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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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Unread postAuthor: BC Pneumatics » Tue Apr 03, 2007 7:40 pm

I think I am missing what exactly you improved?
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Unread postAuthor: noname » Tue Apr 03, 2007 7:49 pm

My version of a block eliminates about a third-one half of the vortex and the shrouds, which makes feeding much faster and improves the power a bit, because the BBs don't swirl around more than once.
<a href="http://s5.photobucket.com/albums/y190/nissan_silvia/Vortex%20Block/?action=view&current=100_1374.jpg">Here's an example,</a> although he could have made the block thinner and more compact. It also looks as if he has shrouds on it, not completely sure though.
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Unread postAuthor: boilingleadbath » Wed Apr 04, 2007 4:32 pm

I vote for building one of those home built phototransistor chronograph set ups, and counting the blips... because it worked so well for that one guy.
I mean, he got the ROF and the speed of the projectiles an once!
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Unread postAuthor: richardbridges » Wed Apr 04, 2007 7:53 pm

Totally f#cking awesome!!! Thats the kind of info I need all around. Best round of posts I've seen in a long time. Anyways, I have a 35 gallon 4.5 or 5.5 horsepower compressor. I have 4 guns that all have 1/2 inch pvc vortex tubes. My main air tank sits between 130 and 150 psi(I've never let it pump up all the way, too damn loud). I have been testing my guns at 100 psi. My hopper holds about 300 bbs. They are gone in less then 3 seconds. I can go through about 2000 bbs before I lose more than 10 psi. in my main tank. This weekend I'm going to do a few 1000 round tests, and with any luck I'll try and get a video up sunday night.

You guys rock!!!!!!!
thanks!!!!! :D
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Unread postAuthor: jimmy101 » Thu Apr 05, 2007 12:15 pm

Measuring the ROF is pretty easy if you have an old PC or laptop laying around. (I can't believe how backwards this forum is.)

Just use the PC to record the sound of the gun firing, or, the sound of the ammo hitting a target. Use any old sound editing software to display the waveform and measure the rof.

I've used a slightly more complex system to measure the ROF (EDIT: and the muzzle velocity) of a vortex gun (http://home.earthlink.net/~jimsluka/Jims_chrono.html). Here is ~1.5 seconds of firing showing something like 50 BBs
Image


For both vortex and cloud designs the ROF is indeed variable. The biggest factors are the drop in the resevoir pressure as the gun is fired (hard to imagine many BBMG'ers have access to a compressor that can keep up with a 1/4" hole in it.) Furthermore, the pressure drop through the typical length of pressure hose is significant. Assuming your valve is at the gun, the hose starts at the resevoir pressure. When you pull the trigger the pressure in the hose drops rapidly and resistance between the moving air and the hose keeps the gun end of the hose significantly below the pressure at the resevoir end. Google something like "pressure drop air hose length" and I'm sure you can find tables that will give you an idea of how much the pressure drops through compressor hose.
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