and with an o instead of a 0, of course), why does the forum put [removed] in it's place?
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: jimmy101 » Tue Jan 29, 2008 4:00 pm

Instead of the piston you could also use an o-ring. Or perhaps something like this.
The generally idea for the firing cycle is;

1. The trigger is pulled, air starts to flow at high velocity into the chamber (and out the barrel) and the cloud/vortex chamber works normally.
2. Eventually a BB loads into the beginning of the barrel but is stopped by the tubing (or an O-ring), sealing the barrel.
3. Pressure builds in the chamber, the cloud/vortex stops working since there is little/no air flow out the barrel.
4. Eventually the pressure in the chamber builds enough to force the BB through the tubing.
5. Since the tubing alone doesn't close off the barrel, air pressure blows the BB out the barrel.
6. The barrel is now unsealed and dumps air, rapidly lowering the pressure in the chamber.
7. As the pressure in the chamber drops, air flow into the chamber increases and the cloud/vortex starts to work again.
8. Eventually a BB loads into the beginning of the barrel but is stopped by the tubing, sealing the barrel... and the cycle repeats.


With a cloud or a vortex design, air pressure will hold the next BB at the breach until the pressure is high enough to launch it. There wouldn't be another BB imediately behind the "chambered" bb since there is no force to hold one there.

When a bb is launched the lag time before the next bb gets blown into the "chambered" position gives the air flow needed to get the first bb out the barrel.

As with Jask's concept, the time the bb is held while "chambered" allows the pressure in the bb resevoir to rise.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 29, 2008 11:17 pm

Indeed Jimmy, this is an extension of the O-ring design, the difference is that while the seal is not as good, the fact that it's adjustable makes it a bit less of a suck-it-and-see approach.
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Unread postAuthor: SPG » Wed Jan 30, 2008 2:59 am

Ah-hah, here's just a thought for one and all. Places like aero-modelling shops sell silicon rubber tubing in a variety of small diameters including one with a 6mm ID.

Now imagine you take a short bit of this, push the barrel end in part way and push the whole thing onto the chamber outlet, LEAVVING a small gap between the two rigid tubes. Now you could do something as simple as wind a piece of wire round this and twist it to constrict the tube. And voila very simple adjustable system, completely air tight and providing a good BB to tubing seal.

Oh and it's cheap stuff but you usually have o by it by the metre/yard, so when one bit wears out you just fit another bit.
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