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What has higher rpm?

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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What has higher rpm?

Unread postAuthor: spudnutbutthut » Thu Jan 22, 2009 4:04 pm

Does a cloud BBMG or a Vortex BBMG have more rpm cause i wanna make a cloud but im hoping its not sucky in comparison to a vortex, How big would a PVC tank at 40psi have to be to last a BBMG 3-5min of constant fire? (a cloud)

I would be using airsoft bbs

Sorry im new, but id like to try spudguns :)
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Unread postAuthor: jrrdw » Thu Jan 22, 2009 4:17 pm

I think your looking for ROF = "Rate Of Fire". That I think is determined by how many shoots per second you can get out of given gun/cannon/launcher. Not usually by the minute, but by the second. If you wish to have enough ammo to last 3-5 minutes, probably a 5 gallon bucket full. Finding enough air power is another problem. I'm not even going to venture a guess at that.

If you all ready have a design in mind it will be easier to help you if you post it.

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Unread postAuthor: Davidvaini » Thu Jan 22, 2009 4:27 pm

a vortex I find has a better rof because it has better feeding. With a cloud you will get some spitting that happens. With a vortex its more steady of s stream and therefor more reliable. In other words...

A gun that shoots 15RPM (I know really slow) but misfires 4 shots really only shoots 11RPM. A cloud tends to spit meaning sometimes it doesnt actually chamber a round and fire it. A vortex has a more reliable feed and therefore decreases the chance of a misfire.

Nothing wrong with a cloud persay.. there are just better designs out there.
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Unread postAuthor: spudnutbutthut » Thu Jan 22, 2009 9:47 pm

is there a way of improving a cloud without a block, because i wont have the tools neccesary to make one and another thing, instead of using a blowgun connected to a nipple (this is for the cloud) can i use one of those compressor hoses that screw into a schrader valve and use a schrader valve instead of a nipple? I would then connect that hose to a PVC air source (backpack carried) that would also screw into a schrader so i could pump it and then use it.

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Another thing is, back to the air tank,How big does a PVC tank at 40 -50 psi have to be to last the gun about 2-3min of constant fire?
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Unread postAuthor: Insomniac » Thu Jan 22, 2009 9:58 pm

spudnutbutthut wrote: Another thing is, back to the air tank,How big does a PVC tank at 40 -50 psi have to be to last the gun about 2-3min of constant fire?


In short: Really f*cking huge. I haven't experimented with clouds yet, but from what I understand they are best suited to a few seconds of extremely high ROF. If you want any decent time of constant shooting you are going to need some way of generating a propellent gas on the fly. Think dry ice in a steel chamber with a regulator, or maybe use the tanks they use for paintball with a regulator. From experiments with a soda bottle, a 2L soda bottle at 80-100 psi will only feed a blowgun for one or two seconds, and the pressure rapidly drops off.
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Unread postAuthor: Davidvaini » Thu Jan 22, 2009 10:13 pm

you need constant flow which means taking the use of a lot of gas. This is why some people on here have been working on a more efficient way of producing BBMGs.

You could have a gas that is held in a liquid state like co2.
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Unread postAuthor: DR » Thu Jan 22, 2009 11:52 pm

40psi is extremely low, for any bbmg (cloud/vortex -airsoft/steel - shot). You would deplete a 2 gallon tank so quickly, you'd be lucky if you were to fire for 3-5 seconds, let alone 3-5 minutes!

2 gallon capacity = (approx) 37 inches of 4" PVC pipe.

Your picture shows the "schrader valve" towards the end of the chamber (BREECH end). - No workie!

..."one of those compressor hoses", as your picture depicts (the kind that come attached to a bicycle pump) has WAY too small of an internal diameter, for the flow requirements of a BBMG --- even an airsoft.

Pumping even a small 2 gallon chamber... with a bicycle pump... will have your arms SO tired, that you probably won't even be able to lift your gun.
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Unread postAuthor: Davidvaini » Thu Jan 22, 2009 11:55 pm

If you were thinking 40 psi would be a good safe level for use in airsoft you can go a lot higher. People have used 120psi in an inline vortex without any problems.
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Unread postAuthor: jimmy101 » Fri Jan 23, 2009 2:09 pm

Couple thoughts ...

1. You really don't want a higher ROF. The ROF of both clouds and vortexes are unreasonably high to begin with. Real machine guns fire at about 300 RPM (5 rounds/second). A mingun fires at 2000 to 3000 RPM (33 to 50 rounds/sec). A typical BBMG fires at something like 1500 RRM (25 rounds/sec). At that fire rate you're really just wasting BBs.

2. Clouds and vortexes are usually run with 120 PSIG air supplies. The actual pressure in the chamber and barrel is down in the vicinity of 15 PSIG. The huge pressure drop is due to the inability of the supply hose to supply air fast enough to keep up with the amount of air being dumped out'a the barrel. With a 50 PSIG supply you'll probably get less than 10 PSIG behind the BBs. The performance will be less than impressive in terms of velocity. I'd WAG the muzzle velocity at less than 100 FPS. (A cheap BB gun will fire BBs at 300 FPS.) This is for copper/steel BBs.
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Unread postAuthor: Davidvaini » Fri Jan 23, 2009 2:30 pm

another thing to note is that jimmy's comment is with heavier bbs (copper/steel). Airsoft BB's do get picked up a lot easier by the stream of air and therefore the ROF is a lot higher and the gun is more effecient but It still goes through a lot of air.

Having a good hopup can actually increase the efficiency of BBMG's for the simple fact that it slowers the ROF and blocks the barrel between shots more effectively.

Most people wouldnt recommend a hopup because it will wear to fast but I always recommend a hopup. After all.. even if it wears down you are still in the same boat with the people who said not to add a hopup in the first place.
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Unread postAuthor: psycix » Fri Jan 23, 2009 6:38 pm

If you want to fire constantly for multiple minutes, and dont want to lug around tons of ammo and air tanks you will need:
-Lower ROF
-Be more efficient with air.
A cloud or vortex is unimaginable inefficient with its air and thus it need ALOT of air. On top of that, it needs alot of ammo.
For a cloud or vortex you actually just NEED a beefy air compressor, or a bunch of people to pump like chuck norris on crack to fire it constantly.
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Unread postAuthor: biged » Sat Jan 24, 2009 10:20 am

ROF: 80 bb per second
Continuous fire: 3 minutes

That's...

BB's fired: 14400
Weight in ammo: 6.35 lbs (.20 gram bb's)
Cubic inches of ammo in the chamber: 2741.6556

///ed///
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Unread postAuthor: jimmy101 » Sat Jan 24, 2009 1:55 pm

biged wrote:ROF: 80 bb per second
Continuous fire: 3 minutes

That's...

BB's fired: 14400
Weight in ammo: 6.35 lbs (.20 gram bb's)
Cubic inches of ammo in the chamber: 2741.6556

///ed///

And you would probably do more damage to the target if you just walked up and dropped the 6.35 lbs of BBs on it. :lol:
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